Jonathan Polfus

• Rosnes, Andreas; Jiang, Bo; Nguyen, Phuong D.; Wang, Luyang; Wenckstern, Holger Von & Prytz, Øystein [Vis alle 7 forfattere av denne artikkelen] (2026). Multiple Stages of Metal Exsolution from Nonstoichiometric Perovskites. Journal of the American Chemical Society. ISSN 0002-7863. 148(31), s. 33486–33495. doi: 10.1021/jacs.6c08762. Fulltekst i vitenarkiv Vis sammendrag

  Exsolution enables controlled solid-state precipitation of metal nanoparticles from metal oxides, resulting in materials that exhibit excellent catalytic properties for electrochemical energy conversion. The diverse characteristics of particles exsolved at different temperatures indicate complex mechanisms that remain unresolved. Through a series of in situ electron microscopy, synchrotron X-ray diffraction, and thermogravimetry experiments on La0.2Ca0.7Ti0.9Sc0.05Cu0.05O3−δ across nanoscale wedges to μm-sized powders, multiple stages of exsolution are deconvoluted with increasing thermal activation: (1) minor exsolution of anchored surface nanoparticles, (2) exsolution of endoparticles within the bulk, and (3) diffusion and coalescing in the bulk and at the surfaces. Reconstruction of the perovskite surface by formation of nanoscopic steps and terraces proceeds concurrently with endoparticle growth. Moreover, distinct exsolution characteristics are observed in the near-surface region and deeper within the bulk, resulting in spherically and orthorhombically shaped endoparticles, respectively.

• Talic, Belma; Dayaghi, Amir Masoud; Singh, Kalpana; Stefan, Elena; Sunding, Martin Fleissner & Malerød-Fjeld, Harald [Vis alle 7 forfattere av denne artikkelen] (2026). Chemical stability of BaZr1−xCexO3−δ-based electrolytes in pressurized CO2. Solid State Ionics. ISSN 0167-2738. 444, s. 1–7. doi: 10.1016/j.ssi.2026.117251. Fulltekst i vitenarkiv Vis sammendrag

  Acceptor doped barium cerates and zirconates are attractive electrolyte materials for use in proton ceramic electrochemical cells. However, the long-term stability of these materials may be compromised by their tendency to react with CO2. In this work, the chemical stability of the Zr-rich electrolyte materials BaZr0.8Ce0.1Y0.1O3−δ (BZCY81) and BaZr0.9Y0.1O3−δ (BZY10), and the Ce-rich electrolyte materials BaZr0.4Ce0.4Y0.2O3−δ (BZCY442) and BaZr0.4Ce0.4Y0.1Yb0.1O3−δ (BZCYYb4411) are studied in 10 bar CO2 at 500 °C for 150 h. X-ray diffraction and scanning electron microscopy analysis showed BaCO3 formation for the Ce-rich electrolytes, while the Zr-rich electrolytes showed excellent stability. The chemical stability of the Zr-rich electrolytes was further confirmed under 10% H2 in CO2 (10 bar) at 800 °C. Addition of NiO sintering aid to the Ce-rich electrolytes did not have a major impact on the chemical stability although the amount of BaCO3 formation appeared to be slightly reduced.

• Roen, Stine; Strandbakke, Ragnar; Norby, Truls & Polfus, Jonathan (2026). Deconvoluting electrode polarization resistances underestimated due to electronic leakage in proton ceramic cells. Electrochimica Acta. ISSN 0013-4686. 575, s. 1–9. doi: 10.1016/j.electacta.2026.149534. Fulltekst i vitenarkiv Vis sammendrag

  Proton ceramic cells lose faradaic efficiency through electronic leakage in the electrolyte that electrochemical impedance spectroscopy cannot resolve directly. Proton conducting electrolytes such as BaZr0.7Ce0.2Y0.1O3 δ (BZCY721) exhibit non-negligible p-type electronic conductivity that short-circuits the electrode polarization processes, causing systematic underestimation of their impedances. Here, we apply a correction procedure in which the electronic resistance is placed in parallel with the faradaic resistances in equivalent-circuit analysis, thus yielding true electrode polarization resistances. The procedure is applied to a symmetric cell comprising porous Ba0.95La0.05Fe0.7Ni0.2Zn0.1O3 δ (BLFNZ) electrodes on BZCY721 and the ionic and electronic transport numbers are obtained by fitting the measured total electrolyte conductivity based on defect chemistry and transport equations. Accounting for the electronic short-circuit markedly alters the deconvoluted electrode polarization resistances, activation energies, pre-exponential factors, and reaction orders. The apparent electrode polarization resistance is underestimated by approximately one order of magnitude at 600◦C, and the activation energy is reduced from the apparent 1.3 eV to 0.8 eV. The corrected charge-transfer and mass-transfer conductances are consistent with proton transfer (p0O2 and p1/2H2O dependences) and combined oxygen exchange and oxide ion diffusion in the electrode (p1/4O2 and p0H2O dependences), respectively. The impact of the electronic leakage is quantified by equivalent circuit analysis of the electronic and faradaic conductances.

• Wen, Yabing; Rosnes, Andreas; Jiang, Bo; Prytz, Øystein; Norby, Truls & Haugsrud, Reidar [Vis alle 7 forfattere av denne artikkelen] (2025). Nickel-Induced Lattice Defects Limit Proton Uptake in Barium Zirconate Electrolytes. Journal of the American Chemical Society. ISSN 0002-7863. 148. doi: 10.1021/jacs.5c13935. Fulltekst i vitenarkiv Vis sammendrag

  Nickel provides essential catalytic properties for hydrogen electrodes in proton-conducting ceramic electrochemical cells. However, Ni diminishes the hydration capability and proton conductivity when incorporated into electrolyte materials including BaZr0.8Yb0.2O3−δ studied here. Through semiquantitative atomic-resolution scanning transmission electron microscopy, density functional theory simulations, X-ray total scattering, and absorption spectroscopy, we reveal that Ni forms point defect clusters with the Yb acceptors wherein oxygen vacancies are trapped and resist hydration. The resulting effective acceptor concentration is described by point defect reactions in quantitative agreement with thermogravimetric measurements of hydration for samples substituted with 2–5 mol % Ni by BaNiO2 addition. Moreover, excess B-site cations due to NiO addition induce the formation of antiphase boundaries (APBs) that are enriched in Yb and thereby deplete the bulk of acceptors, further suppressing hydration. The adverse effects of Ni are thereby resolved into two novel mechanisms, opening new avenues in point defect engineering for high-performance electrolytes.

• Gudmundsdottir, Jonina Björg; Thoreton, Vincent; Jiang, Bo; Pokle, Anuj; Vøllestad, Einar & Haugsrud, Reidar [Vis alle 7 forfattere av denne artikkelen] (2025). Oxygen exchange kinetics of BaGd0.3La0.7Co2O6−δ with exsolved Co3O4 nanoparticles in dry and humid atmospheres. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 27(16), s. 8467–8477. doi: 10.1039/d4cp04791e. Fulltekst i vitenarkiv Vis sammendrag

  The oxygen exchange kinetics of BaGd0.3La0.7Co2O6−δ were investigated with pulsed isotope exchange (PIE) measurements in dry and humid atmospheres in the temperature range 400–600 °C in 0.005–0.21 bar O2. Synchrotron X-ray diffraction and scanning transmission electron microscopy (STEM) revealed exsolved Co3O4 nanoparticles dispersed on the surfaces that may contribute to the catalytic activity of the material towards the oxygen exchange reactions. The obtained oxygen exchange rate was 4.45 × 10−3 mol m−2 s−1 at 600 °C in 0.21 bar O2 with an activation energy of 0.76 eV. The rate determining step of the exchange reaction was determined to be dissociative adsorption of oxygen in both dry and humid atmospheres based on the individual rates of dissociative adsorption and incorporation, as well as pO2 dependencies of the oxygen exchange rate of around 1. The effect of water on the oxygen exchange rate was found to be dependent on the oxygen partial pressure, decreasing the rate at 0.21 bar O2 and 600 °C by a factor of approx. 2, while increasing the rate at 0.02 bar and 0.005 bar O2 by a similar amount. In situ thermogravimetric analysis was used to characterise the oxygen non-stoichiometry of the material throughout the oxygen exchange measurements.

• Triestram, Léna & Polfus, Jonathan M. (2024). Hydride ion diffusion along grain boundaries in titanium nitride. Acta Materialia. ISSN 1359-6454. 270. doi: 10.1016/j.actamat.2024.119853. Fulltekst i vitenarkiv Vis sammendrag

  Density functional theory (DFT) simulations are utilized to study the absorption and diffusion of hydride ions along four types of titanium nitride grain boundaries: open and compact structures of Σ5 (210)[001] and Σ5 (310)[001]. The absorption energy into bulk vacancies ranges from approx. −0.7 eV in TiN0.7 to −0.38 eV for a single vacancy in TiN, and shows a minor dependence on the hydrogen content in the structure. The absorption energy for vacancy sites at the grain boundaries ranges from −0.44 eV to −0.66 eV. Hydrogen absorption into interstitial sites at the grain boundaries is less favourable, in part due to a positive and fairly large zero-point energy contribution, with absorption enthalpies between −0.09 eV and 0.06 eV. The interstitial diffusion barriers are 1.34 eV and 0.83 eV in the open Σ5 (310) and Σ5 (210) grain boundaries, respectively. In the compact grain boundaries, the migrating hydrogen species changed oxidation state from a hydride ion (H0.5−) to a proton (H0.3+) at the transition state as it formed bonds to nitrogen along the diffusion path. The diffusion barriers are larger than in the corresponding open structures: 1.75 eV and 1.02 eV in the compact Σ5 (310) and Σ5 (210) structures, respectively. The considered grain boundaries and diffusion pathways cannot explain the fast interfacial hydride ion transport reported for hydrogen separation membranes based on TiNx thin films with columnar microstructure.

• Rosnes, Andreas; Wenckstern, Holger Von; Polfus, Jonathan & Prytz, Øystein (2024). Identifying transient defects in exsolution of nanoparticles by semi-quantitative ABF STEM imaging. BIO Web of Conferences. ISSN 2273-1709. doi: 10.1051/bioconf/202412925030. Fulltekst i vitenarkiv
• Polfus, Jonathan (2023). One-dimensional carbon chains encapsulated in hollandite. Communications chemistry. 6(1). doi: 10.1038/s42004-023-01011-3. Fulltekst i vitenarkiv Vis sammendrag

  Abstract One-dimensional carbon chains are highly reactive allotropes that are stabilized inside the protective environment of carbon nanotubes. Here we show that carbon chains can be encapsulated in metal oxides containing open structural channels, exemplified by hollandite α-MnO 2 . The α-MnO 2 channels stabilize cumulene chains due to their structural commensurability, whereas the triple bonds in polyyne chains exhibit excessive steric repulsion to the oxide ions bordering the channel. Cumulene exhibits an interaction energy of only 0.065 eV per carbon atom, obtained by first-principles calculations, which is significantly more favorable than for encapsulation in a similarly sized carbon nanotube. Encapsulation of carbon chains is associated with lateral expansion of the α-MnO 2 channel and polarization of the manganese and oxygen charge densities adjacent to the chains. Accordingly, the interaction energy is governed by a balance between van der Waals attraction and steric repulsion between the materials.

• Dayaghi, Amir Masoud; Polfus, Jonathan M.; Strandbakke, Ragnar; Pokle, Anuj; Almar, Laura & Escolastico, Sonia [Vis alle 10 forfattere av denne artikkelen] (2023). Effects of sintering additives on defect chemistry and hydration of BaZr0.4Ce0.4(Y,Yb)0.2O3−δ proton conducting electrolytes. Solid State Ionics. ISSN 0167-2738. 401. doi: 10.1016/j.ssi.2023.116355. Fulltekst i vitenarkiv
• Emhjellen, Linn Katinka Susanne Shi; Liu, Xin; Polfus, Jonathan M. & Haugsrud, Reidar (2022). Native point defects and polaron transport in zirconium pyrovanadate. Solid State Ionics. ISSN 0167-2738. 386, s. 1–8. doi: 10.1016/j.ssi.2022.116033. Fulltekst i vitenarkiv
• Kim, Donghoi; Liu, Zhongxuan; Anantharaman, Rahul; Riboldi, Luca; Odsæter, Lars Hov & Berstad, David Olsson [Vis alle 10 forfattere av denne artikkelen] (2022). Design of a novel hybrid process for membrane assisted clean hydrogen production with CO2 capture through liquefaction. Computer-aided chemical engineering. ISSN 1570-7946. 49, s. 127–132. doi: 10.1016/B978-0-323-85159-6.50021-X. Fulltekst i vitenarkiv Vis sammendrag

  This work introduces a novel hybrid concept to produce H2 from natural gas by using the protonic membrane reformer (PMR) with liquefaction based CO2 capture system. For process intensification, recycling of the off-gas from the capture process and a water gas shift reactor for the retentate gas from the PMR are applied to the hybrid configuration. The suggested concept achieves around 99 % of system H2 and CO2 recovery rates even when the PMR is operated at relatively low hydrogen recovery, resulting in energy efficient H2 production with a low carbon intensity.

• Vøllestad, Einar; Øygarden, Vegar; Graff, Joachim Seland; Sunding, Martin Fleissner; Pietras, John D. & Polfus, Jonathan M. [Vis alle 7 forfattere av denne artikkelen] (2022). On the mechanism of Mn(II)-doping in Scandia stabilized zirconia electrolytes. Acta Materialia. ISSN 1359-6454. 227, s. 1–11. doi: 10.1016/j.actamat.2022.117695. Fulltekst i vitenarkiv Vis sammendrag

  Cubic Scandia-stabilized zirconia (ScSZ) is an attractive electrolyte material for solid oxide cells due to its significant ionic conductivity, provided that the phase transition to its rhombohedral polymorph upon cooling is suppressed. The latter is achieved with addition of a secondary co-dopant, albeit it may be at the detriment of its ionic conductivity Here, we thoroughly investigate how MnO2 (0.5–10 mol%) as a co-dopant impacts on the sinterability, thermal expansion, crystal structure and ionic conductivity of ZrO2 doped with 10 mol% Scandia (10ScSZ), and we provide new insight on the chemistry of dissolved manganese in the fluorite lattice. Reactive sintering of 2 mol% MnO2 mixed with 10ScSZ enables to produce dense electrolyte with significant reduction of the peak sintering temperature and stabilisation of the cubic structure down to room temperature. Combined density functional theory and X-ray photoelectron spectroscopy analyses reveal that manganese predominantly enters the structure as Mn2+ during reactive sintering, with a prevalence of higher valence states at the surface and grain boundaries. The highest oxide ion conductivity is achieved for 2 mol% doped 10ScSZ (120 mScm−1 at 800 °C) and it decreases with increasing Mn concentration. For all compositions, the bulk conductivity remains independent of pO2 – corroborating a limited electronic conductivity contribution from Mn-doping. The grain boundary conductivity is found to decrease with sintering time and pO2, which is attributed to the chemistry and concentration of segregated manganese at the surface and grain boundaries, yielding depletion of oxygen vacancies in the space charge layer.

• Barragan-Yani, Daniel; Polfus, Jonathan M. & Wirtz, Ludger (2022). Native defects in monolayer GaS and GaSe: Electrical properties and thermodynamic stability. PHYSICAL REVIEW MATERIALS. 6(11). doi: 10.1103/PhysRevMaterials.6.114002. Fulltekst i vitenarkiv Vis sammendrag

  Structural, electronic, and thermodynamic properties of native defects in GaS and GaSe monolayers are investigated by means of accurate ab initio calculations. Based on their charge transition levels we assess the influence of the studied defects on the electrical properties of the monolayers. Specifically, we show that native defects do not behave as shallow dopants and their presence cannot account for the experimentally observed intrinsic doping. In addition, we predict that native defects are efficient compensation and recombination centers. Besides pointing out their detrimental nature, we also calculate the corresponding finite-temperature formation energies and provide a window of growth conditions able to reduce the concentration of all relevant native defects.

• Polfus, Jonathan M.; Benthem, Marta; Ali, Ayaz; Barragan-Yani, Daniel; Vullum, Per Erik & Sunding, Martin Fleissner [Vis alle 9 forfattere av denne artikkelen] (2021). Temperature-Dependent Adhesion in van der Waals Heterostructures. Advanced Materials Interfaces. 8(20). doi: 10.1002/admi.202100838. Fulltekst i vitenarkiv Vis sammendrag

  The interlayer coupling between 2D materials is immensely important for both the fundamental understanding of these systems, and for the development of transfer techniques for the fabrication of van der Waals (vdW) heterostructures. A number of uncertainties remain with respect to their adhesion characteristics due to the elusive nature of measured adhesion interactions. Moreover, it is theoretically predicted that the intrinsic ripples in 2D materials give rise to a temperature dependence in adhesion, although the vdW interactions themselves are principally independent of temperature. Here, direct measurements of the adhesion between reduced graphene oxide – coated by solution deposition on atomic force microscopy tips – and graphene, h-BN, and MoS2 supported on SiO2 substrates and as freestanding membranes are presented. The in situ nanomechanical characterization reveals a prominent reduction in the adhesion energies with increasing temperature which is ascribed to the thermally induced ripples in the 2D materials.

• Polfus, Jonathan; Peters, Thijs; Bredesen, Rune & Løvvik, Ole Martin (2021). Vacancy diffusion in palladium hydrides. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 23(24), s. 13680–13686. doi: 10.1039/d1cp01960k. Fulltekst i vitenarkiv Vis sammendrag

  The self-diffusion coefficients of palladium in PdHx (x = 0, 0.25, 0.5, 0.75, 1) were studied using density functional theory to obtain the required thermodynamic and kinetic parameters. The enthalpy of migration decreased from 0.95 eV for Pd to 0.78 eV for PdH. The enthalpy of vacancy formation exhibited a substantial decrease from about 1.1 eV in Pd to 0.4 eV in PdH, which was ascribed to successive filling of antibonding states weakening the Pd–Pd bonds. Concurrently, the Arrhenius pre-exponential was significantly reduced from 4.75 × 10−3 cm2 s−1 for Pd to 5.67 × 10−9 cm2 s−1 for PdH due to softening of the vibrational modes that determine the entropy of vacancy formation and initial/transition state frequencies. A linear correlation between the logarithm of the pre-exponential and the activation energy was interpreted as enthalpy–entropy compensation (Meyer–Neldel rule). The Pd self-diffusion coefficients in the hydrides were within 1 order of magnitude of that in pure palladium above 200 °C for hydrogen pressures up to at least 107 Pa.

• Bondevik, Tarjei; Polfus, Jonathan Marc & Norby, Truls Eivind (2020). Disagreements between space charge models and grain boundary impedance data in yttrium-substituted barium zirconate. Solid State Ionics. ISSN 0167-2738. 353. doi: 10.1016/j.ssi.2020.115369. Fulltekst i vitenarkiv Vis sammendrag

  Although the space charge model is commonly used to explain the high grain boundary resistance in proton conducting yttrium-substituted BaZrO3, it fails in its simplest forms with factors 10–40 to fit experimental data with respect to the characteristic frequency of the grain boundary impedance. We suggest modifications to the model, somewhat improving its fit. Including trapping effects of protons near yttrium substituents reduces the error only by factors less than 1.6. Increasing the width of the grain boundary core reduces the error with factors of 1.5–3. Discretizing the space charge layer, such that protons can only reside on specific, discrete sites, reduces the error with another factor of around 2. Considering reduced proton mobility in the GB by reducing its effective area may give a reduction in the fitting error of a factor of 2. Varying the dielectric constant in the GB does not affect the error considerably. Neither each single modification, nor their combined effect, can, however, account for the majority of the discrepancy between the space charge model and experimental data.

• Yang, Jing; Polfus, Jonathan Marc; Li, Zuoan; Tuller, Harry & Yildiz, Bilge (2020). Role of Adsorbate Coverage on the Oxygen Dissociation Rate on Sr-Doped LaMnO3 Surfaces in the Presence of H2O and CO2. Chemistry of Materials. ISSN 0897-4756. 32(13), s. 5483–5492. doi: 10.1021/acs.chemmater.9b05243. Fulltekst i vitenarkiv Vis sammendrag

  Sr-doped LaMnO3 (LSM) is a promising oxygen reduction reaction electrocatalyst in solid oxide fuel cells and other electrochemical devices. The presence of CO2 and H2O has been reported to promote the oxygen dissociation reaction on LSM surfaces. Here, we investigate the coadsorption mechanism of O2 with H2O or CO2 by combining first-principles calculations of the (0 0 1) surface containing 25–100% Sr with thermodynamic adsorption models. The molecules were found to chemisorb by formation of charged oxygen, hydroxide, and carbonate species, and the adsorption energies were exothermic up to monolayer coverage. Low concentrations of H2O or CO2 do not compete with O2 for adsorption sites under relevant conditions. However, their presence contributes to the total amount of oxygen-containing species. The increased coverage of oxygen species provides a quantitative explanation for the reported enhancement in oxygen dissociation kinetics in the presence of H2O/CO2. This study thereby provides insights into oxygen exchange mechanisms on LSM surfaces.

• Polfus, Jonathan Marc; Løvvik, Ole Martin; Bredesen, Rune & Peters, Thijs (2020). Hydrogen induced vacancy clustering and void formation mechanisms at grain boundaries in palladium. Acta Materialia. ISSN 1359-6454. 195, s. 708–719. doi: 10.1016/j.actamat.2020.06.007. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen has a significant impact on the formation of vacancies, clusters and voids in palladium and other metals. The formation of vacancy-hydrogen complexes in bulk Pd and at Σ3 and Σ5 grain boundaries was investigated using first-principles calculations and thermodynamic models. Equilibrium vacancy and cluster concentrations were evaluated as a function of temperature and hydrogen partial pressure based on the Gibbs energy of formation including vibrational and configurational entropies. Vacancies were found to be significantly stabilized by association with interstitial hydrogen, leading to enhanced concentrations by several orders of magnitude. Vacancy clusters were further stabilized at grain boundaries, with equilibrium concentrations reaching site saturation for clusters comprising up to three vacancies. Nanovoids were investigated based on Wulff constructions from calculated surface energies of the (0 0 1) and (1 1 1) terminations as a function of temperature and coverage of hydrogen adsorbates. The most stable termination changed from (1 1 1) in vacuum to (0 0 1) in H2, and the surface energies were lowered due to hydrogen adsorbates. Consequently, voids were also stabilized in the presence of hydrogen. Coalescing of vacancies into nanovoids was found to be thermodynamically unfavorable due to the loss of configurational entropy. It was therefore concluded that enhanced concentrations of vacancies and clusters does not directly cause the formation of voids. The formation of voids in Pd-based membranes was discussed in terms of microstructural characteristics, and strain due to chemical expansion and plastic deformation.

• Dahl-Hansen, Runar Plunnecke; Polfus, Jonathan Marc; Vøllestad, Einar; Akkopru-Akgun, Betul; Denis, Lyndsey & Coleman, Kathleen [Vis alle 9 forfattere av denne artikkelen] (2020). Electrochemically driven degradation of chemical solution deposited ferroelectric thin-films in humid ambient. Journal of Applied Physics. ISSN 0021-8979. 127. doi: 10.1063/5.0003989. Fulltekst i vitenarkiv Vis sammendrag

  The ambient humidity significantly accelerates the degradation of lead zirconate titanate (PZT) films in microelectromechanical systems; the cause of such degradation is under debate. Here, it is shown that the degradation of chemical solution derived PZT thin-films in humid conditions is driven by the system's electrochemical activity toward water electrolysis. The layer stacks with Pt-based electrodes exhibited a faster degradation rate owing to their higher electrocatalytic activity compared to Au. A degradation model is proposed based on the electrolysis of liquid or gaseous H2O, involving the evolution of oxygen and hydrogen gas at the top and bottom electrodes. Degradation proceeds above the threshold voltage for a given electrode system and is driven by the evolution and pressure build-up of gaseous species at the PZT/electrode interfaces. The pressure build-up causes film cracking, delamination of the film and electrodes, electrothermal breakdown events, and eventually time-dependent dielectric breakdown. Significantly larger post-breakdown crater sizes in humid than in dry conditions suggests that larger cracks through which dielectric breakdown through humidified air can occur. Overall, these effects are shown to cause sample failure up to six orders of magnitude of time earlier than for operation in dry conditions. Thus, in order to improve the resilience of thin-film systems in humid conditions, it is imperative to protect the electrochemically active electrode components of the device.

• Polfus, Jonathan M. & Jayasayee, Kaushik (2019). Robust nanocomposites of a-Fe2O3 and N-doped graphene oxide: Interfacial bonding and chemisorption of H2O. Carbon. ISSN 0008-6223. 152, s. 497–502. doi: 10.1016/j.carbon.2019.05.033. Fulltekst i vitenarkiv Vis sammendrag

  Nanocomposites of a-Fe2O3 (hematite) and (N-doped) graphene oxide (GO) were investigated using first- principles calculations with focus on structure, chemical bonding, electronic structure and H2O adsorption. The nanocomposites were modeled as the interface between the a-Fe2O3 (0 0 0 1) surface and the basal plane of reduced graphene oxide, comprising epoxy groups (C:O ratio of 8) as well as graphitic and pyridinic nitrogen doping. The composite structures exhibited strong chemical bonding by the formation of a bridging FeeOeC bond. The calculated binding energy between the materials was 0.56 eV per FeeOeC bond for GO and up to 1.14 eV for N-doped GO, and the binding energies were found to correlate with the charge of the bridging oxide ion. The composites exhibited partly occupied carbon states close to or above the a-Fe2O3 valence band maximum. Dissociative adsorption of H2O was found to be more exothermic for the composites compared to the individual materials, ranging from about 0.9 to 1.7 eV for the most stable configurations with hydroxide species adsorbed to GO and protons forming NH groups or adsorbed to the a-Fe2O3 surface.

• Li, Zuoan; Polfus, Jonathan Marc; Xing, Wen; Denonville, Christelle; Fontaine, Marie-Laure & Bredesen, Rune (2019). Factors Limiting the Apparent Hydrogen Flux in Asymmetric Tubular Cercer Membranes Based on La27W3.5Mo1.5O55.5−δ and La0.87Sr0.13CrO3−δ. Membranes. 9(126). doi: 10.3390/membranes9100126. Fulltekst i vitenarkiv Vis sammendrag

  Asymmetric tubular ceramic–ceramic (cercer) membranes based on La27W3.5Mo1.5O55.5−δ-La0.87Sr0.13CrO3−δ were fabricated by a two-step firing method making use of water-based extrusion and dip-coating. The performance of the membranes was characterized by measuring the hydrogen permeation flux and water splitting with dry and wet sweep gases, respectively. To explore the limiting factors for hydrogen and oxygen transport in the asymmetric membrane architecture, the effect of different gas flows and switching the feed and sweep sides of the membrane on the apparent hydrogen permeability was investigated. A dusty gas model was used to simulate the gas gradient inside the porous support, which was combined with Wagner diffusion calculations of the dense membrane layer to assess the overall transport across the asymmetric membrane. In addition, the stability of the membrane was investigated by means of flux measurements over a period of 400 h.

• Xing, Wen; Carvalho, Patricia Almeida; Polfus, Jonathan M. & Li, Zuoan (2019). Thermochemically stable ceramic compositemembranes based on Bi2O3 for oxygen separationwith high permeability. Chemical Communications. ISSN 1359-7345. 55(24), s. 3493–3496. doi: 10.1039/c8cc10077b. Fulltekst i vitenarkiv Vis sammendrag

  Ceramic oxygen separation membranes can be utilized to reduce CO2 emissions in fossil fuel power generation cycles based on oxy-fuel combustion. State-of-the-art oxygen permeable membranes based on Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) offer high oxygen permeability but suffer from long-term instability, especially in the presence of CO2. In this work, we present a novel ceramic composite membrane consisting of 60 vol% (Bi0.8Tm0.2)2O3−δ (BTM) and 40 vol% (La0.8Sr0.2)0.99MnO3−δ (LSM), which shows not only comparable oxygen permeability to that of BSCF but also outstanding long-term stability. At 900 °C, oxygen fluxes of 1.01 mL min−1 cm−2 and 1.33 mL min−1 cm−2 were obtained for membranes with thicknesses of 1.35 mm and 0.75 mm, respectively. Moreover, significant oxygen fluxes were obtained at temperatures down to 600 °C. A stable operation of the membrane was demonstrated with insignificant changes in the oxygen flux at 750 °C for approx. one month and at 700 °C with 50% CO2 as the sweep gas for more than two weeks.

• Sazinas, Rokas; Sunding, Martin Fleissner; Thøgersen, Annett; Sakaguchi, Isao; Norby, Truls Eivind & Grande, Tor [Vis alle 7 forfattere av denne artikkelen] (2019). Surface reactivity and cation non-stoichiometry in BaZr1-xYxO3-δ (x=0-0.2) exposed to CO2 at elevated temperature. Journal of Materials Chemistry A. ISSN 2050-7488. 7(8), s. 3848–3856. doi: 10.1039/c8ta11021b. Fulltekst i vitenarkiv Vis sammendrag

  The reactivity of BaZr1−xYxO3−δ (x = 0–0.2) ceramics under 1 atm CO2 at 650 °C for up to 1000 h was investigated in order to elucidate possible degradation processes occurring when the material is applied as a proton-conducting electrolyte in electrochemical devices. The annealed ceramics were characterized by a range of techniques (SEM, TEM, GIXRD, XPS and SIMS) with respect to changes in the phase composition and microstructure. Formation of BaCO3 was observed on the surfaces of the annealed samples and the amount increased with time and was higher for the Y-doped compositions. The subsurface regions were found to be deficient in Ba and, in the case of the Y-doped compositions, enriched in Y in two distinct chemical states as identified by XPS. First-principles calculations showed that they were Y residing on the Zr and Ba-sites, respectively, and that local enrichment of Y both in bulk and on the surface attained a structure similar to Y2O3. Overall, it was substantiated that the reaction with CO2 mainly proceeded according to a defect chemical reaction involving transfer of Y to the Ba-site and consumption of BaZrO3 formula units. It was suggested that a similar degradation mechanism may occur in the case of Ba(OH)2 formation under high steam pressure conditions.

• Polfus, Jonathan M.; Yildiz, Bilge & Tuller, Harry (2018). Origin of fast oxide ion diffusion along grain boundaries in Sr-doped LaMnO3. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 20(28), s. 19142–19150. doi: 10.1039/c8cp02443j. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Pishahang, Mehdi & Bredesen, Rune (2018). Influence of Ce3+ polarons on grain boundary space-charge in proton conducting Y-doped BaCeO3. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 20(23), s. 16209–16215. doi: 10.1039/c8cp00168e. Fulltekst i vitenarkiv Vis sammendrag

  Defect segregation and space-charge formation were investigated for a (0 2 1)[1 0 0] symmetric tilt grain boundary in Y-doped BaCeO3. Density functional theory calculations according to the PBE+U formalism were used to calculate segregation energies for protons, oxygen vacancies and Y-acceptor dopants from the bulk to the grain boundary core. Defect concentration and potential profiles across the grain boundary were obtained from thermodynamic space-charge models. Oxygen vacancies were found to exhibit a particularly exothermic segregation energy of up to −1.66 eV while protons exhibited segregation energies in the range of −0.47 eV to −0.93 eV. The grain boundary was determined to be predominated by protons below 800 K in 3% H2O and the corresponding space-charge potential was 0.4–0.7 V under the Mott–Schottky approximation. The role of electronic defects in the space-charge properties was evaluated, and it was substantiated that electron conduction along the grain boundary could become evident under reducing conditions.

• Xing, Wen; Fontaine, Marie-Laure; Li, Zuoan; Polfus, Jonathan M.; Larring, Yngve & Denonville, Christelle [Vis alle 10 forfattere av denne artikkelen] (2018). Asymmetric tubular CaTi0.6Fe0.15Mn0.25O3-δ membranes: Membrane architecture and long-term stability. Journal of Membrane Science. ISSN 0376-7388. 548, s. 372–379. doi: 10.1016/j.memsci.2017.11.042. Fulltekst i vitenarkiv
• Wachowski, Sebastian Lech; Li, Zuoan; Polfus, Jonathan M. & Norby, Truls Eivind (2018). Performance and stability in H2S of SrFe0.75Mo0.25O3-δ as electrode in proton ceramic fuel cells. Journal of the European Ceramic Society. ISSN 0955-2219. 38(1), s. 163–171. doi: 10.1016/j.jeurceramsoc.2017.08.020. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Yildiz, Bilge; Tuller, Harry & Bredesen, Rune (2018). Adsorption of CO2 and Facile Carbonate Formation on BaZrO3 Surfaces. Journal of Physical Chemistry C. ISSN 1932-7447. 122(1), s. 307–314. doi: 10.1021/acs.jpcc.7b08223. Fulltekst i vitenarkiv Vis sammendrag

  The adsorption of CO2 and CO on BaZrO3 (0 0 1) was investigated by first-principles calculations with a focus on the BaO termination. CO2 was found to strongly chemisorb on the surface by formation of carbonate species with an adsorption enthalpy of up to −2.25 eV at low coverage and −1.05 eV for a full monolayer. An adsorption entropy of −8.8 × 10–4 eV K–1 was obtained from the vibrational properties of the adsorbates. Surface coverages were evaluated as a function of temperature and CO2 partial pressure, and the obtained coverage under 1 bar CO2 was more than 0.8 at 1000 K (conditions relevant for steam methane reforming). The fully saturated surface was stable up to about 400 K under ambient atmosphere, i.e., 400 ppm of CO2. The initial stage of BaCO3 formation was evaluated according to migration of barium to the carbonate overlayer, which was found to result in a significant stabilization of the system. The barium migration was found to be essentially unobstructed with a barrier of only ∼5 meV. In light of the stability of carbonate adsorbates at the surface, the prospect of bulk dissolution of carbonate species was evaluated but ultimately found to be negligible in acceptor-doped BaZrO3.

• Fontaine, Marie-Laure; Denonville, Christelle; Li, Zuoan; Xing, Wen; Polfus, Jonathan M. & Kvello, Jannicke Hatlø [Vis alle 10 forfattere av denne artikkelen] (2018). Fabrication and H2 flux measurement of asymmetric La27W3.5Mo1.5O55.5-δ − La0.87Sr0.13CrO3-δ membranes. Journal of the European Ceramic Society. ISSN 0955-2219. 38(4), s. 1695–1701. doi: 10.1016/j.jeurceramsoc.2017.11.015. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Yang, Jing & Yildiz, Bilge (2018). Interplay between H2O and CO2 coadsorption and space-charge on Y-doped BaZrO3 surfaces. Journal of Materials Chemistry A. ISSN 2050-7488. 6, s. 24823–24830. doi: 10.1039/C8TA09491H. Fulltekst i vitenarkiv Vis sammendrag

  The present work quantifies the equilibrium defect and adsorbate chemistry on oxide surfaces in the presence of multiple gas components at elevated temperatures and sub-surface space charge. The concentrations of chemisorbed H2O and CO2 as well as surface protons and oxygen vacancies were calculated for Y-doped BaZrO3 using a thermodynamic framework with input from first-principles calculations. The overall energy of the system was minimized based on contributions from gas adsorption, interactions between defects and adsorbates, segregation of point defects and space-charge formation, as well as configurational entropy. The coverage dependent adsorption energies were found as −1.44 + 0.34ΘH2O eV and −2.25 + 1.21ΘCO2 eV for chemisorption of H2O and CO2, respectively. The interaction between the adsorbates was found to follow 1.72ΘH2OΘCO2 eV. The coverage of surface protons was above 0.3 up to 1000 K under most considered conditions (0.01–1 bar H2O, 4 × 10−4–1 bar CO2) due to a favorable interaction with both surface hydroxide and CO2 adsorbates. Most importantly, the results show that the coadsorption, adsorbate interactions or space-charge formation each played a major role in the obtained defect concentrations and surface coverages. Thus, the approach in this work demonstrates the importance of considering quantitatively each of these aspects in obtaining accurately the surface equilibria on complex catalytic oxides.

• Sazinas, Rokas; Sakaguchi, Isao; Hasle, Ida Margrete; Polfus, Jonathan M.; Haugsrud, Reidar & Einarsrud, Mari-Ann [Vis alle 7 forfattere av denne artikkelen] (2017). Tracer diffusion of 96Zr and 134Ba in polycrystalline BaZrO3. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 19(32), s. 21878–21886. doi: 10.1039/C7CP04039C. Fulltekst i vitenarkiv Vis sammendrag

  Cation tracer diffusion in polycrystalline cubic BaZrO3 perovskites was studied using the stable isotopes 134Ba and 96Zr in air at 1015–1200 and 1300–1500 °C, respectively. Thin films of 134BaO and 96ZrO2 were deposited on polished BaZrO3 pellets by drop casting of aqueous precursor solutions containing the tracers. Isotope distribution profiles were recorded using secondary ion mass spectrometry. All the depth profiles exhibited two distinct regions, which enabled the assessment of both lattice and grain boundary diffusion using Fick's second law and Whipple–Le Clair's equation. The grain boundary diffusion of both cations was several orders of magnitude higher than the lattice diffusion. The lattice diffusion of Ba2+ was found to be significantly faster than the lattice diffusion of Zr4+, while the activation energies were comparable, respectively 395 ± 44 and 435 ± 67 kJ mol−1. Activation energies for the diffusion of Ba2+ and Zr4+ through a Ba2+ vacancy were calculated by density functional theory using the nudged elastic band method. The calculated and experimental activation energies were in excellent agreement. The cation diffusion data in BaZrO3 are compared to previous data on A and B-site diffusivity in perovskites. Finally, the diffusivity of Zr4+ in compounds with perovskite and fluorite crystal structures is discussed in relation to the chemical stability of BaZrO3-based materials.

• Peters, Thijs; Polfus, Jonathan M.; Stange, Marit Synnøve Sæverud; Veenstra, Peter; Nijmeijer, Arian & Bredesen, Rune (2016). H2 flux inhibition and stability of Pd-Ag membranes under exposure to trace amounts of NH3. Fuel processing technology. ISSN 0378-3820. 152, s. 259–265. doi: 10.1016/j.fuproc.2016.06.012. Fulltekst i vitenarkiv Vis sammendrag

  The long-term performance and flux inhibition of a 10 μm-thick Pd77Ag23 membrane under the exposure to varying concentrations of NH3 ranging from 10 to 500 ppm at a temperature between 300 and 450 °C was investigated. At 450 °C no H2 flux inhibition was found in the presence of 200–500 ppm NH3. However, an inhibition of the H2 flux was observed at lower operating temperatures in the presence of 200 ppm NH3. In addition, a further gradual H2 flux decline is observed giving evidence for NH3 adsorption on the membrane surface. A H2 flux reduction of ~ 36% was observed after 20 h of exposure at 300 °C compared to the H2 flux obtained at this temperature in the absence of any NH3. The subsequent increase in operating temperature back to 450 °C, however, quickly recovered the H2 flux back to its original H2 flux value obtained prior to any NH3 exposure at 450 °C. First-principles calculations, however, indicated that H2 flux decrease upon NH3 exposure could not be accounted for by a simple lowering of the hydrogen surface coverage due to the competitive adsorption of NH3 related species under the experimental conditions. The role of NH3 therefore seems more complex, for instance related to hydrogen dissociation kinetics and incorporation or changes in the Pd-alloy membrane due to surface segregation, but this remains uncertain at this stage.

• Polfus, Jonathan M.; Fontaine, Marie-Laure; Thøgersen, Annett; Riktor, Marit Dalseth; Norby, Truls & Bredesen, Rune (2016). Solubility of transition metal interstitials in proton conducting BaZrO3 and similar perovskite oxides. Journal of Materials Chemistry A. ISSN 2050-7488. 4(21), s. 8105–8112. doi: 10.1039/c6ta02377k. Fulltekst i vitenarkiv Vis sammendrag

  The defect chemistry of foreign transition metals in perovskite oxides was investigated by first-principles calculations with focus on Ni and Zn in Y-doped BaZrO3. Additional transition metals (Cu, Fe, Pd, Pt, and Ag) and perovskites (SrZrO3 and SrTiO3) were considered for comparison. The octahedral interstice coordinated with square-planar oxygen could accommodate smaller cations and Ni2+ was found to be the most stable, particularly in the presence of barium vacancies. Significant solubility of Ni was substantiated only for nominally A-site deficient materials under oxidizing conditions. The computational results were corroborated by experimental studies on BaZr0.85Y0.15O3−δ with 4 mol% NiO or ZnO sintering additives. While synchrotron radiation X-ray powder diffraction of the Ni containing sample showed the presence of a BaY2NiO5 secondary phase, it could not account for the nominal amount of Ni in the sample. STEM and EDS analyses of both the Zn and Ni containing samples showed that Zn accumulated in the grain boundaries while Ni was evenly distributed within the grains and grain boundaries indicating that Ni was dissolved in the BaZrO3 structure. Furthermore, metallic Ni particles appeared on the sample surface after treatment under reducing conditions in accordance with computational predictions. The influence of interstitially dissolved Ni on proton conductivity was evaluated based on trapping of protons. Barium vacancies were found to be strong proton traps, with a binding energy of −0.80 eV, while the binding energy of protons associated with adjacent Ni interstitials was reduced to −0.20 eV.

• Polfus, Jonathan M.; Xing, Wen; Riktor, Marit Dalseth; Sunding, Martin Fleissner; Dahl, Paul Inge & Hanetho, Sidsel Meli [Vis alle 10 forfattere av denne artikkelen] (2016). Enhanced O2 flux of CaTi0.85Fe0.15O3 – d based membranes by Mn doping. Journal of The American Ceramic Society. ISSN 0002-7820. 99(3), s. 1071–1078. doi: 10.1111/jace.14022. Fulltekst i vitenarkiv Vis sammendrag

  Dense symmetric membranes of CaTi0.85−xFe0.15MnxO3−δ (x = 0.1, 0.15, 0.25, 0.4) are investigated in order to determine the optimal Mn dopant content with respect to highest O2 flux. O2 permeation measurements are performed as function of temperature between 700°C–1000°C and as function of the feed side urn:x-wiley:00027820:media:jace14022:jace14022-math-0003 ranging between 0.01 and 1 bar. X‐ray photoelectron spectroscopy is utilized to elucidate the charge state of Mn, and synchrotron radiation X‐ray powder diffraction (SR‐XPD) is employed to investigate the structure symmetry and cell volume of the perovskite phase at temperatures up to 800°C. The highest O2 permeability is found for x = 0.25 over the whole temperature and urn:x-wiley:00027820:media:jace14022:jace14022-math-0004 ranges, followed by x = 0.4 above 850°C. The O2 permeability for x = 0.25 reaches 0.01 mL(STP) min−1 cm−1 at 925°C with 0.21 bar feed side urn:x-wiley:00027820:media:jace14022:jace14022-math-0005 and Ar sweep gas. X‐ray photoelectron spectroscopy indicates that the charge state of Mn changes from approx. +3 to +4 when x > 0.1, which implies that Mn mainly improves electronic conductivity for x > 0.1. The cell volume is found to decrease linearly with Mn content, which coincides with an increase in the activation energy of O2 permeability. These results are consistent with the interpretation of the temperature and urn:x-wiley:00027820:media:jace14022:jace14022-math-0006 dependency of O2 permeation. The sintering behavior and thermal expansion properties are investigated by dilatometry, which show improved sinterability with increasing Mn content and that the thermal expansion coefficient decreases from 12.4 to 11.9 × 10−6 K−1 for x = 0 and x = 0.25, respectively.

• Polfus, Jonathan M.; Li, Zuoan; Xing, Wen; Sunding, Martin Fleissner; Walmsley, John & Fontaine, Marie-Laure [Vis alle 8 forfattere av denne artikkelen] (2016). Chemical stability and H2 flux degradation of cercer membranes based on lanthanum tungstate and lanthanum chromite. Journal of Membrane Science. ISSN 0376-7388. 503, s. 42–47. doi: 10.1016/j.memsci.2015.12.054. Fulltekst i vitenarkiv Vis sammendrag

  Ceramic–ceramic composite (cercer) membranes of (Mo-doped) lanthanum tungstate, La27(W,Mo)5O55.5−δ, and lanthanum chromite, La0.87Sr0.13CrO3−δ, have recently been shown to exhibit H2 permeabilities among state-of-the-art. The present work deals with the long-term stability of these cercer membranes in line with concern of flux degradation and phase instability observed in previous studies. The H2 permeability of disc shaped membranes with varying La/W ratio in the lanthanum tungstate phase (5.35≤La/W≤5.50) was measured at 900 and 1000 °C with a feed gas containing 49% H2 and 2.5% H2O for up to 1500 h. It was observed that the H2 permeability decreased by a factor of up to 5.3 over 1500 h at 1000 °C. Post-characterization of the membranes and similarly annealed samples was performed by SEM, STEM and XRD, and segregation of La2O3 was observed. The decrease in H2 permeability was ascribed to the compositional instability of the cation-disordered lanthanum tungstate under the measurement conditions. Equilibration of the La/W ratio by segregation of La2O3 leads to a lower ionic conductivity according to the materials inherent defect chemistry. Partial decomposition and reduction of the lanthanum tungstate phase, presumably to metallic tungsten, was also observed after exposure to nominally dry hydrogen.

• Polfus, Jonathan M.; Bjørheim, Tor Svendsen; Norby, Truls & Bredesen, Rune (2016). Surface defect chemistry of Y-substituted and hydrated BaZrO3 with subsurface space-charge regions. Journal of Materials Chemistry A. ISSN 2050-7488. 4(19), s. 7437–7444. doi: 10.1039/c6ta02067d. Fulltekst i vitenarkiv Vis sammendrag

  First-principles calculations were utilized to elucidate the complete defect equilibria of surfaces of proton conducting BaZrO3, encompassing charged species adsorbed to the surface, defects in the surface layer as well as in the subsurface space-charge region and bulk. Defect calculations were performed for the BaZrO3 (0 0 1) surface with focus on protons, oxygen vacancies and Y-acceptor dopants as well as adsorbed hydroxide and oxide adions. Protons were found to exhibit a particularly strong tendency to segregate to the surface with a segregation energy of −1.3 eV. While the concentration of negatively charged Y-acceptors and hydroxide species on the outer surface can be quite high, they do not fully charge compensate the protons, yielding a net positive charge of the surface. The resulting surface potential can exceed 1 V, resulting in significant depletion of charge carriers in the subsurface space-charge region. Moreover, the results are discussed in relation to surface adsorption of water, and computational approaches for treating charged point defects in periodic slab cells are evaluated with respect to symmetry and charge compensation.

• Polfus, Jonathan M.; Xing, Wen; Pecanac, Goran; Fossdal, Anita; Hanetho, Sidsel Meli & Larring, Yngve [Vis alle 9 forfattere av denne artikkelen] (2016). Oxygen permeation and creep behavior of Ca1-xSrxTi0.6Fe0.15Mn0.25O3-δ (x=0, 0.5) membrane materials. Journal of Membrane Science. ISSN 0376-7388. 499, s. 172–178. doi: 10.1016/j.memsci.2015.10.016. Fulltekst i vitenarkiv Vis sammendrag

  Oxygen permeation measurements were performed on dense symmetric samples of Ca0.5Sr0.5Ti0.6Fe0.15Mn0.25O3−δ and compared to CaTi0.6Fe0.15Mn0.25O3−δ in order to assess the influence of the perovskite lattice volume on oxygen permeation. Oxygen flux measurements were performed in the temperature range 700–1000 °C and as function of feed side pO2 from 10−2 to 1 bar, and at high pressures up to 4 bar with a pO2 of 3.36 bar. The O2 permeability of the Sr-doped sample was significantly lower than that of the Sr-free sample, amounting to 3.9×10−3 mL min−1 cm−1 at 900 °C for a feed side pO2 of 0.21 bar. The O2 permeability of CaTi0.6Fe0.15Mn0.25O3−δ shows little variation with increased feed side pressures and reaches 1.5×10−2 mL min−1 cm−1 at 900 °C for a feed side pO2 of 3.36 bar. This is approximately 1.5 times higher than the O2 permeability with a feed side pO2 of 0.21 bar. Furthermore, in order to assess the applicability of CaTi0.6Fe0.15Mn0.25O3−δ as an oxygen membrane material, creep tests were performed under compressive loads of 30 and 63 MPa, respectively, in air in the temperature range 700–1000 °C; the results indicate a high creep resistance for this class of materials. The measured O2 permeabilities and creep rates are compared with other state-of-the-art membrane materials and their performance for relevant applications is discussed in terms of chemical and mechanical stability.

• Polfus, Jonathan M.; Løvvik, Ole Martin; Rørvik, Per Martin & Bredesen, Rune (2016). Nanocomposites of few-layer graphene oxide and alumina by density functional theory calculations. Journal of the European Ceramic Society. ISSN 0955-2219. 36(3), s. 719–724. doi: 10.1016/j.jeurceramsoc.2015.11.009. Fulltekst i vitenarkiv Vis sammendrag

  The atomistic and electronic structure and oxygen stoichiometry of nanocomposites between alumina and graphene oxide were investigated by density functional theory calculations. The nanocomposite was described as interfaces between α-Al2O3 (0001) surfaces and graphene oxide; the latter was defined with oxygen bound as epoxy groups and a C:O atomic ratio of 4:1. The optimized composite structure with 1–3 layers of graphene oxide in between Al2O3 contains bridging Alsingle bondOsingle bondC bonds at the interface. Reduction of the composite was investigated by removal of oxygen from the interface Alsingle bondOsingle bondC bonds, within the graphene oxide layers and in Al2O3. It was found that removal of oxygen within the graphene oxide layers is essentially independent of the Al2O3 interface, i.e., the same as in pure graphene oxide. Oxygen was, however, more strongly bound in the interface Alsingle bondOsingle bondC bonds by 0.80 eV, and reduction of graphene oxide to graphene is accordingly preferred within the graphene oxide layers rather than at the oxide interface.

• Polfus, Jonathan M.; Norby, Truls Eivind & Bredesen, Rune (2016). Proton segregation and space-charge at the BaZrO3 (0 0 1)/MgO (0 0 1) heterointerface. Solid State Ionics. ISSN 0167-2738. 297, s. 77–81. doi: 10.1016/j.ssi.2016.10.010. Fulltekst i vitenarkiv Vis sammendrag

  Y-doped BaZrO3 (BZY) can be deposited epitaxially on MgO (0 0 1) and the considered interface serves as a model system for studying heterointerface properties of protonic conductors. In this study, the defect chemistry of the interface between ZrO2-terminated BaZrO3 (0 0 1) and MgO (0 0 1) was investigated by first-principles calculations and space-charge theory. Segregation energies from the BZY bulk to the interface ZrO2 and MgO layers were calculated for effectively charged protons, oxygen vacancies, Y-acceptors as well as cation vacancies. Protons were found to exhibit a strong tendency for segregating to the interface, particularly to an oxide ion in the MgO layer, rendering a net positive charge of the interface. According to the applied thermodynamic space-charge models, the interface potential could reach more than 1 V under the Mott-Schottky approximation, with depletion regions extending up to 2 nm into BZY. With fully equilibrated Y-segregation profiles, the interface potential was significantly diminished to about 0.2 V at 573 K and 0.025 bar H2O. While the interface was found to be close to saturated by protons under most condition, it was concluded that proton conduction along the interface could not contribute significantly to the in-plane conductivity of BZY films deposited on MgO substrate.

• Peters, Thijs; Polfus, Jonathan M.; Berkel, Frans van & Bredesen, Rune (2016). Interplay between propylene and H2S co-adsorption on the H2 flux characteristics of Pd-alloy membranes employed in propane dehydrogenation (PDH) processes. Chemical Engineering Journal. ISSN 1385-8947. 304, s. 134–140. doi: 10.1016/j.cej.2016.06.065. Fulltekst i vitenarkiv Vis sammendrag

  The role of propylene and H2S exposure on Pd-Ag membranes was investigated by hydrogen flux measurements of a magnetron sputtered Pd77Ag23 film and first-principles calculations of hydrogen, sulfur and propylene adsorption on the membrane surface. Upon exposure to 10% propylene, the H2 flux was lowered to 12% of its initial value prior to exposure, which was associated with propylene adsorption and coke formation based on qualitative assessments of the flux degradation kinetics and calculated propylene and hydrogen surface coverages. In the presence of 50–75 ppb H2S, the H2 flux showed a slower gradual decrease upon propylene exposure. Although sulfur adsorption also inhibits H2 flux, this slower decrease resulted in a higher absolute H2 flux in the presence H2S already after 1 h of propylene exposure. Adsorbed sulfur on the membrane surface was suggested to limit coke formation due to a lower calculated surface coverage of propylene as well as a possibly lower migration of propylene and other intermediates across the membrane surface necessary for coke formatio

• Zheng, Kun; Swierczek, Konrad; Polfus, Jonathan M.; Sunding, Martin Fleissner; Pishahang, Mehdi & Norby, Truls (2015). Carbon Deposition and Sulfur Poisoning in SrFe0.75Mo0.25O3-δ and SrFe0.5Mn0.25Mo0.25O3-δ Electrode Materials for Symmetrical SOFCs. Journal of the Electrochemical Society. ISSN 0013-4651. 162(9), s. F1078–FF1087. doi: 10.1149/2.0981509jes. Fulltekst i vitenarkiv Vis sammendrag

  Redox stable SrFe0.75Mo0.25O3-δ and SrFe0.5Mn0.25Mo0.25O3-δ electrode materials were studied in terms of their physicochemical properties and electrochemical performance in symmetrical SOFCs, with focus on their tolerance toward carbon deposition and sulfur poisoning. Both materials possess cubic, B-site cation-disordered Pm-3m structure in air up to high temperatures. SrFe0.5Mn0.25Mo0.25O3-δ was found to transform to a B-site cation-ordered structure after reduction in dry 5 vol% H2/Ar at 1100°C, while no structural changes were observed for SrFe0.75Mo0.25O3-δ. Weight change upon annealing up to 850°C in air and in dry 5 vol% H2/Ar indicated an increase in oxygen deficiency on the order of δ = 0.2. Seebeck coefficient and conductivity dependence on the oxygen partial pressure pO2 showed that both oxides exhibit p-type conductivity in air and n-type conductivity under reducing conditions. Carbon deposition was found to depend on temperature, gas composition (CO or CH4), and presence of Ce0.8Gd0.2O1.9 electrolyte in the composite-type electrode. Stable fuel cell performance, without carbon deposition, was obtained for SrFe0.75Mo0.25O3-δ-based SOFC in 10 vol% of CO in CO2. Also, SOFC operation with CH4 as fuel was achieved without coking at temperatures ≤ 700°C. However, both oxides suffer from sulfur poisoning-related effects in atmosphere with 800 ppm H2S.

• Polfus, Jonathan M.; Xing, Wen; Sunding, Martin Fleissner; Hanetho, Sidsel Meli; Dahl, Paul Inge & Larring, Yngve [Vis alle 8 forfattere av denne artikkelen] (2015). Doping strategies for increased oxygen permeability of CaTiO3 based membranes. Journal of Membrane Science. ISSN 0376-7388. 482, s. 137–143. doi: 10.1016/j.memsci.2015.02.036. Fulltekst i vitenarkiv Vis sammendrag

  Oxygen permeation measurements are performed on dense samples of CaTi0.85Fe0.15O3−δ, CaTi0.75Fe0.15Mg0.05O3−δ and CaTi0.75Fe0.15Mn0.10O3−δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O2 permeability of CaTi1−xFexO3−δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700 and 1000 °C with feed side oxygen partial pressures between 0.01 and 1 bar. The O2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10−3 ml min−1 cm−1 at 900 °C and 0.21 bar O2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x=0.2. While the O2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O2 permeability, i.e., oxygen vacancies and electronic charge carriers.

• Polfus, Jonathan M.; Xing, Wen; Fontaine, Marie-Laure; Denonville, Christelle; Henriksen, Partow Pakdel & Bredesen, Rune (2015). Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system. Journal of Membrane Science. ISSN 0376-7388. 479, s. 39–45. doi: 10.1016/j.memsci.2015.01.027. Fulltekst i vitenarkiv Vis sammendrag

  Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes.

• Polfus, Jonathan M.; Norby, Truls & Bredesen, Rune (2015). Protons in Oxysulfates, and Sulfides: A First-Principles Study of La2O2S, La2O2SO4, SrZrS3, and BaZrS3. Journal of Physical Chemistry C. ISSN 1932-7447. 119(42), s. 23875–23882. doi: 10.1021/acs.jpcc.5b08278. Fulltekst i vitenarkiv Vis sammendrag

  Sulfur-containing materials may be of importance in devices such as proton conducting fuel cells for energy conversion involving fossil or bioderived fuels. First-principles calculations were employed to elucidate the thermodynamics of proton incorporation as well as proton migration barriers in selected sulfides, oxysulfides, and oxysulfates. In this respect, dissolution of H2S and H2O into anion vacancies as SH– and OH–, respectively, was considered for La2O2S, La2O2SO4, and the perovskite sulfides SrZrS3 and BaZrS3. The structurally equivalent A-La2O3 and SrZrO3 were included for comparison. Protons were found to be most stable associated with oxide ions as OH– rather than with the sulfide or sulfate anions in La2O2S and La2O2SO4, respectively. The enthalpies of dissolution of H2O were calculated to −1.31 and −1.21 eV, respectively. However, the low symmetry of the protonated structures implied insubstantial long-range proton transport. SrZrS3 and BaZrS3 both exhibit exothermic enthalpies of dissolution of H2S, −0.86 and −0.58 eV, respectively, which is comparable to dissolution of H2O in several perovskite oxide proton conductors. Furthermore, among the calculated proton migration barriers for an interoctahedral and a rotational pathway in the perovskite sulfides and oxide, BaZrS3 showed the lowest activation energy for proton transport, 0.25 eV.

Se alle arbeider i NVA

• Ewerhardt, Patrick & Polfus, Jonathan M. (2026). Identifying Reaction Pathways in Patterned Ni and Pd Electrodes on BaZr0.7Ce0.2Y0.1O3-δ. Fulltekst i vitenarkiv
• Amedjkouh, Yani Leo; Jiang, Bo; Rosnes, Andreas; Wenckstern, Holger Von & Polfus, Jonathan M. (2025). Combinatoral PLD of proton ceramic electrode materials with exsolved nanoparticles. Fulltekst i vitenarkiv Vis sammendrag

  Protonic ceramic electrochemical cells (PCECs) are poised to be a critical technology for the electrification of energy and chemical industry using hydrogen. One of the main bottlenecks hodling their widespread adoption back is the sluggish oxygen evolution/reduction reactions (OER/ORR) at the positrode. Wang et al. reported that Ba0.875Fe0.875Zr0.125O3-"δ" (D-BFZ) exhibits remarkable performance as a triple conducting PCFC positrode (Wang 2022). Here, we investigate further improvement of this system by exsolving nanoparticles of Co3O4 or noble metals such as Pt, Ir, Rh and Ru for improved OER/ORR kinetics. Combinatorial pulsed-laser deposition (c-PLD) is a novel thin film deposition technique for obtaining thin films with a continuous composition spread (CCS) (von Wenckstern 2020). D-BFZ doped with the cation species to be exsolved is deposited with a gradient in Ba-deficiency across the film. Spatially resolved synchrotron X-ray diffraction (XRD) and absorption spectroscopy (XAS) is utilized to study the impact of Ba-deficiency on the exsolution process and the resulting nanoparticle characteristics. Further studies involve oxygen exchange kinetics of pristine and exsolved materails using pulsed isotope exchange (PIE). Thus, the impact of the transition metal on the oxygen exchange kinetics can be directly compared between it being exsolved as nanoparticles and incorporated in the perovskite lattice.

• Norby, Truls; Bjørheim, Tor Svendsen & Polfus, Jonathan (2024). Modelling and Characterization of Negatrodes in Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Gudmundsdottir, Jonina Björg; Haugsrud, Reidar; Vøllestad, Einar & Polfus, Jonathan (2024). Oxygen Exchange Kinetics of BaGd0.3La0.7Co26-d Air/Steam Electrode for Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Gudmundsdottir, Jonina Björg; Haugsrud, Reidar; Vøllestad, Einar & Polfus, Jonathan (2024). Oxygen Exchange Kinetics of BaGd0.3La0.7Co2O6-d Air/Steam Electrode for Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Ewerhardt, Patrick; Norby, Truls; Polfus, Jonathan M. & Bjørheim, Tor S. (2024). Fabrication and Characterisation of Microelectrodes in Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Roen, Stine; Strandbakke, Ragnar & Polfus, Jonathan M. (2024). Electrochemical Characterization of Ba0.95La0.05(Fe1−x−yMxZny)O3−δ (M = Ni, Cu) as Air/Steam Electrode in Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Ewerhardt, Patrick; Bjørheim, Tor S.; Norby, Truls & Polfus, Jonathan M. (2024). Modelling and Characterization of Negatrodes in Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Småbråten, Didrik Rene; Polfus, Jonathan; Strandbakke, Ragnar; Singh, Kalpana; Veenstra, Peter & Fontaine, Marie-Laure (2023). DFT modelling of thermodynamic and kinetic parameters in electrochemical proton ceramic conducting cells. Fulltekst i vitenarkiv
• Gudmundsdottir, Jonina Björg; Vøllestad, Einar; Haugsrud, Reidar & Polfus, Jonathan (2023). Oxygen Exchange Kinetics of BaGd0.3La0.7Co2O6-d. Fulltekst i vitenarkiv
• Småbråten, Didrik Rene & Polfus, Jonathan (2023). DFT on electrodes for high-temperature electrolysis. Fulltekst i vitenarkiv
• Ewerhardt, Patrick; Wu, Mengxin; Norby, Truls; Bjørheim, Tor Svendsen & Polfus, Jonathan M. (2023). Finite element modelling of kinetic processes in proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Roen, Stine; Norby, Truls; Strandbakke, Ragnar & Polfus, Jonathan M. (2023). Electrochemical characterization of Ba0.95La0.05(Fe0.7Ni0.2Zn0.1)O3-δ for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Kim, Donghoi; Liu, Zhongxuan; Anantharaman, Rahul; Riboldi, Luca; Odsæter, Lars Hov & Berstad, David Olsson [Vis alle 10 forfattere av denne artikkelen] (2022). Design of a novel hybrid clean hydrogen production process with membrane assisted CO2 capture through liquefaction. Fulltekst i vitenarkiv
• Gudmundsdottir, Jonina Björg; Thoreton, Vincent; Vøllestad, Einar & Polfus, Jonathan (2022). Oxygen Exchange Kinetics of BaGd0.3La0.7Co2O6-d Steam Electrodes for Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Dayaghi, Amir Masoud; Polfus, Jonathan; Strandbakke, Ragnar; Vøllestad, Einar; Haugsrud, Reidar & Norby, Truls (2022). Effects of NiO, ZnO and CuO sintering additives on the hydration of BaZr0.4Ce0.4(Y,Yb)0.2O3-δ proton conducting electrolytes. Fulltekst i vitenarkiv
• Polfus, Jonathan; Småbråten, Didrik Rene & Liu, Xin (2022). Linking Atomistic and Electrochemical Modelling of Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Talic, Belma; Dayaghi, Amir Masoud; Vøllestad, Einar; Stefan, Elena; Sunding, Martin Fleissner & Polfus, Jonathan (2022). Chemical Stability of Proton Conducting BaZr1-xCexO3-Based Electrolytes in Pressurized CO2-Containing Atmospheres. Fulltekst i vitenarkiv Vis sammendrag

  Acceptor doped barium cerates and zirconates are attractive electrolyte materials for use in various proton ceramic electrochemical devices such as fuel cells and hydrogen pumps. However, the long-term durability of these materials may be challenged by poor chemical stability in CO2-containing atmospheres. In this work, the chemical stability of the electrolyte material BaZr0.8Ce0.1Y0.1O3 (BZCY81) is studied in CO2 and CO2-H2. Dense pellets prepared by sintering with NiO as a sintering aid were exposed to up to 10 bar CO2(-H2) for up to 150 h at elevated temperatures (400-800°C). After exposure, the pellet surface was analyzed by grazing incidence X-ray diffraction (XRD), scanning electrode microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to search for BaCO3 formation. Overall, the electrolyte material displayed excellent stability towards CO2. A small increase in apparent BaCO3 concentration on the pellet surface was only detected by XPS for samples aged in CO2 and CO2-H2 at 800 °C. However, BaCO3 was not visible by XRD and SEM-EDS, indicating that the reactivity is limited to a nm-thick region of the electrolyte surface. The impact of processing conditions such as sintering temperature and use of NiO sintering aid on the electrolyte stability will be discussed.

• Liu, Zhongxuan; Kim, Donghoi; Polfus, Jonathan Marc; Peters, Thijs & Anantharaman, Rahul (2020). Membrane-Assisted CO2 capture through liquefaction for clean H2 production. Fulltekst i vitenarkiv
• Muñiz, Marta Benthem; Ali, Ayaz; Polfus, Jonathan & Belle, Branson (2019). 2D crystal temperature dependent adhesion in the development of Van der Waals heterostructures. Fulltekst i vitenarkiv
• Dahl-Hansen, Runar Plunnecke; Akkopru-Akgun, Betul; Denis, Lyndsey; Coleman, Kathleen; Polfus, Jonathan M. & Vøllestad, Einar [Vis alle 9 forfattere av denne artikkelen] (2019). PiezoMEMS reliability: why the electrode-material matters in humid ambient. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Yang, Jing & Yildiz, Bilge (2019). Correction: Interplay between H<inf>2</inf>O and CO<inf>2</inf> coadsorption and space-charge on Y-doped BaZrO<inf>3</inf> surfaces(Journal of Materials Chemistry A (2018) 6 (24823-24830) DOI: 10.1039/C8TA09491H). Journal of Materials Chemistry A. ISSN 2050-7488. 7(35), s. 20438–20439. doi: 10.1039/c9ta90210d. Fulltekst i vitenarkiv
• Dahl-Hansen, Runar Plunnecke; Akkopru-Akgun, Betul; Vøllestad, Einar; Polfus, Jonathan M.; Denis, L & Coleman, K [Vis alle 9 forfattere av denne artikkelen] (2019). Degradation of PZT in humid ambient – an electrochemically controlled process. Fulltekst i vitenarkiv
• Belle, Branson; Xing, Wen; Stange, Marit Synnøve Sæverud; Azar, Amin S.; Sunding, Martin Fleissner & Polfus, Jonathan M. (2018). Scalable MoS2 growth via Mo sputtering and post H2S treatment. Fulltekst i vitenarkiv
• Fleischer, Christian; Bjørheim, Tor Svendsen; Polfus, Jonathan M. & Norby, Truls Eivind (2018). Point Defects in Monolayer MoS2. Fulltekst i vitenarkiv
• Fleischer, Christian; Polfus, Jonathan M.; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2018). Defect Chemistry of Few- and Monolayer MoS2. Fulltekst i vitenarkiv Vis sammendrag

  Defect chemistry has given the possibility to control and tune properties to obtain better functional bulk materials. In comparison, and despite the recent interest and prospects of two-dimensional materials, their defect chemistry remains mainly unexplored. We believe that an understanding of the influence of the dielectric environment on the defect chemistry and properties is crucial for further developing new and superior 2D materials. Here, we present results for molybdenum disulphide (MoS2) films on Si/SiO2 substrates. Methods comprise magnetron sputtering of Mo with subsequent annealing in H2S atmosphere and the chemical vapour transport method. The films and defects are characterised by AFM, XPS, photoluminescence, optical microscopy and Raman spectroscopy in addition to electrical measurements in controlled atmospheres. Ab initio computations on a variety of point defects and defect clusters further elucidate the defect chemistry.

• Li, Zuoan; Xing, Wen; Polfus, Jonathan M.; Denonville, Christelle; Fontaine, Marie-Laure & Bredesen, Rune (2018). Ceramic-based composite membranes for gas separation. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Yang, Jing; Tuller, Harry; Yildiz, Bilge & Bredesen, Rune (2018). Interplay between H2O/CO2 coadsorption and space-charge on Y-doped BaZrO3 surfaces. Fulltekst i vitenarkiv
• Norby, Truls Eivind; Min, Chen; Bondevik, Tarjei & Polfus, Jonathan M. (2018). Space Charge Layers and Their Role for Properties of Interfaces in Solid State Ionics. Fulltekst i vitenarkiv
• Polfus, Jonathan M. & Malerød-Fjeld, Harald (2018). Protonic Membrane Reforming of Natural Gas to Hydrogen with Carbon Capture. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Yang, Jing; Tuller, Harry; Yildiz, Bilge & Bredesen, Rune (2018). Coadsorption of H2O and CO2 on BaZrO3-based proton-conducting electrolytes. Fulltekst i vitenarkiv
• Chen, Min; Lozano, Helena Téllez; Druce, John; Matsumoto, Hiroshige; Sazinas, Rokas & Polfus, Jonathan M. [Vis alle 7 forfattere av denne artikkelen] (2017). Surface chemistry of BaZr0.9Y0.1O3-δ and its effect on the electrochemical properties of a Ni/BaZr0.9Y0.1O3-δ interface for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Pishahang, Mehdi & Polfus, Jonathan M. (2017). Defect Chemistry in Grain Boundaries of Proton Conducting BaCeO3. Fulltekst i vitenarkiv
• Li, Zuoan; Fontaine, Marie-Laure; Xing, Wen; Denonville, Christelle; Polfus, Jonathan M. & Henriksen, Partow Pakdel [Vis alle 7 forfattere av denne artikkelen] (2017). Novel molten/solid composite oxygen transport membranes for CO2 capture. Fulltekst i vitenarkiv
• Li, Zuoan; Fontaine, Marie-Laure; Denonville, Christelle; Xing, Wen; Polfus, Jonathan M. & Henriksen, Partow Pakdel [Vis alle 7 forfattere av denne artikkelen] (2017). Designing rules for enhancing surface kinetics in functional oxides for clean energy technologies. Fulltekst i vitenarkiv
• Fontaine, Marie-Laure; Xing, Wen; Bredesen, Rune; Denonville, Christelle; Polfus, Jonathan M. & Strandbakke, Ragnar [Vis alle 10 forfattere av denne artikkelen] (2016). Proton conducting electrolysers with tubular segmented-in-series cells for hydrogen production. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Norby, Truls & Bredesen, Rune (2016). Proton Conduction Across Interfaces in Y-doped BaZrO3 Investigated by First-Principles Calculations. Fulltekst i vitenarkiv
• Henriksen, Partow Pakdel & Polfus, Jonathan M. (2016). Naturgass kan gi grønt hydrogen. s. 31–31. Fulltekst i vitenarkiv
• Grandcolas, Mathieu; Sahoo, Prangya Parimita; Foss, Carl Erik Lie; Xing, Wen; Polfus, Jonathan M. & Sunde, Svein [Vis alle 8 forfattere av denne artikkelen] (2016). Novel photoelectrocatalytic concepts for conversion of nitrogen to fuels and chemicals. Fulltekst i vitenarkiv
• Foss, Carl Erik Lie; Sunde, Svein; Norby, Truls; Sahoo, Prangya Parimita; Grandcolas, Mathieu & Polfus, Jonathan M. [Vis alle 7 forfattere av denne artikkelen] (2016). Photofixation of N2 to NH3/NOx. Fulltekst i vitenarkiv
• Fontaine, Marie-Laure; Vøllestad, Einar; Polfus, Jonathan M.; Denonville, Christelle; Xing, Wen & Li, Zuoan [Vis alle 8 forfattere av denne artikkelen] (2016). Proton Conducting Electrolysers with Tubular Segmented-in-series Cells for Hydrogen Production. Fulltekst i vitenarkiv
• Li, Zuoan; Fontaine, Marie-Laure; Polfus, Jonathan M.; Denonville, Christelle; Xing, Wen & Henriksen, Partow Pakdel [Vis alle 7 forfattere av denne artikkelen] (2016). Fabrication and performance of asymmetric tubular H2 membranes based on LWM-LSC composites. Fulltekst i vitenarkiv
• Hasle, Ida Margrete; Haugsrud, Reidar & Polfus, Jonathan M. (2016). Computational Studies of Cation Transport in Barium Zirconate. Fulltekst i vitenarkiv
• Tilset, Bente Gilbu; Rørvik, Per Martin; Larring, Yngve; Fontaine, Marie-Laure & Polfus, Jonathan M. (2016). Keramiske membraner for hydrogensamfunnet. Fulltekst i vitenarkiv
• Polfus, Jonathan M. (2015). First-principles studies of defects and interfaces in perovskite ceramics. Fulltekst i vitenarkiv
• Sunding, Martin Fleissner; Polfus, Jonathan M.; Zheng, Kun; Svenum, Ingeborg-Helene & Pedersen, Eirik Østbye (2015). Analysing reduced transition metal containing compounds with XPS. Fulltekst i vitenarkiv
• Carcases, Nahum Maso; Polfus, Jonathan M.; Fontaine, Marie-Laure & Norby, Truls (2015). Electrical Properties of Nonstoichiometric BaxZr0.85Y0.15O2.925 Ceramics Prepared by Solid State Reactive Sintering. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Li, Zuoan; Sunding, Martin Fleissner; Xing, Wen; Fontaine, Marie-Laure & Henriksen, Partow Pakdel [Vis alle 7 forfattere av denne artikkelen] (2015). Chemical stability of cercer H2 membranes in the La28-xW4+xO54+3x/2-δ–LaCrO3-δ system. Fulltekst i vitenarkiv
• Polfus, Jonathan M.; Bjørheim, Tor Svendsen; Pishahang, Mehdi; Norby, Truls & Bredesen, Rune (2015). Influence of space-charge on the surface defect chemistry of BaZrO3. Fulltekst i vitenarkiv
• Norby, Truls & Polfus, Jonathan M. (2015). Space Charge Layers and Their Role in Properties of Interfaces in Solid State Ionics. Fulltekst i vitenarkiv
• Norby, Truls; Haugsrud, Reidar & Polfus, Jonathan M. (2015). Defects and transport in proton conducting BZY. Fulltekst i vitenarkiv
• Sahoo, Prangya Parimita; Schrade, Matthias; Grandcolas, Mathieu; Polfus, Jonathan M.; Foss, Carl Erik Lie & Sunde, Svein [Vis alle 7 forfattere av denne artikkelen] (2015). Photoelectrocatalytic conversion of water, carbon dioxide, and nitrogen to fuels and chemicals. Fulltekst i vitenarkiv
• Saeed, Sarmad Waheed; Hancke, Ragnhild & Polfus, Jonathan M. (2015). CO2 capture by hydrogen separation membranes. Fulltekst i vitenarkiv
• Fontaine, Marie-Laure; Denonville, Christelle; Polfus, Jonathan M.; xing, wen; Dahl, Paul Inge & Sunde, Tor Olav Løveng [Vis alle 7 forfattere av denne artikkelen] (2015). Development of proton conducting electrolyser cells. Fulltekst i vitenarkiv
• Norby, Truls & Polfus, Jonathan M. (2015). Grain boundaries in ion conducting ceramics; theory and practice - properties and applications. Fulltekst i vitenarkiv
• Gutterød, Emil Sebastian; Haugsrud, Reidar & Polfus, Jonathan M. (2016). An Experimental and Computational Study of Nitrogen Activation on Promoted Ruthenium Catalysts. Universitetet i Oslo. Fulltekst i vitenarkiv

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