Truls Norby

• Wen, Yabing & Norby, Truls (2026). Thermogravimetric analysis of the H/D isotope effect on hydration thermodynamics of Y-substituted BaZrO<inf>3</inf>. Solid State Ionics. ISSN 0167-2738. 445. doi: 10.1016/j.ssi.2026.117295. Fulltekst i vitenarkiv
• 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.

• Strandbakke, Ragnar; Wachowski, Sebastian Lech; Balaguer, Maria; Vines, Lasse; Sky, Thomas Neset & Szpunar, Iga [Vis alle 12 forfattere av denne artikkelen] (2026). Governing principles of hydration of mixed proton conducting Co-based double perovskites. Nature Communications. 17, s. 1–10. doi: 10.1038/s41467-026-70212-w. Fulltekst i vitenarkiv Vis sammendrag

  Proton ceramic electrochemical cells PCECs hold promise for efficient, sustainable production and use of hydrogen. The positive electrodes are mixed proton conducting perovskites that facilitate water splitting and oxygen reduction, but the factors that determine the protonation are poorly under stood. Here, we establish the governing principles of protonation through a study of hydration of 45 double perovskites with the general formula AIAIICo2O6 δ, having Ba or Ba+Sr on AI and a mix of rare earths (Y and lanthanides Ln =La,Pr,Nd,Sm,Gd,Dy,Tb,Lu)onAII. We show how hydration is coupled to the A-site basicity and disorder as well as population of electron holes in the Co-O bond (Co oxidation state), promoted by a closed or semiclosed Ln 4f shell, i.e., Ln =La,Gd,Lu.

• Jiang, Lulu; Toyoura, Kazuaki; Dayaghi, Amir Masoud; Chen, Huaican; Yuan, Bao & Yin, Wen [Vis alle 10 forfattere av denne artikkelen] (2025). Fast Oxide Ion Conduction in Ba3MoNbO8.5 Enhanced by Acceptor Substitution and Dehydration. Journal of the American Chemical Society. ISSN 0002-7863. 147(50), s. 46515–46515. doi: 10.1021/jacs.5c17115. Fulltekst i vitenarkiv Vis sammendrag

  Ba3MoNbO8.5 (BMN) exhibits high O2– conductivity by disordered partially occupied O2 + O3 sites. Hydration decreases, and certain dopants increase the conductivity, and we present a novel model for defects and transport over two sites that rationalizes these behaviors. A broad experimental and computational study shows that hydration increases the activation energy of migration by immobile protons and fills the O2 + O3 plane. Acceptor substitution reverses this by emptying the O2 + O3 plane and spreading protons, and 5 at % Y substitution yields a bulk oxide ion conductivity exceeding 10 mS·cm–1 at 650 °C and effectively suppresses the effect of humidity. The effects of hydration and acceptor substitution on the grain boundary (GB) resistance suggest a positively charged GB core by vacancy and proton accumulation with adjacent space charge regions with higher filling and activation energy and that doping and GB engineering may pave the way for operando utilization of Ba3MoNbO8.5-related oxide ion conductors.

• 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.

• Dayaghi, Amir Masoud; Almar, Laura; Escolástico, Sonia; Jiang, Bo; Carvalho, Patricia Almeida & Alfaro, Jose Manuel Serra [Vis alle 8 forfattere av denne artikkelen] (2025). On the cation distribution in acceptor doped Ba(Zr,Ce)O3 (Zr,Ce)O2 co-ionic composite electrolytes. Journal of Materials Chemistry A. ISSN 2050-7488. 13(39), s. 33528–33540. doi: 10.1039/d5ta02711j. Fulltekst i vitenarkiv Vis sammendrag

  Composite co-ionic ceramic electrolytes that combine proton and oxide ion conductors hold potential for co-electrolysis of CO2 and H2O for syngas production due to flexible control of the transport numbers of the two charge carriers. Contrary to purely oxide ion co-electrolysis, co-ionic co-electrolysis embodies the supply of CO2 and H2O separately to the negative and positive electrodes, respectively. This study focuses on the development of a chemically stable co-ionic composite electrolyte of an acceptor-doped Ba(Zr,Ce)O3 proton conducting perovskite phase and an acceptor-doped (Ce,Zr)O2 oxide ion conducting fluorite phase, annealed at temperatures between 800 and 1600 °C. Comprehensive evaluations of the composites' microstructure, hydration, and conductivity were performed, revealing that annealing temperature and cation selection significantly impact the properties and performance of co-ionic electrolytes. Higher annealing temperatures drive cation redistribution, with the perovskite phase becoming zirconium-rich at its B-site and depleted in acceptor dopants, resulting in diminished hydration and protonic conductivity. Herein, we show that composites pairing cerium-rich fluorite phases (e.g., Ce0.8Gd0.2O1.9, CGO20, or Ce0.8Y0.2O1.9, CYO20) display markedly improved performance. The BaCe0.8Y0.2O2.9 (BCY20)–CYO20 system (1 : 1 weight ratio) achieved the highest conductivity (σ = 0.01 Scm−1 at 650 °C in wet Ar), establishing itself as a promising candidate for co-ionic electrolyte applications in solid oxide electrochemical cells.

• Wan, Gang; Borodin, Oleg; Norby, Truls; Pollard, Travis P.; Schroeder, Marshall A. & Chen, Chia-Chin [Vis alle 8 forfattere av denne artikkelen] (2025). Hydrogenation of Oxides in Nonaqueous Battery Electrolytes and Beyond. ACS Energy Letters. 10(8), s. 3972–3982. doi: 10.1021/acsenergylett.5c01542. Fulltekst i vitenarkiv
• Ismail, Sara Adeeba; Toyoura, Kazuaki; Jiang, Lulu; Dayaghi, Amir Masoud; Guo, Hui & Avdeev, Maxim [Vis alle 11 forfattere av denne artikkelen] (2025). Ba7Nb4MoO20: A Proton or Oxide Ion Conductor? Journal of the American Chemical Society. ISSN 0002-7863. 147(28), s. 24774–24784. doi: 10.1021/jacs.5c06467. Fulltekst i vitenarkiv Vis sammendrag

  Ba7Nb4MoO20 is a recently emerging fast oxide ion conductor, attracting increasing attention. It was reported to also show proton conduction in a humid atmosphere, which is, however, opposite to the results in this work. Theoretical calculations indicate that protons can hardly move, being stabilized in the perovskite blocks or trapped in the palmierite layers, which is in line with the experimental evidence of almost no H2O/D2O isotope effect and a negligibly small transport number of protons by EMF measurements up to 800 °C. It is thereby clear that Ba7Nb4MoO20 is almost a pure oxide ion conductor even though it can be hydrated upon exposure to moisture. The hydration in fact stabilizes interstitial oxide ions (O5 site) in the palmierite layers by forming Nb2O9H units, leading to reduced bulk conductivity in the pristine and slightly Nb-rich compositions at <400 °C. However, by heating up over 400 °C, the bulk conductivity in the wet atmosphere surpasses that in the dry one, benefitting from an injection of protons into the perovskite blocks to release free O5 ions for oxide ion conduction, indicating that hydration may provide extra oxide ions to enhance the oxide ion conduction.

• Carrillo, Alfonso; Balaguer, M.; Solis, Cecilia; Lopez-Garcia, Andres; Haas, Sylvio & Fabuel, Maria [Vis alle 13 forfattere av denne artikkelen] (2025). Evaluating oxide nanoparticle exsolution on A-site deficient PrBaCo2O6-δ electrodes. Journal of Physics: Energy. 7(2), s. 1–15. doi: 10.1088/2515-7655/ada8de. Fulltekst i vitenarkiv Vis sammendrag

  Nanoparticle exsolution is a powerful technique for functionalizing redox oxides in energy applications, particularly at high temperatures. It shows promise for solid oxide fuel cells and electrolyzers. However, exsolution of other chemistries like metal oxides is not well studied, and the mechanism is poorly understood. This work explores oxide exsolution in PrBa1−xCo2O6−δ (x = 0, 0.05, 0.1, 0.15) double perovskites, practiced electrodes in proton ceramic fuel cells and electrolyzers. Oxide exsolution in PrBa1−xCo2O6−δ aimed at boosting the electrocatalytic activity and was evaluated by varying intrinsic materials-related properties, viz. A-site deficiency and external parameters (temperature, under fixed time, and pO2 = 10−5 atm conditions). The materials were analyzed with conventional characterization tools and synchrotron-based small-angle x-ray scattering. Unlike metal-nanoparticle exsolution, increasing the A-site deficiency did not enhance the extent of oxide-nanoparticle exsolution, whereas larger nanoparticles were obtained by increasing the exsolution temperature. Combined Raman spectroscopy and electron microscopy analysis revealed that BaCoO3, Co3O4, and amorphous BaCO3 nanoparticles were formed on the surface of the double perovskites after the reductive treatments. The present results demonstrate the complexity of oxide-nanoparticle exsolution in comparison with metal-nanoparticle exsolution. Further materials screening and mechanistic studies are needed to enhance our understanding of this method for functionalizing proton ceramic electrochemical cells (PCEC) electrodes.

• Navarrete, Laura; Almar, Laura; Tarach, Mateusz; Vøllestad, Einar; Mahmood, Asif & Catalán-Martinez, David [Vis alle 10 forfattere av denne artikkelen] (2025). Tailoring sintering properties of BaGd0.3La0.7Co2O6-δ steam electrodes for pressurized tubular proton-ceramic electrolysis cells. Journal of the European Ceramic Society. ISSN 0955-2219. 45(5), s. 1–8. doi: 10.1016/j.jeurceramsoc.2024.117162. Fulltekst i vitenarkiv Vis sammendrag

  We herein address manufacturing constraints related to the high-temperature sintering step required for reaching adequate adhesion of oxygen/steam electrodes on proton ceramic electrolytes, particularly in tubular geometry. Incorporating various sintering aids such as Cu, Co, and Ni oxides improves the sinterability of the electrodes and reduces the sintering temperature to 950 °C. The ceramic-ceramic composite electrodes based on BaGd0.3La0.7Co2O6-δ (BGLC37) and BaZr0.7Ce0.2Y0.1O6-δ (BZCY) show good and robust electrode-electrolyte adhesion. Composite electrodes were tested under different operation conditions, i.e., temperatures and oxygen partial pressures in symmetrical cell configuration, achieving apparent polarisation resistances below 0.6 Ω·cm2 at 600 °C in wet air for all the electrodes with sintering aids. Finally, BGLC37/BZCY with 2 wt% of CuO electrodes were successfully applied on pre-reduced and sealed BZCY/Ni-supported tubular half-cells with 16 cm2 active area and measured in electrolysis mode at 600 °C and high steam pressure. The results open a route to manufacturing steam electrodes for large-scale electrolysis cells.

• Roen, Stine; Strandbakke, Ragnar & Norby, Truls (2025). Current-overpotential relationships from electrochemical impedance spectroscopy (EIS) under DC bias – A tutorial exercise applied to a Pt||YSZ electrode. Solid State Ionics. ISSN 0167-2738. 428. doi: 10.1016/j.ssi.2025.116939. Fulltekst i vitenarkiv Vis sammendrag

  Electrochemical impedance spectroscopy (EIS) of electrode polarisation offers the possibility to delineate overpotentials into ohmic, charge transfer kinetic, and transport and other mass transfer contributions, commonly applied and interpreted under open circuit conditions. It is sometimes also applied under DC bias, as it in principle then can provide information about net anodic or cathodic processes. However, the impedances so obtained are seldomly converted to overpotentials and therefore remain as qualitative indicators only. Here, we tutorially derive formalism of converting resistances from EIS under DC bias properly into overpotential contributions to the total overpotential, allowing identification of their origins from their dependencies on the current. We illustrate the methodology by generated model current-voltage curves and then apply it to an experimental data set for a Pt electrode on an yttria-stabilised zirconia (YSZ) oxide ion conducting electrolyte. The result reveals that a dominating electrode polarisation easily taken to reflect mass transfer in fact behaves like a second charge transfer step following Butler-Volmer kinetics, allowing us to hypothesise a new model for the O2,Pt||YSZ electrode. Our tutorial exercise is applicable to both liquid- and solid-state electrochemistry and should apply equally also to EIS under DC bias of any types of junctions.

• Balcerzak, Daria; López-García, Andrés; Carrillo, Alfonso J.; Balaguer, María; Alfaro, Jose Manuel Serra & Norby, Truls [Vis alle 9 forfattere av denne artikkelen] (2025). Tailoring oxide nanoparticle exsolution in La0.5Ba0.5-yCo1-xFexO3-δ. Journal of the European Ceramic Society. ISSN 0955-2219. 45(10), s. 1–12. doi: 10.1016/j.jeurceramsoc.2025.117347. Fulltekst i vitenarkiv Vis sammendrag

  We show that oxide nanoparticles (NPs) exsolve on La0.5Ba0.5-yCo1-xFexO3-δ (x = 0–1, y = 0 or 0.01) in oxidizing conditions. The phenomenon occurs only in Co-containing materials and depends on pO2 and pH2O pressures. Under dry conditions, the smallest NPs average about 30 nm, with 200–300 NPs/µm2 at pO2= 5 × 10−5 atm. For pO2= 1 atm, NP size increases to 100–200 nm, and population drops to a few to about 20 NPs/µm2 depending on A-site nonstoichiometry and x. In humid conditions, the smallest NPs around 50 nm, with a peak of 100 NPs/µm2 exsolve for pO2= 1. Transmission electron microscopy shows that exsolved NPs in La0.5Ba0.5-yCoO3-δ are Ba-O-rich. We propose defect chemistry models, indicating that exsolution is driven by oxidation reactions forming A-site vacancies, increasing exsolved material with higher pO2. We suggest that adsorbed water under humid conditions blocks nucleation sites, altering observed trends.

• Wachowski, Sebastian Lech; Szpunar, Iga; Pospiech, Joanna; Balcerzak, Daria; Mielewczyk-Gryn, Aleksandra & Nadolska, Malgorzata [Vis alle 12 forfattere av denne artikkelen] (2024). Physicochemical properties of La0.5Ba0.5Co1-xFexO3-δ (0 ≤ x ≤ 1) as positrode for proton ceramic electrochemical cells. Acta Materialia. ISSN 1359-6454. 284. doi: 10.1016/j.actamat.2024.120585. Fulltekst i vitenarkiv Vis sammendrag

  We report on essential properties of materials in the series La0.5Ba0.5Co1-xFexO3-δ as positrodes for proton ceramic electrochemical cells (PCECs). The unit cell and thermochemical expansion coefficient (TCEC) of these cubic perovskites decrease with iron content x, the TCEC of La0.5Ba0.5FeO3-δ going as low as 11⋅10-6 1/K. The materials behave as LaMO3 perovskites with small band gaps and Ba acting as acceptors compensated by electron holes and oxygen vacancies. The electrical properties are dominated by p-type conduction with high large polaron mo- bilities for the Co-rich compositions at low temperatures, shifting towards small polaron mobilities with increasing Fe content. X-ray absorption spectroscopy (XAS) shows that Co is in a high spin state and takes on the main part of the cation oxidation state changes, and that hole states are in orbitals overlapping with the O 2p states, confirming the large polaronic behaviour, while holes on Fe are more localised at the cation. Hydration is more pronounced in inert atmospheres, as hydration of oxygen vacancies is easier than hydrogenation and in- creases with Fe content, in line with the commonly accepted finding that delocalization of holes disfavours protonation. Fe-rich compositions benefit from lower TCEC and higher hydration and hence expected proton permeability, at the cost of lower electronic conductivity. The surfaces are hydrophobic irrespective of Fe content, suggesting weak chemisorption of the underlaying water layer, possibly giving relatively many available surface sites for oxygen adsorption, but limited surface proton conductance – both of importance to positrodes for operando PCECs

• Zheng, Haoyu; Sata, Noriko; Han, Feng; Dayaghi, Amir Masoud; Iguchi, Fumitada & Develos-Bagarinao, Katherine [Vis alle 9 forfattere av denne artikkelen] (2024). Hydrogen Production with a Protonic Ceramic Membrane Reactor on Porous Fe-Cr Alloy. ACS Energy Letters. 9(8), s. 3962–3969. doi: 10.1021/acsenergylett.4c01173. Fulltekst i vitenarkiv Vis sammendrag

  A metal supported design is desirable for ceramic electrochemical cells because of its robustness. Yet, a strong alkaline character and a refractory nature of the electrolyte material make it challenging to densify onto a steel component. Here we show a metal supported protonic ceramic cell (MS-PCC) concept enabling ∼90% ceramic material savings compared to traditional cell design. The manufacturing route combines wet ceramic processing with sintering and thin film deposition at temperatures below 1000 °C. The critical diffusive elements were sufficiently confined, and the volume variation of the different functional layers was limited to maintain the integrity of the thin film electrolyte. Applied to steam electrolysis for hydrogen production, the MS-PCC enabled a current density of about −0.84 A cm–2 at 600 °C at a terminal voltage of 1.3 V. This concept offers incomparable perspectives for scale-up and opens up a broad range of applications for hydrogen or Power-to-X applications.

• Petlund, Henrik; Faid, Alaa Yahia; Zhu, Junjie; Pokle, Anuj; Norby, Truls & Sunde, Svein [Vis alle 7 forfattere av denne artikkelen] (2024). Iron and Nickel Substituted Perovskite Cobaltites for Sustainable Oxygen Evolving Anodes in Alkaline Environment. ChemSusChem. ISSN 1864-5631. doi: 10.1002/cssc.202401403. Fulltekst i vitenarkiv Vis sammendrag

  Perovskite oxides have great flexibility in their elemental composition, which is accompanied by large adjustability in their electronic properties. Herein, we synthesized twelve perovskite oxide-based catalysts for the oxygen evolution reaction (OER) in alkaline media. The catalysts are based on the parent oxide perovskite Ba0.5Gd0.8La0.7Co2O6-δ (BGLC587) and are synthesized through the sol-gel citrate synthesis route. To reduce the demand on cobalt (Co), but also increase the intrinsic catalytic activity of BGLC587 for the OER, we substitute Co on the B-site with certain amounts of Fe and Ni, synthesizing catalysts of the general formula Ba0.5Gd0.8La0.7Co2-x-yFexNiyO6-δ. A plethora of physicochemical and electrochemical methods suggest that an Fe content between 30 % and 70 % increases the intrinsic catalytic activity of BGLC587, while Tafel slopes in combination with in-situ Raman spectroscopy suggest the rate determining step is likely a proton-exchange reaction, progressing possibly through the lattice oxygen mechanism (LOM). We apply one of the optimized, Co-substituted perovskites in a monolithic, photovoltaic (PV)-driven electrolysis cell and we achieve an initial solar-to-hydrogen (STH) conversion efficiency of 10.5 % under one sun solar simulated illumination.

• Tirados, Irene Yuste; Liu, Xin; Kjølseth, Christian & Norby, Truls (2024). Boundaries of DC operation of a tubular proton ceramic electrochemical reactor with BZCY electrolyte and Ni-BZCY cermet electrodes. Journal of Power Sources. ISSN 0378-7753. 596. doi: 10.1016/j.jpowsour.2024.234097. Fulltekst i vitenarkiv
• Both, Kevin Gregor; Neagu, Dragos; Prytz, Øystein; Norby, Truls & Chatzitakis, Athanasios (2024). Exsolution of Ni nanoparticles in A-site excess STO films. Nanoscale Advances. doi: 10.1039/d4na00213j. Fulltekst i vitenarkiv Vis sammendrag

  Exsolution is a technique to create metal nanoparticles embedded within a matrix. The phenomenon has previously predominantly been studied in A-site deficient and stoichiometric perovskite powders. Here, we present a systematic study of an A-site excess perovskite oxide based on SrTiO3 thin films, doped with nickel and exsolved under different conditions. The study aims to shed light on particle formation in these novel systems, including the effects of (i) the thin film thickness, (ii) pre-exsolution annealing in an oxidative atmosphere, (iii) a reductive atmosphere during the exsolution step, and (iv) exsolution time on the particle size and particle density. Our results indicate that exsolution occurs quickly, forming nanoparticles both on the surface and in the bulk of the host perovskite. The findings indicate that pre-annealing in an ambient atmosphere leads to fewer but larger exsolved particles compared to samples without pre-annealing. Consequently, while crystallization of the thin film occurs in both atmospheres, the simultaneous crystallization of the thin film and formation of the nanoparticles leads to a smaller apparent average radius. Moreover, we present evidence that metal particles can be found beyond the originally doped region. These findings are a step towards realizing tunable functional materials using exsolution to create metallic nanostructures within a thin film in a predictable manner.

• Guo, Shihang; Jiang, Lulu; Li, Yifeng; Zhong, Peng; Ismail, Sara Adeeba & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2024). From Electrolyte and Electrode Materials to Large-Area Protonic Ceramic Fuel Cells: A Review. Advanced Functional Materials. ISSN 1616-301X. doi: 10.1002/adfm.202304729. Fulltekst i vitenarkiv
• Gaukås, Nikolai Helth; Sunde, Tor Olav Løveng; Arstad, Bjørnar; Reksten, Anita; Stefan, Elena & Thøgersen, Annett [Vis alle 9 forfattere av denne artikkelen] (2024). Effects of Different Doping Strategies on Cubic Li7La3Zr2O12 Solid-State Li-Ion Battery Electrolytes. ACS Applied Energy Materials. 7(24), s. 12141–12154. doi: 10.1021/acsaem.4c02708. Fulltekst i vitenarkiv Vis sammendrag

  Solid-state Li-ion conductors based on cubic Li7La3Zr2O12 (LLZO) garnets have received much attention in recent years as potential next-generation battery electrolytes, enabling safer and more energy-dense Li-ion batteries. Aliovalent doping of the LLZO structure is usually necessary to stabilize the cubic garnet phase and increase the ionic conductivity by increasing the concentration of Li vacancies. Here, we report on the synthesis, characterization, and testing of Li7−3xAlxLa3Zr2O12 ceramics with different amounts of Al doping (x = 0.20−0.40). Phase-pure LLZO with a cubic crystal structure was prepared by an aqueous synthesis route, and dense (>93%) ceramic samples were fabricated by conventional sintering at 1200 °C. By analyzing the composition, microstructure, and electrochemical performance, we found that the optimal Al content in LLZO is x = 0.2, the lowest content needed to stabilize the cubic structure in our series. For the composition with x = 0.2, we found a Li-ion conductivity at room temperature of 3.7 × 10−4 S cm−1 and an activation energy of Ea = 0.3 eV. At a higher doping concentration, the conductivity decreases, and the activation energy increases; for x ≥ 0.35, secondary Al-rich phases appear. These results indicate an inverse relationship between Li-ion conductivity and Al doping, where the optimal amount of doping is the minimum amount necessary to stabilize the cubic LLZO phase. Additionally, we present an analysis of the available literature on chemical modification of LLZO to compare how different doping strategies affect Li conductivity. Based on our literature review, Ga and Ta doping gives the highest conductivities (≤2 × 10−3 S cm−1). The literature analysis also supports our findings that the primary objective of the dopant is to stabilize the cubic structure rather than create Li vacancies.

• Norby, Truls (2024). Protonic conduction on oxide surfaces - role and applications in electrochemical energy conversion. Progress in Energy. 6, s. 043002–043002. doi: 10.1088/2516-1083/ad6c9f. Fulltekst i vitenarkiv Vis sammendrag

  Protonic conduction on surfaces of oxides has over the last two decades drawn attention for its possible utilisation in electrolytes for energy conversion at low temperatures and for its roles in enhancement of catalytic activity. This has led to deeper investigation and increased understanding of the phenomenon and development of quantifiable models. Along with this has emerged apparent demonstrations of use of such conduction in low-drain fuel cells as well as acknowledgement of the role of surface protonic conduction in electrodes for solid-state electrochemical and photoelectrochemical cells. Here is provided a brief review and elaboration of the fundamentals of the interaction of water and hydrogen with oxide surfaces, and models for the resulting protonic conduction in chemisorbed and physisorbed layers. We finally discuss aspects of surface protonic conduction in a range of applications, including sensors, catalysis, and electrochemical and photoelectrochemical energy conversion.

• Gu, Jie; Sun, Xinwei; Jiang, Lulu; Zhang, Zihan; Norby, Truls & Han, Donglin (2024). Surface Protonic Conduction in Porous Alkaline Earth Zirconate Perovskites CaZrO3, SrZrO3, and BaZrO3. Journal of Materials Chemistry A. ISSN 2050-7488. 12, s. 26555–26567. doi: 10.1039/D4TA04438J. Fulltekst i vitenarkiv
• Madathil, Reshma; Thoreton, Vincent; Prytz, Øystein & Norby, Truls Eivind (2023). On the high-temperature oxidation of ZnSb for thermoelectric applications. Corrosion Science. ISSN 0010-938X. 210. doi: 10.1016/j.corsci.2022.110826. Fulltekst i vitenarkiv Vis sammendrag

  Thermoelectric ZnSb has a native surface oxide layer of Sb2O5 +ZnO, while HT oxidation in air resulted in selective oxidation to ZnO, with no detectable Sb by STEM-EDS. The ZnO consisted of an inner nano-granular and a more columnar outer layer. Thermogravimetry showed parabolic oxidation kinetics at 200–325 °C with an activation energy of 117 kJ/mol, comparing well with literature for oxidation of Zn. Two-stage 16O2 +18O2 oxidation followed by SIMS suggests growth by mixed Zn and O diffusion through a protective ZnO layer that still cannot prevent considerable high temperature oxidation in air, with formation of insulating electrical contacts, unless metallised.

• Quina, Imanol; Almar, Laura; Catalán-Martínez, David; Dayaghi, Amir Masoud; Martínez, Agustin & Norby, Truls [Vis alle 8 forfattere av denne artikkelen] (2023). Direct electrocatalytic CO<inf>2</inf> reduction in a pressurized tubular protonic membrane reactor. Chem Catalysis. ISSN 2667-1107. 3(10). doi: 10.1016/j.checat.2023.100766. Fulltekst i vitenarkiv
• Jiang, Lulu; Norby, Truls & Han, Donglin (2023). Thermochemical Expansion and Protonic and Electronic Hole Conductivity of Grain Interior and Grain Boundaries in 10 Mole% Y-Substituted SrZrO<inf>3</inf>. ChemSusChem. ISSN 1864-5631. 16(14). doi: 10.1002/cssc.202300661. Fulltekst i vitenarkiv
• Norby, Truls; Sun, Xinwei & Vøllestad, Einar (2023). A brick layer model for surface conduction in porous ceramics. Solid State Ionics. ISSN 0167-2738. 398. doi: 10.1016/j.ssi.2023.116269. Fulltekst i vitenarkiv Vis sammendrag

  We provide herein a review and in-depth derivation and discussion of a surface brick layer model (SBLM) that scales the conductance of a surface layer – such as protonic conductance in adsorbed water – and the macroscopic conductivity for the porous material. The model is derived on basis of grains and pores of similar sizes and will be most realistic for porous compacts or loosely sintered ceramics of isotropic grains, although it still provides order-of-magnitude guidance also for textured or less porous materials. Brief comparison is made with other relevant models and literature. The model is illustrated and evaluated with data primarily from measurements of surface protonic conduction in porous nanoscopic ceramic oxides.

• Luo, Jiaming; Wang, Zishuo; Li, Yong; Gao, Jing; Li, Huimin & Norby, Truls [Vis alle 8 forfattere av denne artikkelen] (2023). An effective strategy to boost hydrogen separation performance through stable mixed proton-electron conducting membrane. AIChE Journal. ISSN 0001-1541. doi: 10.1002/aic.18199. Fulltekst i vitenarkiv
• 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
• Tirados, Irene Yuste; Liu, Xin; Kjølseth, Christian & Norby, Truls (2023). Impedance of a tubular electrochemical cell with BZCY electrolyte and Ni-BZCY cermet electrodes for proton ceramic membrane reactors. International Journal of Hydrogen Energy. ISSN 0360-3199. doi: 10.1016/j.ijhydene.2023.03.401. Fulltekst i vitenarkiv Vis sammendrag

  In this work, impedance spectroscopy has been employed to explore the electrochemical behaviour of a 15 cm2 complete tubular cell with BaZr0.8Ce0.1Y0.1O3-δ (BZCY) electrolyte and two asymmetric Ni-BCZY cermet electrodes for hydrogen separation. Analyses of impedance spectra at different temperatures and gas compositions reveal that the thick inner electrode contributes most to the total polarisation resistance (Rp). For Rp there are four contributions with well-separated time constants of which gas phase hydrogen diffusion within the porous Ni-BZCY anode is predominant. The other three can be ascribed to proton migration through the space charge layer of the BZCY electrolyte adjacent to the Ni electrode, hydrogen redox charge transfer reactions, and hydrogen diffusion within Ni bulk. The present study guides the way to parameterise and, on this basis, optimise electrodes for scalable proton ceramic electrochemical cells.

• Sobhana, Dilimon Vijayan; Strandbakke, Ragnar & Norby, Truls (2022). Impedance spectroscopy study of Au electrodes on Gd-doped CeO<inf>2</inf> (GDC) – Molten Li<inf>2</inf>CO<inf>3</inf>+Na<inf>2</inf>CO<inf>3</inf> (LNC) composite electrolytes. Journal of Power Sources. ISSN 0378-7753. 522. doi: 10.1016/j.jpowsour.2022.230986. Fulltekst i vitenarkiv Vis sammendrag

  We herein report an impedance spectroscopy study of Au electrodes on Gd-doped CeO2 (GDC) – molten Li2CO3+Na2CO3 (LNC) composite electrolytes in O2 and O2+CO2 atmospheres. Complementary measurements of Au on GDC alone are provided for supporting insight. We find that the adsorption of CO2 on GDC in O2+CO2 atmospheres effectively blocks oxygen adsorption and severely slows oxygen reduction kinetics. The conductivity of the composite is dominated by the GDC phase in the solid-solid temperature region, while the LNC phase dominates above its melting point, and no further enhancement e.g. by interfacial effects are found. The incorporation of LNC melt into GDC results in a significant reduction in the polarisation resistance of Au electrodes in O2 atmospheres, as the melt mediates the reaction by a peroxide mechanism. In O2+CO2 atmospheres, however, the polarisation resistance of Au electrodes on GDC-LNC membranes is significantly higher, higher even than that on GDC. This we assign again to the blocking adsorption of CO2 (or carbonate) on the surfaces of ceria and the sluggish transport and reactions now mediated by carbonate-carried oxide species (CO42−) instead of peroxide species.

• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion. Small. ISSN 1613-6810. 18(29). doi: 10.1002/smll.202201106. Fulltekst i vitenarkiv Vis sammendrag

  There is a growing need to control and tune nanoparticles (NPs) to increase their stability and effectiveness, especially for photo- and electrochemical energy conversion applications. Exsolved particles are well anchored and can be re-shaped without changing their initial location and structural arrangement. However, this usually involves lengthy treatments and use of toxic gases. Here, the galvanic replacement/deposition method is used, which is simpler, safer, and leads to a wealth of new hybrid nanostructures with a higher degree of tailorability. The produced NiAu bimetallic nanostructures supported on SrTiO3 display exceptional activity in plasmon-assisted photoelectrochemical (PEC) water oxidation reactions. In situ scanning transmission electron microscopy is used to visualize the structural evolution of the plasmonic bimetallic structures, while theoretical simulations provide mechanistic insight and correlate the surface plasmon resonance effects with structural features and enhanced PEC performance. The versatility of this concept in shifting catalytic modes to the hydrogen evolution reaction is demonstrated by preparing hybrid NiPt bimetallic NPs of low Pt loadings on highly reduced SrTiO3 supports. This powerful methodology enables the design of supported bimetallic nanomaterials with tunable morphology and catalytic functionalities through minimal engineering.

• Sun, Xinwei; Vøllestad, Einar; Rørvik, Per Martin; Prodinger, Sebastian; Kalantzopoulos, Georgios & Chatzitakis, Athanasios [Vis alle 7 forfattere av denne artikkelen] (2022). Surface protonic conductivity in chemisorbed water in porous nanoscopic CeO2. Applied Surface Science. ISSN 0169-4332. 611, s. 1–12. doi: 10.1016/j.apsusc.2022.155590. Fulltekst i vitenarkiv Vis sammendrag

  CeO2 surfaces play decisive roles in heterogeneous catalysis of important processes. Here, we investigate adsorption and dissociation of water and migration of protons on internal surfaces of nanoscopic porous CeO2. Sorption and thermogravimetry confirm literature suggestions that the surface is hydrogenated to Ce3+ ions and protons H+. The following chemisorption is dissociative, yet weak, and physisorption sets in only at the very highest relative humidities, reflecting hydrophobic behaviour. We link sample conductivities to surface protonic conductances via a brick layer model and show that behaviours at high, intermediate, and low temperatures with, respectively, positive, close to zero, and negative apparent activation energies and pH2O^(1/2), pH2O^1, and pH2O^(3/2) dependences, can be attributed to different models of migration all within the chemisorbed layer, without contribution from physisorbed water. While CeO2 may special in this respect due to the effect of the hydrogenated surface, we believe the extended models of transport in the chemisorbed layer may apply also to other oxides. Unsaturated chemisorption may play an important role for CeO2 as catalyst in that the surface is left available for reactant molecules, still with availability of dissociated and mobile protons in the chemisorbed layer and electronic defects by Ce3+ in the surface.

• Liu, Xin; Risbakk, Sanne; Carvalho, Patricia Almeida; Yang, Mingyi; Backe, Paul Hoff & Bjørås, Magnar [Vis alle 8 forfattere av denne artikkelen] (2022). Immobilization of FeFe-hydrogenase on black TiO2 nanotubes as biocathodes for the hydrogen evolution reaction. Electrochemistry communications. ISSN 1388-2481. 135. doi: 10.1016/j.elecom.2022.107221. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogenases are attractive biocatalysts for utilization in electrochemical devices as potential replacement for Pt in hydrogen evolving electrodes. In this work, we investigate the immobilization of ferredoxin tagged FeFe-hydrogenase (Fd-HydA1) on black TiO2 nanotubes (bTNTs), with uniform nanotube opening diameters of 140 nm. By utilizing an immunogold labelling method, we show that the enzymes attach on the top surface of the bTNTs film rather than on the inner nanotube walls, reflecting the difficulty to insert enzymes into high aspect-ratio nanomaterials for O2-shielding. Nevertheless, cyclic voltammetry demonstrates direct electron transfer between Fd-HydA1 and bTNTs for the hydrogen evolution reaction (HER) in neutral media. This work provides new insight towards design of new nanostructured electrodes for enzyme immobilization.

• Catalán-Martínez, D.; Navarrete, L.; Tarach, M.; Santos-Blasco, J.; Vøllestad, Einar & Norby, Truls [Vis alle 9 forfattere av denne artikkelen] (2022). Thermo-fluid dynamics modelling of steam electrolysis in fully-assembled tubular high-temperature proton-conducting cells. International Journal of Hydrogen Energy. ISSN 0360-3199. 47(65), s. 27787–27799. doi: 10.1016/j.ijhydene.2022.06.112. Fulltekst i vitenarkiv Vis sammendrag

  Electrolysis based on renewable energies offers a promising carbon-free solution for hydrogen generation and storage. The recent developments of proton ceramic electrolysis cells operating at intermediate temperatures bear promise of superior energy efficiency compared to oxide ion conducting electrolytes. Here, a proton ceramic Single Engineering Unit (SEU) design is optimized for steam electrolysis using a computational fluid dynamics (CFD) model implemented in a COMSOL Multiphysics software. The SEU is an all-in-one tubular cell arrangement that constitutes the smallest electrolysis unit and enables efficient, adaptable pressurized hydrogen generation. The parametrical modelling study is conducted for two adiabatic operation scenarios with distinct steam conversion rates and tested for multiple key parameters, namely internal and external chamber pressures and inlet stream temperature. The modelling results show that low steam conversions enable operation at higher current densities and that the thermoneutral voltage for a fixed steam conversion is highly sensitive to the process conditions and operation modes. The increment of the pressure of the generated hydrogen implies a reduced production rate at thermoneutral voltage, although it can be compensated with an enhanced steam pressure or a reduced inlet temperature. Additionally, the introduction of a porous medium as the SEU current collector in the steam chamber enhances heat transport within this chamber. The area specific resistance of the system determines the current density, enforcing an adaption of the area of the electrolyser to satisfy the target hydrogen production and energy efficiency. The resulting proposed SEU design and adapted operational parameters allow effective delivery of pressurized dry hydrogen for a wide range of conditions and applications.

• Zhong, Peng; Toyoura, Kazuaki; Jiang, Lulu; Chen, Lubing; Ismail, Sara Adeeba & Hatada, Naoyuki [Vis alle 8 forfattere av denne artikkelen] (2022). Protonic Conduction in La2NiO4+δ and La2-xAxNiO4+δ (A = Ca, Sr, Ba) Ruddlesden–Popper Type Oxides. Advanced Energy Materials. ISSN 1614-6832. doi: 10.1002/aenm.202200392. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Wragg, David Stephen; Sørby, Magnus Helgerud; Guzik, Matylda; Gunnæs, Anette Eleonora & Szpunar, Iga [Vis alle 12 forfattere av denne artikkelen] (2022). Structural properties of mixed conductor Ba1−xGd1−yLax+yCo2O6−δ. Dalton Transactions. ISSN 1477-9226. 51(48), s. 18667–18677. doi: 10.1039/d2dt02277j. Fulltekst i vitenarkiv Vis sammendrag

  Ba1−xGd1−yLax+yCo2O6−δ (BGLC) compositions with large compositional ranges of Ba, Gd, and La have been characterised with respect to phase compositions, structure, and thermal and chemical expansion. The results show a system with large compositional flexibility, enabling tuning of functional properties and thermal and chemical expansion. We show anisotropic chemical expansion and detailed refinements of emerging phases as La is substituted for Ba and Gd. The dominating phase is the double perovskite structure Pmmm, which is A-site ordered along the c-axes and with O vacancy ordering along the b-axis in the Ln-layer. Phases emerging when substituting La for Ba are orthorhombic Ba-deficient Pbnm and cubic LaCoO3-based R[3 with combining macron]c. When La is almost completely substituted for Gd, the material can be stabilised in Pmmm, or cubic Pm[3 with combining macron]m, depending on thermal and atmospheric history. We list thermal expansion coefficients for x = 0–0.3, y = 0.2.

• Clark, Daniel Ryan; Malerød-Fjeld, Harald; Budd, Michael; Tirados, Irene Yuste; Beeaff, Dustin & Aamodt, Simen [Vis alle 17 forfattere av denne artikkelen] (2022). Single-step hydrogen production from NH3, CH4, and biogas in stacked proton ceramic reactors. Science. ISSN 0036-8075. 376(6591), s. 390–393. doi: 10.1126/science.abj3951. Fulltekst i vitenarkiv Vis sammendrag

  An alternative to directly transporting hydrogen produced at large scales through steam reforming for applications such as vehicular fueling is smaller scale, on-site production from methane or carriers such as ammonia. The hydrogen produced must be separated from co-produced carbon dioxide or nitrogen. Proton ceramic electrochemical reactors can extract pure hydrogen from gas mixtures by electrolytically pumping protons across the membrane at 800°C, but as the extraction proceeds, temperature gradients and entropic effects lead to efficiency drops. Clark et al. developed a nickel-based glass-ceramic composite interconnect that allowed for the design of a more complex reactor pathway (see the Perspective by Shih and Haile). Counterflowing streams balanced heat flows and maintained stable operating conditions that enabled 99% efficiency of hydrogen recovery. —PDS

• Qureishy, Thomas; Løyland, Sverre; Jørgensen, Susanne Jøntvedt; Færgestad, Eline Mosleth; Norby, Truls & Uggerud, Einar (2022). Mechanisms for sonochemical oxidation of nitrogen. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 24(25), s. 15357–15364. doi: 10.1039/d2cp01995g. Fulltekst i vitenarkiv Vis sammendrag

  N2O, and mixtures of N2 and O2, dissolved in water—both in the presence and absence of added noble gases—have been subjected to ultrasonication with quantification of nitrite and nitrate products. Significant increase in product formation upon adding noble gas for both reactant systems is observed, with the reactivity order Ne < Ar < Kr < Xe. These observations lend support to the idea that extraordinarily high electronic and vibrational temperatures arise under these conditions. This is based on recent observations of sonoluminescence in the presence of noble gases and is inconsistent with the classical picture of adiabatic bubble collapse upon acoustic cavitation. The reaction mechanisms of the first few reaction steps necessary for the critical formation of NO are discussed, illustrated by quantum chemical calculations. The role of intermediate N2O in this series of elementary steps is also discussed to better understand the difference between the two reactant sources (N2O and 2 : 1 N2 : O2; same stoichiometry).

• Kang, Xiaolan; Chatzitakis, Athanasios; Aarholt, Thomas; Sun, Xinwei; Negri, Chiara & Norby, Truls (2022). Facet-engineered TiO<inf>2</inf>nanomaterials reveal the role of water-oxide interactions in surface protonic conduction. Journal of Materials Chemistry A. ISSN 2050-7488. 10(1), s. 218–227. doi: 10.1039/d1ta06075a. Fulltekst i vitenarkiv Vis sammendrag

  Water adsorption and surface protonic conduction have been investigated at 25–400 °C in wet (H2O and D2O) atmospheres on nanocrystalline TiO2 hydrothermally grown to a predominance of different crystal facets. In situ Fourier transform infrared spectrometry shows that a portion of the water molecules in the first chemisorbed layer adsorbs dissociatively on the {001} and {100} surfaces, but molecularly on the {101} surface. The next layer of physisorbed molecular water is solid (ice)-like on the {001} and {100} surfaces, a fact that is attributed to relatively strong bonds to the surface terminating hydroxyls. On the other hand, it is looser, liquid-like on the {101} surface due to the lack of rigid hydroxyl groups to bond to. As relative humidity (RH) increases with decreasing temperature, additional water layers physisorb and eventually become liquid-like also on the {001} and {100} surfaces. The differences can be attributed to the different atomic arrangements and surface energies of the different crystal facets. Surface protonic conduction on {001} and {100} dominated samples exhibits high pre-exponentials, indicating a high concentration of sites for dissociative chemisorption, and high activation energies reflecting difficult proton migration in the rigid water layers on those surfaces. The surface protonic conduction on the {101} dominated sample reflects a lower coverage of dissociable water and lower activation enthalpies for protonic migration in the more loosely bonded water. This suggests that, more generally, surfaces with dissociative chemisorption may exhibit high surface protonic conductivity at the highest and lowest temperatures (corresponding to lowest and highest RH, respectively), while surfaces with molecular chemisorption may exhibit a relatively high conductivity (less deep minimum) at intermediate temperatures. H/D isotope effects show that the protonic conduction mechanism changes from Grotthuss to vehicle as the physisorbed water layers gain thickness and become liquid-like. The protonic conductivity decreased when the surface was terminated by more strongly bonded fluoride ions, believed to reflect that they block the sites for water adsorption.

• Madathil, Reshma Krishnan; Schuler, Raphael & Norby, Truls (2022). La1-xSrxMO3 (M = Co, Mn, Cr) interconnects in a 4-leg all-oxide thermoelectric generator at high temperatures. Journal of Physics and Chemistry of Solids. ISSN 0022-3697. 167. doi: 10.1016/j.jpcs.2022.110739. Fulltekst i vitenarkiv Vis sammendrag

  We herein report tests at high temperatures of a 4-leg oxide thermoelectric generator consisting of two pairs of p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO), assembled with various conducting perovskite oxides as interconnects. Using a custom-built testing system, we evaluated performance and stability at a hot side (furnace) temperature of up to 1000 °C under temperature differences up to ΔT = 600 °C in air. With a La0.6Sr0.4CoO3 (LSC) interconnect, a maximum power output of 18 mW was achieved with TH = 940 and TC = 340 °C (ΔT = 600 °C). Power maxima with La0.8Sr0.2MnO3 (LSM) and La0.8Sr0.2CrO3 (LSCr) as interconnects were lower, 6 mW and 2 mW, respectively, under similar conditions, attributed to their lower thermal and electrical conductivities. This demonstrates the requirements and potential of oxide interconnects for stable use of all-oxide thermoelectric generators at high temperatures in ambient air.

• Madathil, Reshma Krishnan & Norby, Truls Eivind (2022). Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators. Solid State Sciences. ISSN 1293-2558. 124. doi: 10.1016/j.solidstatesciences.2021.106801. Fulltekst i vitenarkiv Vis sammendrag

  Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction.

• Both, Kevin Gregor; Reinertsen, Vilde Mari; Aarholt, Thomas; Jensen, Ingvild Julie Thue; Neagu, Dragos & Prytz, Øystein [Vis alle 8 forfattere av denne artikkelen] (2022). Ni-doped A-site excess SrTiO3 thin films modified with Au nanoparticles by a thermodynamically-driven restructuring for plasmonic activity. Catalysis Today. ISSN 0920-5861. 413. doi: 10.1016/j.cattod.2022.11.011. Fulltekst i vitenarkiv Vis sammendrag

  Plasmonically active nanoparticles offer a promising pathway to extend the absorption range of photocatalysts. While not necessarily catalytically active themselves, these particles allow the absorption of lower energy photons in wide band gap photocatalysts. Here, we present A-site excess SrTiO3 thin films, doped with Ni, where through a subsequent exsolution process we created well-socketed Ni nanoparticles in the surface of SrTiO3. These were galvanically replaced by Au, resulting in well-socketed Au nanoparticles with variable size on the surface, depending on the galvanic replacement time. Photoelectrochemical measurements and electron energy loss spectroscopy revealed the improved photoresponse of the thin films by plasmonic activity of the nanoparticles. The energy of the plasmon peak suggests that the main improvement results from the injection of hot charge carriers. Our study opens new avenues for the design and synthesis of the next generation of photocatalytic materials.

Se alle arbeider i NVA

• Wang, Luyang; Sun, Xinwei & Norby, Truls (2026). Surface protonic conduction on oxide and nitride materials at elevated temperatures. Fulltekst i vitenarkiv
• Wang, Luyang; Jiang, Bo; Ferriday, Thomas & Norby, Truls (2026). H2O-modulated surface conduction of NiO: hydration and hydroxylation from ambient to elevated temperatures. Fulltekst i vitenarkiv
• Norby, Truls & Wen, Yabing (2026). Space Charge Layer Impedance of the Solid-Solid Electrode-Electrolyte Interface. Fulltekst i vitenarkiv
• Norby, Truls & Pedersen, Madeeha Khalid (2026). Defect Chemistry for Inherently Disordered LLZO Solid-State Li-Ion Electrolytes. Fulltekst i vitenarkiv
• Wang, Luyang & Norby, Truls (2025). Electronic and protonic surface conduction on Ni1-xO. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Vøllestad, Einar; Singh, Kalpana & Norby, Truls (2025). Influence of bias on electrode reactions for Proton Ceramic Cells. Vis sammendrag

  In this work, we investigate electrode overpotential of positrodes under anodic and cathodic operation. We study how the impedance of several state-of-the-art positrode materials is affected by applied bias and propose a model for decoupling the kinetic and mass transfer contributions to the total electrode polarisation. Furthermore, we investigate how partial electronic conductivity – affected by applied bias – disguise the true electrode impedance. The model is tested for two different electrolytes – BaZr0.7Ce0.2Y0.1O3 (BZCY721) and BaZr0.4Ce0.4Y0.2O3 (BZCY442) – displaying different ionic- to electronic transference numbers and revealing the true influence of p-type conductivity on measured impedance under anodic and cathodic bias. The results enable decoupling of three main charge carriers – electron holes, protons and oxygen vacancies – and show how the partial currents are affected by temperature, pO2 and pH2O. Moreover, the kinetic part of the overpotential is revealed as more influential than previously interpreted from the small low-capacitance charge transfer reaction at the electrolyte-electrode interface as seen by EIS at OCV. The results are obtained by applying voltage over BZCY button-cells with three-electrode configuration in symmetrical atmosphere, and stepwise modelling of electrolyte and electrode impedances for three charge carriers. We propose a correction for the effect of the counter electrode overpotential on p-type conductivity, enabling full modelling of electrode impedance under bias

• Norby, Truls (2025). Advances in solid-state ionics for clean energy through cultural and atomistic diffusion. Fulltekst i vitenarkiv
• Norby, Truls (2025). Development of positrodes for proton ceramic electrolysers. Fulltekst i vitenarkiv
• Petlund, Henrik; Pokle, Anuj; Norby, Truls & Chatzitakis, Athanasios (2025). Front Cover: Iron and Nickel Substituted Perovskite Cobaltites for Sustainable Oxygen Evolving Anodes in Alkaline Environment (ChemSusChem 6/2025). ChemSusChem. ISSN 1864-5631. doi: 10.1002/cssc.202580601. Fulltekst i vitenarkiv
• Norby, Truls; Bjørheim, Tor Svendsen & Polfus, Jonathan (2024). Modelling and Characterization of Negatrodes in Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Wang, Luyang; Sun, Xinwei; Jiang, Bo & Norby, Truls (2024). Water Adsorption and Surface Protonic Conduction on Nickel Oxide (NiO). Fulltekst i vitenarkiv
• Norby, Truls; Sun, Xinwei & Wang, Luyang (2024). Surface protonics - Protonic conduction in adsorbed water on oxide surfaces. Fulltekst i vitenarkiv
• Norby, Truls (2024). Charge and mass transfer in positrodes of proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Wang, Luyang; Sun, Xinwei; Jiang, Bo & Norby, Truls (2024). Minority bulk and surface proton conduction in ceramic positrodes 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
• Sun, Xinwei & Norby, Truls (2024). Charge and mass transfer polarisation of BGLC37 positrodes for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Norby, Truls (2024). Mechanisms and polarisation of electrodes for proton ceramic electrochemical cells (PCECs). Fulltekst i vitenarkiv
• Norby, Truls (2024). Mechanisms and Polarisation of Electrodes for Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv
• Norby, Truls; Sun, Xinwei & Wang, Luyang (2024). Surface protonic conduction in porous oxides. Fulltekst i vitenarkiv
• Norby, Truls; Wu, Mengxin; Ewerhardt, Patrick & Sun, Xinwei (2024). Charge and Mass Transfer Polarisation of Electrodes for 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
• Norby, Truls (2024). Hydrogen og ammoniakk - ren energi. Fulltekst i vitenarkiv
• Norby, Truls (2024). Diffusion and conduction over two sites. Fulltekst i vitenarkiv Vis sammendrag

  A number of crystalline solid electrolytes are based on inherent partial occupancy and disorder rather than aliovalent substitution. Defects and transport can then normally be treated along an extension of the Kröger-Vink notation [1]. However, in some cases, the charge carrying ion diffuses by subsequent jumps through two different partially occupied and disordered sites, as is the case for oxide ions in the complex perovskite-related Ba3MoNbO8.5 (BMN) and Li ions in the cubic garnet polymorph of Li7La3Zr4O12 (LLZO). There is to my knowledge no general treatise of diffusion and conduction in such cases, and specifically there is no adequate defect chemistry for neither BMN nor LLZO. Here, I provide relevant general defect chemical models and show how the transport equations can be derived from the defect chemical reaction rate constants. The result allows prediction of preexponential factors and understanding activation enthalpies, as will be illustrated for BMN and LLZO, and form basis for interpretation of effects of aliovalent doping and nonstoichiometry. [1] T. Norby “A Kröger-Vink-compatible notation for defects in inherently defective sublattices”, J. Korean Ceram. Soc., 47 [1] (2010) 19-25.

• Norby, Truls & Sun, Xinwei (2024). Surface protonics of CeO2. Fulltekst i vitenarkiv
• Norby, Truls (2023). Nomenclature and transport of defects in surface protonics. Fulltekst i vitenarkiv
• Norby, Truls (2023). Transport in electrolytes and electrodes of proton ceramic electrochemical cells (PCECs). Fulltekst i vitenarkiv
• Norby, Truls (2023). Protons in Solids From Young Discovery to Clean Hydrogen Technology. Fulltekst i vitenarkiv
• Norby, Truls (2023). Proton Conducting Ceramics - Science and Applications. Fulltekst i vitenarkiv
• Wang, Luyang; Sun, Xinwei & Norby, Truls (2023). Minority Bulk and Surface Proton Conduction in Positrodes for Proton Ceramic Electrochemical Cells. Fulltekst i vitenarkiv Vis sammendrag

  The positrode is a critical component for proton ceramic steam electrolyzers and fuel cells for hydrogen and ammonia. It constitutes a major contribution to the over-potentials and hence losses in the whole cell, resulting from its limited solubility and diffusivity of protons, which is challenging to characterise and improve. We are introducing a PhD project that aims to establish theoretical frameworks and experimental methodology for measuring protonic conductivities in the bulk and on surfaces of positrode materials. The approaches to reach the goal comprise the use of defect chemistry and transport theory for protons conduction, with the implementation of physiochemical experiments to distinguish signals of protons among other defects and charge carriers and paths on those predominantly electronic conductors. The results will be used as input to other project participants who perform computer simulations and, on that basis, seek strategies for optimization and effects on electrodes in scaled-up cells.

• 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
• Tirados, Irene Yuse; Kjølseth, Christian & Norby, Truls (2023). Understanding the Impedance Puzzle: Analyzing Behavior under Bias of Ni-BZCY Cells for Proton Ceramic Electrochemical Reactor Stacks  . Fulltekst i vitenarkiv
• Norby, Truls (2023). Mechanisms and parameterization of electrodes for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Norby, Truls (2023). Thermodynamics and polarisation of electrodes for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Norby, Truls (2023). Model and parameterisation of positrodes for 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
• Norby, Truls (2023). Solar hydrogen from adsorbed water vapour in all-solid photoelectrochemical cells. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic restructuring of exsolved nanoparticles for plasmonic and electrocatalytic energy conversion. Fulltekst i vitenarkiv
• Sun, Xinwei; Vøllestad, Einar & Norby, Truls (2022). Surface protonic conductivity in chemisorbed and physisorbed water layers in porous nanoscopic CeO2. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Galvanic Restructuring of Exsolved Nanoparticles for Plasmonic and Electrocatalytic Energy Conversion (Small 29/2022 Inside back cover feature). 18(29), s. 2270156–2270156. Fulltekst i vitenarkiv
• Kang, Xiaolan; Chaperman, Larissa; Galeckas, Augustinas; Ammar-Merah, Souad; Mammeri, Fayna & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2022). Water Vapor Photoelectrolysis in an All Solid-State Photoelectrochemical Cell. Fulltekst i vitenarkiv
• Øygarden, Vegar; Vøllestad, Einar; Denonville, Christelle; Vistad, Ørnulv Bjørnsson; Mahmood, Asif & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2022). Development of surface protonic fuel cells. Fulltekst i vitenarkiv
• Chatzitakis, Athanasios; Zhu, Junjie; Gudmundsdottir, Jonina Björg; Strandbakke, Ragnar; Both, Kevin Gregor & Aarholt, Thomas [Vis alle 12 forfattere av denne artikkelen] (2022). A monolithic and noble metal-free photoelectrochemical device of minimal engineering for efficient, unassisted water splitting. Fulltekst i vitenarkiv
• Kang, Xiaolan; Reinertsen, Vilde Mari; Both, Kevin Gregor; Galeckas, Augustinas; Aarholt, Thomas & Prytz, Øystein [Vis alle 9 forfattere av denne artikkelen] (2022). Exsolved nanoparticles, galvanically restructured for tunable photo-electrocatalytic energy conversion. Fulltekst i vitenarkiv
• Balaguer, Maria; Wachowski, Sebastian Lech; Szpunar, Iga; Mielewczyk-Gryn, Aleksandra; Sørby, Magnus Helgerud & Carvalho, Patricia A. [Vis alle 10 forfattere av denne artikkelen] (2022). Double perovskite mixed conductors – Hydration, red-ox, structure and stability. Fulltekst i vitenarkiv
• Clark, Daniel Ryan; Malerød-Fjeld, Harald; Budd, Michael; Tirados, Irene Yuste; Beeaff, Dustin R. & Aamodt, Simen [Vis alle 17 forfattere av denne artikkelen] (2022). Proton ceramic electrochemical reactors for sustainable hydrogen production. Fulltekst i vitenarkiv Vis sammendrag

  Electrochemical gas separation emerges as an attractive technology as the cost of electricity declines. Proton ceramic electrochemical reactors (PCERs) extract hydrogen from reaction mixtures and can offer a compact and efficient approach to hydrogen production [1]. Because of the solid-state and gas-impermeable nature of the membrane, the hydrogen produced can in principle be entirely free of impurities, as unreacted molecules cannot get to the other side of the membrane. Through a one-step process, balancing the energy from the endothermic reactions with the separation and compression of hydrogen allows for much higher efficiencies compared with other hydrogen production technologies. In the case of CH4 reforming, the possibility of extracting H2 at conditions suitable for the reforming reaction enables the overcome of the thermodynamic limitations in terms of CH4 conversion. Furthermore, the electrochemical H2 compression allows to go beyond the driving force limitation of traditional membrane reactors (based for example on Pd membranes). PCERs offer attractive performance including mechanical stability and chemical robustness over a wide range of temperatures (300–800 °C) and pressure conditions (> 50 bar). In our recent work [2], we demonstrate the upscaling of an efficient 36 cell x 15 cm2 reactor with coupled heat, reaction and current distribution. Hydrogen extraction > 99 % shows complete conversion of CH4 for conditions relevant both for natural gas and biogas, and a hydrogen purity up to 99.995 %. The by-product leaving the reactor is a concentrated CO2 stream, which can facilitate the implementation of efficient carbon capture. The results suggests that proton ceramic electrochemical reactors can offer the lowest CO2 intensity for on-site hydrogen production. Furthrmore, to expand on the wide applicability and flexibility of the proposed technology, cell performance for ammonia decomposition will be presented, showing similar conversion with both anhydrous and aqueous NH3.

• Norby, Truls; Ma, Quanbao; Qureishy, Thomas & Uggerud, Einar (2022). Plasma-enhanced ammonia synthesis over nanoscopic Ru/CeO2. Fulltekst i vitenarkiv
• Sun, Xinwei; Vøllestad, Einar & Norby, Truls (2022). Surface protonics - a tutorial. Fulltekst i vitenarkiv
• Norby, Truls (2022). Defects and transport in inherently disordered oxide structures. Fulltekst i vitenarkiv
• Pedersen, Madeeha Khalid & Norby, Truls (2022). Defect Models for Li-Ion Transport in Al- and Nb-Doped LLZO. Fulltekst i vitenarkiv
• Norby, Truls (2022). Chemistry of high-temperature thermoelectric oxides and TEGs. Fulltekst i vitenarkiv
• Norby, Truls (2022). Proton ceramics for energy applications. Fulltekst i vitenarkiv
• Both, Kevin Gregor; Reinertsen, Vilde Mari; Kang, Xiaolan; Aarholt, Thomas; Neagu, Dragos & Prytz, Øystein [Vis alle 8 forfattere av denne artikkelen] (2022). Improved Photoelectrochemical Performance of SrTiO3 by Plasmonically Active Au Nanoparticles. Fulltekst i vitenarkiv
• Both, Kevin Gregor; Reinertsen, Vilde Mari; Kang, Xiaolan; Neagu, Dragos; Prytz, Øystein & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2022). Thin Film Exsolution of Metal Nanoparticles and Their Galvanic Restructuring for Plasmonically Enhanced Photocatalytic Activity. Fulltekst i vitenarkiv
• Norby, Truls (2022). Defects and transport in proton conducting ceramics for energy applications. Fulltekst i vitenarkiv
• Bogen, Mari Saure; Marchetti, Jorge Mario; Norby, Truls & Hektor, Erik Andreas (2023). Recent advances in direct ammonia fuel cells and systems : a literature review. Norges miljø- og biovitenskapelige universitet (NMBU). Fulltekst i vitenarkiv Vis sammendrag

  Ammonia has over the last two decades emerged as a promising carbon-free energy carrier due to its higher volumetric energy density and more widely developed distribution infrastructure compared to hydrogen. This makes ammonia a more encouraging alternative with regard to transportation and energy storage in a low-carbon energy future. The direct use of ammonia in fuel cells has been investigated through a literature review on solid oxide fuel cells (proton conducting (PCFC) and oxide ion conducting (SOFC-O)), and anion exchange membrane (AEMFC) fuel cell technologies. The study has been executed with a particular focus on the most recent advances, in addition to a mapping of which challenges to overcome to enable commercial relevance for these technologies. Oxide ion conducting SOFC-O stands out as the most mature technology for ammonia, with performances similar to H$_{2}$ in larger systems. The proton-conducting PCFC is following close behind with equivalent peak power densities as SOFC-O at cell-level. However, the scale-up within PCFC has not yet been reported for ammonia-fed PCFC. Stability and durability are challenges for both solid oxide technologies, where nickel nitriding is the major degradation mechanism. Another hindrance is the unsatisfactory ammonia decomposition at lowered operating temperatures. The anion exchange membrane fuel cell emerges as a promising, yet immature low-temperature technology that has shown considerable advancements in the last decade. The most notable challenges here are slow ammonia oxidation, membrane stability problems, a significant amount of fuel crossover, and poor interface charge transfer between the electrodes and the membrane.

• Sun, Xinwei & Norby, Truls (2023). Quantification of surface protonic conduction in porous oxides. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The present work provides a fundamental and methodological framework for parameterisation of the thermodynamics and kinetics involved in surface protonic conduction of porous ionic oxides. A novel nomenclature for defect surface species is introduced. The surface protonic conductances have been estimated where various proton migration routes were considered. A brick layer model is developed that connects surface conductance with macroscopic sample conductivity via microstructural parameters. This allows quantitative discrimination between types of adsorption and surface transport in the different water layers on oxide surfaces, supported by water vapour partial pressure dependencies and enthalpies of adsorption and conductivity. The enthalpies for protonic surface mobility for oxides decrease systematically with lower temperatures (higher relative humidity) as the water layers grow in coverage and thickness and protons go from jumping between surface oxide ions to jumping between loosely bonded adsorbed hydroxide ions and water molecules. The findings and models developed in this work contribute to the understanding and control of surface protonics in porous oxides, which is believed to play an important role in electrochemical and photoelectrochemical cells, humidity sensors, and heterogeneous catalysis.

• Both, Kevin Gregor; Chatzitakis, Athanasios; Bergum, Kristin; Hansen, Per-Anders Stensby; Prytz, Øystein & Norby, Truls (2023). Plasmonically Enhanced Photocatalysis: Synthesis, Physical Properties, and Applications. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  In this work, plasmonic metal nanoparticles (MNPs) are utilized to improve the photoelectrochemical (PEC) response of strontium titanate (STO). These MNPs were introduced by either direct exsolution, i.e., nickel (Ni), copper (Cu), iron (Fe), ruthenium (Ru), and silver (Ag), or by galvanically replacing exsolved less noble MNPs, i.e., Ni by Gold (Au), or Cu for Ag. Au, Ag, and Cu were the materials chosen with significant plasmonic activity; Fe, Ru, Pt, and Ni were used to make MNPs with minimal plasmonic response. Two different stoichiometries of STO were synthesized. One, La-doped A-site deficient STO (La0.6Sr0.2Ti0.9Ni0.1O3–x), was exclusively doped with Ni and utilized as powder samples. The other stoichiometry was A-site excess STO (Sr1.07Ti0.93M0.07O3±δ, where M is the dopant) was doped with various metals. These excess perovskites were studied in thin film and powder forms. A-site excess STO thin films were deposited by pulsed laser deposition on silicon substrates. The as-deposited thin films appeared nanocrystalline or amorphous until the exsolution process was engaged. The exsolution step was studied explicitly for these A-site excess STO thin films where the formation of MNPs occurred not only at or near the thin film surface but also on grain interfaces and in bulk. Moreover, the dopant diffused significantly during the process. While the size of the template particles depended on the exsolution conditions, the galvanic replacement reaction determined the shapes and sizes of the newly formed MNPs. The replacement time and the form (thin film/powder) of STO influenced the results, both completely replaced particles and partially replaced particles with complex structures were obtained. Additionally, more prolonged galvanic replacement reactions lead to larger particles. In turn, the specific shape of the plasmonic MNPs determined the localized surface plasmon resonance band shape and peak position. Overall, exsolution leads to well-socketed MNPs, a property seemingly inherited by the MNPs created by galvanic replacement. Well-socketed MNPs are extremely difficult to obtain by any other technique and have a favorable localized surface plasmon resonance peak shift. The PEC response revealed that reducing STO first decreases the material’s response. Reducing it further, however, increases the PEC response significantly. Au MNPs increase the PEC performance until the MNPs reach a specific size and subsequently decrease the PEC performance when growing more prominent. This work highlights the ease by which well-socketed plasmonic MNPs can be created, some impossible to synthesize by another technique, and how different reaction conditions can change the shape and size of the MNPs, ultimately tuning the localized surface plasmon resonance band shape and peak position. The method of exsolution and galvanic replacement reaction was generalized by utilizing different elements, implying that the tuning of catalytic activity depends on the choice of elements and reaction conditions.

• Storhaug, Sjur; Haugsrud, Reidar & Norby, Truls (2022). Sintering and electrical properties of proton conducting BSZCY151020. Universitetet i Oslo. Fulltekst i vitenarkiv
• Chen, Henry; Norby, Truls; Haugsrud, Reidar & Dayaghi, Amir Masoud (2022). Sintering Behavior and Conductivity of (Ba0.85Sr0.15)(Zr0.7Ce0.1Y0.2)O3-δ Doped with ZnO as Sintering Aid. Universitetet i Oslo. Fulltekst i vitenarkiv

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