Athanasios Chatzitakis

• Dahl, Øystein; Sunding, Martin Fleissner; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene; Grandcolas, Mathieu & Andreassen, Magnus [Vis alle 10 forfattere av denne artikkelen] (2023). Interrogation of the Interfacial Energetics at a Tantalum Nitride/Electrolyte Heterojunction during Photoelectrochemical Water Splitting by Operando Ambient Pressure X-ray Photoelectron Spectroscopy. ACS Catalysis. ISSN 2155-5435. 13(17), s. 11762–11770. doi: 10.1021/acscatal.3c02423. Fulltekst i vitenarkiv
• 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.

• 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.

• Touni, Aikaterini; Liu, Xin; Kang, Xiaolan; Papoulia, Chrysanthi; Pavlidou, Eleni & Lambropoulou, Dimitra [Vis alle 9 forfattere av denne artikkelen] (2022). Methanol Oxidation at Platinum Coated Black Titania Nanotubes and Titanium Felt Electrodes. Molecules. ISSN 1431-5157. 27(19), s. 1–15. doi: 10.3390/molecules27196382. 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. ISSN 1613-6810. 18(29). doi: 10.1002/smll.202201106. Fulltekst i vitenarkiv
• Liu, Xin; Risbakk, Sanne; Almeida Carvalho, Patricia; 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.

• 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
• Touni, Aikaterini; Liu, Xin; Kang, Xiaolan; Almeida Carvalho, Patricia; Diplas, Spyridon & Both, Kevin Gregor [Vis alle 8 forfattere av denne artikkelen] (2021). Galvanic Deposition of Pt Nanoparticles on Black TiO2 Nanotubes for Hydrogen Evolving Cathodes. ChemSusChem. ISSN 1864-5631. 14(22), s. 4993–5003. doi: 10.1002/cssc.202101559. Fulltekst i vitenarkiv Vis sammendrag

  A galvanic deposition method for the in-situ formation of Pt nanoparticles (NPs) on top and inner surfaces of high-aspect-ratio black TiO2-nanotube electrodes (bTNTs) for true utilization of their total surface area has been developed. Density functional theory calculations indicated that the deposition of Pt NPs was favored on bTNTs with a preferred [004] orientation and a deposition mechanism occurring via oxygen vacancies, where electrons were localized. High-resolution transmission electron microscopy images revealed a graded deposition of Pt NPs with an average diameter of around 2.5 nm along the complete nanotube axis (length/pore diameter of 130 : 1). Hydrogen evolution reaction (HER) studies in acidic electrolytes showed comparable results to bulk Pt (per geometric area) and Pt/C commercial catalysts (per mg of Pt). The presented novel HER cathodes of minimal engineering and low noble metal loadings (μg cm−2 range) achieved low Tafel slopes (30–34 mV dec−1) and high stability in acidic conditions. This study provides important insights for the in-situ formation and deposition of NPs in high-aspect-ratio structures for energy applications.

• Kang, Xiaolan; Chaperman, Larissa; Galeckas, Augustinas; Ammar, Souad; Mammeri, Fayna & Norby, Truls [Vis alle 7 forfattere av denne artikkelen] (2021). Water Vapor Photoelectrolysis in a Solid-State Photoelectrochemical Cell with TiO2 Nanotubes Loaded with CdS and CdSe Nanoparticles. ACS Applied Materials & Interfaces. ISSN 1944-8244. 13(39), s. 46875–46885. doi: 10.1021/acsami.1c13047. Fulltekst i vitenarkiv
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Backe, Paul Hoff; Ruan, Qiushi; Tang, Junwang & Rise, Frode [Vis alle 8 forfattere av denne artikkelen] (2021). In situ cofactor regeneration enables selective CO2 reduction in a stable and efficient enzymatic photoelectrochemical cell. Applied Catalysis B: Environmental. ISSN 0926-3373. 296. doi: 10.1016/j.apcatb.2021.120349. Fulltekst i vitenarkiv Vis sammendrag

  Mimicking natural photosynthesis by direct photoelectrochemical (PEC) reduction of CO2 to chemicals and fuels requires complex cell assemblies with limitations in selectivity, efficiency, cost, and stability. Here, we present a breakthrough cathode utilizing an oxygen tolerant formate dehydrogenase enzyme derived from clostridium carboxidivorans and coupled to a novel and efficient in situ nicotinamide adenine dinucleotide (NAD+/NADH) regeneration mechanism through interfacial electrochemistry on g-C3N4 films. We demonstrate stable (20 h) aerobic PEC CO2-to-formate reduction at close to 100 % faradaic efficiency and unit selectivity in a bio-hybrid PEC cell of minimal engineering with optimized Ta3N5 nanotube photoanode powered by simulated sunlight with a solar to fuel efficiency of 0.063 %, approaching that of natural photosynthesis.

• Zhu, Junjie; Gudmundsdottir, Jonina Björg; Strandbakke, Ragnar; Both, Kevin Gregor; Aarholt, Thomas & Almeida Carvalho, Patricia [Vis alle 12 forfattere av denne artikkelen] (2021). Double Perovskite Cobaltites Integrated in a Monolithic and Noble Metal-Free Photoelectrochemical Device for Efficient Water Splitting. ACS Applied Materials & Interfaces. ISSN 1944-8244. 13(17), s. 20313–20325. doi: 10.1021/acsami.1c01900. Fulltekst i vitenarkiv Vis sammendrag

  Water photoelectrolysis has the potential to produce renewable hydrogen fuel, therefore addressing the intermittent nature of sunlight. Herein, a monolithic, photovoltaic (PV)-assisted water electrolysis device of minimal engineering and of low (in the μg range) noble-metal-free catalysts loading is presented for unassisted water splitting in alkaline media. An efficient double perovskite cobaltite catalyst, originally developed for high-temperature proton-conducting ceramic electrolyzers, possesses high activity for the oxygen evolution reaction in alkaline media at room temperatures too. Ba1–xGd1–yLax+yCo2O6−δ (BGLC) is combined with a NiMo cathode, and a solar-to-hydrogen efficiency of 6.6% in 1.0 M NaOH, under 1 sun simulated illumination for 71 h, is demonstrated. This work highlights how readily available earth-abundant materials and established PV methods can achieve high performance and stable and monolithic photoelectrolysis devices with potential for full-scale applications.

• Kang, Xiaolan; Berberidou, Chrysanthi; Galeckas, Augustinas; Bazioti, Kalliopi; Sagstuen, Einar & Norby, Truls Eivind [Vis alle 8 forfattere av denne artikkelen] (2021). Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders. Catalysts. ISSN 2073-4344. 11(2). doi: 10.3390/catal11020228. Fulltekst i vitenarkiv
• Chaguetmi, Samiha; Chaguetmi, Salem; Sobti, Nadjah; Belkahla, Hanène; Chaperman, Larissa & Chatzitakis, Athanasios Eleftherios [Vis alle 9 forfattere av denne artikkelen] (2020). Enhancement of the photoelectrochemical properties of TiO2 nanofibers supported on Ti sheets by polyol-made CdSe quantum-dots impregnation. Materials Letters. ISSN 0167-577X. 273. doi: 10.1016/j.matlet.2020.127934.
• Sun, Xinwei; Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2020). Photocatalytic generation of gas phase reactive oxygen species from adsorbed water: Remote action and electrochemical detection. Journal of Environmental Chemical Engineering. ISSN 2213-3437. doi: 10.1016/j.jece.2020.104809. Fulltekst i vitenarkiv Vis sammendrag

  The improvement of indoor environments is of great importance as it can significantly improve human health, comfort and productivity. Herein, different forms of TiO2 nanorods were used as the photocatalyst for generation of reactive oxygen species (ROS) in a gas phase photoreactor under controlled humidity. Several parameters were investigated by monitoring the remote decolourisation of Methylene Blue (MB) embedded in a Nafion film. A decolourisation of 26% under 80% relative humidity was observed when the MB film was 0.5 cm away from the photocatalyst. The length and ratio of light/dark intervals have major impacts on the efficiency of the gas phase photocatalytic process, which we link to the amount of water adsorbed on the photocatalyst, as the source for hydroxyl radicals. Furthermore, the photocatalytic production of ROS was quantified through a polyaniline electrochemical sensor and a rate of 1 · 10*12 of ROS molecules s−1 was estimated. This study contributes to the efficacy of the gas phase photocatalytic method in air decontamination, for the development of efficient air cleaning devices.

• Getz, Marit Norderhaug; Chatzitakis, Athanasios Eleftherios; Liu, Xin; Almeida Carvalho, Patricia; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2020). Voids in walls of mesoporous TiO2 anatase nanotubes by controlled formation and annihilation of protonated titanium vacancies. Materials Chemistry and Physics. ISSN 0254-0584. 239. doi: 10.1016/j.matchemphys.2019.121953. Vis sammendrag

  Amorphous TiO2 nanotubes (TNTs) grown anodically on Ti metal in aqueous electrolytes show a crystallization behaviour strongly dependent on the atmosphere used during annealing at high temperature. In wet oxidizing conditions, the amorphous TNTs walls transform into relatively large and well crystallized anatase-like domains permeated by prismatic voids. On the other hand, crystallization of the amorphous nanotubes under dry reducing conditions induces nanocrystalline aggregates that do not show prismatic voids and exhibit different electronic properties. Supported by density functional theory calculations, it is argued that the formation or absence of voids can be understood in terms of formation and condensation of protonated titanium vacancies. Tunable morphology through defect chemical engineering as such, enables TNTs with increased surface area and catalytic activity, which find potential application in supercapacitors, sensors, photocatalysis, photoelectrochemistry, and dye-sensitized solar cells.

• Barakezehi, Marjan; Montazer, Majid; Sharif, Farhad; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2020). MOF-modified polyester fabric coated with reduced graphene oxide/polypyrrole as electrode for flexible supercapacitors. Electrochimica Acta. ISSN 0013-4686. 336. doi: 10.1016/j.electacta.2020.135743. Fulltekst i vitenarkiv
• Andersen, Håkon; Xu, Kaiqi; Malyshkin, Dmitry; Strandbakke, Ragnar & Chatzitakis, Athanasios Eleftherios (2020). A highly efficient electrocatalyst based on double perovskite cobaltites with immense intrinsic catalytic activity for water oxidation. Chemical Communications. ISSN 1359-7345. 56(7), s. 1030–1033. doi: 10.1039/c9cc08765f.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Risbakk, Sanne; Yang, Mingyi; Backe, Paul Hoff & Grandcolas, Mathieu [Vis alle 8 forfattere av denne artikkelen] (2020). High performance and toxicity assessment of Ta3N5 nanotubes for photoelectrochemical water splitting. Catalysis Today. ISSN 0920-5861. doi: 10.1016/j.cattod.2019.12.031. Fulltekst i vitenarkiv Vis sammendrag

  In this work, Co-based cocatalysts are electrodeposited on mesoporous Ta3N5 nanotubes. The electrodeposition time is varied and the optimized photoelectrode reaches a photocurrent density of 6.3 mA/cm2 at 1.23 V vs. SHE, under simulated solar illumination of 1 Sun, in 1 M NaOH. The best performing electrode, apart from the high photocurrent density, shows improved stability under intense photoelectrochemical water splitting conditions. The dual function of the cocatalyst to improve not only the photoelectrochemical performance, but also the stability, is highlighted. Moreover, we adopted a simple protocol to assess the toxicity of Co and Ta contained nanostructured materials (representing used photoelectrodes) employing the human cell line HeLa S3 as target cells.

• Liu, Xin; Almeida Carvalho, Patricia; Getz, Marit Norderhaug; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2019). Black Anatase TiO2 Nanotubes with Tunable Orientation for High Performance Supercapacitors. Journal of Physical Chemistry C. ISSN 1932-7447. 126(36), s. 21391–21940. doi: 10.1021/acs.jpcc.9b05070. Vis sammendrag

  Black TiO2 is a versatile material that finds many applications in the field of photocatalysis but also in energy storage devices, such as supercapacitors. In this work, a new method is developed for the synthesis of black TiO2 in the form of nanotubes. Amorphous TiO2 nanotubes (TNTs) are annealed and reduced in the presence of CaH2, and by a simple manipulation, we are able to obtain control over the preferred crystal orientation. The reduced TNTs show high power and energy densities, as well as unprecedented stability under intensive charge/discharge cycling. The oriented reduced TNTs show metallic-like behavior with improved conductivity when compared to the polycrystalline analogue. This work contributes to the development of highly robust and efficient oxides for electrode material in supercapacitors.

• Chatzitakis, Athanasios Eleftherios & Longela, Simon Makusudi (2019). Electrochemical characterisation of bovine serum albumin adsorption on phenolic- coated nickel-titanium. Journal of Engineering Science and Technology Review. ISSN 1791-9320. 12(2), s. 1–8. doi: 10.25103/jestr.122.01.
• Sun, Xinwei; Simonsen, Stian Christopher; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2019). Composite Membranes for High Temperature PEM Fuel Cells and Electrolysers: A Critical Review. Membranes. ISSN 2077-0375. 9(7). doi: 10.3390/membranes9070083.
• Grandcolas, Mathieu; Wabende, Brian; Yang, Juan; Mei, Sen; Xu, Kaiqi & Norby, Truls Eivind [Vis alle 7 forfattere av denne artikkelen] (2019). Preparation of TiO2 rutile nanorods decorated with cobalt oxide nanoparticles for solar photoelectrochemical activity. Materials Letters. ISSN 0167-577X. 247, s. 1–3. doi: 10.1016/j.matlet.2019.03.087. Fulltekst i vitenarkiv Vis sammendrag

  The present paper investigates the preparation of titanium dioxide (TiO2) nanorods decorated with cobalt oxide (Co3O4) nanoparticles and its application as solar photoelectrocatalyst. TiO2 rutile nanorods have been prepared on conductive glass via a hydrothermal reaction in acidic media, shaped as squared rods with an average length of 1.7 µm and thicknesses between 50 and 120 nm. Co3O4 nanoparticles with an average diameter of 30 nm were synthesized using a simple precipitation method. Spin coating the nanoparticles on the TiO2 nanorods shows enhanced photocurrents under simulated solar light up to 1.3 mA/cm2 at 1.6 V vs. SHE.

• Barakezehi, Marjan; Montazer, Majid; Sharif, Farhad; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2019). A textile-based wearable supercapacitor using reduced graphene oxide/polypyrrole composite. Electrochimica Acta. ISSN 0013-4686. 305, s. 187–196. doi: 10.1016/j.electacta.2019.03.058.
• Chatzitakis, Athanasios Eleftherios & Sartori, Sabrina (2019). Recent Advances in the Use of Black TiO2 for Production of Hydrogen and Other Solar Fuels. ChemPhysChem. ISSN 1439-4235. 20(10), s. 1272–1281. doi: 10.1002/cphc.201801094. Fulltekst i vitenarkiv
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Vøllestad, Einar; Ruan, Qiushi; Tang, Junwang & Norby, Truls Eivind (2019). Hydrogen from wet air and sunlight in a tandem photoelectrochemical cell. International Journal of Hydrogen Energy. ISSN 0360-3199. 44(2), s. 587–593. doi: 10.1016/j.ijhydene.2018.11.030. Fulltekst i vitenarkiv
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Jensen, Ingvild Julie Thue; Grandcolas, Mathieu & Norby, Truls Eivind (2019). Ta3N5/Co(OH)x composites as photocatalysts for photoelectrochemical water splitting. Photochemical and Photobiological Sciences. ISSN 1474-905X. 18(4), s. 837–844. doi: 10.1039/c8pp00312b. Fulltekst i vitenarkiv
• Sun, Xinwei; Xu, Kaiqi; Fleischer, Christian; Liu, Xin; Grandcolas, Mathieu & Strandbakke, Ragnar [Vis alle 9 forfattere av denne artikkelen] (2018). Earth-abundant electrocatalysts in proton exchange membrane electrolyzers. Catalysts. ISSN 2073-4344. 8:657(12), s. 1–41. doi: 10.3390/catal8120657. Fulltekst i vitenarkiv Vis sammendrag

  In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.

• Fleischer, Christian; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2018). Intrinsic photoelectrocatalytic activity in oriented, photonic TiO2 nanotubes. Materials Science in Semiconductor Processing. ISSN 1369-8001. 88, s. 186–191. doi: 10.1016/j.mssp.2018.08.009. Vis sammendrag

  In this work, we grow oriented photonic TiO2 nanotubes (TNTs) with a well-established anodization method and their intrinsic catalytic and electronic properties are studied by means of (photo)electrochemical methods. The oriented photonic TNTs are assessed by the RctCdl (ΩF) product, which is a measure of the intrinsic photoelectrocatalytic activity (IPA) of the material. The RctCdl product decouples any surface area effects and it can be applied at any potential and accompanied reaction without knowing the actual electrochemically active surface area (EASA). Moreover, electrochemical impedance spectroscopy (EIS) is used in order to investigate the frequency dispersion in the single frequency Mott-Schottky (MS) measurement. The choice of frequency and the frequency dispersion in MS measurements in nanostructured and of high surface area semiconductors are rarely addressed and can result in erroneous values of two important parameters, i.e. flat band position and donor or acceptor densities. This work provides further insights into important electrochemical aspects and catalytic properties of high surface area nanomaterials for photoelectrochemical applications.

• Longela, Simon M & Chatzitakis, Athanasios Eleftherios (2017). In vitro corrosion behaviour of phenolic coated nickel-titanium surfaces. Biosurface and Biotribology. ISSN 2405-4518. 6(1), s. 25–30. doi: 10.1016/j.bsbt.2017.10.002.
• Chatzitakis, Athanasios Eleftherios; Grandcolas, Mathieu; Xu, Kaiqi; Mei, Sen; Yang, Juan & Jensen, Ingvild Julie Thue [Vis alle 8 forfattere av denne artikkelen] (2017). Assessing the photoelectrochemical properties of C, N, F codoped TiO2 nanotubes of different lengths. Catalysis Today. ISSN 0920-5861. 287, s. 161–168. doi: 10.1016/j.cattod.2016.11.040. Fulltekst i vitenarkiv Vis sammendrag

  The aim of this work has been the photoelectrochemical (PEC) study of nanostructured photoanodes based on TiO2. Highly ordered and well adhered TiO2 nanotubes (TNTs) of different lengths (∼2–20 μm) were prepared in a two-step process in ethylene glycol solutions containing fluorides, and detailed XPS analysis showed that they have become co-doped with C, N and F. PEC measurements revealed that increasing surface area is not followed by increase in the photoconversion efficiency, but rather that an optimal balance between electroactive surface area (ESA) and charge carrier concentration exists. TNTs of around 10 μm show the optimum incident photon-to-current efficiency (IPCE) of ∼33% and an overall photoconversion efficiency of ∼6.3% under UV illumination of 4 mW cm−2 light intensity. Finally, Mott-Schottky analysis revealed significant frequency dispersion of the estimated space charge layer capacitance, which renders the accurate estimation of the flatband position and charge carrier concentration unreliable. On the other hand, more realistic charge carrier concentrations can be obtained by normalizing the capacitance per ESA.

• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios & Norby, Truls (2017). Solid-state photoelectrochemical cell with TiO2 nanotubes for water splitting. Photochemical and Photobiological Sciences. ISSN 1474-905X. 16(1), s. 10–16. doi: 10.1039/c6pp00217j. Fulltekst i vitenarkiv

Se alle arbeider i Cristin

• Dahl, Øystein; Sunding, Martin Fleissner; Thøgersen, Annett; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene & Grandcolas, Mathieu [Vis alle 10 forfattere av denne artikkelen] (2023). Direct observation of interfacial energetics at Ta3N5/electrolyte and Ta3N5/NiOx/electrolyte heterojunctions by operando ambient pressure X-ray photoelectron spectroscopy during photoelectrochemical water splitting.
• Dahl, Øystein; Sunding, Martin Fleissner; Thøgersen, Annett; Killi, Veronica Anne-Line Kathrine; Svenum, Ingeborg-Helene & Grandcolas, Mathieu [Vis alle 10 forfattere av denne artikkelen] (2023). Operando observation of interfacial energetics at the Ta3N5/electrolyte heterojunction by ambient pressure X-ray photoelectron spectroscopy for photoelectrochemical water splitting .
• 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.
• 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.
• 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 .
• 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.
• 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.
• 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). Small. ISSN 1613-6810. 18(29).
• 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 .
• Chatzitakis, Athanasios (2021). Her splittes vann til hydrogen og oksygen bare ved hjelp av sollys.
• Kuvshinov, Mikhail; Karazhanov, Smagul; Hallsteinsen, Ingrid & Chatzitakis, Athanasios (2021). Synthesis and characterization of Ni-Mo alloy for applications as cathodes in photoelectrochemical (PEC) cells.
• Chatzitakis, Athanasios (2021). Solar Hydrogen Production.
• Chaperman, Larissa; Mammeri, Fayna; Chatzitakis, Athanasios & Ammar, Souad (2021). Functionally graded, soft chemistry processed titania photoanode for water-splitting in liquid and gas phases.
• Chatzitakis, Athanasios (2021). Fuel(s) from the Sun.
• Karazhanov, Smagul; Zavorotynska, Olena & Chatzitakis, Athanasios (2021). Organizing online international school "Materials and processes for production of solar hydrogen" within the “Complex of online and onsite lectures on materials for hydrogen generation by solar water splitting” med acronym” (COOL LONGBOAT) project.
• Karazhanov, Smagul; Zavorotynska, Olena & Chatzitakis, Athanasios (2021). Book of abstracts of the online international school "Materials and processes for production of solar hydrogen".
• Touni, Aikaterini; Liu, Xin; Chatzitakis, Athanasios Eleftherios; Kang, Xiaolan; Spyridou, Olga & Sotiropoulos, Sotiris (2021). Platinized Black Titania Nanotube HER Cathodes prepared by the Galvanic Deposition Method at CaH2-reduced Titania Nanotubes.
• Liu, Xin; Risbakk, Sanne; Almeida Carvalho, Patricia; Yang, Mingyi; Backe, Paul Hoff & Bjorås, Magnar [Vis alle 8 forfattere av denne artikkelen] (2020). Hydrogenase-assisted catalysis on titania electrode oxides. Vis sammendrag

  The widespread use of fuel cells and water splitting devices for energy generation and storage is limited by the dependence on noble metal catalysts. There is thus a tremendous need for the development of efficient electrocatalysts based on Earth-abundant elements. Nature inspired hydrogenases (HydA) are metallo-enzymes that catalyze the reversible reaction of H2 to protons and electrons. Hydrogenases containing Fe at the active sites, known as [FeFe]-HydA, show activities comparable to that of Pt. This work addresses a new class of electrodes for [FeFe]-HydA attachment and bio-assisted catalysis based on TiO2 nanotubes. The conducting oxide material provides suitable electronic conduction and hydrophilicity, while the nanostructure ensures tunability (tube length, crystal orientation and pore diameter) and high surface area for HydA attachment. In this work, electron microscopy is used to characterize the bio-electrodes. Based on the experimental findings, density functional theory (DFT) calculations are used to probe the catalytic reaction sites on the HydA and address the interaction between enzymes and TiO2. The novel bioelectrode will be employed in a system of artificial photosynthesis and generation of solar fuels by simultaneous water splitting and CO2 capture and utilization.

• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Backe, Paul Hoff; Ruan, Qiushi; Tang, Junwang & Bjørås, Magnar [Vis alle 8 forfattere av denne artikkelen] (2020). The use of NMR to assess the activity of formate dehydrogenase biocatalysts for CO2 utilization.
• Chatzitakis, Athanasios (2019). Sol + luftfuktighet = hydrogen = ren energi.
• Chatzitakis, Athanasios Eleftherios (2019). Prospects of photoelectrochemical water electrolysis and the production of solar fuels.
• Liu, Xin; Chatzitakis, Athanasios Eleftherios; Almeida Carvalho, Patricia; Risbakk, Sanne; Yang, Mingyi & Backe, Paul Hoff [Vis alle 7 forfattere av denne artikkelen] (2019). Enzyme-assisted Catalysis on Titania Electrodes.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Norby, Truls Eivind & Bjørheim, Tor Svendsen (2019). Ta3N5 nanotubes loaded with Co(OH)x/Co-Pi-high photocurrent densities and improved photocorrosion resistance .
• Chatzitakis, Athanasios Eleftherios (2019). Artificial Photosynthesis: Mimicking nature for a sustainable energy future.
• Chatzitakis, Athanasios Eleftherios (2019). Can we make fuel in the future from… simply air? .
• Sun, Xinwei; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2019). Composite membranes for high temperature PEM fuel cells and electrolysers. Vis sammendrag

  Polymer electrolyte membrane(PEM) fuel cells and electrolysers offer efficient use and production of H2 for emission-free transport and sustainable energy systems. In order to reduce the cost,complexity,flooding,catalyst poisoning and degradation,operation above 80°C and at lower relative humidities(RH) is preferable. Acid doped polybenzimidazole(PBI),sulfonated polyetheretherketone(SPEEK) and their composites are being investigated for high temperature and low RH operation with sufficient conductivities. We take a critical view and a surface protonic approach to gain fundamental insight.

• Sun, Xinwei; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2019). Polymer-ceramic composite membranes for intermediate temperature PEM fuel cells.
• Xu, Kaiqi; Grandcolas, Mathieu; Yang, Juan; Mei, Sen; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2019). Photoelectrochemical water splitting on Ta3N5 nanotubes for H2 production .
• Liu, Xin; Chatzitakis, Athanasios Eleftherios; Almeida Carvalho, Patricia; Backe, Paul Hoff; Yang, Mingyi & Bjørås, Magnar [Vis alle 7 forfattere av denne artikkelen] (2018). Enzyme-assisted Catalysis on Black Titania Electrodes.
• Sun, Xinwei; Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2018). Can hydroxyl radicals travel far? Gas phase transport and detection after photocatalytic generation at TiO2 nanorods.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Vøllestad, Einar; Ruan, Qiushi; Tang, Junwang & Norby, Truls Eivind (2018). Solid-state tandem photoelectrochemical cell for wet air electrolysis and hydrogen production .
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2018). Surface modification of Ta3N5 nanotubes as photocatalyst for photoelectrochemical water splitting.
• Chatzitakis, Athanasios Eleftherios; Simonsen, Stian; Fontaine, Marie Laure; Thomassen, Magnus & Norby, Truls Eivind (2018). Conductivity of polymer-ceramic composite membranes at high T and p(H2O) using a novel PEEK sample holder.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Vøllestad, Einar; Ruan, Qiushi; Tang, Junwang & Norby, Truls Eivind (2018). Solid-state photoelectrochemical cell for wet air electrolysis and hydrogen production.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Norby, Truls Eivind; Grandcolas, Mathieu; Yang, Juan & Mei, Sen (2018). Ta3N5 / Co(OH)x composite as the photocatalyst for photoelectrochemical water splitting.
• Grandcolas, Mathieu; Wabende, Brian; Yang, Juan; Mei, Sen; Xu, Kaiqi & Chatzitakis, Athanasios Eleftherios [Vis alle 7 forfattere av denne artikkelen] (2018). TiO2 Nanorods Decorated With Cobalt oxide as Photoanodes for a Bio-Hybrid PEC Cell.
• Fontaine, Marie-Laure; Chatzitakis, Athanasios Eleftherios; Vøllestad, Einar; Thomassen, Magnus & Norby, Truls Eivind (2018). Principles of proton conduction in polymer-ceramic composite membranes for PEM applications.
• Chatzitakis, Athanasios Eleftherios (2017). (Photo)electrochemical applications of TiO2 nanotubes .
• Fleischer, Christian; Chatzitakis, Athanasios Eleftherios; Grandcolas, Mathieu; Mei, Sen & Norby, Truls Eivind (2017). Solid-state photoelectrochemical water splitting: Application and properties of TiO2 nanotubes.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Norby, Truls Eivind; Mei, Sen; Juan, Yang & Grandcolas, Mathieu [Vis alle 7 forfattere av denne artikkelen] (2017). Solid-state photoelectrochemical Cell with Tantalum Nitride Nanotubes as Photoanode.
• Yang, Juan; Mei, Sen; Grandcolas, Mathieu; Simon, Christian; Xu, Kaiqi & Chatzitakis, Athanasios Eleftherios [Vis alle 10 forfattere av denne artikkelen] (2017). Synthesis of Nanosized Cobalt Oxides and Application in a Bio-hybrid Photoelectrochemical Cell for CO2 Utilization. Vis sammendrag

  CO2 capture and utilization (CCU) can alleviate the disastrous effects of greenhouse gas (GHG) emissions form the use of fossil fuels. The use of CO2 emission as feedstock for direct conversion into valuable chemicals has attracted increasing research interest worldwide. A number of approaches, such as chemical, electrochemical, photochemical and biological routes have used CO2 as a sustainable carbon resource for the production of chemicals. In the present CO2BioPEC project, a novel hybrid photoelectrochemical concept, based on solar energy and formate dehydrogenase biocatalyst is applied, as illustrated in Figure 1 (left). This multidisciplinary project aims at demonstrating a bio-hybrid photoelectrochemical cell, in which solar energy is efficiently captured and utilized to convert CO2 into energy-rich compounds, using formate dehydrogenase enzymes as biocatalysts. Cobalt oxide is a low-cost material with a band gap that can absorb visible light. It is also a promising co-catalyst that has been widely used for oxygen evolution route. In the present work, nanosized cobalt oxide was synthesized and used as a co-catalyst on the photoanode. The results showed that the formation of cobalt oxides (Co3O4, CoOOH and Co(OH)2) is strongly dependent on the temperature and reaction time. The photochemical efficiency will be further investigated by impregnating nanosized cobalt oxides onto Ta3N4 /TaON nanotubes.

• Chatzitakis, Athanasios Eleftherios; Xu, Kaiqi & Norby, Truls Eivind (2017). TiO2 nanotubes as photoanode electrodes in solid-state photoelectrochemical cells.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2017). Tantalum oxynitride for photoelectrochemical water splitting.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2017). Fuels from the sun, sea and air-by solid-state photoelectrochemical cell.
• Fleischer, Christian; Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2016). Development of high surface area TiO2 photo-electrodes and the significance of solid-state proton conductor in water splitting photoelectrochemical cell.
• 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.
• Xu, Kaiqi; Chatzitakis, Athanasios Eleftherios & Norby, Truls (2016). An All-Solid-State Photoelectrochemical Cell for Water Splitting.
• Chatzitakis, Athanasios Eleftherios; Grandcolas, Mathieu; Xu, Kaiqi; Mei, Sen; Yang, Juan & Simon, Christian [Vis alle 7 forfattere av denne artikkelen] (2016). Assessing the photoelectrocatalytic activity of C, N, F codoped TiO2 nanotubes of different lengths for oxygen evolution.
• Chatzitakis, Athanasios Eleftherios & Norby, Truls (2015). Solar hydrogen production.
• Chatzitakis, Athanasios Eleftherios & Norby, Truls (2015). Solid electrolytes for photoelectrochemical cells.
• Chatzitakis, Athanasios Eleftherios; Xu, Kaiqi; Boye, Ole; Backe, Paul Hoff; Bjorås, Magnar & Dalhus, Bjørn [Vis alle 13 forfattere av denne artikkelen] (2015). Solar based H2 generation in a novel photoelectrochemical-enzymatic hybrid cell.
• Both, Kevin Gregor; Chatzitakis, Athanasios; Bergum, Kristin; Hansen, Per-Anders Stensby; Prytz, Øystein & Norby, Truls (2023). Plasmonically Enhanced Photocatalysis: Synthesis, Physical Properties, and Applications. University of Oslo Livrary. ISSN 1501-7710. 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.

• Kang, Xiaolan; Norby, Truls & Chatzitakis, Athanasios (2021). Novel nanostructured materials for energy applications. Universitetet i Oslo, Det matematisk-naturvitenskapelige fakultet. ISSN 1501-7710. 2021(2465). Vis sammendrag

  Nanomaterials and nanotechnology have been flourishing greatly over the last decades and their applications are spreading almost over all the branches of science and technology. In this work, we zoomed into the synthesis and characterization of nanostructured materials. The central focus was to manipulate the compositions, morphology and structures of nanomaterials by combining various strategies like defect engineering and exsolution. Several interesting features and properties of nanostructured materials were investigated and highlighted, including the optical, plasmonic, electronic and surface properties. This process deepened our fundamental understanding of surface protonic conduction of nanocrystalline oxides and increased our control over nanostructuring of materials in order to achieve targeted functionalities. The as-prepared nanomaterials have been applied in energy- and environment-related applications, showing improved and controllable efficiency in pollutants degradation and water (vapor) splitting in photocatalytic, (photo) electrocatalytic, as well as in a solid-state photoelectrocatalytic systems.

• Andersen, Karoline Sjøen; Norby, Truls; Sartori, Sabrina & Chatzitakis, Athanasios (2020). Hydrophobic coatings for offshore PV modules: Impact of precipitation from seawater on the protective glass. 7Letras.
• Xu, Kaiqi; Norby, Truls Eivind; Chatzitakis, Athanasios Eleftherios & Bjørheim, Tor Svendsen (2020). Artificial photosynthesis – Advanced nanomaterials and use of biocatalysts for novel photoelectrochemical cells. Matematisk Naturvitenskapelig fakultet, Universitetet i Oslo. ISSN 1501-7710. 2020( 2254). Vis sammendrag

  The capture and storage of solar energy in chemical form by a photoelectrochemical (PEC) cell is an elegant and simple solution to the increasing energy demands and needs for chemicals and fuels from non-fossil sources. We first developed a facile fabrication method of a monolithic solid-state PEC (SSPEC) cell, which utilizes a solid-state polymer electrolyte and minimizes the distance between the two electrodes. The recent progress in understanding of surface proton conduction in porous ceramic-based electrolytes led to the idea of using the SSPEC cell for hydrogen production through water vapor splitting. The traditionally Pt-based cathode was replaced by an earth-abundant photocathode, g-C3N4, which increased the intrinsic photo-induced electrical field by a factor of three. Such a monolithic SSPEC cell working fully in the gas phase was demonstrated first time, and can play an important role for clean energy production in rural or other areas where grid infrastructure and clean water sources are limited or absent. CO2 utilization is considered a key player in a carbon-free energy economy, emphasising the importance of CO2 capture and conversion. We have successfully demonstrated how a bio-catalyst (enzyme) can be coupled with traditional chemical engineering for this purpose. To approach this, a stable, highly photo-active material - Ta3N5 nanotubes - has been synthesized and tested in a photoelectrochemical cell. It reaches close to its theoretical performance in photo-assisted water splitting. We then coupled the Ta3N5 nanotubes as the photoabsorber together with an optimised enzyme - formate dehydrogenase (FDH) - in a photoelectrochemical cell. The aim is to mimic natural photosynthesis to reduce CO2 into a valuable chemical form – formic acid. A solar-driven reduction of CO2 and water to formic acid at close to 100% faradaic efficiency has been reached.

• Andersen, Karoline Sjøen; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2020). Hydrophobic coatings for offshore PV modules: Impact of precipitation from seawater on the protective glass. Universitetet i Oslo.
• Andreassen, Magnus Haga; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2020). Synthesis, characterization, and optimization of Cu2O photocathodes for solid-state photoelectrochemical cells. Universitetet i Oslo.
• Simonsen, Stian Christopher; Norby, Truls Eivind & Chatzitakis, Athanasios Eleftherios (2020). Nafion®-Ceramic Composite Electrolytes for Proton Exchange Membrane Fuel Cells at Elevated Temperatures. Universitetet i Oslo.

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