Proper assessment of oxygen evolution reaction (OER) catalyst performance requires recognising that doping can introduce simultaneous changes to structure, morphology, and electronic properties that together influence the observed electrochemical behaviour. In this study, Ni-doped RuO2 is used as a model system to systematically investigate how dopant concentration and synthesis temperature affect catalyst morphology and electronic structure. These trends are correlated with OER mass activity (MA), intrinsic activity, and stability enabling the morphological and intrinsic electronic contributions to catalyst performance to be distinguished. The acid-stable limit for bulk Ni incorporation in RuO2 is found to be approximately 10 mol%. Ni incorporation affects the rutile structure and inhibits particle growth, while lower synthesis temperatures decrease particle size. The best-performing Ni-doped RuO2 catalyst here shows up to a tenfold increase in OER MA compared with undoped RuO2. Surface area-based normalisation of MA reveals that this enhancement is partly caused by increased accessible surface area and includes an additional contribution from increased intrinsic OER activity. X-ray photoelectron spectroscopy reveals Ni-dependent changes in the Ru 3d and O 1s regions (electronic effect), which correlate with the increase in intrinsic OER activity. S-number measurements further indicate an approximately twofold improvement in catalyst stability caused by doping.

LaxSr0.9-xTiyNi1-yO3-delta (LSTN) has been proposed as a promising group of mixed ionic-electronic (MIEC) perovskites for solid oxide fuel- and electrolysis cell applications. In this study thin film as-prepared (before redox treatment) La0.31Sr0.58Ti0.97Ni0.03O3-delta (LSTN3) pulsed laser deposited (PLD) electrodes were characterised electrochemically and using in situ near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) at different H-2/H2O ratios and electrode potentials at 650 degrees C. The electrochemical activity of LSTN3|gas surface increased with water content in a hydrogen environment. Ti XPS spectra revealed rutile-like coordinated Ti surface termination of LSTN3 and Ti3+/Ti4+ ratio changes in the surface layer as a function of oxygen activity in LSTN3. Change in the kinetics of the electrochemical process at similar to 0.3 V in H-2 with 1.6 % H2O was observed and explained as oxidation of exsolved Ni. La and Sr XPS spectra were independent of polarisation and depended only on water content in the gas. The changes in La(OH)(3) concentration at the surface (influenced by water content in the gas) match with the changes in the electrochemical activity.

In today's complex technologies, the systematic development of theoretical knowledge and techniques is important, which can only take place in close cooperation between research institutions and companies. The research of solid oxide complex materials and fuel cells (SOFC) began at the UT in 2001 and 2008, respectively [1-6]. The main aim of the cooperation with Elcogen OY was to develop the materials for so-called medium temperature (500–650 °C) SOFC, using ceria-based electrolytes, activated perovskite-type cathodes and Ni-cermet anodes with optimized micro-, meso- and macro-porosity established using BET analysis method. It has been found that for moderate temperature SOFC, the meso- and macroporosity of cathodes and anodes is very important. In 2005, after intensive studies, patent applications were completed and finally granted in 2007 [3]. Nowadays, Elcogen OÜ is one of the world’s leading SOFC stack producers, having received the European Union innovation prize in 2019. In addition to methods of synthesizing materials, the properties of the materials change during the real operation of the SOFC stacks [1-6]. In order to establish correlations between porosity and operation characteristics, the various analysis methods - FIB-SEM-EDX, thermogravimetry, FIB-TOF-SIMS and operando electrochemical high temperature XRD under electrode polarization have been introduced and applied. It was found that the effect of the synthesis and operation temperature, i.e. reversible expansion of crystallographic lattice depends on the chemical composition and atom mass of a A position cation (La 1-x Sr x CoO 3-δ , Pr 1-x Sr x CoO 3-δ and Gd 1-x Sr x CoO 3-δ ) depends on the temperature, electrode and cell potential, etc. applied. Influence of humidified synthetic air feeding conditions on the stoichiometry of (La 1-x Sr x ) y CoO 3-δ and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathodes under applied potential has been analyzed according to the data measured by electrochemical in situ high-temperature XRD method(y from 1.0 to 0.98).This phenomenon will be analyzed in more detail in the presentation. One very big complication is that very clean fuels are needed for long-lasting effective generation of electricity, however the real fuels usually contain various contaminants. Since 2014, the fully ceramic cathode and anode materials with optimized porosity and chemical composition are under intensive study in order to find possibilities to avoid the contamination of Ni nanoclusters with sulphur and other contaminants [7,8,9,10,11]. Operando redox dynamics of sulphur at Ni/GDC (Ce 1-x Gd x O 2-δ ) has been studied by S K-edge XANES method [4] and lately by near ambient pressure XPS [5,6]. The time stability of fully ceramic La 0.7 Sr 0.3 VO 3-δ -Ce 0.85 Sm 0.15 O 2-δ (SDC) perovskite material as an alternative anode and La 0.8 Sr 0.2 CoO 3-δ -SDC as a cathode was obtained using H 2 fuel for 220 h under 0.6 V cell polarization and working temperature 600 o C. Both electrodes were prepared by infiltration of the electrode material solution into the highly porous electrolyte material to have electrodes with high porosity and specific surface area [7, 8,9]. Based on the results of the studies, the contract with H2Electro was signed in 2021 for detailed development and electrochemical characterization of fully ceramic materials and reversible SOFC devices with CV, impedance, constant current charge/discharge and constant power methods. Good stability up to 10000 charge/discharge cycles has been achieved. Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3-δ and Gd0.1Ce0.9O1.95-δ is thoroughly investigated. Microstructures and compositions are systematically varied around the percolation thresholds of both phases by modification of phase volume fractions, particle size distributions and firing temperature. Differential impedance spectroscopy, FIB-TOF-SIMS, SEM-EDX, XRF, XRD synchrotron XPS, etc. have been applied for post-mortem analysis of tested cells for detailed characterisation of materials degradation processes during long-lasting electrochemical polarisation. Influence of A-site deficiency and chemical composition of B-site (concentration of Ni, Mn, and Cr) on electrochemical performance of hydrogen electrode in the (La 1-x Sr x ) y Cr 0.5-z Mn 0.5-w Ni z+w O 3-δ |(Sc 2 O 3 ) 0.1 (CeO 2 ) 0.01 (ZrO 2 ) 0.89 |La 0.8 Sr 0.2 FeO 3-δ reversible solid oxide fuel cell has been studied and discussed. To make solid oxide fuel cell systems commercially attractive it is essential to reduce manufacturing cost and improve the stability of membrane electrode assembly (MEA). Therefore, development of active ceramic hydrogen electrodes with high stability is an important challenge for developing SOFC. Herein, a set of cubic perovskite-type La/Ca/Fe-doped strontium titanates (La 0.2 Sr 0.7-x Ca x Ti 0.95 Fe 0.05 O 3-δ ) was synthesized. Their crystallographic and electrical properties, catalytic activity, and stability, as well as performance as fuel electrode has been established[10,11]. The highest stability was observed in the case of La 0.21 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3-δ anode composition [11]. The best electrochemical performance was observed in the case of La 0.21 Sr 0.37 Ca 0.37 Ti 0.95 Fe 0.05 O 3-δ , which showed low polarization resistance value (0.44 Ω cm 2 after 100 h of stabilization at 800 °C in humidified H 2 (1.7% H 2 O)). During the stability test, the fuel cell with optimal anode composition of 50 wt% La 0.21 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3-δ + 50 wt% Ce 0.9 Gd 0.1 O 2-δ showed power density of 437 mW cm −2 at 850 °C in 98.3% H 2 + 1.7% H 2 O atmosphere. However, in comparison with Ni or Co nanoclusters activated anodes, the fully ceramic material based SOFCs are less active and future improvements are inevitable. Based on the knowledge collected in the field of development of SOFC/SOEL systems, the synthesis and full-scale analysis of complex solid oxide catalysts for moderate temperature polymer electrolyte and anion exchange membrane fuel cells and electrolysis cells are carried out since 2014 [12,13,14,15]. Intensive scientific cooperation with Stargate Hydrogen Solutions OY started in 2020. CeO 2 and Pr 6 O 11 nanoclusters activated Pt/MMMP carbon electrodes have been developed, and very high methanol oxidation activity has been observed [ 13,14,15]. In addition to the development of energy conversion devices, the regeneration and recycling of the materials of the devices outlived their time are no less important. The cycle economy principles including extraction of rare earth elements from exhausted SOFC/SOEL stacks and from Estonian company AS Silmet [1,2, 3, 15, 16] as well as from Estonian phosphorite ore have been applied since 2016 using the novel ionic liquid based extraction methods [17,18,19]. The systematic study of various energy conversion devices and their materials has given our working group the opportunity to compile a sustainable green electricity and hydrogen generation-storage complex, consisting of solar cells (60kW), battery storage unit (500 kWh), electrolyser (10kW), hydrogen storage unit and different fuel cells (SOFC, PEMFC etc.) for electricity regeneration. The 300 bar hydrogen compressor has been installed (2019) inevitable to storage electrolytic hydrogen in tanks and to refuel the hydrogen powered cars. The 3.0 kW PEMFC was completed and installed into the self-driving vehicle “Iseauto” under the contract between AuveTech OY and the University of Tartu. The Iseauto has been demonstrated for public in Tartu and also in Tallinn [15]. Acknowledgements This work was supported by the Estonian Ministry of Education and Research project by Estonian Centre of Excellence (TK 210) and by the project „Increasing the knowledge intensity of Ida-Viru entrepreneurship“ co-funded by the European Union (ÕÜF 1, ÕÜF 2, ÕÜF 12 and ÕÜF 13). References Lust, P. Möller, I. Kivi, G. Nurk, S. Kallip, P. Nigu, K. Lust, Optimization of the cathode composition for the intermediate-temperature SOFC. J. Electrochem. Soc. 152 (2005) A2306−A2308. Lust, G. Nurk, P. Möller. I. Kivi, S. Kallip, A. Jänes, H. Kurig, Method for the preparation of a solid oxide fuel cell single cell and the named cell. Patent No. EP-2160785-B1, WO2007EE00010, 2007. Kivi, J. Aruväli, K. Kirsimäe, A. Heinsaar, G. Nurk, E. Lust, Kinetic Response of La 0.6 Sr 0.4 CoO 3-δ Lattice Parameters to Electric Potential Change in Porous Cathode at In Situ Solid Oxide Fuel Cell Conditions, J. Electrochem. Soc. 62 (2015) F354-F358. Nurk,T. Huthwelker, A. Braun, Chr. Ludwig, E. Lust, R.P.W.J. Struis, Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: an operando S K-edge XANES study, J Power Sources 240 (2013) 448–457. Nurk, K. Kooser, S. Urpelainen, T. Käämbre, U. Joost, M. Kodu, I. Kivi, R. Kanarbik, E. Kukk, E. Lust, Near ambient pressure X-ray photoelectron - and impedance spectroscopy study of NiO – Ce 0.9 Gd 0.1 O 2-δ anode reduction using a novel dual-chamber spectroelectrochemical cell, J. Power Sources 378 (2018) 589-596. Koose, T. Käämbre, M. Vestli, U. Joost, S. Urpelainen, Mati Kook, F. Bournel, J.-J- Gallet. E. Lust, E. Kukk, G. Nurk, Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni - Ce 0.9 Gd 0.1 O 2-δ solid oxide fuel cell anode, Inter. J. Hydrogen Energy 45 (2020) 25286-25298. Tamm, P. Möller, G. Nurk, E. Lust, Investigation of Time Stability of Sr-Doped Lanthanum Vanadium Oxide Anode and Sr-Doped Lanthanum Cobalt Oxide Cathode Based on Samaria Doped Ceria Electrolyte Using Electrochemical and TOF-SIMS Methods, J. Electrochem. Soc. 163 (2016) F586-F592. Maide, P. Paiste, P. Möller, E. Lust, G. Nurk, Influence of A- and B-Site Modifications of (La 1-x Sr x ) y Cr 0.5-z Mn 0.5-w Ni z+w O 3-δ on Electrochemical Impedance Characteristics of Reversible Solid Oxide Cell, j. Electrochem. Soc. 166 (2019) F1148-F1156. Korjus, P. Möller, K. Kooser, T. Käämbre, O. Volobujeva, J. Nerut, S. Kotkas, E. Lust, G. Nurk, Influence of Ni concentration on electrochemical and crystallographic properties of La 0.25 Sr 0.25 Ca 0.4 Ti 1-x Ni x O 3−δ solid oxide fuel cell anode, J. Power Sources 494 (2021) 229739. Heinsaar, I. Kivi, P. Möller, K. Kooser, T. Käämbre, J. Aruväli, G. Nurk, E. Lust, Influence of Carbon Dioxide and Humidity on the Stability of (La 0.6 Sr 0.4 ) 0.99 Co 1-x Ti x O 3- δ Cathode, J. Electrochem. Soc. 169 (2022) 014514. Paydar, K. Kooser, O. Volobujeva, S. Granroth, G. Nurk, Influence of A-Site Deficiency and Ca Concentration on the Electrical and Crystallographic Properties of (Nd 2 Sr 0.7-x Ca x ) y Ti 0.95 Fe 0.05 O 3-δ -Based Fuel Electrode for Solid Oxide Cells, ACS Applied Energy Materials 7 (2024) 5745-5754. Lust, K. Vaarmets, J. Nerut, I. Tallo, P. Valk, S. Sepp, E. Härk. Influence of specific surface area and microporosity-mesoporosity of pristine and Pt-nanoclusters modified carbide derived carbon electrodes on the oxygen electroreduction, Electrochim. Acta 140 (2024) 294-303. Valk, J. Nerut, R. Kanarbik, I. Tallo, J. Aruväli, E. Lust, Synthesis and characterization of platinum-cerium oxide nanocatalysts for methanol oxidation. J Electrochem. Soc. 165 (2018) F315–F323. Valk, J. Nerut, R. Kanarbik, J. Aruväli, P. Paiste, I. Tallo, E. Lust, Synthesis and characterization of platinum-praseodymium oxide nanocatalysts for methanol electrooxidation. J Electrochem. Soc. 166 (2019) F1062-F1069. Pikma, H. Ers, L. Siinor, J. Zhao, O. Oll, T. Romann, V. Grozovski, C. Siimenson, M. Väärtnõu, M. Paalo, R. Härmas, K. Lust, T. Thomberg, A. Jänes, J. Nerut, R. Jäger, P. Valk, I. Kivi, M. Maide, P. Möller, R. Kanarbik, G. Nurk, E. Lust, The review of advances in interfacial electrochemistry in Estonia: electrochemical double layer and adsorption studies for the development of electrochemical devices, J. Solid State Electrochem. 27 (2023) 1547−1591. Q.V. Ngyen, J. Nerut, H. Kasuk, T. Thomberg, T. Romann, J. Aruväli, E. Lust. Ultra-Small Ceria Nanoclusters at Carbon Surface Synthesised by Ultrasound Sonification: A Study of Highly Active Platinum –Cerium Bifunctional Catalysts for Methanol Oxidation and Oxygen Reduction, ECS Trans. 111 (2023) 17-28. Jürjo, L. Siinor, C. Siimenson, P. Paiste, O. Oll, E. Lust, Two-Step Solvent Extraction of Radioactive Elements and Rare Earths from Estonian Phosphorite Ore Using Nitrated Aliquat 336 and Bis(2-ethylhexyl) Phosphate, Minerals 11 (2021) 388. Jürjo, O. Oll, P. Paiste, M. Külaviir, J.Z hao, E. Lust, Electrochemical co-reduction of praseodymium and bismuth from 1-butyl-1-methylpyrrolidinium bis (fluorosulfonyl) imide ionic liquid, Electrochem. Commun. 138 (2022) 107285. Jürjo, O. Oll, E. Lust, Yttrium Separation from Phosphorite Using Liquid Extraction with Room Temperature Ionic Liquids Followed by Electrochemical reduction, Metals 14 (2024) 927.

Lanthanum doped strontium titanate (LST) fuel electrode materials for SOFC application have been studied quite extensively. These materials have shown good stability, but relatively poor catalytic activity [1]. B-site doping of LST with Ni and other elements and exsolution of these has been used [2] to increase the catalytic activity of the surface of titanates. La 0.31 Sr 0.58 Ti 0.97 Ni 0.03 O 3- d (LSTN3) as one promising composition from this material group has been studied in this work. According to the results available in the literature, electrodes with very similar stoichiometry, as La 0.3 Sr 0.55 Ti 0.95 Ni 0.05 O 3−δ demonstrate high resistance to coking and ability to recover from sulfur poisoning [3]. In this work, pulsed laser deposited (PLD) thin film LSTN3 electrodes were studied in situ before and after electrochemical activation in different gas atmospheres and electrode polarisations using near ambient pressure XPS (NAP–XPS) method at TEMPO beamline (SOLEIL synchrotron) using a dual-chamber cell [4]. Additionally, the characteristics of the electrochemically activated surface were compared to the characteristics of as-prepared (before electrochemical activation) LSTN3 studied at Bessy 2 ISISS end station. Complementary electrochemical measurements at normal pressure (but otherwise at the same gas environments) with circular LSTN3 microelectrodes were performed in addition to the in situ EIS measurements to link the surface chemistry data from NAP–XPS experiments to electrochemical behavior of the surface (Pt current collectors enhanced the activity of the LSTN3 electrodes measured in situ during the NAP–XPS experiments [5]). The cell for dual chamber NAP–XPS experiment was produced as follows. First, porous highly active LSCT counter electrode was produced on one side of 15 mm diameter Kerafol 10Sc1CeSZ electrolyte and sintered. Then 200 nm Pt current collector with 6 µm wide stripes with 48 µm spacing were applied on the other side of the electrolyte using lift-off photolithography and magnetron sputtering of Pt. Then 2 µm thick LSTN3 film was pulsed laser deposited through Inconel mask onto the current collectors at 800 °C, 1.0·10 -2 mbar O 2 pressure and 3.0 J·cm -2 laser fluence. The composition of LSTN deposited on these conditions was determined with XRF and microwave plasma atomic emission spectroscopy (MP–AES). Next, the cell was mounted into our dual chamber NAP–XPS setup [4], wires connecting to LSCT counter electrode were connected with Pt-paste, glass seal connecting the cell to the holder was applied, the assembly was sintered at 870 °C for 10 h. The cell holder was then laser welded shut to seal off the counter electrode chamber. The cells used for electrochemical characterisation of LSTN3 microelectrodes had porous Pt-GDC counter electrodes prepared (GDC paste prepared according to [6]), LSTN3 microelectrodes were pulsed laser deposited through laser cut 60 µm thick stainless steel shadow mask with circular holes. For electrochemical measurements LSTN3 microelectrodes were contacted with tip of 70Pt30Ir wire and characterised at 2 electrode configuration in series with porous Pt-GDC electrode. The impedance spectra of the microelectrodes were fitted with simple R s (R low ||CPE) circuit model in the frequency range of 1 to 0.01 Hz to avoid over-parametrisation. More complex model describing partial ionic conductivity limitation through thin film mixed conductor [7] yielded to very similar R low values as the simplified model. R low describes LSTN3|gas surface electrochemical activity and the constant phase element parameter Q describes the chemical capacitance of LSTN3, R s describes the contact resistance between 70Pt30Ir probe and microelectrode. The influence of electrochemical activation on NAP–XPS spectra of LSTN3 model electrode was studied at two gas environments, 0.5% H 2 O + 99.5% H 2 and 30% H 2 O + 70% H 2 and at three different potentials: 0, +0.2 and −0.2 V vs OCV. At first, the XPS characterisation was carried out before electrochemical activations and then after different activations at 850 °C in 0.5% H 2 O + 99.5% H 2 atmosphere: (1) holding at OCV for 3 h; (2) polarising at −1 V for 150 s; (3) polarising at -1V for 450 s. XPS measurements at OCV were also performed in 0.5% H 2 O + 99.5% H 2 at 650 °C after the first and second activations. The same activation procedure was applied to 150 µm circular LSTN3 microelectrodes. The effect of activation on impedance spectra of LSTN3 microelectrode can be seen on fig 1. Holding the electrode at 850 °C for 3 h caused only a minimal decrease in R low . Most likely the temperature is too low to enable sufficient diffusion of Ni into Ni exsoluted particles. Electrochemical activation via polarising at −1 V for 150 s at 850 °C in 0.5% H 2 O + 99.5% H 2 caused the 4.1 times decrease of R low (measured 650 °C and OCV in 0.5% H 2 O + 99.5% H 2 gas environment) and activation with −1 V for 450 s at 850 °C caused R low to decrease 6.6 times compared to the values before activation. The effect of activation is highest when comparison of R low is carried out at anodic polarisation. At −0.2 V cathodic polarisation the effect is similar to the behaviour at OCV. The increase in surface activity is likely to be caused by the Ni exsolution (confirmed by HR–SEM) at extremely reducing conditions in MIEC material (pO 2 is 1.5 ∙10 -40 bar) caused by the high cathodic polarisation. The effect of activation gradually decreases with time. The CPE parameter Q remains unaffected by the electrochemical activation, which is unexpected, because the highly cathodic polarisation affect the whole LSTN3 film and therefore activation should cause change in stoichiometry of the perovskite troughout the film, although in the case of highly A-site deficient titanates, surface is preferred location for exolutes [8]. Unaffected Q value indicates that the bulk LSTN3 is unable to exsolve Ni or the exolution has only tiny effect on chemical capacitance or the activation time is too short to create the defined condition (pO 2 is 1.5 ∙10 -40 bar) in whole electrode (limited oxide ion conductivity) and only surface of LSTN3 electrode is significantly affected. Highest changes caused by activation could be seen in Ti 2p XPS spectra. Surface sensitive scans with 510 eV photon energy are shown on Fig 2. Ti signal intensity on the surface increases with electrochemical activations (note that the spectra before first activation is missing on the figure). The activation causes the reduction of fraction of Ti 4+ to Ti 3+ , i.e. the Ti 3+ peak becomes visible after the 150 s activation and is well pronounced after the 450 s activation. Anodic polarisation at 650 °C with +0.2 V after activations had no effect on the Ti 2p spectra, thus the surface states are more or less “freezed in” at typical operating temperatures. Spectral changes caused by electrochemical activation could be also observed in the XPS spectra of La, Sr, Ni and O. Ni 3p lines show increase in Ni signal on the surface (no chance in bulk signal) as a result of activations, this indicates clearly that exsolution likely took place only on the MIEC│gas surface and agrees well with unchanged Q value. The increased Ni content on the surface remains unchanged during following tests at 650 °C. In O spectra, the most visible effect of activations is the disappearance of CO x species as a result of electrochemical activation. La 3d spectra shows only slight changes. All changes are analysed in detail and will be presented in this work. Acknowledgements This work was supported by Estonian Research Council grant PRG551 and by the project „Increasing the knowledge intensity of Ida-Viru entrepreneurship“ (ÕÜF2) co-funded by the European Union, and by Estonian Ministry of Education and Research (TK210). Part of the research was conducted using the NAMUR+ core facility supported by the Estonian Research Council (TT 13). References [1] X. Zhou, N. Yan, K.T. Chuang, J. Luo, Progress in La-doped SrTiO 3 (LST)-based anode materials for solid oxide fuel cells, RSC Adv 4 (2014) 118–131. https://doi.org/10.1039/C3RA42666A. [2] D. Neagu, G. Tsekouras, D.N. Miller, H. Menard, J.T.S. Irvine, In situ growth of nanoparticles through control of non-stoichiometry ´, Nat. Chem. 5 (2013) 916–923. https://doi.org/10.1038/nchem.1773. [3] P. Steiger, D. Burnat, H. Madi, A. Mai, L. Holzer, J. Van Herle, O. Kröcher, A. Heel, D. Ferri, Sulfur Poisoning Recovery on a Solid Oxide Fuel Cell Anode Material through Reversible Segregation of Nickel, Chem. Mater. 31 (2019) 748–758. https://doi.org/10.1021/acs.chemmater.8b03669. [4] K. Kooser, T. Käämbre, M. Vestli, U. Joost, S. Urpelainen, M. Kook, F. Bournel, J.J. Gallet, E. Lust, E. Kukk, G. Nurk, Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode, Int. J. Hydrog. Energy 45 (2020) 25286–25298. https://doi.org/10.1016/j.ijhydene.2020.06.228. [5] M. Ainsar, K. Kooser, M. Kodu, T. Romann, G. Nurk, Electrochemical Study of La0.31Sr0.58Ti0.97N0.03O3-δ Thin Film and Pt-10Sc1CeSZ Electrodes, ECS Trans. 111 (2023) 419–428. https://doi.org/10.1149/11106.0419ecst. [6] A. Nenning, J. Fleig, Electrochemical XPS investigation of metal exsolution on SOFC electrodes: Controlling the electrode oxygen partial pressure in ultra-high-vacuum, Surf. Sci. 680 (2019) 43–51. https://doi.org/10.1016/j.susc.2018.10.006. [7] R. Huang, C.G. Carr, C.B. Gopal, S.M. Haile, Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors, ACS Appl. Mater. Interfaces 14 (2022) 19629–19643. https://doi.org/10.1021/acsami.2c05417. [8] D. Neagu, J.T.S. Irvine, Structure and Properties of La 0.4 Sr 0.4 TiO 3 Ceramics for Use as Anode Materials in Solid Oxide Fuel Cells, Chem. Mater. 22 (2010) 5042–5053. https://doi.org/10.1021/cm101508w. Fig. 1 . The effect of electrochemical activation on impedance spectra in 0.5% H 2 O + 99.5% H 2 at 650 °C, 1 bar, at OCV. Fig. 2. The effect of electrochemical activation on Ti 2p XPS spectra in 0.5% H 2 O + 99.5% H 2 at 650 °C, 3 mbar. Photon energy is 510 eV. Figure 1

In this work, we propose hydroxyapatite (HA) as a hard template to unlock the porosity of Fe-N-C catalyst materials. Using HA, a naturally occurring mineral that can be removed with nitric acid, in the synthesis generates a catalyst material with a unique porous network comprising abundant pores and interparticle cavities ranging from 10 to 3000 nm. Hard templating with HA alongside ZnCl2 as a micropore former results in a Fe-N-C catalyst based on naturally abundant peat with excellent oxygen reduction activity in alkaline conditions. A half -wave potential of 0.87 V vs RHE and a peak power density of 1.06 W cm-2 were achieved in rotating ring disk electrode and anion exchange membrane fuel cell experiments, respectively, rivaling the performance of other state-of-the-art platinum-free catalysts presented in the literature. A combined approach of using renewable peat as a carbon source and HA as a hard template offers an environmentally friendly approach to high-performance Fe-N-C catalysts with abundant porosity.

Radiation therapy uses ionizing radiation to break chemical bonds in cancer cells, thereby causing DNA damage and leading to cell death. The therapeutic effectiveness can be further increased by making the tumor cells more sensitive to radiation. Here, we investigate the role of the initial halogen atom core hole on the photofragmentation dynamics of 2-bromo-5-iodo-4-nitroimidazole, a potential bifunctional radiosensitizer. Bromine and iodine atoms were included in the molecule to increase the photoionization cross-section of the radiosensitizer at higher photon energies. The fragmentation dynamics of the molecule was studied experimentally in the gas phase using photoelectron-photoion-photoion coincidence spectroscopy and computationally using Born-Oppenheimer molecular dynamics. We observed significant changes between shallow core (I 4d, Br 3d) and deep core (I 3d) ionization in fragment formation and their kinetic energies. Despite the fact, that the ions ejected after deep core ionization have higher kinetic energies, we show that in a cellular environment, the ion spread is not much larger, keeping the damage well-localized. A study on photodissociation dynamics of 2-bromo-5-iodo-nitroimidazole - a model radiosensitizer - using coincidence spectroscopy and computational methods.

Photoelectron recoil strongly modifies the high kinetic energy photoemission spectra from atoms and molecules as well as from surface structures. In most cases studied so far, photoemission from atomic-like inner-shell or core orbitals has been assumed to be isotropic in the molecular frame of reference. However, in the presence of molecular field splitting of p or d orbitals, this assumption is not justified per se. We present a general theoretical treatment, linking the orientational distribution of gas-phase molecules to the electron emission and detection in a certain direction in the laboratory frame. The approach is then applied to the S 2p photoemission from a linear molecule such as CS2 and we investigate, how the predicted orientational anisotropies due to molecular field splitting affect the photoelectron recoil excitations. Lastly, experimental S 2p high-kinetic-energy photoelectron spectra of SF6 and CS2 are analyzed using the modeled recoil lineshapes representing the anisotropy-affected recoil effects.

This study explores the impact of A-site deficiency and Sr/Ca ratio on the electrochemical and crystallographic properties of a (Nd0.2Sr0.7-xCax)(y)Ti0.95Fe0.05O3-delta hydrogen electrode for solid oxide cells under reducing and air atmospheres. 5% and 10% A-site deficient (Nd0.2Sr0.7-xCax)(y)Ti0.95Fe0.05O3-delta (x = 0.35-0.45, y = 1.05, 1) (referred to as 5NSCTF-x and 10NSCTF-x) materials were studied, while the ratio between A-site cations was kept the same with both deficiencies. The results demonstrate that the extent of A-site deficiency and the Ca concentration in the A-site have a significant impact on the microstructure (sinterability), conductivity, and catalytic activity of electrodes. Segregation of Nd from the lattice with 5% A-site deficiency was observed as a result of thermal treatment at low pO(2). Among the studied materials, the highest total electrical conductivity of porous electrode layer at 850 degrees C and in 97% H-2 + 3% H2O atmosphere was 4.8 S cm(-1) observed for the Nd0.2Sr0.35Ca0.35Ti0.95Fe0.05O3-delta (10NSCTF-35). The highest electrochemical performance was observed in the case of Nd0.2Sr0.25Ca0.45Ti0.95Fe0.05O3-delta (10NSCTF-45), which showed a polarization resistance value equal to 0.19 Omega cm(2) after 100 h of stabilization at 800 degrees C in a humidified (1.7% H2O) H-2 atmosphere. The best electrochemical performance with 606 mW cm(-2) power density at 850 degrees C in 98.3% H-2 + 1.7% H2O atmosphere was demonstrated by a 50 wt % Nd0.2Sr0.25Ca0.45Ti0.95Fe0.05O3-delta + 50 wt % Ce0.9Gd0.1O2-delta composite

Heavy elements and some nitroimidazoles both exhibit radiosensitizing properties through different mechanisms. In an effort to see how the overall radiosensitivity might be affected when the two radiosensitizers are combined in the same molecule, we studied the gas-phase photodissociation of two brominated nitroimidazoles and a bromine-free reference sample. Synchrotron radiation was employed to initiate the photodynamics and energy-resolved multiparticle coincidence spectroscopy was used to study the ensuing dissociation. We observed the brominated samples releasing high amounts of potentially radiosensitizing fragments upon dissociation. Since bromination also increases the likelihood of the drug molecule being ionised per a given X-ray dose, we conclude that heavy-element substitution of nitroimidazoles appears to be a viable path towards new, potent radiosensitizer drugs.

La and Ni-doped Sr-titanates, LaxSr1-xTi1-yNiyO3- d, are considered to be promising solid oxide fuel cell anode materials with Ni exsolution possibilities [1]. In this work two different types of La0.31Sr0.58Ti0.97Ni0.03O3-δ (LSTN) thin film microelectrodes were studied. Electrodes with photolitographycally microstructured Pt current collectors under ceramic electrode layer [2] and microelectrodes without current collectors were made using pulsed laser deposition and measured using EIS at different temperatures around 650 ℃ in water-hydrogen atmosphere at reduced pressures (0.5, 1 and 1 mbar) and at 1 atm ambient pressure. Measurements were carried out using single chamber 2-electrode configuration where large area porous GDC-Pt electrode was used as counter electrode [3]. Main aim of this study was to collect additional information to understand electrochemical data collected during in situ NAP-XPS measurements of LSTN thin film electrode and also link the data collected at ambient pressure with data measured at pressures where NAP-XPS experiments are performed. The measurements showed differences between electrodes with Pt current collectors and microelectrodes without Pt current collectors. LSTN electrodes without Pt showed weak relationship between anodic overpotential and polarization resistance suggesting that overpotential acted mainly on LSTN defect chemistry while electrodes with Pt current collectors were activated more by anodic overpotential. Oxide ion transport resistance from electrolyte to thin film | gas phase surface seems to be the main contributor to the resistance of the electrodes. J. T. S. Irvine et al., Nature Energy, 1, 15014 (2016). A. Nenning, A. K. Opitz, T. M. Huber, and J. Fleig, Phys. Chem. Chem. Phys., 16, 22321–22336 (2014). A. Nenning and J. Fleig, Surface Science, 680, 43–51 (2019).

Photodissociation molecular dynamics of gas-phase 2,5-diiodothiophene molecules was studied in an electron-energy-resolved electron-multi-ion coincidence experiment performed at the FinEstBeAMS beamline of MAX IV synchrotron. Following the photoionization of the iodine 4d subshell and the Auger decay, the dissociation landscape of the molecular dication was investigated as a function of the Auger electron energy. Concentrating on an major dissociation pathway, C4H2I2S2+ → C4H2S+ + I+ + I, and accessing the timescales of the process via ion momentum correlation analysis, it was revealed how this three-body process changes depending on the available internal energy. Using a generalized secondary dissociation model, the process was shown to evolve from secondary dissociation regime towards concerted dissociation as the available energy increased, with the secondary dissociation time constant changing from 1.5 ps to 129 fs. The experimental results were compared with simulations using a stochastic charge-hopping molecular mechanics model. It represented the observed trend and also gave a fair quantitative agreement with the experiment.

To improve catalytic activity of La x Sr 0.9-x Ti y M 1-y O 3-δ , La 1-x Sr x Cr y M 1-y O 3-δ based materials, doping of perovskite B-site with metals (M) like Ni, Co, Mo or Cu has been proposed. It has been demonstrated, that at elevated temperatures and in reducing atmosphere these dopants exsolve to perovskite surface and form nanometer scale catalyst particles. Exsolution process could be accelerated by using electrochemical polarization. In the present study thin film La 0.31 Sr 0.58 Ti 0.97 Ni 0.03 O 3-δ electrodes was prepared using pulsed laser deposition (PLD) technique. Current collectors were made from Pt (using magnetron sputtering) and placed under the thin film electrode layer. Electrodes were characterized using XPS and EIS method at near ambient pressure conditions (1-5 mbar) at 650 °C, activated electrochemically and characterized again to see the effect of activation. Changes on the electrochemical performance as well as on XPS data caused by electrochemical activation were observed and analyzed.

To make solid oxide fuel cell (SOFC) systems commercially attractive it’s essential to reduce manufacturing cost and improve the stability of membrane electrode assembly (MEA). In this research, the influence of A-site modification on electrical and electrochemical performance of 5% A-site deficient La 0.21 Sr 0.74−x Ca x Ti 0.95 Fe 0.05 O 3− δ (x = 0.26 − 0.69) (LSCTF5-x) hydrogen electrode has been studied. Results indicate that the magnitude of A-site deficiency and Ca concentration in A-site influence the conductivity, catalytic activity and stability of the electrodes considerably. The highest stability was observed in the case of La 0.21 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3− δ anode composition. The maximal total electrical conductivity of porous electrode layer made of LSCFT5-x was 3.5 S cm −1 at 850 °C characteristic of the La 0.211 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3− δ material in 97% H 2 + 3% H 2 O atmosphere. The best electrochemical performance was observed in the case of La 0.21 Sr 0.37 Ca 0.37 Ti 0.95 Fe 0.05 O 3− δ , which showed polarization resistance value equal to 0.44 Ω cm 2 after 100 h of stabilization at 800 °C in humidified (1.7% H 2 O) H 2 atmosphere. During the stability test the fuel cell with optimal anode composition 50 wt% La 0.21 Sr 0.26 Ca 0.48 Ti 0.95 Fe 0.05 O 3− δ + 50 wt% Ce 0.9 Gd 0.1 O 2-δ showed power density of 437 mW cm −2 at 850 °C in 98.3% H 2 + 1.7% H 2 O atmosphere.

In this work thin film SOFC anode MIEC La 0.31 Sr 0.58 Ti 0.97 Ni 0.03 O 3-δ (LSTN) electrodes with embedded 200 nm thick Pt current collectrors (CC-s) and electrodes without CC-s deposited on 10Sc1CeSZ electrolyte were studied in 650 °C in 98.5% H 2 and 1.5 % H 2 O at ambient pressure. Additionally Pt-10Sc1CeSZ electrodes were characterized to determine CC-s own electrochemical activity. It was found that the embedded Pt was the most active part of an LSTN electrode with Pt CC despite the common presumption that covering Pt current collector with dense MIEC layer makes it inactive. Diffusion of H 2 through both LSTN and Pt layers and reaction on the Pt-10Sc1CeSZ interface is proposed. Formation of bubbles under embedded Pt in hydrogen atmosphere was seen and is explained with formation of trapped H 2 O.

(La0.6Sr0.4)(0.99)CoO3-delta is a very promising cathode material due to its excellent electronic and ionic conductivity. However, non-artificial air from the ambient atmosphere contains impurities such as H2O and CO2, which cause degradation and performance loss of the cathode. Introduction of Ti into the B-site of (La0.6Sr0.4)(0.99)CoO3-delta improves the chemical stability of the material. (La0.6Sr0.4)(0.99)Co1-xTixO3-delta (0 <= x >= 0.1) electrodes prepared in this work were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Studied (La0.6Sr0.4)(0.99)CoO3-delta materials with Ti in B-site showed reversible degradation under gas mixture with carbon dioxide addition. Improved stability was observed for (La0.6Sr0.4)(0.99)Co1-xTixO3-delta materials with Ti in B-site compared to unmodified (La0.6Sr0.4)(0.99)CoO3-delta in gas mixture containing water vapour.

Development of active ceramic hydrogen electrodes with high stability is an important challenge for developing solid oxide fuel cells (SOFC). Herein, a set of cubic perovskite-type La/Ca/Fe-doped strontium titanates, La0.2Sr0.7–xCaxTi0.95Fe0.05O3-δ (LSCTF), was synthesized. Their crystallographic and electrical properties, catalytic activity, and stability, as well as performance as fuel electrodes in the solid oxide fuel cell (SOFC) have been evaluated. It was confirmed by the results that the LSCTF behave like semiconductors, and the conductivity, catalytic activity, and stability of the electrodes significantly depend on the Ca concentration in the A-site. In the case of an optimal composition of the La0.2Sr0.35Ca0.35Ti0.95Fe0.05O3−δ fuel electrode, a polarization resistance value of 0.21 Ω cm2 at 850 °C in a humidified (1.7% H2O) H2 atmosphere was obtained. During the stability test, the fuel cell with the 50 wt % La0.2Sr0.35Ca0.35Ti0.95Fe0.05O3−δ + 50 wt % Ce0.9Gd0.1O2−δ anode showed a power density of 322 mW cm–2 at 850 °C in a 98.3% H2 + 1.7% H2O atmosphere.

(La0.6Sr0.4)0.99CoO3−δ is a very promising cathode material due to its excellent electronic and ionic conductivity. However, non-artificial air from the ambient atmosphere contains impurities such as H2O and CO2, which cause degradation and performance loss of the cathode. Introduction of Ti into the B-site of (La0.6Sr0.4)0.99CoO3−δ improves the chemical stability of the material. (La0.6Sr0.4)0.99Co1−xTixO3−δ (0 ≤ x ≥ 0.1) electrodes prepared in this work were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Studied (La0.6Sr0.4)0.99CoO3−δ materials with Ti in B-site showed reversible degradation under gas mixture with carbon dioxide addition. Improved stability was observed for (La0.6Sr0.4)0.99Co1−xTixO3−δ materials with Ti in B-site compared to unmodified (La0.6Sr0.4)0.99CoO3−δ in gas mixture containing water vapour.

(La0.6Sr0.4)0.99CoO3 - δ oxygen electrode material is a very promising oxygen electrode material due to its excellent electron and ionic conductivity. However, when using non-artificial air from the ambient atmosphere, it contains impurities such as H2O and CO2. These chemicals increase the degradation rate of the oxygen electrode. Introducing Ti into the B-site of (La0.6Sr0.4)0.99CoO3 - δ B-site increases the chemical stability of this oxygen electrode material. Synthesized and fabricated (La0.6Sr0.4)0.99Co1 - xTixO3 - δ (0 ≤ x ≥ 0.1) electrodes and half cells were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and with electrochemical impedance spectroscopy (EIS). Results indicate that doping of (La0.6Sr0.4)0.99CoO3 - δ B-site with Ti makes this material more resilient to form unwanted compounds on the oxygen electrode surface.

Absorption of x-ray photons by atomic inner shells of light-element organics and biomolecules often leads to formation of dicationic electronic states and to molecular fragmentation. We investigated the x-ray-induced dissociation landscape of a representative medium-sized organic molecule, thiophene, by femtosecond x-ray pulses from the Super Photon Ring-8 GeV (SPring-8) Angstrom Compact Free-Electron Laser (SACLA). Holes, created in the sulfur 2p orbital by photoemission, were filled by the Auger process that created dicationic molecular states within a broad range of internal energies-a starting point particular to x-ray-induced dynamics. The evolution of the ionized molecules was monitored by a pump-probe experiment using a near-infrared (800 nm) laser pulse. Ion-ion coincidence and ion momentum analysis reveals enhanced yields of ionic fragments from multibody breakup of the ring, attributed to additional ionization of the highly excited fraction of the dicationic parent molecular states. The transient nature of the enhancement and its decay with about a 160-fs time constant indicate formation of an open-ring parent geometry and the statistical survival time of the parent species before the dissociation events. By probing specific Auger final states of transient, highly excited nature by near-infrared light, we demonstrate how pump-probe signatures can be related to the key features in dynamics during the early period of the x-ray-induced damage of organic molecules and biomolecules.

In this work, we studied the effects of Ni-doping level on the catalytic activity, stability and mobility of A-site cations of the La0.25Sr0.25Ca0.4TiO3?? (LSCT) fuel electrode. Results indicate that Ni concentration in B-site influences the phase properties, element ratios on the surface, element mobility during preparation, conductive properties and catalytic activity of electrode significantly. The best performance was measured for La0.25Sr0.25Ca0.4Ti0.95Ni0.05O3?? having very low polarization resistance value 0.084 ? cm2 at 850 ?C (at OCV). The results of the experiments indicate excellent stability of the material ? Rp remained stable during the 120 h test. Ni-doping also stabilizes the LSCT structure and makes it more stable in different gas atmospheres and suppresses segregation of CaO to the electrode surface. Moreover, it even suppresses significantly A-site cation mobility during electrode processing, which was one of the most relevant problems with pure LSCT. The accumulation of Sr at the zirconate electrolyte surface and formation of SrZrO3, which was one of the vital issues observed for undoped LSCT, has been avoided in the case of Ni-doped materials.