As energy storage becomes increasingly more important in contemporary and future energy solutions... more As energy storage becomes increasingly more important in contemporary and future energy solutions, the ability of a solid oxide cell (SOC) to work reversibly as an electrolyzer/fuel cell gives this technology great potential for use in large energy storage projects1,2. In theory, it is possible to use the state-of-the-art solid oxide cells in electrolysis operation to produce fuel (i.e. split water into oxygen and hydrogen) or generate electricity and heat using the so-called fuel cell regime. In addition, it is possible to produce syngas (H2 + CO)1,2 by co-electrolyzing water and CO2. While the performance and stability of the solid oxide fuel cell (SOFC) are in focus of most research regarding this technology, the technological possibilities of reversible solid oxide cells (RSOC) are far less studied. Although both technologies mostly share their device composition and main architecture, using the SOC in electrolysis mode creates new degradation mechanisms and technological proble...
(La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic condu... more (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell. The material is catalytically active for oxidation of hydrogen and hydrocarbons. A significant amount of attention has been paid to stability issues if the material is used as an anode in a solid oxide fuel cell. So far, there is a lack of information about the dependence between A-site stoichiometry and stability performance of LSCMN surface. The La/Sr ratio and deficiency of A-site, i.e. A-site stoichiometry of (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ were varied and chemical composition of LSCMN surface and lattice parameters was studied. The chemical and structural changes of the material surface (segregation of some LSCMN components onto the surface and decomposition of perovskite phase) have a key role in the electrochemical performance and initial degradation rate of the electrode. XRD results for studied electrode powders showed significant dependence of the lattice parameters on the A-site composition. Materials were treated in synthetic air and in H2 environment. TOF SIMS analysis demonstrated the dependence of the surface stoichiometry on the A-site composition of bulk electrode as well as on the different gas environments after heat treatment. To improve the durability of the solid oxide cell fuel electrodes, it is inevitable to understand the degradation mechanisms during the cell operation and during cell fabrication.
(La0.6Sr0.4)0.99CoO3−δ is a very promising cathode material due to its excellent electronic and i... more (La0.6Sr0.4)0.99CoO3−δ is a very promising cathode material due to its excellent electronic and ionic conductivity. However, when using non-artificial air from the ambient atmosphere, it contains impurities such as H2O and CO2. These chemicals 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 this 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 with 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. Under gas mixture with water 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.
Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as ... more Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as solid oxide electrolysis cell (SOEC) materials from the commercialization perspective. To improve the understanding about degradation mechanisms solid oxide cells with different electrode compositions should be studied. In this work, Ni-Zr0.92Y0.08O2-δ (Ni-YSZ)| Zr0.92Y0.08O2-δ (YSZ)|Ce0.9Gd0.1O2-δ (GDC)|Pr0.6Sr0.4CoO3-δ (PSC) cells are tested in the SOFC regime for 17,820 h at 650 °C, and in the SOEC regime for 860 h at 800 °C. The SOFC experiment showed a degradation speed of 2.4% per 1000 h at first but decreased to 1.1% per 1000 h later. The electrolysis test was performed for 860 h at 800 °C. The degradation speed was 16.3% per 1000 h. In the end of the stability tests, an electrode activity mapping was carried out using a novel 18O tracing approach. Average Ni grain sizes were measured and correlated with the results of the oxygen isotope maps. Results indicate that Ni coarsening i...
Characteristics of the porous Gd0.15Sr0.85CoO3−δ and La0.6Sr0.4CoO3−δ cathodes were compared usin... more Characteristics of the porous Gd0.15Sr0.85CoO3−δ and La0.6Sr0.4CoO3−δ cathodes were compared using the data measured at different electrode potentials and oxygen partial pressures. The electrochemical high‐temperature in situ XRD (HT‐XRD) method combined with electrochemical impedance spectroscopy has been used. The response of the crystallographic parameters and impedance values on the changes of electrode potential has been discussed. Reversible changes of the lattice parameters for both cathodes, slower for Gd0.15Sr0.85CoO3−δ compared with La0.6Sr0.4CoO3−δ, were observed depending on temperature (T), electrode potential (E), and oxygen partial pressure (pO2). The crystallographic parameters are determined by the vacancy formation kinetics as well as by vacancy formation energy in/at the cathode grain structure. Calculated impedance data were fitted to the experimental data and characteristics were obtained in context of crystallographic changes of the cathode materials studied.
Stability of electrochemical performance in time is one of the most important properties of SOFC/... more Stability of electrochemical performance in time is one of the most important properties of SOFC/SOEC materials looking from the commercialization point of view. Long term characterization is resource consuming and therefore only commercially more interesting compositions are tested in time range of several thousand hours [1]. However, for better understanding of reasons and mechanisms of degradation processes alternative materials should also be tested in addition for the more attractive ones. Pr0.6Sr0.4CoO3-δ (PSC) is an alternative material for widely used La0.6Sr0.4CoO3-δ with excellent activity as medium temperature SOFC cathode. However, so far there is lack of long-term test results for PSC. This study concentrates on the long term electrochemical characterization and microstructural post-test analysis of Ni-YSZ|YSZ|GDC|Pr0.6Sr0.4CoO3-δ 5 × 5 cm single cell, where YSZ is the yttria stabilized zirconia and GDC is the gadolinia doped ceria. Performance test conducted in SOFC mode at 650 °C and at cell potential 0.85 V was 17820 h long. Initial degradation of electrochemical performance was 2.6 % per 1000h. During second half of experiment degradation was only 1% per 1000h. Total power loss during test was 34.6 %. Moderate increase of total activation energy Etot at 0.8 V cell potential takes place (ΔEtot = 0.38 eV) and it increases from 0.57 eV to 0.95 eV. At 1V cell potential ΔEtot = 0.22eV, from 0.34 to 0.56 eV. Post mortem HR-SEM and TOF-SIMS analysis of tested cell has been performed and collected data show that minor structural changes caused by nickel coarsening in porous anode have been taken place. TOF-SIMS mappings of 5 × 5 cm electrode visualize the mobility of Sr from cathode into the electrolyte interface during electrode preparation. Some mobility of Si from gas-sealing glas to electrode as well as Cr deposition from Crofer 22APU current collector into electrode surface has been established. [1] L. Blum, U. Packbier, I. C. Vinke, L.G. J. de Haart, Fuel Cells, 13 (4) 646-653
In this study, catalytically active nickel catalyst was grown via redox exsolution on the surface... more In this study, catalytically active nickel catalyst was grown via redox exsolution on the surface of A-site deficient La1-xSrxCr1-yMnyO3-δ based electrode with 6 % of Ni on B-site impregnated onto porous matrix made from Sc0.1Ce0.01Zr0.89O2- δ. Influence of A site deficiency on the electrochemical performance and effect of conditions of electrolysis and nanocatalyst properties on the outlet gas composition were studied.
Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-d or Ni Zr0.92Y0.08O2-d supporting an... more Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-d or Ni Zr0.92Y0.08O2-d supporting anodes, bi-layered Zr0.92Y0.08O2-d | Ce0.9Gd0.1O2-d or Zr0.9Sc0.1O2-d | Ce0.9Gd0.1O2-d electrolytes and micro-meso-porous La0.6Sr0.4CoO3-d, Gd0.6Sr0.4CoO3-d or Pr0.6Sr0.4CoO3-d cathodes prepared from nano-micro-powders at different sintering temperatures and pore former additions in the raw cathode and anode pastes have been studied using XRD, FIB-SEM, AFM, BET, cyclic voltammetry, chronoamperometry and electrochemical impedance methods. Influence of the anode and cathode porosity, depending on the electrode preparation methods, and also of the bi-layered electrolyte properties (chemical composition, thickness, etc.) on the power density of the single cells has been shown and discussed.
Estonian solid oxide fuel cell program started in 2001. Solid oxide fuel cell single cells based ... more Estonian solid oxide fuel cell program started in 2001. Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-δ or Ni-Zr0.92Y0.08O2-δ supporting anodes, bi-layered Zr0.92Y0.08O2-δ | Ce0.9Gd0.1O2-δ or Zr0.9Sc0.1O2-δ | Ce0.9Gd0.1O2-δ electrolytes and micro-meso-porous La0.6Sr0.4CoO3-δ, Gd0.6Sr0.4CoO3-δ or Pr0.6Sr0.4CoO3-δ cathodes prepared from nano/microporous powders at different sintering temperatures and pore former additions in the raw cathode and anode pastes have been studied. Different physical (XRD, high-temperature XRD under electrochemical working conditions, FIB-SEM, AFM, and BET) and electrochemical (cyclic voltammetry, chronoamperometry and electrochemical impedance) methods have been applied. Influence of the anode and cathode porosity, depending on the electrode preparation methods, and also of the bi-layered electrolyte properties (chemical composition, thickness, etc.) on the power density of the single cells has been shown and discussed. During last two years ...
As energy storage becomes increasingly more important in contemporary and future energy solutions... more As energy storage becomes increasingly more important in contemporary and future energy solutions, the ability of a solid oxide cell (SOC) to work reversibly as an electrolyzer/fuel cell gives this technology great potential for use in large energy storage projects1,2. In theory, it is possible to use the state-of-the-art solid oxide cells in electrolysis operation to produce fuel (i.e. split water into oxygen and hydrogen) or generate electricity and heat using the so-called fuel cell regime. In addition, it is possible to produce syngas (H2 + CO)1,2 by co-electrolyzing water and CO2. While the performance and stability of the solid oxide fuel cell (SOFC) are in focus of most research regarding this technology, the technological possibilities of reversible solid oxide cells (RSOC) are far less studied. Although both technologies mostly share their device composition and main architecture, using the SOC in electrolysis mode creates new degradation mechanisms and technological proble...
(La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic condu... more (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell. The material is catalytically active for oxidation of hydrogen and hydrocarbons. A significant amount of attention has been paid to stability issues if the material is used as an anode in a solid oxide fuel cell. So far, there is a lack of information about the dependence between A-site stoichiometry and stability performance of LSCMN surface. The La/Sr ratio and deficiency of A-site, i.e. A-site stoichiometry of (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ were varied and chemical composition of LSCMN surface and lattice parameters was studied. The chemical and structural changes of the material surface (segregation of some LSCMN components onto the surface and decomposition of perovskite phase) have a key role in the electrochemical performance and initial degradation rate of the electrode. XRD results for studied electrode powders showed significant dependence of the lattice parameters on the A-site composition. Materials were treated in synthetic air and in H2 environment. TOF SIMS analysis demonstrated the dependence of the surface stoichiometry on the A-site composition of bulk electrode as well as on the different gas environments after heat treatment. To improve the durability of the solid oxide cell fuel electrodes, it is inevitable to understand the degradation mechanisms during the cell operation and during cell fabrication.
(La0.6Sr0.4)0.99CoO3−δ is a very promising cathode material due to its excellent electronic and i... more (La0.6Sr0.4)0.99CoO3−δ is a very promising cathode material due to its excellent electronic and ionic conductivity. However, when using non-artificial air from the ambient atmosphere, it contains impurities such as H2O and CO2. These chemicals 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 this 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 with 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. Under gas mixture with water 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.
Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as ... more Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as solid oxide electrolysis cell (SOEC) materials from the commercialization perspective. To improve the understanding about degradation mechanisms solid oxide cells with different electrode compositions should be studied. In this work, Ni-Zr0.92Y0.08O2-δ (Ni-YSZ)| Zr0.92Y0.08O2-δ (YSZ)|Ce0.9Gd0.1O2-δ (GDC)|Pr0.6Sr0.4CoO3-δ (PSC) cells are tested in the SOFC regime for 17,820 h at 650 °C, and in the SOEC regime for 860 h at 800 °C. The SOFC experiment showed a degradation speed of 2.4% per 1000 h at first but decreased to 1.1% per 1000 h later. The electrolysis test was performed for 860 h at 800 °C. The degradation speed was 16.3% per 1000 h. In the end of the stability tests, an electrode activity mapping was carried out using a novel 18O tracing approach. Average Ni grain sizes were measured and correlated with the results of the oxygen isotope maps. Results indicate that Ni coarsening i...
Characteristics of the porous Gd0.15Sr0.85CoO3−δ and La0.6Sr0.4CoO3−δ cathodes were compared usin... more Characteristics of the porous Gd0.15Sr0.85CoO3−δ and La0.6Sr0.4CoO3−δ cathodes were compared using the data measured at different electrode potentials and oxygen partial pressures. The electrochemical high‐temperature in situ XRD (HT‐XRD) method combined with electrochemical impedance spectroscopy has been used. The response of the crystallographic parameters and impedance values on the changes of electrode potential has been discussed. Reversible changes of the lattice parameters for both cathodes, slower for Gd0.15Sr0.85CoO3−δ compared with La0.6Sr0.4CoO3−δ, were observed depending on temperature (T), electrode potential (E), and oxygen partial pressure (pO2). The crystallographic parameters are determined by the vacancy formation kinetics as well as by vacancy formation energy in/at the cathode grain structure. Calculated impedance data were fitted to the experimental data and characteristics were obtained in context of crystallographic changes of the cathode materials studied.
Stability of electrochemical performance in time is one of the most important properties of SOFC/... more Stability of electrochemical performance in time is one of the most important properties of SOFC/SOEC materials looking from the commercialization point of view. Long term characterization is resource consuming and therefore only commercially more interesting compositions are tested in time range of several thousand hours [1]. However, for better understanding of reasons and mechanisms of degradation processes alternative materials should also be tested in addition for the more attractive ones. Pr0.6Sr0.4CoO3-δ (PSC) is an alternative material for widely used La0.6Sr0.4CoO3-δ with excellent activity as medium temperature SOFC cathode. However, so far there is lack of long-term test results for PSC. This study concentrates on the long term electrochemical characterization and microstructural post-test analysis of Ni-YSZ|YSZ|GDC|Pr0.6Sr0.4CoO3-δ 5 × 5 cm single cell, where YSZ is the yttria stabilized zirconia and GDC is the gadolinia doped ceria. Performance test conducted in SOFC mode at 650 °C and at cell potential 0.85 V was 17820 h long. Initial degradation of electrochemical performance was 2.6 % per 1000h. During second half of experiment degradation was only 1% per 1000h. Total power loss during test was 34.6 %. Moderate increase of total activation energy Etot at 0.8 V cell potential takes place (ΔEtot = 0.38 eV) and it increases from 0.57 eV to 0.95 eV. At 1V cell potential ΔEtot = 0.22eV, from 0.34 to 0.56 eV. Post mortem HR-SEM and TOF-SIMS analysis of tested cell has been performed and collected data show that minor structural changes caused by nickel coarsening in porous anode have been taken place. TOF-SIMS mappings of 5 × 5 cm electrode visualize the mobility of Sr from cathode into the electrolyte interface during electrode preparation. Some mobility of Si from gas-sealing glas to electrode as well as Cr deposition from Crofer 22APU current collector into electrode surface has been established. [1] L. Blum, U. Packbier, I. C. Vinke, L.G. J. de Haart, Fuel Cells, 13 (4) 646-653
In this study, catalytically active nickel catalyst was grown via redox exsolution on the surface... more In this study, catalytically active nickel catalyst was grown via redox exsolution on the surface of A-site deficient La1-xSrxCr1-yMnyO3-δ based electrode with 6 % of Ni on B-site impregnated onto porous matrix made from Sc0.1Ce0.01Zr0.89O2- δ. Influence of A site deficiency on the electrochemical performance and effect of conditions of electrolysis and nanocatalyst properties on the outlet gas composition were studied.
Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-d or Ni Zr0.92Y0.08O2-d supporting an... more Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-d or Ni Zr0.92Y0.08O2-d supporting anodes, bi-layered Zr0.92Y0.08O2-d | Ce0.9Gd0.1O2-d or Zr0.9Sc0.1O2-d | Ce0.9Gd0.1O2-d electrolytes and micro-meso-porous La0.6Sr0.4CoO3-d, Gd0.6Sr0.4CoO3-d or Pr0.6Sr0.4CoO3-d cathodes prepared from nano-micro-powders at different sintering temperatures and pore former additions in the raw cathode and anode pastes have been studied using XRD, FIB-SEM, AFM, BET, cyclic voltammetry, chronoamperometry and electrochemical impedance methods. Influence of the anode and cathode porosity, depending on the electrode preparation methods, and also of the bi-layered electrolyte properties (chemical composition, thickness, etc.) on the power density of the single cells has been shown and discussed.
Estonian solid oxide fuel cell program started in 2001. Solid oxide fuel cell single cells based ... more Estonian solid oxide fuel cell program started in 2001. Solid oxide fuel cell single cells based on Ni-Ce0.9Gd0.1O2-δ or Ni-Zr0.92Y0.08O2-δ supporting anodes, bi-layered Zr0.92Y0.08O2-δ | Ce0.9Gd0.1O2-δ or Zr0.9Sc0.1O2-δ | Ce0.9Gd0.1O2-δ electrolytes and micro-meso-porous La0.6Sr0.4CoO3-δ, Gd0.6Sr0.4CoO3-δ or Pr0.6Sr0.4CoO3-δ cathodes prepared from nano/microporous powders at different sintering temperatures and pore former additions in the raw cathode and anode pastes have been studied. Different physical (XRD, high-temperature XRD under electrochemical working conditions, FIB-SEM, AFM, and BET) and electrochemical (cyclic voltammetry, chronoamperometry and electrochemical impedance) methods have been applied. Influence of the anode and cathode porosity, depending on the electrode preparation methods, and also of the bi-layered electrolyte properties (chemical composition, thickness, etc.) on the power density of the single cells has been shown and discussed. During last two years ...
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