Factors governing surface exchange kinetics in undoped and strontium/iron co-substituted La2NiO4+δ |
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| Affiliation: | 1. Institute of High Temperature Electrochemistry of the Ural Branch of the Russian Academy of Sciences, Russia;2. Ural Federal University, Institute of Hydrogen Energy, Russia;1. Department of Chemistry and Chemical Engineering, Lyuliang University, Lyuliang 033001, China;2. College of Biological, Chemical Science and Engineering, Jiaxing University, Jiaxing 314001, China;3. Department of Chemical Engineering, COMSATS University Islamabad (CUI), Lahore Campus, 54000, Punjab, Lahore, Pakistan;4. Sustainable Process Integration Laboratory, SPIL, NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology, VUT Brno, Technická 2896/2, 616 00, Brno, Czech Republic;5. Department of Chemical Engineering Technology, College of Applied Industrial Technology (CAIT), Jazan University, Kingdom of Saudi Arabia;6. Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, Leuven, 3001, Belgium;1. Ural Federal University, Ekaterinburg 620002, Russia;2. Institute of High Temperature Electrochemistry. Ural Branch Russian Academy of Sciences, 620137 Russia;1. Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620016, Russia;2. Ural Federal University, Yekaterinburg 620002, Russia;3. Institute of High Temperature Electrochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620137, Russia;1. School of Resources, Environment and Safety Engineering, University of South China, Hengyang, Hunan Province 421001, China;2. School of Electrical Engineering, University of South China, Hengyang, Hunan Province 421001, China;3. Hangzhou Yanqu Information Technology Co., Ltd, Hangzhou 310003, China |
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| Abstract: | Surface oxygen exchange in the La2NiO4+δ and La1.5Sr0.5Ni1-yFeyO4+δ (y = 0.3, 0.4) oxides is analyzed using the data on oxygen permeability through the membranes with different thicknesses measured under various oxygen partial pressure P(O2) gradients in the 800–1000 °C range. The increase in P(O2) gradient induced surface limitations in La2NiO4+δ leading to a predominant role of surface exchange in the overall oxygen flux. The origin of surface exchange limitations in La2NiO4+δ is ascribed to a relatively fast decrease in oxygen excess and Ni3+ concentration with P(O2) reduction compared to La1.5Sr0.5Ni0.7Fe0.3O4+δ and La1.5Sr0.5Ni0.6Fe0.4O4+δ, which retained an oxygen excess. Faster surface exchange kinetics for La1.5Sr0.5Ni0.6Fe0.4O4+δ in comparison with that for La1.5Sr0.5Ni0.7Fe0.3O4+δ is interpreted on the basis of surface microstructure obtained by electron backscatter diffraction (EBSD). It is suggested that the observed changes in size, shape and crystallographic orientation of grains in La1.5Sr0.5Ni0.6Fe0.4O4+δ (compared to La1.5Sr0.5Ni0.7Fe0.3O4+δ) could result in a higher amount of 3d-metal cations in surface layers of the oxide. |
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| Keywords: | Surface exchange Surface limitations Surface structure |
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