Chizhik Stanislav A, Bychkov Sergey F, Voloshin Bogdan V, Popov Mikhail P, Nemudry Alexander P
Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 630128 Kutateladze 18, Novosibirsk, Russia and Novosibirsk State University, 630090 Pirogova 2, Novosibirsk, Russia.
Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 630128 Kutateladze 18, Novosibirsk, Russia.
Phys Chem Chem Phys. 2021 Jan 21;23(2):1072-1081. doi: 10.1039/d0cp04856a.
Perovskite related oxides ABO3-δ exhibiting mixed ionic-electronic conductivity (MIEC) possess large deviations from the oxygen stoichiometry. When providing excellent application potential, this feature also makes it very difficult to study the reaction mechanism between such oxides and molecular oxygen, also known as the oxygen reduction reaction. The complexity of the theoretical interpretation of kinetic experiments originates from the significant dependence of the kinetic and equilibrium properties of MIEC oxides on δ. It is proposed to consider such grossly nonstoichiometric oxides having different oxygen nonstoichiometry as chemical homologues participating in the oxygen exchange reaction and forming a series continuous in δ. The continuous homologous series approach is considered using the example of SrCo0.9Ta0.1O3-δ, an SOFC cathode material. The equilibrium and kinetic properties of the oxide were studied by new methods of oxygen partial pressure relaxation and oxygen release. Linear free-energy relationships have been discovered in the homologous series: thermodynamic and kinetic enthalpy-entropy compensations, as well as the Brønsted-Evans-Polanyi relation. A relationship has been established between the change in the observed LFERs and the morphotropic phase transition in the oxide.
具有混合离子-电子传导性（MIEC）的钙钛矿相关氧化物ABO₃₋δ与氧化学计量比存在较大偏差。在具有出色应用潜力的同时，这一特性也使得研究此类氧化物与分子氧之间的反应机制（即氧还原反应）变得极为困难。动力学实验理论解释的复杂性源于MIEC氧化物的动力学和平衡性质对δ的显著依赖性。有人提出将具有不同氧非化学计量比的这种严重非化学计量氧化物视为参与氧交换反应并形成δ连续系列的化学同系物。以固体氧化物燃料电池（SOFC）阴极材料SrCo₀.₉Ta₀.₁O₃₋δ为例来考虑连续同系物系列方法。通过氧分压弛豫和氧释放的新方法研究了该氧化物的平衡和动力学性质。在同系物系列中发现了线性自由能关系：热力学和动力学的焓-熵补偿以及布朗斯特-埃文斯-波兰尼关系。已观察到的线性自由能关系的变化与氧化物中的变晶相转变之间建立了一种关系。
