Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 630128 Kutateladze 18, Novosibirsk, Russia.
Phys Chem Chem Phys. 2018 Jul 11;20(27):18447-18454. doi: 10.1039/c8cp02924e.
A novel methodology for the analysis of oxygen exchange in practically important nonstoichiometric oxides with mixed ionic electronic conductivity (MIEC) is suggested. It is based on the fact that the kinetic and thermodynamic properties of such oxides vary continuously with oxygen stoichiometry. This allows MIEC oxides to be considered as a homologous series, with the difference that traditional series are discrete in their chemical composition whereas MIEC oxides are continuous in oxygen stoichiometry. Analysis of the relations between Gibbs energies of reactions and activation barriers traditionally performed for homologous series can be useful in studies of oxygen exchange in MIEC oxides. To demonstrate the approach, thermodynamic and oxygen-exchange kinetics parameters are measured as functions of oxygen nonstoichiometry δ for two perovskites, SrCo0.8Fe0.2O3-δ and SrFeO3-δ, having metal-like and p-type semiconducting conductivities, respectively. Both oxides are shown to obey linear free energy relationships of the Brønsted-Evans-Polanyi form in spite of their different types of electronic structures. The results open up new possibilities for understanding the mechanism of the rate determining step of oxygen exchange in MIEC oxides.
提出了一种分析具有混合离子电子导电性（MIEC）的实用非化学计量氧化物中氧交换的新方法。其基础是此类氧化物的动力学和热力学性质随氧化学计量连续变化。这使得 MIEC 氧化物可以被视为同系物，不同之处在于传统系列在化学成分上是离散的，而 MIEC 氧化物在氧化学计量上是连续的。对于同系物传统上进行的关于反应吉布斯能和活化势垒之间关系的分析，在 MIEC 氧化物的氧交换研究中可能是有用的。为了演示该方法，测量了两种钙钛矿 SrCo0.8Fe0.2O3-δ和 SrFeO3-δ 的氧非化学计量 δ 与热力学和氧交换动力学参数之间的关系，这两种氧化物分别具有金属型和 p 型半导体导电性。尽管这两种氧化物具有不同类型的电子结构，但它们都表现出符合布朗斯特-埃文斯-波兰尼形式的线性自由能关系。这些结果为理解 MIEC 氧化物中氧交换的速率决定步骤的机制开辟了新的可能性。
