In interfacial charge-transfer reactions, the complexity of the reaction pathway increases with the number of charges transferred, and becomes even greater when the reaction involves both electrons (charge) and ions (mass). These so-called mixed ion and electron transfer (MIET) reactions are crucial in intercalation/insertion electrochemistry, such as that occurring in oxygen reduction/evolution electrocatalysts and lithium-ion battery electrodes. Understanding MIET reaction pathways, particularly identifying the rate-determining step (RDS), is crucial for engineering interfaces at the molecular, electronic and point defect levels. Here we develop a generalizable experimental and analysis framework for constructing the reaction pathway for the incorporation of O₂(g) in Pr_0.1Ce_0.9O_2−x. We converge on four candidates for the RDS (dissociation of neutral oxygen adsorbate) out of more than 100 possibilities by measuring the current density–overpotential curves while controlling both oxygen activity in the solid and oxygen gas partial pressure, and by quantifying the chemical and electrostatic driving forces using operando ambient pressure X-ray photoelectron spectroscopy.

在界面电荷转移反应中，反应路径的复杂性随转移的电荷数而增加，并且在反应同时涉及电子（电荷）和离子（质量）时变得更加复杂。这些所谓的混合离子和电子转移（MIET）反应对于插层/插入电化学至关重要，例如发生在氧还原/逸出电催化剂和锂离子电池电极中的化学反应。了解MIET反应途径，尤其是确定速率决定步骤（RDS），对于分子，电子和点缺陷水平的工程界面至关重要。在这里，我们开发了一个通用的实验和分析框架，用于构建在Pr _0.1 Ce中掺入O ₂（g）的反应途径_0.9 O _{2− x}。通过测量电流密度-过电势曲线，同时控制固体和氧气分压中的氧气活度，以及量化化学和静电，我们汇集了100多种可能性中的四种RDS（中性氧吸附物的解离）候选物使用操作环境压力X射线光电子能谱分析驱动力。