Unraveling the elusive electrokinetics and energetics of the sluggish Oxygen Reduction Reaction (ORR) is critical for the development of efficient Proton Exchange Membrane Fuel Cells (PEMFCs). Physical microkinetic modeling, Transition State Theory (TST), Transmission Line Modeling and Degree of Rate Control (DRC) analysis was employed to simulate analytically both the experimental Electrochemical Impedance Spectra (EIS) and the polarization curve data of a High Temperature PEMFC. The excellent fitting results revealed that: i) O_2(g) dissociative adsorption is the main limiting step responsible for the high ORR overpotentials, ii) both EIS and polarization resistance are dominated by the intrinsic ORR kinetic inertia due to the competitive nature of the elementary reaction steps on the coverages of the adsorbed species (O_ad and OH_ad). Finally, from TST the activation energies (kinetics) and the reaction steps’ free energies (thermodynamics) were extracted, which can serve as a guide for catalyst design optimizing the oxygen binding strength.

解开缓慢的氧还原反应 (ORR) 难以捉摸的电动学和能量学对于开发高效的质子交换膜燃料电池 (PEMFC) 至关重要。采用物理微动力学建模、过渡态理论 (TST)、传输线建模和速率控制度 (DRC) 分析来分析模拟高温 PEMFC 的实验电化学阻抗谱 (EIS) 和极化曲线数据。出色的拟合结果表明：i) O _2(g)解离吸附是导致高 ORR 过电势的主要限制步骤，ii) EIS 和极化电阻均由固有的ORR 动力学惯性决定由于基本反应步骤对吸附物种（O _ad和 OH _ad）覆盖率的竞争性。最后，从 TST 中提取了活化能（动力学）和反应步骤的自由能（热力学），这可以作为优化氧结合强度的催化剂设计的指南。