Observation of a new degradation mechanism involving electrocatalyst nanoparticle growth in hydrogen PEM fuel cells associated to reduction

We aim to elucidate the relationship between oxidation state and stability of electrocatalyst for automotive proton exchange membrane fuel cells (PEMFCs) by operando and in situ characterization. The structural evolution of Pt nanoparticles will be tracked in a representative device under accelerated protocols able to capture the effect of low potential excursions, which occur in the application during the stops and were recently recognized as critical for Pt nanoparticles growth and dissolution. The mechanisms (oxidation/reduction, morphological reconstruction, dissolution) rising under the cathodic scan to low potential (<0.4 V) will be elucidated by W/SAXS techniques. The study of different catalyst coated membranes and operating PEMFC conditions can clarify the electrochemical drivers that lead the degradation in this process. The work helps to improve aging mitigation strategies and Pt degradation model, and define PEMFC operational boundaries in dependence on material properties.

我们旨在通过operando表征（operando）与原位（in situ）表征手段，阐明车用质子交换膜燃料电池（PEMFCs）用电催化剂的氧化态与其稳定性之间的内在关联。本研究将在典型测试装置中，借助可捕捉低电位偏移效应的加速实验方案，追踪铂（Pt）纳米颗粒的结构演化历程；这类低电位偏移出现于实际应用的停机工况中，近期被证实对铂纳米颗粒的生长与溶解过程具有关键性影响。本研究将通过广角/小角X射线散射（W/SAXS）技术，阐明阴极扫描至低电位（<0.4 V）时触发的氧化还原、形貌重构与溶解等失效机制。通过对不同催化剂涂层膜片以及PEMFC运行工况的系统研究，可明确该过程中驱动催化剂降解的电化学因素。本研究有助于优化抗老化策略与铂基催化剂降解模型，并可基于材料特性确定PEMFC的合理运行边界。