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.

本研究旨在通过操作中原位（operando）表征与原位表征技术，阐明车用质子交换膜燃料电池（proton exchange membrane fuel cells, PEMFCs）用电催化剂的氧化态与稳定性之间的关联。本研究将在典型燃料电池装置中，通过可捕捉低电势偏移效应的加速老化方案，追踪铂纳米颗粒的结构演化过程；此类低电势偏移发生在燃料电池实际应用的停机阶段，近期研究已证实其对铂纳米颗粒的生长与溶解具有关键影响。针对低电势（<0.4 V）阴极扫描过程中产生的氧化还原、形貌重构以及溶解等机制，本研究将通过广角与小角X射线散射（W/SAXS）技术进行阐明。通过对不同催化剂涂覆膜以及PEMFC运行工况的研究，可明确该过程中引发催化剂降解的电化学驱动因素。本研究有助于优化老化缓解策略与铂催化剂降解模型，并可基于材料特性界定PEMFC的运行边界。