固/液界面与固/聚电解质界面电催化剂活性差异根源探究

Recent progress has been made in the research of non-precious metal Pt alternative catalysts for fuel cells. Although some of the non-precious metal catalysts (Co3O4, FeNC, etc.) show oxygen electrode catalytic activity comparable or even better than that of Pt in alkaline solution, their fuel cell performance is much lower than that of Pt. Such differences in activity is related to the transformation of catalyst/electrolyte interface, lead to the results obtained in water system cannot accurately predict the catalyst performance in fuel cells. In this project, we propose the study on the origin of the activity difference between solid/liquid interface and solid/polyelectrolyte interface electro-catalyst. Through the study of the water content and activity differences, differences in the behavior of ion migration, polyelectrolyte and catalyst interaction on the catalyst activity in the two interfaces, we expect to reveal the key factors that lead to differences in the catalytic activity of the two interfaces. This project will start with the basic problem of the electro-catalysis interface, and systematically study the structure-activity relationship of the catalysts under the operation of fuel cells, which will not only has the basis of scientific value, and also play a guiding role in actual application.

燃料电池非贵金属代Pt催化剂方面的材料研究近年来不断取得进展。尽管一些非贵金属催化剂(如Co3O4、FeNC等)在碱性溶液中表现出与Pt相当、甚至优于Pt的氧电极催化活性，但其燃料电池性能大多明显低于Pt。上述活性差异的产生与催化剂/电解质界面的性质转变存在关联，导致水体系中获得的性能结果并不能准确预测催化剂在燃料电池中的表现。本项目拟开展固/液界面与固/聚电解质界面电催化剂活性差异的根源探究。通过研究两种界面下水含量及活度差异、离子传导行为差异、聚电解质与催化剂相互作用及催化剂自身物理性质等因素对催化剂活性的影响，揭示两种界面下导致催化剂活性差异的关键因素。本项目将从电催化界面的基础问题入手，系统研究燃料电池工况下催化剂的构效关系，既具有基础科学价值，也将对实际应用起指导作用。

本项目的研究目标为揭示固/液界面及固/聚电解质界面催化剂活性差异的关键因素。截止目前，建立了衰减全反射拉曼方法研究固/聚电解质界面处物种的吸附信号，通过构建模拟催化层对固/聚电解质界面处聚电解质的物理流失进行了明确指认。将露点仪引入碱性聚电解质燃料电池的水管理实时监测，结合阻抗-弛豫时间分布方法对电池的水淹情况进行检测，并成功使用憎水聚电解质解决了电池放电初期性能陡降问题。指出MnCo尖晶石ORR催化剂中Mn的变价和流失是导致其电池稳定性下降的主要原因，最终使用不含Mn的Co3O4催化剂成功实现了1400 h的电池稳定性，达到了本项目提升催化剂在固/聚电解质界面活性和稳定性的预期目标，并指出水含量的差异是导致两种界面催化剂性能差异的根本原因之一。