Experimental investigation on degradation mechanism of membrane electrode assembly at different humidity under automotive protocol

Humidity can affect the attenuation of MEA (membrane electrode assembly), however, the relationship between humidity and MEA decays is complex and ambiguous in realistic application. Herein, we design a simulating automotive protocol, performed on five single fuel cells under RH (relative humidity) 100 %, RH 80 %, RH 64 %, and RH 40 %, RH 10 %, respectively, to study the relationship of MEA decays and humid-ity and suggest optimized humidity range to extend the durability. With the electrochemical impedance spectroscopy, cyclic voltammetry, X-ray fluorescence, X-ray diffraction, transmission electron micro-scope, X-ray photoelectron spectroscopy, the four degradation mechanisms about catalyst layer, includ-ing Pt dissolution, Pt coarsening, carbon corrosion and ionomer degradation, are observed. Pt coarsening and carbon corrosion are accelerated by higher water content at high humidity. Ionomer degradation and Pt dissolution are enhanced in low humidity. With the linear sweep voltammetry, ion chromatography, nuclear magnetic resonance, tensile test and scan electron microscope, chemical and mechanical degra-dation in proton exchange membrane are all observed in these five fuels. Chemical degradation, charac-terized by membrane thinning and more fluoride loss, occurred markedly in RH 10 %. Mechanical degradation, characterized by the non-uniformity thickness and bad mechanical properties, is more pro-nounced in RH 100 %, RH 80%, RH 64 %. These two degradations are in a moderate level in RH 40 %. The research suggests that the RH range from 64 % to 40 % is conductive to mitigate the degradation of MEAs operated in automotive applications.(c) 2022 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.