Inhomogeneous degradation mechanism of proton exchange membrane fuel cell stack based on inter-cell and intra-cell cases

Abstract

Proton exchange membrane fuel cells (PEMFCs) face significant durability challenges due to spatially heterogeneous degradation under dynamic operating conditions. This study investigates the inhomogeneous degradation mechanisms of a 3-cell metal plate PEMFC stack through a 1,000h dynamic load cycling test, combining in-situ electrochemical diagnostics and post-mortem characterization. Voltage and high-frequency resistance monitoring revealed accelerated degradation in the end-cell (cell#1), with a 10 % voltage decay at 1000 mA cm⁻², compared to 3.28 % and 1.97 % for cell#2 and cell#3, respectively. Electrochemical impedance spectroscopy showed a 29.17 % increase in ohmic resistance (R_s) and a 2.14-fold rise in mass transport resistance (R_mt) for cell#1, linked to interfacial corrosion of bipolar plates and thinning of the membrane and catalyst layer. Spatial analysis of the membrane electrode assembly revealed localized catalyst layer degradation near the hydrogen inlet, with a 40.88 % decrease in electrochemical active surface area and Pt particle agglomeration. Hydrophobicity loss further exacerbated flooding risks. These findings highlight the effects of thermal-mechanical stress, reactant distribution, and material corrosion on degradation, offering insights for optimizing stack design and operating protocols.