Bubble-Induced Current Heterogeneity and Spatially Nonuniform Degradation of OER Electrodes in PEM Water Electrolysis

Abstract

Understanding bubble-related phenomena during the oxygen evolution reaction (OER) is essential for devising strategies that ensure stable operation in proton exchange membrane water electrolysis, as oxygen bubbles play a critical role in accelerating the degradation of catalytic performance. Specifically, elevated local current densities induced by bubble accumulation at the electrode surface are known to accelerate catalyst over-oxidation and dissolution, leading to irreversible degradation; however, there has been no direct experimental analysis elucidating the relationship between local activity, durability, and bubble shielding. In this study, spatiotemporally resolved scanning electrochemical microscopy (SECM) was employed to elucidate the impact of bubble shielding on the local activity and durability of OER electrodes; (a) SECM analysis revealed that local current density concentrated predominantly at the bubble-free electrode center, reaching values 1.3–1.7 times higher than those in bubble-covered regions. This intensification strongly correlated with accelerated degradation, evidenced by severe local dissolution and a current density decay rate 2.9–3.6 times higher in the bubble-free region compared to the shielded area. (b) This non-uniform current distribution persisted regardless of the interlayer material, though its magnitude varied with the catalyst composition. (c) Further experiments with miniaturized electrodes demonstrated that bubble accumulation could completely occlude the active surface, exacerbating degradation. Collectively, these findings highlight that the non-uniform current distribution induced by bubble shielding plays a decisive role in electrode failure by driving heterogeneous catalyst dissolution. By leveraging SECM to map these localized disparities, this work successfully identifies a degradation mechanism that remains elusive to conventional macroscopic techniques.