Gas bubble accumulation and transport play a critical role in the electrochemical performance and reaction uniformity of proton exchange membrane water electrolysis (PEMWE), particularly at high current density. However, the quantitative coupling between bubble coverage and local electrochemical activity remains insufficiently clarified. In this work, a visualization PEMWE combined with a printed circuit board (PCB)-based segmented measurement technique was developed to simultaneously characterize the spatial distributions of bubble coverage and local current density (LCD) under different current densities and operating temperatures. The results showed that both bubble coverage and LCD exhibited pronounced in-plane non-uniformity. The LCD generally displayed lower values in the central region and higher values near the edges, whereas high bubble coverage regions were mainly concentrated in the central and outlet-side areas. As the average current density increased from 0.5 A/cm2 to 2.0 A/cm2, the LCD range expanded from 0.43 to 0.53 A/cm2 to 1.75–2.20 A/cm2, while the local bubble coverage increased from 0.24 to 0.34 to 0.86–0.91. A clear negative spatial correlation between bubble coverage and LCD was identified, and this correlation became stronger with increasing current density. Moreover, the correlation exhibited marked spatial dependence, following the E5 > C3 > E1 > A5 > A1 order. Increasing the operating temperature from 50 to 70 °C alleviated the local heterogeneity, but it did not alter the fundamental coupling trend. These results demonstrate that bubble accumulation is a key factor governing current redistribution and local reaction non-uniformity in PEMWE, and they provide guidance for flow field optimization and high current density operation.
Chen et al. (Fri,) studied this question.