Bubble dynamics matters at high-rate water electrolysis
Lizhen Wu, Qing Wang, Shu Yuan, Wenzhi Li, Xiaohong Zou, Mingcong Tang, Kouer Zhang, Xiaohui Yan, Liang An
Abstract
Bubbles accumulation in the electrode limits anion exchange membrane water electrolyzer performance at industrial current densities (>1.0 A cm-2). Currently, conventional electrode designs prioritize the optimization of the electrochemically active surface area. However, this study reveals that bubble dynamics matters high-rate water electrolysis efficiency in anode-feeding mode in three ways:1) cover active sites at the anode; 2) hinder water diffusion through the membrane; 3) cause water shortage at the cathode. Based on this mechanism, we propose an easy-to-prepare gradient stainless steel square hole mesh electrode. It not only offers a low cost ($8-150/m2), but also improves bubble dynamics. As a result, it reduces the cell voltage by 0.14 V at a current density of 5.0 A cm-2, even with a lower electrochemically active surface area compared to the stainless steel felt electrode. And it maintains a stable operation over 400 hours. This work redefines electrode engineering paradigms, shifting focus from electrochemically active surface area-centric approaches to two-phase flow management in water electrolyzers for industrial current densities-scale hydrogen production. Efficient hydrogen production at industrial current densities is hindered by bubbles blocking water flow to electrodes in water electrolyzers. Here, the authors report a low-cost gradient mesh electrode that effectively manages bubble removal, ensuring stable and high-efficiency operation.