Mesoporosity Regulates Microbubble Emergence and Interfacial Bubble Accumulation during Electrocatalytic Hydrogen Evolution

Abstract Gas bubbles generated during water electrolysis alter electrolyte access, ionic conduction, and local mass transport, thereby influencing electrochemical performance. Directly resolving this process is often challenging because numerous bubbles evolve and interact simultaneously on conventional gas-evolving electrodes. Here, we establish mesoporous Pt microelectrodes as a simplified model system to examine how the nanoscale porous architecture affects H2 bubble evolution relative to nonporous Pt electrodes with the same macroscopic disk geometry at matched nominal H2 generation rates. The mesoporous Pt electrode exhibited smaller detachment diameters and shorter detachment periods during single H2 bubble evolution in H2SO4. During multiple H2 bubble evolution in HClO4, the mesoporous electrode concentrated microbubble emergence into fewer locations and developed a less crowded near interface bubble population, with a smaller current-induced resistance increment. These results show how the nanoscale porous architecture can reorganize collective bubble evolution and thereby modify the associated ohmic penalty during electrocatalytic hydrogen evolution.