Nanoparticle Electrodes Trigger Bubble Detachment and Enhance Gas Evolution Efficiency

Abstract

Nanobubble formation and binding to nanoelectrodes significantly hinder the efficiency of gas evolution reactions, limiting the potential of hydrogen production technologies. This work uncovers the pivotal role of the nanoelectrode shape in influencing catalytic performance and nanobubble detachment. Using molecular dynamics simulations supported by experimental evidence, we establish that nanoparticle electrodes with convex geometries (e.g., hemispheres, spheres, and cubes) sustain higher catalytic performance by maintaining greater reactive surface exposure than flat or concave electrodes. Most importantly, we demonstrate that convex nanoparticle electrodes mitigate bubble pinning by promoting unlimited growth and spontaneous detachment. We develop a diffusional theory that explains and generalizes our simulations, predicting the onset currents that drive nanobubbles into a nonstationary growth regime. This theory reveals that the transition to continuous bubble growth occurs when the electrochemically generated gas rate surpasses the diffusion-limited escape rate, independent of electrode size and convex shape but sensitive to the electrode support. The theoretical model extends the predictions to other gas-evolving electrochemical processes, highlighting its relevance to diverse catalytic systems. Surprisingly, our calculations reveal that bubble detachment contributes minimally to the total current. Instead, the enhanced catalytic efficiency of convex electrodes stems from their ability to sustain an exposed reactive surface, even during bubble growth. These findings provide a fundamental framework for designing nanoelectrodes that optimize gas evolution by prioritizing surface exposure rather than relying solely on bubble detachment.