Role of Microstructures on Bubble Detachment and Electrochemical Response in Wicking Electrodes

Gas bubble evolution at electrode surfaces reduces the electrode–electrolyte interfacial area and limits the efficiency of gas-evolving electrochemical reactions. While structured electrodes have been widely shown to improve bubble management, the independent contribution of individual geometric parameters to bubble nucleation, detachment, and electrochemical behavior remains poorly understood. Here, bubble-templated electrodeposition is used as a model fabrication platform to systematically vary structural width and height across two morphologically distinct electrode families, stochastic pillar arrays and circular-wall structures, while characterizing double-layer capacitance, current density, bubble detachment diameter, and bubble number density. Three-dimensional wicking architecture is shown to outperform a flat hydrophilic electrode in both electrochemical characterizations and bubble management. At constant height, increasing structural width raises double-layer capacitance but reduces current density and increases detachment diameter─a decoupling attributed to reduced structural unit density and reproduced across both morphological families. Increasing structural height alongside width raises both capacitance and current density simultaneously, demonstrating that height-driven surface area gains outweigh the concurrent reduction in projected bubble number density. Finally, the macroscopic captive bubble contact angle is shown to quantitatively predict the electrolytic bubble contact angle across the electrode series, establishing that on wicking electrodes, a simple ex-situ wettability measurement reliably captures in situ bubble detachment behavior. These findings identify structural unit density and interfacial aerophobicity as the key descriptors governing bubble-mediated electrochemical behavior in structured wicking electrodes.