Effects of coalescence inhibition on multi-bubble detachment dynamics during water splitting

Promoting bubble detachment is crucial for enhancing the efficiency of water splitting reactions. However, the existing detachment theories, derived from single- or dual-bubble scenarios, fail to fully explain the multi-bubble detachment characteristics under practical application conditions. In this work, multi-bubble detachment characteristics are investigated during photoelectrochemical water splitting on a TiO₂ nanorod array photoelectrode by varying the current density and the electrolyte concentration. We find that, in addition to the bubble coalescence, micro-convection from adjacent bubble detachment also significantly affects the bubble detachment radius. During the evolution of multiple bubbles, the coalescence inhibition related to the electrolyte concentration alters the detachment mode by changing mutual bubble interactions, leading to different relationship between the average detachment radius and current density. Specifically, in a low-concentration electrolyte, bubble detachment is governed by coalescence-induced detachment, whereas in a high-concentration electrolyte, enhanced coalescence inhibition promotes a transition to microconvection-induced detachment. While this work successfully reveals the multi-bubble detachment laws on a superhydrophilic electrode under specified quiescent and neutral pH conditions—thereby clarifying how varied bubble-bubble interactions affect detachment characteristics—its extrapolation to industrial scales requires further cross-validation under the coupled influences of external flow fields, extreme pH, and altered surface wettability.