Effect of laser spot diameter on mass transfer mechanisms in photoelectrochemical water splitting.

This article investigates the influence of laser spot diameter on bubble nucleation, detachment, and mass transfer mechanisms during photoelectrochemical (PEC) water splitting on TiO2 photoelectrodes. Using a synchronized high-speed camera and electrochemical workstation, the study finds that increasing the laser spot diameter from 700 to 1176 μm raises the nucleation potential and terminal rising velocity of oxygen bubbles, while decreasing the mass transfer coefficient by approximately 46%. The results indicate that smaller spot diameters enhance mass transfer efficiency and facilitate bubble nucleation and detachment, with gas evolution efficiency increasing as spot diameter grows due to a higher proportion of gas molecules entering bubbles. These findings highlight the critical role of laser spot size in optimizing PEC water splitting performance and provide a foundation for designing more efficient photoelectrochemical systems.