Effect of the shear flow field on the bubble behaviors during photoelectrochemical water splitting

The regulation of bubble dynamics on the photoelectrode surface through the application of external physical fields significantly influences the efficiency of photoelectrocatalytic reactions. This study investigates the evolution and detachment characteristics of bubbles on the photoelectrode surface under varying flow velocities and laser powers, focusing on the impact of shear flow on mass transfer and gas evolution efficiency. The results indicate that increasing flow velocities effectively enhance the reaction current within the system. Notably, for single bubbles, the effect of flow velocity on the reaction current is significantly more pronounced at high laser power than at low laser power. Shear flow promotes the detachment of bubbles from the photoelectrode surface, with the detachment diameter decreasing as the flow velocity increases. Additionally, applying a shear flow field enhances convective flow on the photoelectrode surface. Consequently, the combined mass transfer coefficient on the surface of the photoelectrode increases with increasing flow velocity, wherein the forced convection mass transfer plays a predominant role. However, higher mass transfer rates correspond to a decline in gas evolution efficiency for single-bubble electrodes. In addition to single bubbles, the results for multiple bubbles reveal that the number of bubbles on the photoelectrode surface initially increases and then decreases with increasing flow velocity. This study provides valuable guidance for the rational utilization of shear flow fields and the regulation of the bubble evolution process, thereby contributing to the enhancement of the photoelectrocatalytic system reaction efficiency.