Coalescence and detachment of bubbles for photoelectrochemical water splitting driven by linear Gaussian beam

In photoelectrochemical water splitting system, the adhesion of bubbles reduces the active area of the electrode and increases the reaction resistance of the system. This paper adopts linear Gaussian beam to regulate the bubble coalescence, and the electrochemical characteristics corresponding to the evolution of multi-bubble are investigated, and the coalescence of double bubbles is analyzed. The results indicate that the growth period of multi-bubble is shorter than that of single-bubble due to bubble coalescence. When the laser power is 10 mW, the period is shortened by 81.22 %. The growth rate of bubbles and photocurrent increase with increasing laser power, while the gas evolution efficiency is minimum at 20 mW. Additionally, the influence of bubble radius ratio and the distance of bubble centers on coalescence are analyzed, and three bubble coalescence modes are determined, Coalescence-Moving, Coalescence-Jumping, and Coalescence-Detachment. It is found that the smaller the bubble radius ratio is, the more likely the Coalescence-Jumping mode appears. Under the condition of the bubble radius ratio is less than 3.2, when the distance of bubble centers is greater than 0.64 times the detachment diameter predicted by the buoyancy-driven model, the bubble coalescence induced bubble detachment, and the coalescence mode is Coalescence-Detachment.