Enhanced photoelectrochemical water oxidation by micro− nano bubbles: Measurements and mechanisms

Micro-nano bubbles (MNBs) have attracted far-ranging attention owing to their special properties, such as large surface area, high surface energy and production of reactive oxygen species (ROS), which enable potential applications of MNBs in photocatalytic sewage treatment. Here, we proposed combining MNBs and a photoelectrochemical (PEC) reaction system to achieve efficient PEC water oxidation. The results indicated that the metal oxide photoanodes (TiO2, BiVO4 and WO3) achieved a 10%−26% improvement in photocurrent density and markedly enhanced efficiencies of charge injection and separation in MNB electrolytes. The improved PEC performance in MNBs is attributed in part to the detachment effect on the photoanode surface, which can promote oxygen bubble departure from the electrode and expose more active sites, and in part to the generated hydroxyl radical OH., which can capture photogenerated electrons quickly and increase the energy band bending between the photoanode and the electrolyte, resulting in accelerated hole transport efficiency and a reduced reaction barrier at the interface. This work illustrates a new design strategy combining MNBs to improve the performance of PEC application systems.