Electrochemical creation of surface charge transfer channels on photoanodes for efficient solar water splitting

Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water-splitting photoelectrodes. In our previous study, the electrochemical activation of Mo-doped BiVO 4 electrodes was ascribed to the removal of MoO x segregations, which are considered to be surface recombination centers for photoinduced electrons and holes. However, this proposed mechanism cannot explain why activated Mo-doped BiVO 4 electrodes gradually lose their activity when exposed to air. In this study, based on various characterizations, it is suggested that electrochemical treatment not only removes partial MoO x segregations but also initiates the formation of H y MoO x surface defects, which provide charge transfer channels for photogenerated holes. The charge separation of the Mo-doped BiVO 4 electrode was significantly enhanced by these charge transfer channels. This study offers a new insight into the electrochemical activation of Mo-doped BiVO 4 photoanodes, and the new concept of surface charge transfer channels, a long overlooked factor, will be valuable for the development of other (photo)electrocatalytic systems.