Improved hole extraction and durability of BiVO4 photoanode for solar water splitting under extreme pH condition

The artificial photosynthesis system relies on the semiconductors that are chemically stable and can efficiently capture solar energy. However, material stability and water splitting efficiency are often poor under the harsh conditions because of thermodynamic and kinetic challenges that hamper its practical use in large-scale integrated devices. Here, we integrate BiVO4 photoanode into a metal-insulator-semiconductor (MIS) device to provide high stability. In addition, graphene is employed as hole extraction layer between catalyst and insulator layer to provide high-density states at the interface of the insulator to efficiently improve hole tunneling efficiency in BiVO4 MIS photoanode without reducing the light absorption. With graphene hole extraction layer, the photocurrent of BiVO4 photoanode can be increased nearly 1.5 times. More importantly, BiVO4 MIS photoanode exhibits high stability in alkaline environments (pH = 13).