Nanoarchitectonics on Z-scheme and Mott-Schottky heterostructure for photocatalytic water oxidation dual-cascade charge-transfer pathways.

The bottleneck for water splitting to generate hydrogen fuel is the sluggish oxidation of water. Even though the monoclinic-BiVO (m-BiVO)-based heterostructure has been widely applied for water oxidation, carrier recombination on dual surfaces of the m-BiVO component have not been fully resolved by a single heterojunction. Inspired by natural photosynthesis, we established an m-BiVO/carbon nitride (CN) Z-scheme heterostructure based on the m-BiVO/reduced graphene oxide (rGO) Mott-Schottky heterostructure, constructing the face-contact CN/m-BiVO/rGO (CNBG) ternary composite to remove excessive surface recombination during water oxidation. The rGO can accumulate photogenerated electrons from m-BiVO through a high conductivity region over the heterointerface, with the electrons then prone to diffuse along a highly conductive carbon network. In an internal electric field at the heterointerface of m-BiVO/CN, the low-energy electrons and holes are rapidly consumed under irradiation. Therefore, spatial separation of electron-hole pairs occurs, and strong redox potentials are maintained by the Z-scheme electron transfer. These advantages endow the CNBG ternary composite with over 193% growth in O yield, and a remarkable rise in ·OH and ·O radicals, compared to the m-BiVO/rGO binary composite. This work shows a novel perspective for rationally integrating Z-scheme and Mott-Schottky heterostructures in the water oxidation reaction.