Nanoarchitectonics on Z-scheme and Mott–Schottky heterostructure for photocatalytic water oxidation via 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(4) (m-BiVO(4))-based heterostructure has been widely applied for water oxidation, carrier recombination on dual surfaces of the m-BiVO(4) component have not been fully resolved by a single heterojunction. Inspired by natural photosynthesis, we established an m-BiVO(4)/carbon nitride (C(3)N(4)) Z-scheme heterostructure based on the m-BiVO(4)/reduced graphene oxide (rGO) Mott–Schottky heterostructure, constructing the face-contact C(3)N(4)/m-BiVO(4)/rGO (CNBG) ternary composite to remove excessive surface recombination during water oxidation. The rGO can accumulate photogenerated electrons from m-BiVO(4) 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(4)/C(3)N(4), 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(2) yield, and a remarkable rise in ·OH and ·O(2)(−) radicals, compared to the m-BiVO(4)/rGO binary composite. This work shows a novel perspective for rationally integrating Z-scheme and Mott–Schottky heterostructures in the water oxidation reaction.