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.