A review of metal oxide-based Z-scheme heterojunction photocatalysts: actualities and developments

Metal oxide-based Z-scheme heterojunction photocatalyst can effectually separate electrons and holes and simultaneously ensure that photocatalysts can maintain appropriate conduction band (CB) and valence band (VB) positions, thus maintaining a strong redox capacity. This article introduced the mechanism and types of Z-scheme heterojunction photocatalysts. Nevertheless, direct Z-scheme photocatalytic mechanism was gradually replaced by new S-scheme heterojunction mechanism. Thus, this review also briefly discussed the improved Z-scheme mechanism, that is, S-scheme heterojunction, so that the mechanism of the charge transfer process could be understood more intuitively and clearly. Then we emphatically summarized the applications of different types of heterojunctions in the field of photocatalysis, ranging from environmental remediation to energy conversion. In addition, several typical traditional methods and new strategies for preparing Z-scheme heterojunctions were summed up. Finally, the breakthrough and development prospect of Z-scheme heterojunction were discussed.