Transient Metal Centers at the Covalent Heterointerface Favor Photocatalytic Hydrogen Evolution.

Abstract

Semiconductor heterostructures effectively promote the transfer and separation of interfacial photoinduced charges for the photocatalytic process. Herein, we constructed a direct Z-scheme SnSe2/CdS heterojunction photocatalyst. N-type SnSe2 semiconductors are suitable candidate materials for oxidation half-reactions in Z-scheme heterojunctions. The intimate atomic-level interfacial contact through Cd-Se bonds provides a better interfacial charge transport channel for the photoinduced charges. Moreover, the transient Sn4+/Sn0 centers caused by the photoredox process boost the interfacial charge transport/separation at the interface. Besides, the presence of S vacancies acting as electron enrichment centers further enhances the redox ability for hydrogen production. Therefore, the SnSe2/CdS heterostructure showed a superior visible-light photocatalytic H2-production activity of 13.6 mmol·g-1·h-1 using ascorbic acid as a sacrificial agent, which is 9.7 times higher than that of pristine CdS. The apparent quantum yield reaches 10.5% at λ = 420 nm. This work provides a useful way to improve charge transfer in the Z-scheme heterojunction photocatalyst for hydrogen production.