Engineering an Interfacial Facet of S-Scheme Heterojunction for Improved Photocatalytic Hydrogen Evolution by Modulating the Internal Electric Field.

Constructing a step-scheme (S-scheme) heterojunction represents a promising route to overcome the drawbacks of single-component and traditional heterostructured photocatalysts by simultaneously broadening the optical response range and optimizing the redox ability of the photocatalytic system, the efficiency of which greatly lies in the separation behaviors of photogenerated charge carriers with strong redox capabilities. Herein, we demonstrate interfacial facet engineering as an effective strategy to manipulate the charge transfer and separation for substantially improving the photocatalytic activities of S-scheme heterojunctions. The facet engineering is performed with the growth of ZnIn2S4 on (010) and (001) facet-dominated BiOBr nanosheets to fabricate ZIS/BOB-(010) and ZIS/BOB-(001) S-scheme heterojunctions, respectively. It is disclosed that a larger Fermi level difference between BiOBr-(001) and ZnIn2S4 enables the formation of a stronger built-in electric field with more serious band bending in the space charge region around the interface. As a result, the directional migration and recombination of pointless photoexcited electrons in the conduction band (CB) of BiOBr and holes in the valence band (VB) of ZnIn2S4 with weak redox ability are speeded up enormously, thereby contributing to more efficient spatial separation of powerful CB electrons of ZnIn2S4 and VB holes of BiOBr for participating in overall redox reactions. Profiting from these merits, the ZIS/BOB-(001) displays a significant superiority in photocatalytic H2 evolution over ZIS/BOB-(010) and mono-component counterparts. This work provides new deep insights into the rational construction of a S-scheme photocatalyst based on an interfacial facet design from the viewpoint of internal electric field regulation.