Rational Construction of Z-Scheme CuInS2/Au/g-C3N4 Heterostructure: Experimental Results and Theoretical Calculation

Graphical Photocatalysis : The traditional p–n junction charges transfer mode at the interface of CuInS 2 /g-C 3 N 4 can be switched to Z-scheme mode in CuInS 2 /Au/g-C 3 N 4 heterostructure through Au integration by weakening the built-in electric field and improving the interfacial bonding. Two dimensional (2D) heterojunction based on g-C 3 N 4 and CuInS 2 (CIS) nanosheets has been successfully constructed with the assistance of biomolecules L-cysteine. We demonstrated that a typical p–n junction charges transfer mode of CIS/PCN (protonated g-C 3 N 4 ) can be switched to Z-scheme transfer mode through the integration of Au by weakening the role of built-in electric field. The morphology of CIS/Au/PCN can be well adjusted through the formation of Au−S covalent bond and the electrostatic adsorption between Au and PCN during the hydrothermal process. Furthermore, the intimate interface contact inside CIS/Au/PCN heterojunction was indeed constructed, which may promote the charges separation and transfer process at the interface as evidenced by ESR spectra and time-resolved PL spectra. Under visible light illumination, the CIS/Au/PCN exhibited an enhanced CO (19.46 μmol/g) and CH 4 (1.18 μmol/g) yield in CO 2 reduction, which was about 5.04 times and 2.03 times higher than pure PCN. The composite heterojunction also showed excellent photocatalytic activity for tetracycline degradation with a 87 % degradation efficiency in 1 hour, which was 2.07 times higher than pure PCN. The experimental and theoretical calculation results demonstrated that an all-solid-state Z-scheme heterojunction was formed in the CIS/Au/PCN system, which was different from the typical p–n junction charges transfer mechanism in CIS/PCN.