Dual-functional, highly efficient CaIn2S4/PDA@SnO2 photocatalyst with Z-Scheme for photocatalytic hydrogen production from water splitting and organic pollutant degradation

Abstract

Heterojunction can be used to develop semiconductor catalysts with high photocatalytic activity. In this work, a Z-Scheme CaIn2S4(CIS)/PDA@SnO2 photocatalyst was successfully synthesized. Firstly, SnO2 hollow nanospheres were prepared by hydrothermal method. On this basis, SnO2 hollow nanospheres wrapped by polydopamine (PDA) were obtained via self-polymerization of dopamine. Finally, the CIS/PDA@SnO2 composites were synthesized via a one-step oil bath method. The heterojunction has successfully achieved effective separation of electron-hole pairs. PDA acted as a photosensitizer and an electron transfer medium in the heterojunction. Multiple characterization techniques such as XRD, SEM, TEM, BET, XPS, PL, UV–vis DRS, EPR and photoelectrochemical measurements were used for material structure and performance analysis. The photocatalytic performance of the photocatalysts was tested by photocatalytic hydrogen production from water splitting and RhB solution degradation. A flower-like close contact between CaIn2S4 and PDA@SnO2 interfaces can be obviously observed via SEM and TEM images. The band gap energies (Eg) of CaIn2S4 and PDA@SnO2 are 2.06 eV and 3.74 eV. CaIn2S4/PDA@SnO2-1(CPS-1) exhibits stronger light absorption together with lower transfer resistance compared to other samples. CPS-1 showed excellent photocatalytic hydrogen production and RhB degradation performance. Furthermore, the results of active species capture experiments, Mott-Schottky curve, XPS measurement and other tests show that it is logical to use the Z-Scheme charge mobility process to explain the better photocatalytic activity of the CIS/PDA@SnO2 composite. This work will present an efficient option for the fabrication of Z-Scheme heterojunctions and possibly further develop a new avenue for the control of the structure of semiconductor photocatalysts.