One-step synthesis of configurational-entropy In-doped Zn(O,S)/Zn-doped In(OH)3-xSx composite for visible-light photocatalytic hydrogen evolution reaction

Abstract

Configurational entropy composites of In-doped Zn(O,S)/Zn-doped In(OH)3-xSx has been synthesized with a one-step hydrothermal method and carefully characterized with XRD, XPS, SEM, TEM, DRS, PL, EIS, TPC, CV, and MS analyses. The composites were prepared with different sulfur amounts to obtain the optimum performance of visible-light photocatalytic HER. The primary phases of ZnS and In(OH)3 were formed after the hydrothermal process. However, the results indicated In and O were doped into ZnS lattice and induced lower bandgap values (~2.71–2.84 eV) which are active in visible-light illumination. Simultaneously, the excess Zn and S were also doped to In(OH)3 with lower bandgap values (~3.38–4.63 eV). The variation of bandgap values is due to the hybridization of In 5s5p to Zn 4s4p and O 2p to S 3p orbitals. As a result, In-doped Zn(O,S) and Zn-doped In(OH)3-xSx will be a visible-light active material for photoreaction and a favorable phase for electron transfer, respectively. Furthermore, it is also related to a possible antisite-defect formation with InZn+ to help the electron trapping and enhance the photocarrier separation, leading to an efficient photocatalytic activity. ZI-S1 with additional 5-mmol thioacetamide was found as the catalyst with the highest HER performance which achieved 730 μmol/g·h under visible-light illumination. A plausible photocatalytic HER mechanism is discussed and proposed in this work.