One-step hydrothermal synthesis of S-defect-controlled ZnIn2S4 microflowers with improved kinetics process of charge-carriers for photocatalytic H2 evolution

Engineering lattice defects in two-dimensional (2D) sulfide semiconductors has been accepted as an effective strategy to enhance the efficiency of the solar-to-fuels conversion. Although many researches have proven the lattice defect-mediated photocatalytic activity of ZnIn2S4, the artificial control of S defects for optimizing the charge-carrier kinetics process in ZnIn2S4 has long been a challenging task. Herein, we report a facile one-step method to modulate the lattice S-content of ZnIn2S4 microflowers (MFs) only through adjusting the used amount of S-precursor in the hydrothermal solution that contains the metal precursors with a fixed Zn/In stoichiometric ratio at 1:2. We also demonstrated that the S vacancies at the In facets were the main type of lattice defects in the formed ZnIn2S4 MFs, which could enhance both the separation and migration processes of the photoinduced charge-carriers due to the existence of discrete defect energy-levels (DELs) and the reduced effective mass of electrons, as evidenced by the first-principles calculations and the electron spectra analyses. The ZnIn2S4 MFs with the optimal content of S-vacancy obtained by a hydrothermal treatment of the precursors with the Zn/In/S stoichiometric ratio of 1:2:8 possessed the long-lived photoinduced electron (-94.64 ns) for contributing to the photo-physical and-chemical processes. Thus, upon visible light irradiation, the H-2-evolution rate of this sample reached 2.40 mmol h(-1) g(-1) with an apparent quantum efficiency of 0.16% at 420 nm even though only using 5 mg of photocatalysts without any cocatalysts. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

Modulating the lattice S-content of ZnIn2S4 microflowers through a one-step method can enhance the separation and migration processes of photoinduced charge-carriers, leading to improved solar-to-fuels conversion efficiency. The optimized ZnIn2S4 microflowers exhibit long-lived photoinduced electrons under visible light irradiation, contributing to both photo-physical and -chemical processes.