Mixed solvothermal synthesis of hierarchical ZnIn2S4 spheres: specific facet-induced photocatalytic activity enhancement and a DFT elucidation

Abstract

A series of ZnIn₂S₄ materials have been synthesized by a simple mixed solvothermal process in a water–ethanol solution. It was found that the solvent composition had a large impact on the photocatalytic activity. A fluffy structure of ZnIn₂S₄ synthesized with 1.5 mL of water presents the highest H₂ evolution rate (268 μmol h⁻¹) under visible light (λ > 400 nm) in a SO₃²⁻/S²⁻ aqueous solution. Combining results from TEM, the intensity ratio of diffraction peaks and dye adsorption analysis, we found that the increase of {100} facets generated in the mixed solvothermal process led to a distinct enhancement of photoreactivity. To investigate the origin of the facet-dependent photocatalytic activity, an electrostatic potential calculation was conducted to investigate the electron process, which indicated that photoexcited carriers preferentially migrate to atomic steps on the {100} facets. This cooperative effect between the {100} facets and the electron diffusion process meant that the {100} facets improve the photoreactivity of ZnIn₂S₄.