Fabrication of ZnMn2O4@ZnIn2S4 ball-in-ball hollow microspheres as efficient photocatalysts for hydrogen evolution†

Semiconductor photocatalytic hydrogen evolution (PHE) has emerged as a feasible solution to address the problem of energy shortage. Hydrogen energy can thus be developed by creating a photocatalyst with a high activity for producing hydrogen and an effective charge transfer route. This study describes the preparation of innovative hierarchical ZnMn₂O₄@ZnIn₂S₄ (ZMOZ) ball-in-ball hollow microspheres as photocatalysts using a straightforward solvothermal technique. Remarkably, the PHE rate of 10% ZMOZ can reach 11.12 mmol g⁻¹ h⁻¹, which is roughly 4.9 times greater than that of pure ZnIn₂S₄ (ZIS). Aside from the benefits of building heterojunctions, the regulation of the morphology, such as hollow structures, can provide more exposed active sites and enhance the light-absorption capability by internal multilight scattering. Density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and time-resolved PL (TRPL) spectroscopy demonstrated that the charge separation efficiency in the composite was notably improved. This work offers a cost-effective and environmentally friendly method for utilizing visible light for an effective PHE.