Synthesis of hexagonal and cubic ZnIn2S4 nanosheets for the photocatalytic reduction of CO2 with methanol

Abstract

ZnIn₂S₄ nanosheets with hexagonal and cubic structures have been prepared through a liquid ultrasonic exfoliation method and another strategy involving a lamellar hybrid, respectively. The structure, morphology, and composition properties of the as-prepared samples were characterized using X-ray powder diffraction, UV-vis spectrophotometry, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The photocatalytic activities of the as-prepared ZnIn₂S₄ samples were evaluated by methyl formate formation from CO₂ photoreduction in methanol as a solution of absorbing CO₂ and reducing agent, and the activity over hexagonal ZnIn₂S₄ was better than over cubic ZnIn₂S₄. In addition, both hexagonal and cubic ZnIn₂S₄ nanosheets displayed much higher reactivity than ZnIn₂S₄ microspheres prepared by the hydrothermal method. The electronic structures of the two phases of ZnIn₂S₄ were investigated in the light of density functional theory.