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

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.