(359g) Composition and Shape Controlled Syntheses of ZnxCd1-Xs Photocatalysts for Reducing CO2 to Methyl Formate in Methanol

 Band structure-controlled Zn_xCd_1-xS photocatalysts were prepared at 160 ^oC by the hydrothermal synthesis method and used for reducing CO₂ to methyl formate (MF) in methanol via ultraviolet irradiation. The structures, morphologies and optical properties of the obtained samples had been characterized by X-ray diffraction (XRD), energy dispersive X-ray spectra (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis absorption spectra (UV-vis). The band gap of such a solid solution of the photocatalysts could be tuned between 2.59 and 3.18 eV by varying composition x. In XRD analysis, the peaks systematically shifted to larger angles as the Zn content increased. The shape of the Zn_xCd_1-xS photocatalysts changed from microsphere to inflorescence and then to rod with a decrease of Zn content in the particles. Under ultraviolet light (λ=365 nm) irradiation, the photocatalysts showed composition-dependent photocatalytic efficiencies for reducing CO₂ to MF. The samples prepared at the condition of composition x=0.42, 160 ^oC, 12 h possessed the best activity with the MF formation rate of 85.7 mmol/h/g•cat. The catalytic performance was due to an optimal balance among the crystalline structure, the morphology and the light absorption properties.