Photocatalysis of ordered arrays of Zn:CuInS2 nanostructures for methanol formation

G-T Pan, T.F.-R. Shen, T.C.-K. Yang, C-C Chen, C-M Huang
National Taipei University of Technology, TW

Keywords: photochemical performance, photocatalysts, CO2 reduction, CuInS2

Summary:

CO2-to-CH3OH hydrogeneration reaction is one of the promising solutions to retard the greenhouse effect and produce valuable chemicals. In this study, semiconductor Zn:CuInS2 arrays were synthesized by template-assisted chemical bath deposition. The arrays were characterized by means of X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), PEC measurements, Hall measurement, Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT), Mass Spectroscopy (MS) and Gas Chromatography (GC). XRD results show that main peak of CuInS2 shifts to the higher angles when the doping concentrations of Zn increase. As molar ratios of Zn in the bath solution were higher than 0.4, the semiconductor property of the sample changed from n-type to p-type. The carrier densities of the Zn:CuInS2 arrays were found to be in the range of 1.32×1017 ~ 9.45×1020 cm-3. Additionally, water isotopes of H2O, D2O, and H218O were applied to identify the intermediates and reaction mechanism of photocatalysis. The maximum photocurrent density was 2.02 mA/cm2 for Zn-doped CuInS2 arrays (p-type). Furthermore, the rate of CH3OH production was found to be 0.032 M/hr, which is better than that of the reference CBD film (0.003 M/hr) deposited on non-porous substrate made of the same composition.