Composition, morphology and photocatalytic activity of Zn-In-S composite synthesized by a NaCl-assisted hydrothermal method

Zn-In-S composites were synthesized by a NaCl-assisted hydrothermal method and characterized by an X-ray diffractometer (XRD), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), BET, UV-Vis absorption spectrometer and inductively coupled plasma-atomic emission spectrometer (ICP). The products obtained by the hydrothermal method are a single ZnIn2S4 or a composite of ZnIn2S4, ZnmIn2Sm+3, ZnS and In2S3, depending on the NaCl concentration. The samples are consisted of microspheres and sheet-like grains with a marigold-like superstructure. The grain size of the products increases and the specific surface area decreases with an increase of the NaCl concentration. Their photoactivities were evaluated by hydrogen evolution from an aqueous triethanolamine solution under visible light ([small lambda] [greater-than-or-equal] 420 nm) irradiation. 0.50 wt% Pt was deposited on the samples for the photocatalytic hydrogen evolution by in situ photoreduction. The sample obtained in the presence of 0.20 mol L-1 NaCl exhibits the highest activity for hydrogen evolution, ca. 4 times as high as that of the sample prepared without NaCl. A possible mechanism was discussed.