Enhanced adsorption and near-infrared photo reduction of Cr(Ⅵ) on polyaniline modified SnS2 nanosheets

Promoting the photocatalytic activity of narrow bandgap materials in the near-infrared region is an economical and efficient but challenge strategy to increase the utilization of sunlight. In this work, SnS2 nanosheet is modified with polyaniline (PANI/SnS2) and employed as photocatalyst for the reduction of hexavalent chromium to trivalent chromium. With the introduction of PANI, the absorbance of PANI/SnS2 increases about three times than that of SnS2 under 800 nm wavelength irradiation, and the adsorption rate of PANI/SnS2 increases about 50 times than that of SnS2. The transient photovoltage data show that the surface effective charge (ne) of 3 % PANI/SnS2, PANI, and SnS2 are 0.32, 0.06 and 0.07, respectively, indicating the highly efficient electron-hole separation and rapid electron transfer of PANI/SnS2 composites. In acidic solution, PANI/SnS2 (10 mg) can reduce 20 mg/L Cr(VI) (30 mL contaminated water) within 2 h of solar light irradiation. It is interesting to find that PANI/SnS2 also realizes excellent photocatalytic performance with the degradation efficiency of 35 % under near-infrared light irradiation, and the Cr(VI) reduction constant rate of PANI/SnS2 is about 3 times than that of SnS2 in this wavelength range. The synergistic effect of PANI and SnS2 enables the catalyst to be applied for efficient photocatalytic degradation. This design strategy can also be used for the design of catalysts for other catalytic systems.