Ti3+ Defective SnS2/TiO2 Heterojunction Photocatalyst for Visible-Light Driven Reduction of CO2 to CO with High Selectivity

In recent years, defective TiO2-based composite nanomaterials have received much attention in the field of photocatalysis. In this work, TiB2was used as a precursor to successfully prepare Ti3+defective TiO2(TiO2-B) with a truncated bipyramidal structure by a one-step method. Then, the SnS2nanosheets were assembled onto the as-prepared TiO2-B through simple hydrothermal reaction. TiO2-B exhibits strong visible light absorption properties, but the recombination rate of the photo-generated electron-hole pair was high and does not exhibit ideal photocatalytic performance. Upon introducing SnS2, the heterojunction catalyst SnS2-Ti3+defective TiO2(SnS2/TiO2-B) not only possesses the strong light absorption from UV to visible light region, the lowest photo-generated charge recombination rate but also achieves a more negative conduction band potential than the reduction potential of CO2to CO, and thereby, exhibits the significantly enhanced selectivity and yield of CO in photocatalytic CO2reduction. Notably, SnS2/TiO2-B produces CO at a rate of 58 µmol·h−1·g−1with CO selectivity of 96.3% under visible light irradiation, which is 2 and 19 times greater than those of alone TiO2-B and SnS2, respectively. Finally, a plausible photocatalytic mechanism on SnS2/TiO2-B was proposed that the electron transfer between TiO2and SnS2follows the Z-scheme mode. Our results present an effective way to gain highly efficient TiO2based photocatalysts for CO2reduction by combining different modification methods of TiO2and make full use of the synergistic effects.Keywords:photocatalytic CO2reduction;TiO2nanoplates;SnS2nanosheets;Ti3+defective TiO2