Photocatalytic reduction of CO₂with H₂O to CH₄over ultrathin SnNb₂O₆2D nanosheets under visible light irradiation

Monolayer SnNb2O6two-dimensional (2D) nanosheets with high crystallinity are prepared by an one-pot and eco-friendly hydrothermal method without any organic additives. For the first time, these SnNb2O6nanosheets are applied to the photocatalytic reduction of CO2with H2O to CH4in the absence of co-catalysts and sacrificial agents under visible light irradiation. The structural features, morphology, photoabsorption performance, and photoelectric response have been investigated in detail. Results show the as-prepared SnNb2O6samples with typical 2D nanosheets in the thickness of about 1 nm. Owing to the unique features of the nanosheets, the surface area, photoelectrical properties and the surface basicity of SnNb2O6are greatly improved compared with the counterpart prepared by traditional solid state reaction. Furthermore, the adsorption capacity of CO2on SnNb2O6nanosheets is much higher than that of layered SnNb2O6. Thus, the photocatalytic activity of SnNb2O6nanosheets for the reduction of CO2is about 45 and 4 times higher than those of the references (layered SnNb2O6and common N-doped TiO2), respectively. To understand the interactions between the CO2molecule and the surface of the photocatalyst, and the reactive species in the reduction process, the intermediates have also been detected by in situ FTIR with and without visible light irradiation. Finally, a possible mechanism for the photocatalytic reduction of CO2with H2O to CH4on SnNb2O6nanosheets is proposed. We believe this work will provide new opportunities for expanding the family of visible-light driven photocatalysts for the reduction of CO2.