Photocatalytic reduction of CO2 with H2O to CH4 over ultrathin SnNb2O6 2D nanosheets under visible light irradiation

Abstract

Monolayer SnNb₂O₆ two-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 SnNb₂O₆ nanosheets are applied to the photocatalytic reduction of CO₂ with H₂O to CH₄ in 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 SnNb₂O₆ samples 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 SnNb₂O₆ are greatly improved compared with the counterpart prepared by traditional solid state reaction. Furthermore, the adsorption capacity of CO₂ on SnNb₂O₆ nanosheets is much higher than that of layered SnNb₂O₆. Thus, the photocatalytic activity of SnNb₂O₆ nanosheets for the reduction of CO₂ is about 45 and 4 times higher than those of the references (layered SnNb₂O₆ and common N-doped TiO₂), respectively. To understand the interactions between the CO₂ molecule 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 CO₂ with H₂O to CH₄ on SnNb₂O₆ nanosheets is proposed. We believe this work will provide new opportunities for expanding the family of visible-light driven photocatalysts for the reduction of CO₂.