In Situ Observations of Molecular CO2 Interaction on SnS2 Thin Film for Gas-Phase Photocatalytic CO2 Reduction Activity

Abstract

Among the several approaches, the gas phase photocatalytic conversion of CO2 to useful fuels with the help of renewable energy sources and water vapor has attracted widespread attention. In this system, the gas-solid interaction between a CO2 molecule and a solid catalyst surface is a crucial step. However, the adsorbate-catalyst surface interaction in the gas-phase of CO2 reduction system on the surface of semiconductor photocatalysts remains unaddressed.In this report, high-quality SnS2 thin film was prepared through a chemical vapor transport process followed by controlled carbon implantation to form C-SnS2. Our material design and characterization approaches, which involve in-situ observations enabled us to correlate the adsorbate-catalyst surface interactions and their implications on photocatalytic CO2 reduction. Using in-situ dark current and in-situ Raman spectroscopy, under different gas ambient conditions, we have observed that, the C-SnS2 surface exhibited a strong affinity towards CO2 molecule and higher photon to electron conversion efficiency under light illumination. In addition, the optimized carbon implanted SnS2 sample has demonstrated more than 108 times enhancement in the CO2 conversion efficiency and about 89% product selectivity towards CH4 formation. Additional information on the mechanism of interfacial charge transfer was obtained using angle-dependent XANES, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) analysis.We anticipate that the adsorbate-catalyst surface interaction studies applied in this report can be extended to be used as a benchmark in design and material selection in the gas-phase CO2 photoreduction applications. We further expect that C-SnS2 with its promising photocatalytic performance and high affinity toward CO2 adsorption and activation; will inspire the development of new semiconductor photocatalysts by modifying it with metal or non-metal dopants towards CO2 conversion into useful products. The detail characterization and experimental results with the future perspective of this study will be presented.