(Invited) Defect Engineering and Surface Probing of Few-Layer MoS2 As Photocatalyst for CO2 Reduction to Solar Fuels

(Invited) Photocatalytic CO2 conversion to hydrocarbon fuels, which makes solar energy harvesting and CO2 reduction reaction (CO2RR) simultaneously, is a killing two birds with one stone approach to solving the energy and environmental problems. However, challenges are the low photon-to-fuel conversion efficiency of the photocatalysts and lack of the product selectivity. Recently, 2D-layered nanomaterials with defect engineering, e.g. the carbon interstitial-doped SnS2 nanosheets [Nature Comm. 9, 169 (2018)], have shown promise for CO2RR. Here, I will present a different case, MoS2 with vacancies controlled by plasma. Productivity and selectivity of CO2RR were found to be dependent strongly with the different Mo/S ratios of the MoS2 of single to few layers. Orders-of-magnitude enhancement in productivity and selectivity of C2 product over 97% has been obtained. The role and interplay of the defects and the hosting materials, and their effects on the adsorption of CO2 and subsequent CO2RR, studied by the near-ambient pressure X-ray photoemission spectroscopy, along with density functional theory will be discussed.