Photo-Initiated Reduction of CO₂ by H₂ on Silica Surface

The reduction of CO₂ is a promising route to produce valuable chemicals or fuels and create C-neutral resource cycles. Many different approaches to CO₂ reduction have been investigated, but the ability of vacuum UV (VUV) irradiation to cleave C-O bonds has remained largely unexplored for use in processes that convert CO₂ into useful products. Compared with other photo-driven CO₂ conversion processes, VUV-initiated CO₂ reduction can achieve much greater conversion under common photochemical reaction conditions when H₂ and non-reducible oxides are present. Infrared spectroscopy provides evidence for a chain reaction initiated by VUV-induced CO₂ splitting, which is enhanced in the presence of H₂ and silica. When the reaction is carried out in the presence of silica or alumina surfaces, CO yields are increased and CH₄ is formed as the only other detected product. CH₄ production is not promoted by traditional photocatalysts such as TiO₂ under these conditions. Assuming improvements in lamp and reactor efficiencies with scale up, or coupling with other available CO/CO₂ hydrogenation techniques, these results reveal a potential, simple strategy by which CO₂ could be valorized.