Exploration of the basic reactant in CO2 photoreduction: New insights from photophysics and photochemistry

Photoreduction of CO2 as an attractive path for CO2 conversion has drawn widespread interest. Experiments demonstrating the photoreduction of CO2 are conducted in water solution in the excited state, and solvent molecules play a major role in the reaction mechanism. Thus, a simple gas-phase CO2 model of the ground-state cannot fully demonstrate the characteristics of aqueous CO2 and the mechanisms of CO2 photoreduction in the excited state. A deep understanding of the characteristics of aqueous CO2 as the basic reactant is the cornerstone for the development of photocatalysts. In this study, a systemic investigation involving photophysics and photochemistry was performed to determine its existential status, kinetic and thermodynamic characteristics. In the excited state, H2CO3 as the main inorganic carbon in pure water should be considered in the photoreduction of CO2, and the development of photocatalysts should compatible with its characteristics.