Elucidating Photo-Kinetic Control in Photothermal Reverse Water-Gas Shift Reaction

Unlike the well-known charge-carrier kinetics in traditional photocatalysis, a knowledge gap remains regarding the photo-kinetic effects in heterogeneous photothermal catalysis. Conventionally, light is mainly regarded as a source of charge carriers and localized heating, yet how these light-induced effects alter intrinsic reaction kinetics, particularly the rate-determining step (RDS), remains unclear. Here, we provide direct kinetic evidence that illumination tunes the RDS in an archetypal Mars-van Krevelen (MvK) reverse water-gas shift (RWGS) reaction over In-doped MoO₂. Under illumination, photogenerated electrons enrich In sites, promoting H₂ activation and spillover while accelerating H₂O desorption, thereby shifting the RDS from the H₂-reduction half-reaction to the CO₂-oxidation half-reaction. This kinetic modulation significantly enhances catalytic performance and lowers the apparent activation energy. Overall, this work elucidates the kinetic role of light in photothermal CO₂ conversion, offering new insights into optimizing solar-driven catalytic processes.