Identification of Active Sites for Reverse Water-Gas Shift Reactions on Pt/TiO₂ Cluster Catalysts

The reverse water-gas shift (RWGS) reaction is a key process for CO₂ conversion and sustainable fuel production, yet the nature of the active sites on Pt/TiO₂ cluster catalysts remains elusive. Using first-principles microkinetic simulations, we systematically investigated the catalytic behavior of Pt clusters on TiO₂ under operational reaction conditions. We studied three distinct catalytic sitesPt cluster surfaces, oxygen vacancies (O_V) on TiO₂, and Pt-O_V-Ti interfacesand revealed that the Pt-O_V-Ti interface exhibited the highest RWGS activity via a redox mechanism. This synergy enhances CO₂ activation and facilitates oxygen reduction more effectively than the isolated O_V on TiO₂, which show 4-fold lower activity. In contrast, CO-covered Pt clusters show minimal CO₂ activation but serve as H₂ dissociation sites, enabling hydrogen spillover to adjacent O_V on TiO₂, thereby sustaining the RWGS process. Kinetic analysis revealed OH reduction to H₂O as the rate-determining step on both interfacial Pt-O_V-Ti and at the O_V on the TiO_2-X support. These findings highlight the pivotal role of the Pt-O_V-Ti interface in driving the RWGS and offer a design strategy for optimizing high-temperature CO₂ hydrogenation catalysts by maximizing the number of interfacial active sites.