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

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