Identification of Active Sites for Reverse Water-Gas Shift Reactions on Pt/TiO(2) Cluster Catalysts

The reverse water-gas shift (RWGS) reaction is a key process for CO(2) conversion and sustainable fuel production, yet the nature of the active sites on Pt/TiO(2) cluster catalysts remains elusive. Using first-principles microkinetic simulations, we systematically investigated the catalytic behavior of Pt clusters on TiO(2) under operational reaction conditions. We studied three distinct catalytic sitesPt cluster surfaces, oxygen vacancies (O(V)) on TiO(2), 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 CO(2) activation and facilitates oxygen reduction more effectively than the isolated O(V) on TiO(2), which show 4-fold lower activity. In contrast, CO-covered Pt clusters show minimal CO(2) activation but serve as H(2) dissociation sites, enabling hydrogen spillover to adjacent O(V) on TiO(2), thereby sustaining the RWGS process. Kinetic analysis revealed OH reduction to H(2)O 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 CO(2) hydrogenation catalysts by maximizing the number of interfacial active sites.