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

High Resolution Image Download MS PowerPoint Slide 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.