Identification of Active Sites for Reverse Water–Gas Shift Reactions on Pt/TiO2Cluster Catalysts

Abstract

The reverse water–gas shift (RWGS) reaction is a key process for CO2conversion and sustainable fuel production, yet the nature of the active sites on Pt/TiO2cluster catalysts remains elusive. Using first-principles microkinetic simulations, we systematically investigated the catalytic behavior of Pt clusters on TiO2under operational reaction conditions. We studied three distinct catalytic sites─Pt cluster surfaces, oxygen vacancies (OV) on TiO2, and Pt–OV–Ti interfaces─and revealed that the Pt–OV–Ti interface exhibited the highest RWGS activity via a redox mechanism. This synergy enhances CO2activation and facilitates oxygen reduction more effectively than the isolated OVon TiO2, which show 4-fold lower activity. In contrast, CO-covered Pt clusters show minimal CO2activation but serve as H2dissociation sites, enabling hydrogen spillover to adjacent OVon TiO2, thereby sustaining the RWGS process. Kinetic analysis revealed OH reduction to H2O as the rate-determining step on both interfacial Pt–OV–Ti and at the OVon the TiO2–Xsupport. These findings highlight the pivotal role of the Pt–OV–Ti interface in driving the RWGS and offer a design strategy for optimizing high-temperature CO2hydrogenation catalysts by maximizing the number of interfacial active sites.