Identification of relevant active sites and a mechanism study for reverse water gas shift reaction over Pt/CeO2 catalysts

摘要

Reverse water gas shift (RWGS) reaction can serve as a pivotal stage in the CO2 conversion processes,which is vital for the utilization of CO2.In this study,RWGS reaction was performed over Pt/CeO2 catalysts at the temperature range of 200-500 ℃ under ambient pressure.Compared with pure CeO2,Pt/CeO2 catalysts exhibited superior RWGS activity at lower reaction temperature.Meanwhile,the calculated TOF and Ea values are approximately the same over these Pt/CeO2 catalysts pretreated under various calcination conditions,indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO2.TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO2 support and remarkably increased the content of Ce3+ sites on the catalyst surface.Furthermore,the CO TPSR-MS signal under the condition of pure CO2 flow over Pt/CeO2 catalyst is far lower than that under the condition of adsorbed CO2 with H2-assisted flow,revealing that CO2 molecules adsorbed on Ce3+ active sites have difficult in generating CO directly.Meanwhile,the adsorbed CO2 with the assistance of H2 can form formate species easily over Ce3+ active sites and then decompose into Ce3+-CO species for CO production,which was identified by in-situ FTIR.