CO2 Activation and Reduction on Pt-CeO2-Based Catalysts

CO2 conversion plays a critical role in sustainable carbon cycling. In this work, reduction of CO2 over three Pt-decorated/undecorated CeO2-based catalysts (partially reduced CeO2(111), Pt decorated partially reduced CeO2(111), and Pt decorated partially reduced Sm0.2Ce0.8O1.9(111) (SDC) surfaces) is investigated via both density functional theory (DFT) and electrical conductivity relaxation (ECR) methods. DFT results indicate that a Pt cluster over a CeO2-based surface could effectively enhance CO2 adsorption energies and depress the energy barriers for CO2 dissociation, beneficial to the CO2 conversion. This should be ascribed to the electron transferring from the CeO2-based surface to the Pt cluster, which makes the Pt d-band center closer to the Fermi level and thus enhances the interaction between CO2 and Pt d-electrons. Intensive investigation indicates that without the Pt cluster, the CO2 molecule needs to form CO32– first and then dissociates into CO, different from the direct activation of CO2 on the Pt cluster. Importantly, the microkinetic analyses of CO2 reactions suggest that the CO2 reduction rates follow the sequence of Pt-decorated SDC surface > Pt-decorated CeO2 surface > CeO2 surface. This result is consistent with ECR measurements.