Revealing the positive and negative effects of strong metal support interactions on CO oxidation for Pt-supported different crystals (β- and γ-) MnO2 catalysts: Pt oxides and carbonate species

Strong metal support interaction (SMSI) between precious metals and metal oxide support is an effective strategy to improve catalyst activity. However, the interfacial effects of SMSI on the catalyst surface are not clear. In this paper, Pt/MnO₂ catalysts with different MnO₂ crystal structures (β- and γ-) are used as research objects, and operando TPR-DRIFTS-MS is used as characterization technique. Pt/β-MnO₂ exhibited the highest CO oxidation activity (200 °C) and CO₂ selectivity (100 °C) due to its excellent redox properties. Among them, β-MnO₂ surface Pt mainly exists in the form of elemental Pt, while γ-MnO₂ surface Pt mainly exists in the form of PtO₂. Different forms of Pt have positive and negative effects on different MnO₂ crystals. DFT results show that Pt/β-MnO₂ has strong adsorption capacity for CO. Operando DRIFTS results indicate that Pt/β-MnO₂ surface PtO first reacts with CO to produce PtO_v (O_v represent oxygen vacancy) at low temperature. As the temperature rises, MnO and Pt-O-Mn also participate in CO reaction, forming MnO_v, Pt-O_v-Mn and gas-phase CO₂. It is worth noting that the formation of Pt-O_v-Mn plays an important role in the activation of O₂. The surface carbonate of the catalyst inhibited the activation of Pt-O_v-Mn. More PtO sites are conducive to the production of monodentate carbonate and the easier decomposition at low temperature, which is the decisive step of CO oxidation. These findings provide strong support for understanding the effect of SMSI effect on the intrinsic configuration of catalysts.