In situ surface chemical properties and catalytic performances of Pt/CeO2 catalyst in methane partial oxidation under different conditions

The changes of oxygen vacancies and Pt valence on ceria supported precious metals materials often occur in methane partial oxidation reaction, leading to catalyst and reactivity variability. In this work, in situ X-ray photoelectron spectroscopy were used to investigate the surface chemical properties under no or different gas-phase oxygen concentrations and reaction temperatures, then the correlation between the chemistries with reaction performance were proposed. When only methane is present, reactive oxygen on catalyst surface are the oxygen source for methane oxidation. The oxygen vacancies on catalyst are abundant and part of Pt is reduced to zero valence. However, when the mixture of methane and oxygen is present at low temperature, gas-phase oxygen cannot be utilized directly, but could absorb on the oxygen vacancies and Pt, making oxygen vacancies reduction and Pt oxidation. Only when the temperature is higher than 400 °C, it can be converted into reactive oxygen species to participate in reaction, simultaneously, oxygen vacancy generation and Pt reduction, promoting the reaction continuous. Before the reaction begins, it is necessary to keep the catalyst rich in oxygen vacancies and metallic state of Pt for methane conversion at low temperature. The research is helpful to design catalysts and improve reactivity.