Promoting the Methane Oxidation on Pd/CeO2 Catalyst by Increasing the Surface Oxygen Mobility via Defect Engineering

Methane is a useful chemical resource, but removing it, a powerful greenhouse gas, is important to prevent global warming. In this study, the methane oxidation activity of conventional Pd/CeO2 catalyst was improved by enhancing the oxygen mobility of ceria surface via the simple defect engineering. Raman spectroscopy demonstrates that the defect concentration of ceria surface is reduced after high temperature treatments. Cryogenic hydrogen-temperature-programmed-reduction curves indicate that the surface oxygen of ceria in Pd/CeO2 catalysts with the reduced defect concentration became mobile, resulting in the facile reduction at the lower temperature. X-ray diffraction, X-ray photoelectron and X-ray adsorption spectroscopies show that the improvement in the surface oxygen mobility does not originate from the change in PdOx particle size nor its oxidation state. As a result, the temperature of 50 % conversion of methane shifted by 25 degrees C to the lower temperature on Pd/CeO2 catalyst with the reduced defect concentration. This work highlights that the catalytic activity can be enhanced by promoting the active participation of the surface oxygen of support.