Electric field promoted ultra-lean methane oxidation over Pd-Ce-Zr catalysts at low temperature

A novel catalytic system combining oxidation catalyst with electric field was applied for low-temperature CH 4 oxidation at low CH 4 concentration (0.2% CH 4 ). Compared with conventional catalytic process, significant improvement in activity was observed over PdCeZrO x catalyst in electric field. For example, the light-off temperature (T 50 ) of CH 4 (0.2% CH 4 ) of 1 wt % PdCe 0.75 Zr 0.25 O x catalyst was approximately 255 °C in an electric field with 3 mA electric current. The impact of electric field in CH 4 oxidation over PdCeZrO x catalyst was thoroughly investigated. The XRD and XPS results revealed that electric field provided free electrons that facilitated the release of lattice oxygen in the ceria-zirconia solid solution, therefore reinforced Pd0 oxidation and the formation of palladium oxide (PdO x , x  > 0) on catalyst surface. Electric field also enhanced the reducibility of the PdO x , which provided active oxygen for CH 4 oxidation at low temperature. With in-situ FTIR technique, it was found that electric field greatly promotes the chemisorption and dehydrogenation of CH 4 , thereby accelerates the chemical reactions of the intermediate products, so as to promotes CH 4 oxidation. The mechanism of catalytic oxidation of CH 4 in electric field was proposed based on comprehensive investigations above.