Pd on anionic conductive ZrO2 for low-concentration methane oxidation: Synergetic effect of plasma and catalysis

Methane (CH 4 ) is the second largest greenhouse gas; its emission should be controlled. A plasma reactor coupled with a catalyst was used to control CH 4 emission via oxidation. Compared with the traditional catalytic process, the activity of Pd/ZrO 2 /Al 2 O 3 catalyst is significantly improved, the light-off temperature ( T 50 ) is at a level of 290 °C. X-ray photoelectron spectroscopy characterization results proved that synergetic effect of plasma and catalysis on CH 4 oxidation was due to the increase in the amount of lattice oxygen on zirconia after plasma oxidation and the enhancement of the oxidation of Pd 0 to PdO on 1.0Pd/10ZrO 2 /γ-Al 2 O 3 catalyst. An operando plasma diffuse reflectance infrared Fourier transform spectroscopy mass spectrometer was used to demonstrate that CH 4 oxidation on Pd/ZrO 2 /Al 2 O 3 catalyst. It was found that 1.0Pd/10ZrO 2 /γ-Al 2 O 3 with plasma can efficiently promote CH 4 oxidation and convert surface formate and carbonate to gaseous CO 2 and H 2 O. The plasma-generated O atoms can react with surface H 2 O to yield reactive OH radicals which can obviously improve CH 4 oxidation at a temperature higher than 130 °C, this finding provides important enlightenment for the development of catalysts for plasma catalytic oxidation of CH 4 . The mechanism of CH 4 plasma-catalysis oxidation was discussed.