Effect of electric field on Ce doped TiO2: Lattice phase transition, Pd valence distribution and enhancement of methane oxidation activity

Abstract Electric field assisted catalysis is regarded as an emerging approach for methane catalytic oxidation in recent years. In this paper, the catalytic performance of Pd/Ce-Ti nano-catalyst for methane oxidation in an electric field was evaluated. We found appropriate Ce doping with TiO2 lattice structure are beneficial to enhance the catalytic activity (Catalyst with Ce/Ti = 0.1 has 90% CH4 conversion at 256 ℃ with 3 mA current, 30,000 mL·g−1·h−1). XRD, Raman, BET, TEM, XPS and H2-TPR were used to study the surface properties and structure changes of the catalyst in electric field. It was found metallic Pd0 generation on surface is beneficial to improve the reaction activity and electric field could promote the reduction of Pd2+ to Pd0. For Ce-Ti solid solution, electric field can induce the transformation from anatase to rutile. During the dynamic lattice phase transition, catalytic activity increased significantly in a short time, but the CH4 conversion decreased gradually as the structure became stable. In addition, Ce-Ti amorphous structure has better stability in an electric field.