Nonthermal plasma catalysis for toluene decomposition over BaTiO_3-based catalysts by Ce doping at A-sites: The role of surface-reactive oxygen species

摘要

The insights on the primary surface-reactive oxygen species and their relation with lattice defects is essential for designing catalysts for plasma-catalytic reactions. Herein, a series of Ba1-xCexTiO3 perovskite catalysts with high specific surface areas (68.6-85.6 m(2)g(-1)) were prepared by a facile in-situ Ce-doping strategy and investigated to catalytically decompose toluene. Combining the catalysts with a nonthermal plasma produced a significant synergy effect. The highest decomposition efficiency (100%), COx selectivity (98.1%), CO2 selectivity (63.9%), and the lowest O-3 production (0 ppm) were obtained when BC4T (Ce/Ti molar ratio = 4:100) was packed in a coaxial dielectric barrier discharge reactor at a specific input energy of 508.8 J L-1. The H-2-TPR, temperature-programmed Raman spectra, EPR and OSC results suggested that superoxides (center dot O-2(-)) were the primary reactive oxygen species and were reversibly generated on the perovskite surface. Molecular O-2 was adsorbed and activated at the active sites (Ti3+-V-o) via an electron transfer process to form center dot O-2(-) Surface-adsorbed center dot O-2(-) had a greater effect on the heterogeneous surface plasma reactions than the dielectric constant, and enhanced the toluene decomposition and intermediate oxidation. A possible reaction path of toluene decomposition was also proposed.