Double dielectric barrier discharge incorporated with CeO2-Co3O4/γ-Al2O3 catalyst for toluene abatement by a sequential adsorption–discharge plasma catalytic process

As a promising technique to remove volatile organic compounds (VOCs), non-thermal plasma (NTP) has been paid much attention recently. However, the practical implementation of NTP is limited owing to its disadvantages such as low mineralization rate, unsatisfactory energy efficiency and the generation of multiple byproducts. Reactor configuration optimization and plasma coupled catalysis are the two alternatives to improve the efficiency of NTP. A packed bed double dielectric barrier discharge (DDBD) system was established and the performance of CeO2-Co3O4 catalysts for toluene abatement was evaluated in a sequential process. It was found that complete toluene removal could be achieved in the DDBD reactor packed with different catalysts. Among them, CeO2-Co3O4 binary catalysts showed higher toluene degradation performance than monometallic samples and Ce1Co3 had the best mineralization rate (89.68%) and energy yield (3.04 g/kWh). The effects of Ce/Co ratio on the structural and redox characteristics of the samples were analyzed by BET, XRD, TEM, XPS and H2-TPR. The superior catalytic activity was attributed to the interplay between Ce and Co species, which created abundant defects and oxygen vacancies and improved the concentration of surface adsorbed oxygen and the reducibility of catalyst. The effects of the relative parameters, such as applied voltage, toluene adsorbed amount and discharge time on the toluene degradation efficiency were also explored. Finally, the toluene decomposition mechanism in the DDBD catalytic system was speculated according to the detected organic products. The findings in this work can provide vital insight in plasma catalytic degradation of VOCs by sequential process.