Toluene decomposition by non-thermal plasma assisted CoOx − γ-Al2O3: The relative contributions of specific energy input of plasma, Co3+ and oxygen vacancy

Abstract

Cobalt oxide (CoOx) is a common catalyst for plasma catalytic elimination of volatile organic compounds (VOCs). However, the catalytic mechanism of CoOx under radiation of plasma is still unclear, such as how the relative importance of the intrinsic structure of the catalyst (e.g., Co3+ and oxygen vacancy) and the specific energy input (SEI) of the plasma for toluene decomposition performance. CoOx − γ-Al2O3 catalysts were prepared and evaluated by toluene decomposition performance. Changing the calcination temperature of the catalyst altered the content of Co3+ and oxygen vacancies in CoOx, resulting in different catalytic performance. The results of the artificial neural network (ANN) models presented that the relative importance of three reaction parameters (SEI, Co3+, and oxygen vacancy) on the mineralization rate and CO2 selectivity were as follows: SEI > oxygen vacancy > Co3+ , and SEI > Co3+ > oxygen vacancy, respectively. Oxygen vacancy is essential for mineralization rate, and CO2 selectivity is more dependent on Co3+ content. Furthermore, a possible reaction mechanism of toluene decomposition was proposed according to the analysis results of in-situ DRIFTS and PTR-TOF-MS. This work provides new ideas for the rational design of CoOx catalysts in plasma catalytic systems.