Post-plasma-catalytic removal of toluene using MnO2-Co3O4 catalysts and their synergistic mechanism

To improve toluene removal efficiency and reduce unnecessary reaction products, a system combining a dielectric barrier discharge reactor with MnO2-Co3O4 catalysts was developed. The addition of a catalyst enhanced the toluene removal efficiency, energy yield (EY), COx yield and CO2 yield, and markedly suppressed O-3 and NO2 generation compared with the non-thermal plasma (NTP) alone system. The Mn/Co molar ratio could alter the physicochemical properties of the catalysts and further influence their catalytic activity. The Mn1Co1 catalyst demonstrated the highest catalytic activity, which might be ascribed to the interactions of Mn and Co species (such as crystal structure, oxygen mobility and redox pairs of Mn4+/Mn3+ and CO2+/Co3+). In the post-NTP-catalytic system over Mn1Co1 catalyst, the toluene removal efficiency, EY, COx yield and CO2 yield were increased by 26.77%, 1.76 g kWh(-1), 25.65% and 21.07%, respectively, compared with that in the NTP alone system at specific energy densities of 423.58 J L-1, 92.59 J L-1, 456.76 J L-1 and 456.76 J L-1, respectively. The pathway of toluene degradation in the post-NTP-catalytic system over Mn1Co1 catalyst was also investigated to further understand the synergistic effect of the hybrid system.