Enhanced removal of toluene by pulse discharge plasma coupled with MgO cathode and graphene Mn-Ce bimetallic oxide

Herein, MgO cathode and graphene Mn-Ce bimetallic oxide were utilized to jointly enhance the removal of toluene in pulsed discharge plasma (PDP). Compared to the common cathode, the MgO cathode enhanced the density of high energy electrons, and then induced to higher removal of toluene. However, the removal of toluene by PDP/MgO system was still insufficient, and there was a large amount of underutilized O₃ in the products. Based on this, Mn-Ce/graphene catalysts were introduced into PDP/MgO system. The Mn-Ce (8:1)/graphene catalyst had the highest catalytic activity. Under the discharge power of 2.1 W, toluene degradation rate and CO₂ selectivity increased by 27.5% and 22.0%, respectively. This was ascribed to the synergistic effect of the solid solution formed between MnO_x and CeO_x, increasing the proportion of O_ads on the surface of the catalyst. The higher O_ads/O_latt ratio lead to the better catalytic activity, which was conducive to the complete transformation of the intermediate products to CO₂ and H₂O. According to the detected products, the degradation pathway and the mechanism of toluene degradation were proposed finally. The PDP itself, field emission effect of MgO cathode and catalytic effect of Mn-Ce/graphene for jointly improve the toluene removal and CO₂ selectivity.