Synergistic toluene degradation by Co/Fe foam monolithic catalyst coupled with floating electrode plasma

A plasma-catalytic system coupled with floating electrode discharge with metal foam-supported catalysts was developed for efficient toluene degradation. The influences of different transition metal oxides (Co, Mn, Ce) loaded onto Fe foam (FF) substrates on the crystal structure, surface morphology and catalytic performance were systematically investigated. Catalysts were symmetrically placed on both sides of the floating electrode. Among the investigated metal oxides, Co was found to form a uniformly distributed CoFe 2 O 4 surface layer on the FF substrate, while Mn and Ce were heterogeneously dispersed as MnO 2 and CeO 2 , respectively. All metal-loaded catalysts enhanced the discharge power of the reactor, attributed to surface charge accumulation on metal oxides. The Co/FF catalyst exhibited the highest toluene degradation efficiency, CO 2 selectivity and O 3 decomposition capability. This plasma-Co/FF system significantly reduced the O 3 concentration from 112 ppm (plasma alone) to 26.2 ppm at a specific input energy (SIE) of 232 J/L. Density functional theory (DFT) calculations suggest that Co sites in CoFe 2 O 4 possess a lower O 3 adsorption energy and higher charge density potential to a higher oxygen vacancy formation tendency, promoting O 3 activation. This study provides an understanding of the mechanistic basis for the rational design of efficient plasma-catalytic systems for toluene removal.