Plasma-catalytic removal of toluene over bimetallic M/Mn-BTC catalysts in dielectric barrier discharge reactor

In this study, novel bimetallic metal–organic frameworks (MOFs) catalysts were synthesized using a simple solvothermal method. These catalysts involved the incorporation of transitional metals such as Co, Cu, Ce, and Fe into Mn-BTC, which served as the precursor substrate. This approach was undertaken to address the limitations of catalytic degradation of toluene observed in both plasma-based and traditional catalytic materials. The physicochemical characterization confirmed successful synthesis of the bimetallic MOFs with well-defined crystal shape and structure. In toluene degradation experiments, the DBD-coupled bimetallic MOFs (M/Mn-BTC) presented higher toluene removal efficiency, CO2 selectivity, mineralization degree, and fewer by-products when compared to both DBD-coupled single metal MOFs and the DBD-alone system. Besides, the catalytic activity of the DBD-coupled M/Mn-BTC followed the order: Co/Mn-BTC > Cu/Mn-BTC > Ce/Mn-BTC > Fe/Mn-BTC. Furthermore, it was observed that the Co/Mn molar ratio played a significant role in influencing the properties of MOFs catalysts and subsequently had an impact on their performance. The highest catalytic activity was observed at a Co/Mn molar ratio of 1:1. Under conditions of an energy density of 808.99 J‧L-1 and an oxygen fraction of 4% (v/v), Co/Mn-BTC exhibited a CO2 selectivity of 54.1%, a mineralization degree of 93.9%, and a toluene abatement efficiency of 96.2%. Additionally, an energy efficiency of 8.32 g·kWh−1 was achieved. The mechanism of toluene degradation was analyzed, uncovering a synergistic effect between DBD and Co/Mn-BTC. High-energy electron and adsorbed oxygen (denoted as Oads), along with active oxygen species (O*) from O3 decomposition, played crucial roles in the catalytic oxidation reaction. The interactions between Mn and Co enhanced electron mobility and accelerated the formation of Oads and O*, thereby facilitating toluene oxidation within the hybrid catalytic system.