Enhanced Plasma-Catalytic Oxidation of Toluene over Spinel Oxide-Mesoporous SiO2 Composites

Plasma-catalytic oxidation is a promising approach for the abatement of volatile organic compounds (VOCs), yet its efficiency is often limited by the ineffective utilization of plasma-generated reactive oxygen species and incomplete oxidation pathways. In this work, a composite catalyst was constructed by integrating spinel-type NiCo2O4 with three-dimensional cubic mesoporous KIT-6 to couple efficient mass transfer with redox-active surface functionality for plasma-catalytic degradation of toluene. The performance of NiCo/KIT-6 was systematically evaluated in a dielectric barrier discharge (DBD) reactor and compared with Ni/KIT-6, Co/KIT-6, and NTP-only systems. XPS, O2-TPD, H2-TPR, and apparent dielectric measurements were employed to elucidate catalyst properties relevant to plasma–surface interactions. NiCo/KIT-6 exhibits superior overall performance in terms of toluene conversion, COx selectivity, and CO2 selectivity over a wide range of specific input energies. This enhancement is closely associated with the integrated regulation of surface redox properties, oxygen activation capability, and apparent dielectric response by the NiCo2O4/KIT-6 composite structure, which may promote reactive oxygen utilization and facilitates effective plasma–surface redox processes. These results provide insights into the rational design of composite catalysts for plasma-assisted oxidation of aromatic VOCs.