Boosting Toluene Oxidation over Ru-Doped CoMn2O4 Spinel Catalysts by Constructing Ru–O–Mn/Co Chains

The development of efficient spinel oxide catalysts for low-temperature oxidation of volatile organic compounds (VOCs) remains an important research objective. In this work, Ru was doped into a CoMn2O4 spinel to enhance its catalytic activity toward toluene oxidation and the underlying promotion mechanism of Ru doping was systematically investigated. The resulting Ru-CoMn2O4 catalyst showed remarkable performance, with T90 reaching approximately 224 °C at a WHSV of 60,000 cm3 g−1 h−1 and nearly 100% CO2 selectivity above 200 °C. Mechanism studies revealed that the reaction followed both Mars–van Krevelen (MvK) and Eley–Rideal (E–R) pathways. The reaction rates were strongly influenced by the oxidizing capacity of the catalyst, the abundance of highly valent surface species (namely Co3+, Mn4+, and Ru4+), adsorbed toluene, lattice oxygen, gaseous toluene, and adsorbed oxygen. With Ru doping, new Ru–O–Mn and Ru–O–Co chains formed in the CoMn2O4 spinel structure, leading to a moderate enhancement in oxidizing ability and a moderate increase in the concentration of highly valent surface species, adsorbed toluene, and lattice oxygen. Although a slight reduction in adsorbed oxygen was observed, Ru doping significantly boosted the overall toluene oxidation activity of CoMn2O4. In summary, Ru-CoMn2O4 represented a promising catalyst for the efficient oxidation of VOCs.