Performance of toluene oxidation on different morphologies of α-MnO₂ prepared using manganese-based compound...

The proper disposals of spent lithium-ion batteries (LIBs) and volatile organic compounds (VOCs) both have a significant impact on the environment and human health. In this work, different morphologies of α-MnO₂ catalysts are synthesized using a manganese-based compound as the precursor which is high-selectively recovered from spent lithium-ion ternary batteries. Different synthesis methods including the co-precipitation method, hydrothermal method, and impregnation method are used to prepare different morphologies of α-MnO₂ catalysts and their catalytic activities of toluene oxidation are investigated. Experimental results show that MnO₂-HM-140 with stacked nanorods synthesized using the hydrothermal method exhibits the best catalytic performance of toluene oxidation (T₉₀ of 226 °C under the WHSV of 60,000 mL g^-1·h^-1), which could be attributed to its better redox ability at low temperature and much more abundant adsorbed oxygen species at low temperature. The adsorption abilities of toluene and the replenish rate of surface lattice oxygen can be enhanced due to the increase of oxygen vacancies on the surface of MnO₂-HM-140. Furthermore, the results of in-situ DRIFTS and TD/GC-MS imply that benzoate species are the main intermediate groups and then the reaction pathway of toluene oxidation on the surface of MnO₂-HM-140 is proposed.