Mg-dominated defect engineering in Co-Mn spinels: unlocking low-temperature catalytic activity for VOC removal via...

Volatile organic compounds (VOCs), key pollutants in the atmosphere that cause air quality issues and environmental damage, are a crucial focus for catalytic oxidation. However, challenges like high operating temperatures and catalyst deactivation remain major obstacles. Herein, a Mg-dominated defect engineering approach in Co-Mn spinels was proposed to enable low-temperature catalytic activity for VOC removal through cooperative oxygen vacancy formation. Using a combined dual-liquid simultaneous titration co-precipitation method with high-temperature solid-state reactions, a series of Mg-doped MnCo₂O₄ spinels (MMC-x) with adjustable Mg/Mn molar ratios were synthesized. Structural characterization showed that Mg doping caused lattice contraction and oxygen vacancy formation, while XPS and H₂-TPR analyses confirmed increased oxygen mobility and redox activity. The MMC-0.5 catalyst showed better performance, reaching a T₉₀ (temperature for 90 % toluene conversion) of 273 °C, which is much lower than that of the undoped MnCo₂O₄(MC) catalyst (317 °C). Operando FTIR spectroscopy unveiled that the defect engineering of Mg-dominated accelerated the deep mineralization of toluene. Moreover, MMC-0.5 demonstrated excellent stability under water vapor exposure and thermal cycling. Notably, the new spinel catalyst defect engineering method discussed in this work can be applied in heavy-emission industries through low-temperature operation, thereby conserving energy and extending catalyst service life.