Modulating Co Species Charge Distribution in Co ₃ O ₄ for Boosted Low-Temperature Complete Oxidation of VOCs: Surface Co ²⁺ –O Sites Induced Reactant Adsorption and Activation

Excessive emissions of volatile organic compounds (VOCs) into the atmosphere have posed significant risks to the environment and human health. The Co₃O₄ spinel is a promising transition metal oxide (TMO) catalyst for highly toxic benzene-series VOC elimination, and its catalytic oxidation performance is strongly dependent on the internal efficient electronic cycles of Co²⁺ ↔ Co³⁺. However, the actual contribution of Co²⁺-O during VOC removal has long been overlooked and remains unclear, which seriously hinders the further targeted design and application of the Co₃O₄ catalyst. Herein, without introducing other metal ions, the surface Co²⁺-O content and Co species charge distribution of Co₃O₄ were modulated by a H₂ reduction treatment. Compared to the original Co₃O₄ nanorods, the as-prepared Co₃O₄-HM with abundant surface Co²⁺-O exhibited significantly improved catalytic activity with a temperature reduction of 25 °C at 90% <i>m</i>-xylene conversion. Comprehensive structural characterizations combined with DFT calculations revealed that the surface Co²⁺ was reduced from bulk spinel and in situ constructed CoO-Co₃O₄ interfaces, and the rich Co²⁺-O with unpaired electrons promoted the electron transfer and redistribution. This effect further optimized the adsorption and activation of <i>m</i>-xylene and O₂, accelerating the oxidation of intermediate species to CO₂ at low temperatures. This work provides new insights into further clarifying the role of surface cation charge reconstruction in reactant molecule activation, which can guide the exploration and development of high-performance TMO catalysts.