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 Co 3 O 4 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 Co 2+ ↔ Co 3+ . However, the actual contribution of Co 2+ –O during VOC removal has long been overlooked and remains unclear, which seriously hinders the further targeted design and application of the Co 3 O 4 catalyst. Herein, without introducing other metal ions, the surface Co 2+ –O content and Co species charge distribution of Co 3 O 4 were modulated by a H 2 reduction treatment. Compared to the original Co 3 O 4 nanorods, the as-prepared Co 3 O 4 –HM with abundant surface Co 2+ –O exhibited significantly improved catalytic activity with a temperature reduction of 25 °C at 90% m -xylene conversion. Comprehensive structural characterizations combined with DFT calculations revealed that the surface Co 2+ was reduced from bulk spinel and in situ constructed CoO-Co 3 O 4 interfaces, and the rich Co 2+ –O with unpaired electrons promoted the electron transfer and redistribution. This effect further optimized the adsorption and activation of m -xylene and O 2, accelerating the oxidation of intermediate species to CO 2 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.