Modulating Co Species Charge Distribution in Co3O4 for Boosted Low-Temperature Complete Oxidation of VOCs: Surface Co2+-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% m-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 m-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.