Unveiling the critical role of surface adsorbed oxygen species for efficiently photothermocatalytic oxidation of VOCs: Replenishing the active surface lattice oxygen sites

Surface oxygen species play a crucial role in the photothermocatalytic oxidation of volatile organic compounds (VOCs), but their exact functions and evolutionary processes remain unclear. Herein, a series of spinel Co_xMn_3-xO₄ catalysts are synthesized and employed for photothermocatalytic oxidation of toluene. Co_1.5Mn_1.5O₄ catalysts achieve 91.6 % toluene degradation and 81.2 % CO₂ yield in a continuous flow reaction under 400 mW/cm² light intensity, as well as remarked stability and water resistance. During the reaction, surface lattice oxygen on Co_xMn_3-xO₄ serves as the active sites, directly participating in the oxidation of VOCs. The replenishment pathway of surface lattice oxygen is investigated through a series of designed in situ experiments, revealing O₂ molecules adsorbed on the catalyst surface to be O₂^- species, which are then activated to O^- species via increase in temperature. The active O^- species effectively replenish the consumed surface lattice oxygen species, facilitating subsequent oxidation reactions. This study provides valuable insight into the replenishment mechanism of surface lattice oxygen during oxidation of VOCs.