Coaxial electrospun TiO₂@CuO heterojunctions with interfacial charge rearrangement for photothermal oxidation of toluene

Constructing heterojunctions is an effective route to enhance photothermal toluene oxidation. In this work, TiO₂@CuO heterojunction catalysts with different Ti/Cu molar ratios were fabricated by coaxial electrospinning and evaluated for toluene oxidation. The activity increased with decreasing CuO loading: 1TiO₂@0.5CuO > 1TiO₂@1CuO > 1TiO₂@2CuO > CuO > TiO₂, which was attributed to greater exposure of TiO₂–CuO interfacial sites, improved charge separation, and enhanced activation of toluene and oxygen species. The optimized catalyst exhibited a pronounced photothermal synergistic effect, achieving a toluene conversion that was 28% higher at 250 °C compared with that under purely thermal catalysis. Oxygen vacancies on TiO₂ acted as electron traps, which induced interfacial electron transfer (CuO → TiO₂) and increased both the Cu²⁺ fraction and oxygen vacancy at the interface. A higher density of Cu²⁺ sites supplied more adsorption sites and reactive oxygen species, facilitating toluene activation. In situ DRIFTS resolved the pathway on 1TiO₂@0.5CuO: toluene → benzyloxy → benzaldehyde → benzoate → CO₂, with benzaldehyde oxidation as the rate-determining step; interfacial vacancies provided a route for O₂ replenishment. These findings highlight coaxial electrospinning as a promising strategy for constructing strongly coupled heterojunctions for efficient VOC oxidation under photothermal conditions.