Identification of active sites for formaldehyde oxidation on mesoporous Pt/CeO2 catalyst at ambient temperature and low humidity

Identification of active sites governing the performance of indoor formaldehyde (HCHO) oxidation at ambient temperature and low humidity is crucial for developing improved catalysts, but remains challenging. It has recently been discovered that the effective dissociation of water is of importance for HCHO oxidation at low humidity. Here, we have elaborately designed a Pt supported on three-dimensionally ordered mesoporous CeO₂ catalyst (Pt/kit-CeO₂). The Pt/kit-CeO₂ catalyst achieves ∼ 95 % CO₂ yield for a long time. The results indicate that the abundant oxygen vacancies and single coordination-unsaturated Ce sites on mesoporous CeO₂ enhance H₂O dissociation, leading to the generation of a substantial amount of terminal hydroxyl groups (OH_t). These OH_t groups promote the oxidation of intermediate dioxymethylene (DOM) and formate species, thereby regulating the catalytic activity. Additionally, the dispersed Pt facilitates the activation of O₂, generating active oxygen species (O*) that work synergistically with OH_t groups to promote the conversion of formates into CO₂. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) further elucidated the mechanism of catalyst promoting HCHO oxidation: HCHO (+O*) → DOM (+OH_t) → HCOO^–/HCOOH (+OH_t/O*) → CO₃^2–→ CO₂. We anticipate that this knowledge will inspire the development of Pt-based catalysts specifically tailored for low humidity.