Catalytic decomposition and mechanism of formaldehyde over Pt–Al₂O₃ molecular sieves at room temperature

To overcome the drawbacks of powder-like catalysts in practical application, an Al₂O₃ molecular sieve supported Pt (Pt-Al₂O₃) catalyst was prepared by the impregnation method combined with dilute hydrochloric acid solution pretreatment. The role of the pretreatment solution in catalyst preparation and formaldehyde (HCHO) decomposition over Pt-Al₂O₃ catalysts was investigated. The acid solution with pH = 1 was optimal for Pt dispersion on the Al₂O₃ surface. The Pt-Al₂O₃ catalyst was capable of achieving complete and stable HCHO oxidation at ambient temperature. In addition, the excellent activity for HCHO removal was promoted by the mesoporous structure, large specific surface area and high adsorption ability of Al₂O₃ molecular sieves, as determined by N₂-sorption studies. Dioxymethylene (DOM) and formate species were identified as major intermediates by in situ DRIFTS studies. These intermediates were subsequently oxidized into CO₂ and H₂O at ambient temperature. Moreover, a possible reaction mechanism of HCHO removal and a regeneration pathway of surface hydroxyls were proposed. This study provides new insights into the preparation of practical, low-cost catalysts for indoor air purification.