Facet-controlled Pt/CeO₂ unlocks low-humidity HCHO oxidation via terminal hydroxyls

Room-temperature catalytic oxidation is a promising route for indoor formaldehyde abatement, yet its efficiency sharply declines under low-humidity conditions because insufficient H₂O supply limits the generation of reactive surface hydroxyls. Here, Pt/CeO₂ catalysts were tailored through facet engineering of CeO₂ nanocrystals to regulate Pt-CeO₂ interfacial structure and H₂O dissociation. Among the catalysts, the {111}-dominated layered Pt/CeO₂ catalyst (Pt/CeO₂-L) exhibited the best low-humidity HCHO oxidation performance, achieving a CO₂ yield of ∼73% at 30 °C under 20 ppm HCHO, RH = 30%, and a weight hourly space velocity (WHSV) of 210,000 mL·g^-1·h^-1. Spectroscopic and kinetic results revealed that its superior activity originated from a stronger ability to continuously generate terminal hydroxyls (OH_t) from limited H₂O and to accelerate the conversion of DOM/formate intermediates, together with efficient O₂ activation at the Pt-CeO₂ interface. These findings demonstrate that dynamic OH_t supply, rather than static oxygen vacancy abundance, is the key descriptor for low-humidity HCHO oxidation and provides a strategy for designing hydroxyl-mediated oxidation catalysts.