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 (OHt) 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 OHt 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.