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ABSTRACT Hydroxyl groups on advanced material catalysts typically facilitate catalytic reactions, especially in formaldehyde (HCHO) oxidation, where active hydroxyl species are crucial to the rate‐determining step, with water vapor often promoting the reactivity. However, this study observed a completely opposite effect. A hydroxy‐rich palladium/silicon dioxide catalyst (Pd/SiO 2 (H)) displayed reduced performance in HCHO oxidation under water vapor conditions, attributed to pronounced surface hydrophilicity and hydroxyl‐mediated electron depletion in Pd species, which impaired water dissociation capability. In contrast, the hydroxyl‐deficient SiO 2 support (named as SiO 2 (L)) exhibited strong interaction with loaded Pd particles, resulting in electron enrichment of the Pd species. This electronic modification enhanced the water dissociation capability, generating reactive hydroxyl species, which facilitated HCHO oxidation reactions. Combined in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) analysis and density functional theory (DFT) calculations revealed the preferential adsorption of HCHO at Pd‐Si(OH) interfacial sites, following a direct formate oxidation pathway (HCHO → HCOO → CO 2 + H 2 O). In addition to the above pathway, on hydroxyl‐deficient Pd/SiO 2 (L) catalyst, HCHO primarily adsorbs on metallic Pd particles, proceeding via a formyl (HCO) decomposition pathway (HCHO → HCO → CO + H). This study provides robust theoretical guidance for the directed design of advanced materials.
Wang et al. (Mon,) studied this question.