A Nonoxide Catalyst System Study: Alkali Metal-Promoted Pt/AC Catalyst for Formaldehyde Oxidation at Ambient Temperature

Metal oxides have been extensively used as supports in noble metal-based catalysts for formaldehyde (HCHO) oxidation, utilizing the benefit of the strong metal–support interaction (SMSI). Non-oxide supported noble metal catalysts are still rarely investigated in the field of HCHO oxidation. Herein, a series of Pt catalysts supported on a nonoxide, that is, activated carbon (AC), were studied in detail. Pt/AC catalysts with or without addition of the alkali metal Na were prepared and tested for HCHO oxidation. HCHO could be completely oxidized to form H2O and CO2 at 25 °C on the Na–Pt/AC–R (reduced Na–Pt/AC) catalyst, but in contrast, the Pt/AC–R catalyst only achieved 40% HCHO conversion under the same reaction conditions. The characterization results indicated that Na addition to the Na–Pt/AC–R catalyst could induce the formation of Pt–Ox–Na species, which improves the stability of Pt species, increases Pt dispersion, and enhances the activation of chemisorbed oxygen and water to form abundant surface-active hydroxyl groups. Meanwhile, HCHO–TPD confirmed that HCHO could be transformed into CO2 and H2O directly because of the presence of abundant OH groups on the Na–Pt/AC–R catalyst. In this study, the promotion effect of alkali metals on supported Pt catalysts for HCHO oxidation was further extended to a catalyst system with a nonoxide carrier.