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 degrees 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-O-x-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.