HCHO oxidation on Pt-Na/SiO2 catalyst with ultralow Pt loading: New insight into the effect of Si support and Na promoter

Modulating the electronic metal-support interaction (EMSI) is one of the effective means to promote catalytic activity because it can adjust the electron occupancy of the d-band of noble metals, further facilitating the activation of reactants. Herein, we prepared a Pt/SiO2 catalyst with an ultralow Pt loading of 0.05% and found that its catalytic activity in HCHO oxidation outperformed that of the Pt/TiO2 counterpart, owing to the EMSI effect between Pt and SiO2. On this basis, the alkali metal Na was used as a promoter, and the formation of highly active Pt-O-x(OH)-Na clusters enabled the complete oxidation of HCHO at room temperature. With ultralow Pt loading, the Pt-Na/SiO2 catalyst reduces the cost of practical application remarkably. In situ DRIFTS and DFT calculations confirmed that the reaction pathways were distinct on Pt/SiO2 and Pt-Na/SiO2. Specifically, on Pt-Na/SiO2, the reaction follows the mechanism of the direct degradation of formate species with the assistance of active hydroxyls; while on Pt/SiO2, CO is the only intermediate formed by the dehydrogenation of HCHO, due to the lack of active hydroxyls. These findings provide new insights into the reaction pathway of HCHO oxidation.