Unravelling the critical role of silanol in Pt/SiO2 for room temperature HCHO oxidation: An experimental and DFT study

Abstract

In the present work, Pt/SiO2 catalysts have been prepared by impregnating as-prepared Pt NPs onto commercial SiO2 of tailored silanol density (2.3, 3.1 and 4.5 OH nm−2) produced through hexamethyldisilazane passivation. The resulting Pt/SiO2 catalysts were then tested for formaldehyde (HCHO) total oxidation. The catalytic tests showed that high surface silanol density led to lower apparent activation energy (from 40.7 kJ⸱mol−1 at 2.3 OH nm−2 to 21.9 kJ⸱mol−1 at 4.5 OH nm−2)), allowing formaldehyde total oxidation in dry and wet conditions (100% conversion into CO2 over Pt/SiO2 (4.5 OH nm−2) at room temperature in dry condition, among the best catalytic performances reported). DFT calculations described the different interaction behaviours of HCHO, H2O, CO and CO2 on pure SiO2 and Pt/SiO2 (1.1–7.2 OH nm−2) surface, showing the critical role of silanols in the total oxidation of formaldehyde over Pt/SiO2 in different humid conditions.