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

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 & BULL;mol-1 at 2.3 OH nm- 2 to 21.9 kJ & BULL;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.

Automated summary

In this study, Pt/SiO2 catalysts with tailored silanol density were prepared by impregnating Pt NPs onto commercial SiO2 treated with hexamethyldisilazane passivation. The catalytic tests showed that high surface silanol density led to lower apparent activation energy, allowing for the total oxidation of formaldehyde in dry and wet conditions. DFT calculations demonstrated the critical role of silanols in the interaction and oxidation of formaldehyde over the Pt/SiO2 catalysts.