HCHO oxidation over highly dispersed Au nanoparticles supported on mesoporous silica with superior activity and stability

Abstract

We firstly reported highly active Au nanoparticles catalyst supported on mesoporous silica for low-temperature HCHO oxidation. Amine as the positively charged groups was post grafted onto the surface of mesoporous silica before gold loading (PG), and it showed 15% HCHO conversion to CO2 at room temperature and complete conversion was obtained at 55 °C. No activity decrease was observed within 8 h. As comparison, mesoporous silica supported Au catalysts was also prepared by straightforward chemical reduction (CR) and impregnation (IM), which behaved poor HCHO catalytic activity with complete conversions at 200 °C and 90 °C respectively. The activation energy (Ea) for HCHO oxidation over PG was 17.6 kJ/mol, which was much lower than those (22.2–50.2 kJ/mol) over IM and CR samples. It was found that amine-functionalized mesoporous silica contributed to the well-dispersed and uniform Au nanoparticles with the optimal size distribution about 2–4 nm, and large amounts of low-coordinated Au atoms and electronic structure like bulk Au were observed on these Au nanoparticles, which accelerated HCHO adsorption and transformation into intermediate species like DOM, formate and CO(a). Particularly, the interaction between amine and Au effectively inhibited the reduction of Auδ+ to Au0, which positively contributed to the best catalytic performance. Moreover, Au/SiO2 system prepared by amine post-grafting method showed poor activity of complete combustion at 210 °C. Comparatively, it was proposed that MCM-41 with well-ordered and open ends of pore structure showed better HCHO adsorption-diffusion capacity and the ability of controlling Au particles in high dispersion, which was great benefit to the high catalytic activity of HCHO oxidation.