Gold catalysts supported on the mesoporous nanoparticles composited of zirconia and silicate for oxidation of formaldehyde

Gold was loaded onto porous nanocomposite of ZrO2 and silicate by deposition–precipitation. The resulting Au/ZrO2-nanocomposites are found to be superior catalysts for removal of formaldehyde from indoor air at moderate temperature by oxidation. They have large specific surface areas and allow the gold to be adequately dispersed as small nanoparticles (NPs). According to the analysis of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in the as-prepared catalyst, gold was well dispersed and in an oxidized state of Au3+; and it was reduced to metallic crystals (Au0) during its use as catalyst. The temperature programmed desorption (TPD) results show that gold species in the two states strongly adsorb HCHO molecules at ambient temperature. The adsorbed HCHO molecules convert rapidly into formate species, as observed by the infrared spectra. The temperature programmed surface reaction (TPSR) study reveals that at temperatures below 450K, the HCHO oxidation involves reaction between adsorbed formate species and adsorbed oxygen molecules. This explains why the gold species in both states are the active sites for HCHO oxidation, and also indicates that HCHO adsorption on the gold species and oxygen adsorption on the support are crucial steps for the oxidation.