Synergistic effects of acid-metal dual-site of Ag-Fe/SBA-15 catalyst boosting the elimination of formaldehyde

High performance and low cost HCHO oxidation catalysts are urgently required for indoor air purification. Herein, novel Ag-Fe/SBA-15 catalysts with dual active sites were prepared and exhibited excellent HCHO catalytic oxidation activity. The dual-site Ag-2Fe/SBA-15 catalyst greatly enhanced the HCHO oxidation conversion by 25 times (100 % vs 4 %) at 65 °C compared with Ag/SBA-15 sample. The incorporation of Fe into the framework of SBA-15 changed the surface properties by generation of Lewis acidic sites, which affected the HCHO adsorption and transformation processes. Meanwhile, the metallic Ag nanoparticles were more uniformly dispersed and the average particle size became smaller. The synergistic effects between Lewis acidic sites and Ag nanoparticles remarkably enhanced the HCHO oxidation activity. HCHO was more likely to adsorb on Lewis acidic sites, and then was converted to dioxymethylene (DOM) and formate species, successively, which was finally oxidized to CO2 by O2 activated on metallic Ag nanoparticles. The activation of HCHO and O2 took place separately on the surface medium Lewis acidic sites and metallic Ag nanoparticles. These results may open a new avenue for designing high efficiency catalysts for HCHO removal by the synergistic effects of acidic and metal sites.