A potential recyclable catalyst: In situ growth of bimetallic Cu-Ag nanoalloy on the magnetic SiO2/Fe3O4-SiO2-NH2 nanocomposite support using a green approach

Abstract

In this study, bimetallic Cu-Ag alloy nanoparticles (NPs) are anchored on the surface of magnetic functional SiO2/Fe3O4-SiO2-NH2 nanocomposite support using glucose as a green reducing agent. SiO2/Fe3O4-SiO2-NH2 nanocomposite support is prepared in one-pot via simultaneous co-precipitation of iron salts and alkaline hydrolysis-condensation reaction of tetraethyl orthosilicate (TEOS) in presence of SiO2 sphere. Hexamethylene diamine (HMDA) and cetyltrimethylammonium bromide (CTAB) are used as functional agent and structure directing agent, respectively. Finally, Cu-Ag NPs are formed on the functional nanocomposite support via in-situ green reduction protocol to obtain SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst. A comparative study of catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) showed that calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst possessed higher reduction kinetics compared to corresponding non-calcined nanocatalyst. Similar enhancement in catalytic property for unsupported bimetallic Cu-Ag NPs is noticed after calcination. The incorporation of magnetic Fe3O4 in the SiO2/SiO2-NH2 support material also considerably enhanced the catalytic property of the nanocatalyst. The reduction reaction favorably followed pseudo-first-order kinetic rate model and the rate constants of non-calcined and calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalysts are 0.0517 and 0.0998 min−1, respectively. The magnetically separable non-calcined SiO2/Fe3O4-SiO2-NH2/Cu-Ag nanocatalyst is recyclable up to five cycles with fairly acceptable conversion.