Amine-functionalized reduced graphene oxide-supported silver nanoparticles for superior catalytic reduction of organic pollutants.

Abstract

In this work, a simple and environmentally friendly approach has been followed to synthesize amine-functionalized reduced graphene oxide (RGO)-supported silver nanoparticle (AgNPs) having superior catalytic efficiency towards the reduction of organic pollutants. RGO/AgNPs nanohybrid was synthesized by a one-pot hydrothermal reduction of silver nitrate in the presence of amino-propyl trimethoxy silane (APTMS)-functionalized graphene oxide (GO) nanosheets. The structural and morphological characterization of as-synthesized RGO/AgNPs nanohybrid was done by using XRD, SEM, TEM, FT-IR, and Raman spectroscopy techniques. APTMS plays an important role in controlling the size of anchored AgNPs on the nanohybrid in the present study. The -NH2 groups on the surface of APTMS-modified GO function as effective and well-organized nucleation centers facilitating uniform growth of discrete and smaller-sized spherical AgNPs on the surface of RGO nanosheets. In the absence of APTMS, the nanohybrid comprised of bigger-sized AgNPs with few hundred of nanometers in dimension. The catalytic efficiency of RGO/AgNPs nanohybrid was evaluated for the reduction of two model organic pollutants: 4-nitrophenol (4-NP) and methylene blue (MB). Due to the synergistic effects of RGO, APTMS, and Ag components, RGO/AgNPs nanohybrid developed in the present study exhibited superior catalytic activity towards the reduction of 4-NP and MB in comparison with previously reported graphene/graphene oxide/reduced graphene oxide-supported AgNPs catalysts. The catalytic reduction of 4-NP and MB followed pseudo-unimolecular kinetics and the rate constants were found to be 18.83 × 10-3 s-1 and 131.5 ×10-3 s-1 respectively for 4-NP and MB. Furthermore, RGO/AgNPs nanohybrid showed admirable recyclability with negligible loss in its activity until five recycle runs. The superior catalytic activity, favorable kinetic parameters, and sustained catalytic efficiency after recycling make RGO/AgNPs nanohybrid a promising catalyst for the reduction of organic pollutants in environmental remediation.