Reduced graphene oxide supported AgxNi100-x alloy nanoparticles: a highly active and reusable catalyst for the reduction of nitroarenes

The synthesis of supported, small sized, monodisperse, surfactant free bimetallic nanoparticles (NPs) is of great importance in the field of catalysis. In this paper, we report a facile and green method to synthesize AgxNi100-x (x = 25, 50, 75, and 100) alloy NPs decorated on reduced graphene oxide (RGO) nanosheets by an in situ chemical co-reduction process for the first time. The resulting products were well characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray photoelectron microscopy (XPS) and inductively coupled plasma atomic absorption spectroscopy (ICP-AES). The in situ synthesized AgxNi100-x/RGO alloy nanocomposites showed remarkable composition dependent catalytic activity towards the reduction of 4-nitrophenol by NaBH4 with one of the best activity parameters (968 s(-1) g(-1)). The enhanced catalytic performance was observed for RGO supported NPs as compared to that of bare AgNi alloy NPs and the in situ synthesized Ag50Ni50/RGO sample was identified to be the highest active among the as-obtained nanocomposite samples. The Ag50Ni50/RGO sample catalyzed the reduction of other nitroarenes in such a way that we obtained the best ever activity parameter for those reactions also. Furthermore, the effect of support materials (activated carbon, SBA-15 or RGO) and reducing agents (ammonia borane or sodium borohydride) was studied on the catalytic activity of Ag50Ni50 alloy NPs. In addition, AgxNi100-x/RGO nanocomposites showed excellent recycling stabilities which may lead to the use of the present nanocatalyst in many more industrially important catalytic applications.