▎ 摘　　要

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.