Bimetallic Au-Cu alloy nanoparticles on reduced graphene oxide support: Synthesis, catalytic activity and investigation of synergistic effect by DFT analysis

Highly active and well defined Au-Cu nanoparticles supported on reduced graphene oxide (rGO) were synthesized by a simple and one-step deposition-precipitation method. The nanoparticles were thoroughly characterized by UV-vis, X-ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), Scanning transmission electron microscope (STEM) with line scanning and line mapping energy dispersive X-ray spectroscopy (EDS), Raman and X-ray photoelectron spectroscopy (XPS). The composition dependant catalytic activity for the synthesized catalyst was evaluated in the reduction of 4-nitrophenol (4-NP). Among different metal and bimetallic Au-Cu compositions, Au-3-Cu-1 exhibited highest activity with rate constant of 96 x 10(-3) s(-1), which is superior to all other reported work. Within the density functional theory framework, theoretical investigations of our catalyst were carried out to find the reason behind its superior catalytic activity. It has been found that unique synergistic effect between the highly dispersed Au-Cu nanoparticles and rGO support helps in the efficient adsorption of 4-NP on Au-3-Cu-1/rGO catalyst, highlighting the importance of hybrid bimetallic nanoparticle-GO structure for enhanced catalytic activity. Moreover, effect of various support materials such as activated carbon and alumina was studied on the catalytic activity of Au-Cu nanoparticles. In addition, our catalyst demonstrated excellent activity for the reduction of toxic azo dyes (congo red, methyl orange, and erichrome black T), demonstrating its ability for multiple reduction reactions. Moreover, the efficient removal of the produced amines after the reduction reaction was demonstrated via a convenient waste management strategy using an industrial solid waste red mud. Our results will lead to the possibility of designing suitable GO-based bimetallic system with superior catalytic performance in environmental remediation applications. (C) 2017 Elsevier B.V. All rights reserved.