Preparation of Graphene-Co/Ni/Fe₃O₄ Nanocomposites and Their Electrocatalytic Activity for Reduction of p-Nitrophenol.

Graphene-based nanocomposites of graphene-Co, graphene-Ni, and graphene-Fe3O4 were synthesized via improved chemical-carbothermal reduction using graphite and nitrates as starting materials. The Co, Ni, and Fe3O4 nanoparticles are uniformly loaded on the surfaces of graphene nanosheets without serious folds and conglomeration. The average dimensions of the Co, Ni, and Fe3O4 nanoparticles attached to graphene are approximately 50, 60, and 5 nm, respectively. Subsequently, three novel types of graphene-Co/Ni/Fe3O4 nanocomposite-modified glassy carbon electrodes (GCEs) were fabricated, and their electrocatalytic activity for reduction of p-nitrophenol was investigated by cyclic voltammetry in phosphate buffer solution. Results show that the current values increase as the scanning rate is increased from 70 mV.s(-1) to 100 mV.s(-1) and that the electrochemical reactions on the surface of the graphene-Co/Ni/Fe3O4-modified GCEs are diffusion controlled. Compared with the bare GCE, the graphene-Co/Ni/Fe3O4 nanocomposite-modified GCEs display considerably higher reduction peak current, which proves that the graphene-Co/Ni/Fe3O4 nanocomposites possess favorable electrocatalytic ability for reduction of p-nitrophenol.