Synthesis of copper nanowire decorated reduced graphene oxide for electro-oxidation of methanol

Abstract

Hierarchical copper nanowires (Cu NWs) having structures of rose-like stems with nano-thorns, with an average length and width of 6 ± 4 μm and 100 ± 15 nm, respectively, are prepared through a simple hydrothermal approach. In the presence of catechin, nano-thorn growth readily occurs from the side faces (200) of rose-like stems that are partially covered with ethylenediamine (EDA) that acts as a complexing agent for Cu²⁺. The size and morphology of Cu NWs are highly dependent on the concentrations of catechin, EDA, and reaction time. The hydrothermal approach is further applied to the preparation of a Cu NW decorated reduced graphene oxide (Cu NW@RGO) composite in the presence of graphene oxide (GO) and catechin as a reducing agent. The Cu NWs in Cu NW@RGO have a similar structure to that of Cu NWs prepared in bulk solution, with an average length and width of 4 ± 2 μm and 200 ± 4 nm, respectively. The Cu NW@RGO relative to Cu NWs has greater dispersion in aqueous solution, mainly because of greater hydrophilicity of RGO than Cu NW. The Cu NW@RGO-GCE relative to the bare glassy carbon electrode (GCE) (236 Ω) and Cu NW-GCE (322 Ω) has a small charge transfer resistance value (87 Ω), because of the facile electron transfer ability and good conductivity provided by RGO. The Cu NW@RGO composite featuring low-cost, high durability, low onset potential (ca. 0.48 V) and high mass activity (1.11 mA μg⁻¹) exhibits a superior catalytic activity for methanol oxidation in an alkaline medium.