Electrochemical fabrication of three-dimensional fern-like Au nanostructure and its electrocatalytic activity towards methanol oxidation

Hierarchical nanostructures are very universal in the natural world. However, to date most of synthetic approaches are just capable of producing simple nanomaterials, such as nanospheres, nanorods, nanowires, nanopolyhedrons, etc. Fabrication of complex nanostructures has to depend on the assembly of single nano-building blocks and e-beam lithography. Thus, it is imperative to create complex nanostructures by direct synthetic methods. Herein, three-dimensional fern-like Au nanostructures (3DFGNs) were achieved simply by one-step glycine-assisted electrodeposition. The effects of glycine concentration, electrode substrate and deposition potential on the growth of Au nanostructures were explored. Over the range of glycine concentration from 1.0 mmol/L to 10 mmol/L, all Au nanostructures are 3DFGNs except for the difference of the average diameter of branches. The oriented growth of 3DFGN is attributed to the specific adsorption of NH2 groups of glycine. Each fern-like dendrite of 3DFGN is a four-fold symmetric single-crystal growing along the (111) direction. As-prepared 3DFGNs show morphology- and size-dependent electrocatalytic performance towards methanol oxidation. Optimized 3DFGN exhibits satisfactory electrocatalytic activity and long-term durability, ∼3 times in the specific activity better than island-like Au aggregates electrodeposited without glycine.