Single pulse deposition of Pd-Ag alloy nanowires on highly oriented pyrolytic graphite: A mechanistic assessment

Single pulse electrodeposition, which differs from the method of multi-pulse electrodeposition, is a process of fabricating nanowires by synchronous nucleation and growth. This report discusses the mechanistic aspect of the effect of overpotentials on the formation of Pd-Ag alloy nanowires on Highly Oriented Pyrolytic Graphite (HOPG) in the process of single pulse electrodeposition. The experiment results show that the deposition of Pd-Ag alloy nanowires at the overpotential of 100-150 mV can be described as an instantaneous nucleation mechanism on active sites of HOPG and a diffusion-controlled 3-D growth. However, when the overpotentials are below 100 mV or over 150mV, the diffusion-controlled growth is not obeyed in the process of electrodeposition of Pd-Ag alloy. The Pd-Ag alloy nanowires with diameters ranging from 60 to 150 nm and lengths up to 300 mu m have been obtained on HOPG by single pulse electrodeposition at the overpotential of 120-150 mV. The alloy nanowire arrays thus deposited are continuous, parallel, and ordered. The Ag content of the alloy nanowires is found to be in the range of 16-25%. These results are discussed to assess some of the mechanistic aspects of the electrodeposition process. (C) 2007 Elsevier Ltd. All rights reserved.