Synthesis of Ultralong, Monodispersed, and Surfactant-Free Gold Nanowire Catalysts: Growth Mechanism and Electrocatalytic Properties for Methanol Oxidation Reaction

The understanding of factors influencing the growth of nanowires is critical for the precise control of the nanowire morphologies and the design of active nanowire catalysts for fuel cell reactions. While the formation of gold nanoparticles followed by self-assembly into short strings of nanowires is known, little is understood in terms of the control of the morphologies and surface properties toward enhanced electrocatalytic properties. This report describes novel findings of an investigation of the growth mechanism of ultralong, highly monodispersed, and surface surfactant-free gold nanowires (Au NWs) synthesized by a galvanic replacement reaction of Te NWs as an initial template. By manipulating reaction time and Au precursor concentration, an aggregative growth mechanism in terms of 1D and 3D growth pathways for the NW length and diameter, respectively, is revealed to be operative in the template-directed Au NW formation process, shinning some fresh insight into the controllability of the nanowire morphologies. In contrast to the use of various organic surfactants in most previous synthesis of Au NWs and catalysts, the surfactant-free Au NWs synthesized in this work have been demonstrated to exhibit enhanced electrocatalytic activities for methanol oxidation reaction, outperforming those for Au NWs with surface surfactants and Au NP counterparts.