Fabrication of Ni nanowires for hydrogen evolution reaction in a neutral electrolyte

Hydrogen evolution reaction in 1 M Na2SO4 was investigated using Ni nanowires in diameter of 250 nm with exposed lengths of 20, 35, and 45 mu m, respectively. The Ni nanowires were fabricated by a direct-current pulse electrodeposition technique using an anodic aluminum oxide template, followed by selective removal of the supporting pore walls. Scanning Electron Microscope images revealed structural stabilities and X-ray diffraction pattern indicated a polycrystalline fcc phase. In current-potential (i-V) polarizations, the Ni nanowires with longer exposed lengths demonstrated larger current responses. Analysis from impedance spectroscopy confirmed increasing double-layer capacitances with longer Ni nanowires. in galvanostatic lifetime experiments, the freestanding Ni nanowires exhibited a reduced overpotential over that of supported ones. Similar procedures were performed for the oxygen evolution reaction in both i-V and lifetime measurements. For the Ni nanowires of 45 pm length, we estimated the energy cost for hydrogen production was 5.24 x 10(5) J/mole. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.