Sputter deposited nanocrystalline Ni and Ni-W films as catalysts for hydrogen evolution

Nanocrystalline nickel (nc-Ni) and Ni-W alloy coatings prepared by dc magnetron sputtering deposition method are very interesting materials due to their enhanced mechanical, catalytic and corrosion properties. The XRD analysis revealed that the grain-size of the as prepared Ni-films is about 10 nm. The Ni-W films exhibited microcrystal line structure in the examined composition range Ni95W5-Ni75W25. Their catalytic properties for the hydrogen evolution reaction (HER) were investigated in an alkaline electrolyte solution and comparative measurements were conducted on the electrodeposited Ni-electrode. The kinetic parameters deduced from linear polarization and electrochemical impedance spectroscopy (EIS) measurements indicated outstandingly high electrocatalytic activity of Ni-W and nc-Ni films. The best performance toward the HER demonstrates the Ni90W10 alloy in accordance with the prediction based on the electronic structure calculations and the enhanced density of states at the Fermi level of the 3d Ni band. Improved catalytic activity for the HER of nc-Ni in comparison with polycrystalline Ni was in accordance with 28% increase in the intercrystalline volume fraction at the very small grain size of sputter deposited Ni. (c) 2006 Elsevier B.V. All rights reserved.