ELECTROCATALYTIC BEHAVIOR OF NONEQUILIBRIUM BCC NICKEL

We report on the electrocatalytic activity for the hydrogen evolution reaction (HER) on non-equilibrium b.c.c. nickel electrodes in a concen trated alkaline solution (30 wt.% NaOH). These electrodes were prepare d by mechanical alloying a mixture of nickel and aluminum powders, fol lowed by a leaching treatment. Transmission electron microscopy observ ations and X-ray diffraction patterns show the transformation of the p ure elemental powders to a nanocrystalline phase with a B2-type struct ure. After being treated with 20 wt.% KOH at 70-degrees-C, nearly all the aluminum atoms were removed and a porous b.c.c. Raney nickel was o btained. It was found that the thermodynamic potential of Ni/Ni2+ was 23 mV lower on the metastable b.c.c. nickel than that on the f.c.c. ni ckel electrode. The analysis of the HER kinetic parameters indicates a lower activity of the b.c.c. nickel, when compared with that of the f .c.c. Raney nickel catalyst. Both b.c.c. and f.c.c. nickel catalysts s how a Tafel slope of about 120 mV decade-1, but a lower roughness fact or of the b.c.c. nickel surface was deduced from the coulometric measu rements.