Nickel–cobalt electrodeposited alloys for hydrogen evolution in alkaline media

A highly active hydrogen evolution electrocatalyst based on a cobalt–nickel sulfide composite electrode

“…Such synergistic effects had also been previously observed in Ni-Co alloys for hydrogen evolution, which were found to be superior to pure Ni or pure Co catalysts. 46 Our hypothesis was also supported by electrochemical impedance spectroscopy (EIS) measurements, which further unveiled the main differences in the electrochemical properties of the mono and bimetallic catalysts. The Nyquist plots for the Co 9 S 8 -Ni x S y /Nif and Ni 3 S 2 /Nif are reported in Fig.…”

Electrocatalytic Activity of the Ni57.3Co42.7 Alloy for the Hydrogen Evolution

“…Thus jo of 1.7 × 10 -6 A cm -2 obtained for polycrystalline Ni is in a good accordance with the values of jo equal to of 1.1 × 10 -6 A cm -2 [29] and 1.8 × 10 -6 A cm -2 [30] reported for Ni. The value for jo equal to 5.6 × 10 -7 A cm -2 obtained for Co is comparable with the values jo equal to of 8.4 × 10 -6 A cm -2 [12] and 6.8 × 10 -7 A cm -2 [31] reported for Co. The obtained value of jo for Ni-Ca alloy, 1.8 × 10 -6 A cm -2 , is significantly higher than the value for Co, but little lower than that for polycrystalline Ni.…”

“…Obtained values for cathodic Tafel slopes bc and exchange current densities are in good accordance with the values obtained from quasipotentiostatic dc measurements. Lupi et al [31] have shown that the highest exchange current densities were measured for the Ni-Co alloys with the Co content between 41 and 64 weight percent. It means that the synergism of the catalytic properties of nickel (low hydrogen over-potential) and of cobalt (high hydrogen adsorption) is best realized at these electrodes.…”

Alkaline Electrolysis with Skeletal Ni Catalysts

“…This material was compared with Ni electrodes finding an exchange current density (io) seven times larger, obtaining a good chemical stability in alkaline solutions. On the other hand, studies on Ni-Co alloys [13], also prepared by electrodeposition, have shown that the overpotential for the hydrogen evolution reaction is smaller when the material has Cobalt content between 41%-65% weight percent. Additional work [14], where Ni was alloyed with 47.7% weight percent Co, showed good electrocatalyst activity and electrochemical studies revealed that the Volmer reaction is the controlling step of the hydrogen evolution reaction, promoting the Ni-Hads species formation.…”