Hydrogen Evolution In Alkaline Media Research Articles

Nickel–cobalt electrodeposited alloys for hydrogen evolution in alkaline media

Abstract A study on the electrocatalytic performances of nickel–cobalt alloys for hydrogen evolution in alkaline media has been carried out. After preparing, by electrodeposition on aluminium net supports, Ni–Co alloys of various compositions ranging from 0 to 100% Ni, the alloys were examined by polarization measurements, to evaluate their discharge potential and Tafel parameters. Moreover a durability test has been done on the alloys showing, among all, the best performance. The hydrogen over-potential appears to be lower in the case of Ni concentrations ranging between 35 and 59 weight percent. The synergism among the nickel catalytic properties, having low hydrogen over-potential and high hydrogen adsorption of cobalt, is best realized in this conditions and allow obtaining a largest value of exchange current density.

Electrocatalytic properties of Ni-S-Co coating electrode for hydrogen evolution in alkaline medium

Amorphous Ni-S-Co alloy was prepared by means of chemical electro-deposition method on the foam nickel matrix. The surface morphology and microstructure of Ni-S-Co coatings were studied usmg SEM and XRD, and the electrochemical properties were tested by electrochemical methods. The results show that the coating has amorphous structure and the particles of the surface are fine with large specific surface area. The Ni-S-Co alloy is more active with lower potential for hydrogen evolution, higher exchange current density and lower activation energy compared with Ni and Ni-S electrode. Its hydrogen evolution reaction(HER) is enhanced, the size of particles of surface decreases and the surface area increases after being activated by KOH alkaline solution.

Reactivation of nickel cathodes by dissolved vanadium species during hydrogen evolution in alkaline media

Abstract Nickel undergoes significant deactivation as a cathode during alkaline water electrolysis in 8 mol/l KOH at 70 °C. Addition of dissolved V 2 O 5 was found to result in reactivation of the nickel cathode and formation of a vanadium-bearing deposit. Tafel measurements at different electrode states indicated no change in the Tafel parameters for the fresh (or initial) and vanadium-modified states. Furthermore, vanadium addition did not appear to enhance the electrocatalytic activity beyond that for fresh nickel. A rotating ring-disk electrode was used for detection of solution intermediates of the hydrogen evolution reaction in KOH with and without dissolved V 2 O 5 . Based on cyclic voltammograms for the ring (with a hydrogen-evolving Ni disk), no solution intermediates were detected before or after vanadium addition. The action of vanadium was through a solid surface species as opposed to a homogeneous species in solution. A mercury electrode was then used to shift hydrogen evolution cathodically, revealing the potential region masked by large hydrogen currents on a nickel electrode. Cyclic voltammetry on mercury in KOH with dissolved V 2 O 5 showed a cathodic peak that was absent in voltammograms for blank KOH. Therefore, formation of the deposit occurred at a potential coincident with that of hydrogen evolution on nickel.

Formation of nickel hydrides by hydrogen evolution in alkaline media: effect of temperature

Abstract The effect of temperature on the hydrogenation of sintered Ni by the hydrogen evolution reaction (her) in 0.6 M K 2 CO 3 +H 2 O electrolyte was investigated in the range 25–95°C. At 25°C, hydrogenation leads to the formation of three different species, provisionally identified as β -Ni-, hexagonal-Ni- and α -Ni-hydride phases, based on their respective redox potentials and thermostability. Their penetration into the metal ranged from a few tens to a few hundred monolayers. Above room temperature, the overall efficiency and penetration of Ni hydrogenation increased significantly. Furthermore, there is definite evidence that, at T ≥65°C, the β -Ni-hydride phase evolves into new Ni–hydrogen species of higher thermal stability, regarding which there is no previous knowledge. The results of electrolytic Ni deuteration by electrolysis of K 2 CO 3 +D 2 O conformed to those obtained in light water.

Formation of nickel hydrides by hydrogen evolution in alkaline media

Abstract The feasibility of obtaining Ni hydride through electrolytic reduction of aqueous 0.6 M K 2 CO 3 at Ni electrodes of different types (solid Ni, Ni-fiber composite and sintered Ni) was investigated. It was found that potentiostatic electrolyses at the beginning of the hydrogen evolution reaction (her) lead to the formation of several hydrogenated species of Ni, which generally become degraded when more negative potentials are applied. The species oxidized reversibly with the her was identified as the β -Ni hydride phase, whereas the nature of the Ni hydrides oxidized at more positive potentials could not be definitely established. The interaction of Ni samples on open circuit with H 2 dissolved in the electrolyte was found to form the same Ni hydride species as that achieved after electrolysis.