A significant improvement in material of foam

Journal of Alloys and Compounds (Impact Factor: 2.73). 10/2013; 573:128–132. DOI: 10.1016/j.jallcom.2013.04.023

ABSTRACT In investigation of different materials for electrodes used in electrolysers for hydrogen production, nickel foam shows wide interests in hydrogen scientific community. This paper brings novel results of performed experiments on pure nickel foam and nickel foam silver coated. The electrochemical behavior of chosen material in high concentrated alkaline media was studied using potentiostatic and potentiodynamic DC and AC electrochemical methods: linear polarization, electrochemical impedance spectroscopy. It was shown that using silver coatings enable higher hydrogen generation. There is defined linear region of the hydrogen production with evidence that an increasing of the electrodes overvoltage decreases the resistance to the charge transfer.


Available from: Ankica Đukić, Dec 11, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nickel catalysts were characterized for the hydrogen evolution reaction (HER) using rotating disk electrode (RDE) and electrochemical impedance spectroscopy (EIS). The theoretical Levich slope was calculated on the basis of the HER mechanism in alkaline solution. Kinetic and thermodynamic parameters of the reaction were obtained for fresh polished nickel electrode (Nif), and for nickel after a quick chronoamperometric aging procedure (Nipc). Koutecky-Levich analysis indicated that the rate determining step on Nif is the one-electron Volmer reaction, while for Nipc decreases from one to 0.68 and exhibits a strong temperature dependence. A loss of catalytic activity, corresponding to an increase of 0.3 V of the HER onset potential, was observed after aging. Furthermore, from the EIS-Tafel analysis we concluded that the H adsorption changes from a Langmuir type for Nif, to a Temkin type for Nipc.
    Electrochimica Acta 03/2015; 159:210-218. DOI:10.1016/j.electacta.2015.01.110 · 4.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrocatalytic cobalt oxide layers have been prepared on nickel substrates using thermal decomposition and electrochemical deposition methods. Importantly, it was confirmed that the electrochemical deposition method could be applied to nickel foam substrates for use in zero-gap alkaline water electrolysis cells. The oxide layers produced were then investigated for their activity towards the oxygen evolution reaction in 30 wt % KOH solution and found to be superior compared with the uncoated nickel substrate. Layers produced by both methods had similar electrochemical behaviour, provided that the layers were annealed at temperatures ≥350 ∘C. This thermal treatment was required to mechanically stabilise the electrochemically deposited cobalt oxide layer. Due to this finding, the effect of annealing temperature was investigated for the electrochemically deposited layer, and it was found that the overpotential for oxygen evolution increased with increasing annealing temperature. Using cyclic voltammetry and impedance spectroscopy, it is concluded that the decrease in performance with increasing annealing temperature is largely caused by the corresponding decrease in active surface area. However, for annealing temperatures ≥400 ∘C, additional resistances are introduced that cause lower performance. The impedance data suggest that these additional resistances are caused by either a decrease in the conductivity of the cobalt oxide layer itself, or the formation of a passivating-like nickel oxide layer between the active cobalt oxide and the nickel substrate, or both. The resistances’ dependence on potential suggests that they originate from a semi-conducting material and these additional resistances ultimately give rise to non-linear Tafel behaviour.
    10/2014; 5(4). DOI:10.1007/s12678-014-0212-3