Kinetics of hydrogen evolution reaction in alkaline electrolysis on a Ni cathode in the presence of Ni-Co-Mo based ionic activators

This paper presents investigations on the influence of in-situ ionic activation using combination of three D-metals: Ni, Co and Moon the hydrogen evolution reaction (HER) mechanism and kinetics. Polarization measurements were performed to obtain kinetic parameters for the HER and the results are presented to show Tafel slopes, exchange current densities and apparent energy of activation. The values of the kinetic parameters confirm the existence of two Tafel slopes, in the case of NiCoMo based ionic activators (i.a.) in the investigated temperature range, with very high values of the exchange current density. Electrochemical impedance spectroscopy measurements were employed to further investigate the origin of the obtained electrocatalytic effect on the HER. The measurements were performed at several overpotentials and temperatures. It was found that co-deposition of Ni, Co and Mo species on the Ni cathode results in a large number of active sites for hydrogen adsorption, and a synergetic effect giving electronic structure suitable for the HER, are the main factors contributing to the enhanced HER kinetics. It was shown that EIS measurements had a crucial role in determining the HER mechanism, especially with the complex in-situ activation of the alkaline electrolysis. (C) 2015 Published by Elsevier B.V

Novel ternary Ni-Co-Mo based ionic activator for efficient alkaline water electrolysis

In this manuscript we have presented the results of the use of ternary ionic activator in the alkaline water electrolysis. Novel Ni-Co-Mo based ionic activator was added in-situ to standard electrolyte. Energy consumption of the alkaline electrolyzer was determined at different current densities and elevated temperatures. Energy saving was higher at higher temperatures and higher operating current densities. Results showed that the reduction in energy consumption using Ni-Co-Mo based ionic activator was about 17%, compared to standard 6 M KOH. SEM morphology investigation proved the deposition of nickel, cobalt and molybdenum species on the cathode, greatly increasing the active surface area. UV/VIS spectroscopy was used to monitor changes in the electrolyte composition during the electrolytic process, and results show the decrease in the ionic activator concentration in the 6 M KOH. Our experiments point out a strong possibility of the usage of these ternary ionic activators in industrial alkaline electrolyzers. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved