Electrocatalytic activities of nanocomposite Ni81P16C3 electrode for hydrogen evolution reaction in alkaline solution by electrochemical impedance spectroscopy

Kinetics of hydrogen evolution reaction (HER) was studied in 1M NaOH at 298K on nickel-phosphorous-carbon (Ni81P16C3) composite electrode. Evaluation of the electrode activities was carried out by steady-state polarization Tafel curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The kinetic parameters obtained by Tafel curves revealed that Ni-P composites modified by incorporation of carbon from L-lysine source during the electroplating process were active toward the HER. Thus, to study more precisely the electrode activities, the EIS measurements were performed. A surface roughness factor (R-f) more than three orders of magnitude was obtained for the Ni81P16C3 electrode. The HER rate constants were estimated using Tafel-impedance data assuming the Volmer-Heyrovsky path. Analysis of the Rf in conjunction with the values obtained for rate constantans showed that the increase in activity of the electrode was originated by 18% from increase in Rf and by 82% from increase in the intrinsic activity (synergetic effect). Microstructure and composition of the electrodes were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and elemental microanalysis (EDX). Besides the good electrocatalytic activity, excellent chemical and electrochemical stability was observed for Ni81P16C3 composite electrode toward the HER. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.