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

Abstract

Kinetics of hydrogen evolution reaction (HER) was studied in 1 M NaOH at 298 K on nickel-phosphorous-carbon (Ni81 P16 C3) 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 (Rf) more than three orders of magnitude was obtained for the Ni81 P16 C3 electrode. The HER rate constants were estimated using Tafel-impedance data assuming the Volmer-Heyrovský 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 Ni81 P16 C3 composite electrode toward the HER. © 2008 International Association for Hydrogen Energy.