3D nanostructured nickel film supported to a conducting polymer as an electrocatalyst with exceptional properties for hydrogen evolution reaction

Abstract

A two-layer system was applied to a nickel substrate for use as the electrocatalyst of the hydrogen evolution reaction (HER) in a phosphate buffer solution. It was comprised of a three-dimensional (3D) porous underlayer of nickel nanoparticles with a size of less than 35 nm, followed by an electrodeposited top layer of poly (aniline-co-pyrrole). The underlayer and top coating were both synthesized by applying a constant potential to a three-electrode system. The catalyst characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectrometry. The electrocatalytic activity of the fabricated electrodes was measured by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry. The electrode exhibited an overpotential of 520 mV at a current density of 10 mA cm−2, comparable to 530 mV of platinum. Furthermore, the Tafel slope of the electrode was 90 mV dec−1, almost equal to that of platinum. This exceptional performance was explained by the synergistic interaction between 3D-Ni and poly (aniline-co-pyrrole) layers. Such a synergism was demonstrated by the fact that the resulting electrode lacked substantial catalytic activity when each of these two layers was deposited on the substrate alone. The Nyquist diagrams revealed that the 3D-Ni film resulted in minimal charge transfer resistance, allowing fast kinetics of HER. The coupling of this property with the ability of the polymer to adsorb H+ ions led to the high electrocatalytic activity of the proposed electrode. This electrode performed better than platinum, which was a promising result. This indicated that a lower voltage input was required to generate hydrogen gas using the prepared electrode.