Electroplating of Nanocrystalline Ni–Co Alloys Using Cysteine and Their Electrochemical Behaviour in NaOH Solution

Abstract

Electroplated Ni–Co alloys show superior electrocatalytic activity towards hydrogen evolution reaction. In this work, the cysteine and sodium gluconate obtained from natural products were utilized to electroplate the nanocrystalline Ni–Co alloys. The electroplating baths were characterized using cathodic polarization technique. The effect of sodium gluconate, cysteine and boric acid on the surface morphology of the electroplated Ni–Co alloys was studied using scanning electron microscopy (SEM). Chemical composition of the electroplated Ni–Co alloys was determined using the energy dispersive X-ray (EDX), and their crystal lattice system was examined by X-ray diffraction (XRD) analysis. The X-ray diffraction pattern confirms that the electroplated Ni–Co alloys with Co% of 1–75% arranged in face-centred cubic (FCC) structure, while the electroplated Ni–Co alloys with Co% more 76% positioned in hexagonal closed-package (HCP) structure. The thickness of the Ni–Co alloys varied between 14.61 and 27.94 µm. The cathodic polarization data show that gluconate and cysteine enhance electroplating of Ni–Co alloys by decreasing the overpotential of Ni2+ and Co2+ reduction reaction. Potentiodynamic polarization was utilized to study the electrochemical behaviour of the Ni–Co alloys in NaOH aqueous solutions, which indicated that electroplated Ni–Co alloys with low Co% displayed the low rate of corrosion.