Electrodeposition of Ni-Mo-rGO composite electrodes for efficient hydrogen production in an alkaline medium

The mechanism and kinetics of the hydrogen evolution reaction (HER) on Ni-Mo-rGO composite electrodes in 1.0 M KOH solution were investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and potentiodynamic polarization techniques. Ni-Mo-rGO composite coatings were deposited on a copper substrate by an electrodeposition method at a current density (c.d.) ranging from 1.0 to 4.0 A dm(-2). The change in surface morphology and chemical composition was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). It was shown that the carbon content of the composite coatings was affected by c.d. With the increase in the carbon content in the Ni-Mo-rGO composite coatings, the onset potential was decreased and the exchange current density was increased during the HER. The minimum onset potential and maximum exchange current density of Ni-Mo-rGO composite coatings for the HER were -401.6 mV and 4.31 A cm(-2). The best composite coating exhibited a maximum peak current density of -0.517 A cm(-2) at -1.6 V, which is approximately 3 times better than that of the binary Ni-Mo alloy, indicating the best activity for hydrogen production. The potentiodynamic polarization measurements revealed that composite coatings are much more resistant to corrosion than binary alloy coatings.