Nanostructured nickel–cobalt alloy/rGO-SWCNT thin film as an efficient electrocatalyst for hydrogen evolution reactions

Abstract

Electro-catalytic water splitting is widely viewed as an efficient and viable strategy for green hydrogen production. Herein, we designed nanostructured nickel–cobalt alloy grown on the reduced graphene oxide-single walled carbon nanotube (rGO-SWCNT) thin film by means of electro-deposition, which was used to catalyze water splitting for hydrogen evolution reaction (HER) in an alkaline medium. It was found that the HER performance of nickel–cobalt alloys was determined by the Co/Ni ratio and better than their corresponding single components Co and Ni. Nickel–cobalt alloy with a Co/Ni ratio of 2 (CoNi21) exhibited the most notable HER efficiency with an overpotential of 83.5 mV and 291.8 mV vs. reversible hydrogen electrode at 10 mA cm⁻² and 100 mA cm⁻², respectively. Furthermore, the significantly lower Tafel slope (112.6 mV dec⁻¹) of CoNi21 indicates that the HER kinetics of the nickel–cobalt alloy is accelerated due to the synergistic effect of Ni and Co. The charge-transfer resistance of CoNi21 is significantly low compared to any single component, validating the intensified interfacial charge transfer. Besides, CoNi21 has the highest active surface area of 147.1 mF cm⁻² on the basis of the ECSA measurements, which can be beneficial for providing rich active sites. The CoNi21 catalyst offered excellent durability for HER in the alkaline medium. This work provides a combinatorial method integrating rich interfaces of Co–Ni alloy on highly conductive carbon substrate to design efficient and low-cost electrocatalysts for improving the HER performance.