Synergism effect of first row transition metals in experimental and theoretical activity of NiM/rGO alloys at hydrogen evolution reaction in alkaline electrolyzer

A series of nanostructure alloys composed of Ni with a non-precious metal (M: Co, Fe, Mn, Cr, Cu and Zn) on the reduced graphene oxide as NiM/rGO are synthesized through a facile solvothermal procedure. Hydrogen evolution reaction (HER) activity of prepared electrocatalysts is evaluated by various electrochemical techniques and performance in alkaline anion exchange membrane (AAEM) electrolyzer. Among the prepared NiM/rGO series, NiCo/rGO electrocatalsyt with Ni/Co mol ratio of 3/1 exhibits the highest HER activity. The measured overpotential at 10 mA cm(-2) for a low catalyst loading electrode of NiCo/rGO is as much as 137 mV less than Ni/rGO. The potential of electrolytic cell with Co3O4/rGO and NiCo/rGO electrodes as the anode and cathode, at 0.1 A cm(-2) is 1.9 V, lower than that of cell with the same anode but Ni/rGO as the cathode (2.2 V). The differences in NiM/rGO series HER activities are interpreted by various theories such as hypo-hyper-d-electronic combinations, M-H band strength and metals locations in volcano plot. Density functional theory results are also applied along with the experimental data for the explanation of NiM/rGO series HER activity trend. The results confirm the competency of employed procedure for assembling nickel alloys electrodes for alkaline water electrolysis. (C) 2020 Elsevier Ltd. All rights reserved.