Highly efficient hybrid Ni/nitrogenated-graphene electrocatalysts for hydrogen evolution reaction

Abstract

Two nickel/nitrogenated graphene hybrid electrodes (Ni-NrGONH3 and Ni-NrGOAPTES) were synthesized, and their catalytic activity with respect to the hydrogen evolution reaction (HER) in alkaline media was analyzed. Incorporation of nitrogen to the carbon structure in graphene oxide (GO) or reduced GO (rGO) flakes in aqueous solutions was carried out based on two different configurations. NrGONH3 particles were obtained by a hydrothermal method using ammonium hydroxide as the precursor, and NGOAPTES particles were obtained by silanization (APTES functionalization) of GO sheets. Aqueous dispersions containing NrGONH3 and NGOAPTES particles were added to the traditional nickel Watts plating bath in order to prepare the Ni-NrGONH3 and Ni-NrGOAPTES catalysts, respectively. Nickel substrates were coated with the hybrid nickel electrodeposits and used as electrodes for hydrogen production. The Ni-NrGO catalysts show a higher activity than the conventional nickel electrodeposited electrodes, particularly the ones containing APTES molecules because they allow obtaining a hydrogen current density 130% higher than conventional Ni-plated electrodes with a Watts bath in the absence of additives. In addition, both catalysts show a low deactivation rate during the ageing treatment, which is a sign of a longer midlife for the catalyst. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were used for examination of the catalytic efficiency of hybrid Ni-NrGO electrodes for HER in KOH solution. High values of exchange current densities, 8.53 × 10-4 and 2.53 × 10-5 mA cm-2 for HER in alkaline solutions on Ni-NrGONH3 and Ni-NrGOAPTES electrodes, respectively, were obtained.