Fabrication of nanoporous gold-islands via hydrogen bubble template: An efficient electrocatalyst for oxygen reduction and hydrogen evolution reactions

Abstract

In this report, the fabrication of a high surface area nanoporous gold-island (NPG-islands) onto a glassy carbon (GC) surface by a simple one-step electrodeposition procedure based on a dynamic hydrogen bubble template method is described. The surface morphology, purity and crystalline structure of the porous NPG-islands were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) techniques. Cyclic voltammetry and linear sweep voltammetry methods were used for electrochemical studies and the electrocatalytic activity of the NPG-islands surface was investigated towards the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Electrochemical results revealed exceptional ORR activity of the NPG-islands evaluated by the shift of the onset potential towards less negative values compared to bare GC (0.55 V) and Au (0.25 V) electrodes, respectively, with a 3-fold increased current density in neutral PBS solution (pH 7). Rotating-disk measurements indicate a direct conversion of oxygen to water via a four-electron reduction pathway. The electrocatalytic activity was also evaluated for HER in 0.5 mol L−1 H2SO4 solution and a benchmark current density of 10 mA cm−2 at a very low overpotential of −0.075 V was obtained, which is similar to bulk Pt performance. The plausible mechanism of the HER was realized from the Tafel plot and the obtained slope of 46 mV dec−1 suggests the Volmer-Heyrovsky mechanism takes place in such electrochemical process. Furthermore, the durability of the catalyst was also studied and exceptional stability was observed in cyclic voltammetry (up to 2000 cycles) and chronopotentiometry (at 10 mA cm−2 for 19 h).