Galvanostatic Electrodeposition of Thin-Film Ir–Ni Electrocatalyst on Copper Foam for HER Performance in Alkaline Electrolyte

Abstract

Iridium–nickel (Ir–Ni) film is of great interest for catalytic and corrosive environment applications. Ir–Ni thin films as an electrocatalyst for hydrogen evolution reaction (HER) were galvanostatically electrodeposited on copper (Cu) foam from an electrolyte containing 13.5 mM sodium hexabromoiridate(III) and 40.5 mM Ni sulphate hexahydrate, simultaneously compared with electrodeposited Ir and Ni thin films. The top surface morphology of the film was characterized by scanning electron microscopy. The chemical composition of the film was determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. The electrocatalytic performance was performed by linear sweep voltammogram and cyclic voltammetry. The results showed that Ir–Ni thin film adhered to Cu foam and the surface appeared much rougher than the surface of Ni film. The chemical composition of Ir in the deposit was 80 ± 1.2 at.%. The film was composed of nanograins. The top surface of as-deposited film was mainly composed of metallic state. However, the top surface of the film consisted of oxides states, such as Ni oxides or Ni(OH)2, and Ir oxides after electrochemical measurements. As-deposited Ir–Ni thin film with large real active area exhibited high efficient electrocatalytic activity for HER, and achieved a current density of 10 mA cm2 at an overpotential of 60 mV and a Tafel slope of 40 mV dec−1, which is superior to pure Ir and Ni thin films. The remarkable increase in electrocatalytic activity for Ir–Ni film was ascribed to both increased surface area of active centers due to relatively rough and electrocatalytic synergism of Ir and Ni for the HER. Ir–Ni thin film electrodeposited on a foam copper electrode was used as an electrocatalyst for HER. The surface of as-deposited film was composed of metallic state. As-deposited Ir–Ni thin film with large real active area exhibited high efficient electrocatalytic activity for HER, and achieved a current density of 10 mA cm2 at an overpotential of 60 mV and a Tafel slope of 40 mV dec−1, which is superior to pure iridium and Ni thin films. As-deposited film possessed a good stability by accelerated degradation studies.