Hydrogen discharge on electrodeposited Ni–Mn–Fe coatings in 30 w⧸o koh

Abstract

The hydrogen evolution reaction (HER) has been investigated on Ni–Mn–Fe electrocoated cathodes in 30 w⧸o KOH at 30°C. Ni–Mn–Fe alloys were electrodeposited on mild steel as thin coatings from sulphate baths with ammonium sulphate as additive. The effects of bath composition and deposition current density have been studied. The cathodes were pre-electrolysed at a cathodic current density i c of 500 mAcm −2 for 30 min before the kinetic parameters of the HER were determined. Ni–Mn–Fe coatings plated from Ni-rich electrolytes and at very high current densities showed improved activity towards the HER in 30 w⧸o KOH due to significant increase in the exchange current density. Microstructure examinations indicated that the superior electrocatalytic activity, seen in coatings obtained at high deposition current densities, is due to the presence of multi-textures. The coatings, in which formation of nanocrystalline grains and development of voids at grain interfaces occurs, exhibit the maximum electrocatalytic activity towards the HER.