Co-deposition of Co-Fe alloy catalysts for hydrogen evolution reaction based on ethylene glycol system

•Co+2 can accelerate the Co-Fe deposition, while Fe+2 can inhibit reduction of Co+2.•Co-Fe alloys with various Fe contents can be obtained from ethylene glycol system.•Co-Fe alloys presents a high catalytic activity for hydrogen evolution reaction. The co-deposition behavior of Co+2 and Fe+2 in ethylene glycol (EG) are investigated using cyclic voltammetry (CV) techniques. These results imply that Co+2 species can accelerate the Co-Fe co-deposition, while Fe+2 can inhibit the reduction of Co+2. Moreover, the two effects can be improved as Co+2 or Fe+2 concentration increases. Microstructural and compositional characteristics of the samples show that Co-Fe deposits with various Fe content can be obtained from anhydrous FeCl2 and CoCl2 in EG. Scanning electron microscopy imaging of the surfaces of these Co-Fe alloy coatings shows that they present a dense structure with spherical “nodules”, the size of which is related to the Fe content. The electrocatalytic activity for hydrogen evolution reaction (HER) on the Co-Fe coatings is also investigated. These results indicate that its electrocatalytic activity can be improved as Fe contents increase from 2.2 to 9.8 wt.% and the Co-Fe alloy with 9.8 wt.% Fe exhibits the high electrocatalytic activity for HER with an overpotential of 124 mV at 10 mA cm−2 in 1 M KOH.