Study of Co-W crystalline alloys as hydrogen electrodes in alkaline water electrolysis

Binary Co-W crystalline alloys, Co95W5, Co90W10, Co85W15, Co80W20 and Co70W30 (atomic %) were investigated in view of their possible applications as electrocatalytic materials for hydrogen evolution reaction (HER). The electrocatalytic efficiency of the electrodes was studied on the basis of electrochemical data obtained from steady-state polarization and electrochemical impedance spectroscopy (EIS) techniques in oxygen-free 1 M NaOH solution at 298 K. The results were compared with those obtained on polycrystalline Co. Moreover, literature data concerning the electrocatalytic activity of polycrystalline Ni and Ni-Mo alloys, which are considered good electrocatalyst materials for the hydrogen evolution reaction in alkaline solutions, were also reported for comparison. The values of Tafel slope, b, exchange current density, j0, and overpotential at the current density of 250 mA cm−2, η250, indicated outstandingly high electrocatalytic activity of Co-W electrodes. The best performance towards the HER demonstrates the Co90W10 alloy in accordance with the prediction based on the electronic structure calculations and the enhanced density of states at the Fermi level of the 3d Co band.