Kinetics of the hydrogen evolution reaction on Fe–Mo film deposited on mild steel support in alkaline solution

The mechanism and kinetics of the hydrogen evolution reaction were studied in 1.0 mol dm−3 NaOH solution on Fe–Mo alloy electrodes prepared by electrodeposition at constant current densities from a pyrophosphate bath. A series of electrode containing 34–59 at.% Mo was prepared. Electrodes displayed porous character, and electrochemical impedance spectroscopy was used to characterized real surface area. It was found that within the whole potential region the mechanism of the HER is a consecutive combination of the Volmer step, followed dominantly by a rate controlling Heyrovsky step, while the contribution of the parallel Tafel step is negligible. The kinetic parameters of the HER were determined. With an increase in the molybdenum content, the electrodes become more active, and an increase in the real surface area is observed. The main factor influencing the electrode activity seems to be the real surface area.