Electrodeposited NiFeCo and NiFeCoP alloy cathodes for hydrogen evolution reaction in alkaline medium

• Amorphous alloys are obtained electrochemically at various current densities.
• Fe and Co co-deposited with Ni reduce strongly the overvoltage of the HER.
• NiFeCoP alloys exhibit the best electrocatalytic activity for the HER.

The present paper reports on the electrodeposition of crystalline NiFeCo and amorphous NiFeCoP alloys at various conditions of the electrolysis process (different current densities) leading to differences in component composition. Alloys are characterized by SEM, XRF, EDX, XRD and XPS methods. The electrocatalytic activity of the materials for hydrogen evolution reaction (HER) is studied in a 6 M KOH solution using polarization curves and electrochemical impedance spectroscopy (EIS). Presence of iron and cobalt in nickel alloys decreases significantly overvoltage of hydrogen evolution and the charge transfer resistance is about 1000 times smaller compared to pure nickel. Alloy amorphization by inclusion of phosphorus enhances additionally electroactivity of these materials for the HER. Results from both electrochemical methods indicate that the best electrocatalytic behavior is demonstrated by amorphous alloys having high iron content. The latter is associated with a more developed surface of these materials and possible synergy among Ni, Fe and Co.