The activity of nanocrystalline Fe-based alloys as electrode materials for the hydrogen evolution reaction

• The electrochemical activity of nanocrystalline Fe-base alloys was examined.
• Fe alloys benefit from the formation of a porous and nanocrystalline surface layer.
• The metalloids (B, Si) were leached out of the surface layer (dealloying).
• Co boosts the intrinsic activity of Fe electrodes.

In view of alkaline water electrolysis, the activities for the hydrogen evolution reaction of nanocrystalline Fe-based electrode materials were investigated and compared with the activities of polycrystalline Fe and Ni. Electrochemical methods were used to elucidate the overpotential value, the charge transfer resistance and the double layer capacity. Structural properties of the electrode surface were determined with SEM, XRD and XPS analyses. Thus, a correlation between electrochemical and structural parameters was found. In this context, we report on a cyclic voltammetric activation procedure which causes a significant increase of the surface area of Fe-based electrodes leading to a boost in effective activity of the activated electrodes. It was found that the intrinsic activity of activated Fe-based electrodes is very high due to the formation of a nanocrystalline surface layer. In contrast, the activation procedure influences only the intrinsic activity of the Ni electrodes without the formation of a porous surface layer.