Surface-Oxidized Iron-Cobalt-Nickel Alloy with Continuous Variable Composition for Hydrogen and Oxygen Evolution Reaction

Composition is the key to optimizing the electroactivity of the alloy-based electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a library of surface-oxidized iron-cobalt-nickel-based (FeCoNi-based) alloys, FeCoNi and FeCoNi/OH, with continuous variable compositions are built as HER and OER electrocatalysts. The FeCoNi alloys with a low content of Fe display higher HER intrinsic activity, while the alloys with low Co content exhibit higher OER activity. Because the electrochemical specific area is evidently increasing with the addition of Fe and Co, the Fe6Co4Ni0 exhibits the outstanding HER activity and stability. Benefiting from the synergistic effect, the alloys' HER activity for most compositions is enhanced by the surface hydroxides. However, the surface-oxidized hydroxides barely affect OER activity for most compositions of the alloys. After a year of storage, the FeCoNi and FeCoNi/OH electrodes exhibit high stability for HER but not for OER. These trends may help to exploit higher activity electrocatalysts for hydrogen production by water electrolysis.

Automated summary

The composition of alloy-based electrocatalysts plays a key role in optimizing their electroactivity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This study investigates the electrocatalytic properties of FeCoNi-based alloys with varying compositions. The results show that alloys with low iron content exhibit higher HER activity, while alloys with low cobalt content exhibit higher OER activity. The addition of iron and cobalt increases the electrochemical specific area, leading to improved HER activity and stability. Surface hydroxides enhance the HER activity of most compositions, but have little effect on OER activity.