Iron tuned Ni–Co–Fe alloy films via electrodeposition for hydrogen evolution reaction

Compositionally tuned Ni-Co-Fe alloy films with iron (Fe) concentration from 1 to 14 at% are electrodeposited on stainless steel. The effect of iron addition to Ni-Co alloy on electrocatalytic hydrogen evolution reaction (HER) is studied in 1 M KOH. Iron (Fe) is incorporated to lower the nickel (Ni) content from ∼45 at% to ∼31 at% in Ni-Co alloys, resulting in notable changes in structural, morphological, and electronic properties. Structural and morphological analysis confirm that the Ni-Co-Fe (Fe = 4 at%) alloy film possesses the highest crystallinity with a larger grain size among the other electrodeposited alloy films. Fe appears in mixed valence states (Fe²⁺/Fe³⁺), while shifts in Ni 2p and Co 2p binding energies suggest strong electronic interactions and enhanced charge delocalization. The Ni-Co-Fe alloy film with 4 at% of iron demonstrates better electrocatalytic performance with a lower overpotential value than other compositions. The Ni-Co-Fe (Fe = 4 at%) alloy film exhibits the lowest charge transfer resistance, along with superior electrochemical surface area, roughness, and wettability among the electrodeposited alloy films. The Ni-Co-Fe alloy film with 4 at% Fe exhibits stable performance toward the hydrogen evolution reaction (HER). Thus, iron (Fe) can effectively substitute a significant amount of nickel (Ni) in Ni-Co alloys, enabling the development of cost-effective HER catalysts.