Electrodeposition of Fe-Ni alloy on Au(111) substrate: Metastable BCC growth via hydrogen evolution and interactions

The electrodeposition of Fe-Ni alloy is usually complicated by the effects of anomalous codeposition and hydrogen evolution. Although the influence of the deposition conditions on the alloy composition has been studied extensively, very few works considered the influence of growth conditions on the phase constitution. In this work, various electrodeposition conditions were investigated to grow Fe-Ni alloy films (<30 nm) with similar compositions in the Invar-to-equiatomic range on Au (111) substrate. Highly (110) oriented BCC phase Fe-Ni with a Ni fraction (ca. 40 at.% Ni) well beyond the equilibrium solubility limit (5 at.% Ni) was obtained with a significant alloy deposition partial current. An increase in the fraction of the BCC phase was found to be associated with a higher alloy deposition partial current, but not necessarily with an increase in the hydrogen evolution partial current. Motivated by the findings from this work, the formation of the metastable BCC phase is speculated to depend on the competing kinetics between the inclusion and desorption of hydrogen adatoms at the electrodeposited growth front. (C) 2020 Elsevier Ltd. All rights reserved.