Interface engineering and anion etching facilitating electronic modulation and surface reconstruction of FeSe@NiSe heterostructure catalysts to promote water splitting

Abstract Transition metal selenides (TMSs) are effective pre‐electrocatalysts and are commonly used in electrochemical processes. During the electrocatalytic oxygen evolution reaction (OER), metal cations in TMSs are in‐situ reconstructed and converted into high‐valence metal oxyhydroxides. However, a limited understanding of the effects of electro‐oxidation and anion leaching has resulted in insufficient theoretical guidance for the rational design of efficient catalysts. Herein, FeSe@NiSe nanorods were fabricated for the OER using a facile hydrothermal selenization method supported on FeNi foam. In‐situ Raman spectroscopy and multiple characterization techniques were employed to elucidate the mechanism of FeSe@NiSe surface evolution. Metal cations on the catalyst surface were reconstructed and converted into OER‐active species Fe/NiOOH at low potential. As the applied potential increased, electro‐oxidation and leaching of Se occurred, resulting in SeO 4 2− adsorption on the catalyst surface, which further enhanced catalytic activity. As a result, the reconstructed FeSe@NiSe/iron‐nickel foam (INF) exhibited exceptional catalytic activity for OER, achieving an ultralow overpotential of 283 mV at a current density of 100 mA·cm −2 . Notably, the bifunctional FeSe@NiSe/INF electrode facilitated overall water splitting, affording a current density of 10 mA·cm −2 only at 1.53 V, even superior to the noble RuO 2 (+)||Pt/C(−). This work offers valuable insights into the surface evolution and electrocatalytic mechanisms of TMSs.