Interface Engineering of Ni3Se2@FeOOH Heterostructure Nanoforests for Highly-Efficient Overall Water Splitting

Abstract Rational construction of interface engineering is a highly effective strategy for modifying the surface properties and enhancing the intrinsic activity of a catalyst. Herein, the three-dimensional (3D) hierarchical Ni3Se2@FeOOH heterostructure nanoforests with rich heterointerfaces were integrated into nickel foam (Ni3Se2@FeOOH/NF) for electrochemical overall water splitting. Coupling FeOOH with Ni3Se2 can favor the formation of oxygen-containing intermediate (*OOH) and facilitate the dissociation of H2O and adsorption of hydrogen (*H), thus dramatically boosting the electrocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) simultaneously. Furthermore, the self-supported electrode with Ni3Se2@FeOOH heterostructure nanoforests in-situ grown on NF can reduce the indirect contact resistance between the electrocatalyst and substrate, provide abundant electroactive sites, and promote the release of the generated bubbles from electrode timely. Consequently, the Ni3Se2@FeOOH/NF displays outstanding electrocatalytic activity with low overpotentials of 224 mV and 87 mV at 10 mA.cm-2 for OER and HER, respectively. When used as a bifunctional electrocatalyst in a 1 M KOH electrolyzer, the Ni3Se2@FeOOH/NF exhibits a low cell voltage of 1.54 V to drive 10 mA.cm-2 and retains long-term durability over 20 h. This work demonstrates the significance of the heterostructure for improving the catalytic performance of non-noble composite electrocatalysts.