Interfacial Engineering of Copper–Nickel Selenide Nanodendrites for Enhanced Overall Water Splitting in Alkali Condition

Abstract Fabricating heterogeneous interfaces is an effective approach to improve the intrinsic activity of noble‐metal‐free catalysts for water splitting. Herein, 3D copper–nickel selenide (CuNi@NiSe) nanodendrites with abundant heterointerfaces are constructed by a precise multi‐step wet chemistry method. Notably, CuNi@NiSe only needs 293 and 41 mV at 10 mA cm −2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Moreover, the assembled CuNi@NiSe system just requires 2.2 V at 1000 mA cm −2 in anion exchange membrane (AEM) electrolyzer, which is 2.0 times better than Pt/C//IrO 2 . Mechanism studies reveal Cu defects on the Cu 2−x Se surface boost the electron transfer between Cu atoms and Se atoms of Ni 3 Se 4 via Cu 2−x Se/Ni 3 Se 4 interface, largely lowering the reaction barrier of rate‐determining step for HER. Besides, the intrinsic activity of Ni atoms for in situ generated NiOOH is largely enhanced during OER because of the electron‐modulating effect of Se atoms at Ni 3 Se 4 /NiOOH interface. The unique 3D structure also promotes the mass transfer during catalysis process. This work emphasizes the essential role of interfacial engineering for practical water splitting.