In Situ Fabrication of Heterostructure on Nickel Foam with Tuned Composition for Enhancing Water‐Splitting Performance

Abstract Exploiting economical and high‐performance bifunctional electrocatalysts toward hydrogen and oxygen evolution reactions (HER/OER) is at the heart of overall water splitting in large‐scale application. Herein, an in situ and stepwise strategy for synthesizing core–shell Ni 3 (S 1− x Se x ) 2 @NiOOH (0 ≤ x ≤ 1) nanoarray heterostructures on nickel foam with tailored compositions for enhancing water‐splitting performance is reported. A series of Ni 3 (S 1− x Se x ) 2 nanostructures is firstly grown on nickel foam via an in situ reaction in a heated polyol solution system. Ni 3 (S 1− x Se x ) 2 @NiOOH nanocomposites are subsequently prepared via electrochemical oxidation and the oxidation degree is systematically investigated by varying the oxidation time. Benefitting from the vertical standing architecture, abundant exposed active sites, and synergetically interfacial enhancement, Ni 3 (S 0.25 Se 0.75 ) 2 @NiOOH heterojunctions with electrochemical polarization for 8 h exhibit superior HER and OER behaviors, achieving a water‐splitting current density of 10 mA cm −2 at a small overpotential of 320 mV as well as boosted reaction kinetics and long‐term stability. This work should shed light on the controllable synthesis of metal‐based hybrid materials and provide a promising direction for developing the highest‐performing electrocatalysts based on interfacial and heterostructural regulation for advanced electrochemical energy conversion technologies.