Hierarchical coral-like FeNi(OH) /Ni via mild corrosion of nickel as an integrated electrode for efficient overall water splitting

Efficient, stable, and noble-metal-free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low-cost commercial water-splitting electrolyzers. Herein, a cost-effective and ecofriendly strategy is reported to fabricate coral-like FeNi(OH) x /Ni as a bifunctional electrocatalyst for overall water splitting in alkaline media. With the assistance of mild corrosion of Ni by Fe(NO 3 ) 3 , in situ generated FeNi(OH) x nanosheets are intimately attached on metallic coral-like Ni. Integration of these nanosheets with the electrodeposited coral-like Ni skeleton and the supermacroporous Ni foam substrate forms a binder-free hierarchical electrode, which is beneficial for exposing catalytic active sites, accelerating mass transport, and facilitating the release of gaseous species. In 1.0 mol L −1 KOH solution, a symmetric electrolyzer constructed with FeNi(OH) x /Ni as both the anode and the cathode exhibits an excellent activity with an applied potential difference of 1.52 V at 10 mA cm −2 , which is superior to that of an asymmetric electrolyzer constructed with the state-of-the-art RuO 2 -PtC couple (applied potential difference of 1.55 V at 10 mA cm −2 ). This work contributes a facile and reliable strategy for manufacturing affordable, practical, and promising water-splitting devices. A coral-like FeNi(OH) x /Ni integrated electrode for efficient overall water splitting ( V cell = 1.52 V at 10 mA cm −2 ) is prepared with the assistance of an environmental friendly, low-cost strategy, namely, controlled corrosion, hydrolysis.