V-Doping Triggered Formation and Structural Evolution of Dendritic Ni₃S₂@NiO Core–Shell Nanoarrays for Accelerating Alkaline Water Splitting

Abstract

Developing highly efficient electrocatalysts with hierarchical structures while revealing their electrochemical reaction mechanism is crucial for pushing commercial water splitting applications. Herein, a V-doping triggered self-assembly strategy is reported to synthesize dendritic V-Ni3S2@NiO core–shell nanoarrays on nickel foam (V-Ni3S2@NiO/NF), which consist of an ultrathin V-doped NiO nanoshell (2–7 nm) and high-crystalline Ni3S2 core. The unique hierarchical structure offers multidimensional mass and charge transport channels and plentiful catalytically active sites for water splitting reactions, resulting in improved water electrolysis kinetics. More importantly, benefiting from the rapid anodic oxidation and evolution process due to the partial leaching of vanadium(IV) in the V-Ni3S2@NiO/NF material, the highly active amorphous NiOOH phase is immediately generated on the surface of V-Ni3S2@NiO/NF (V-Ni3S2@NiO/NiOOH/NF), which contributes to enhancing the adsorption of OH– and exposing abundant unsaturated active sites and thus remarkably enhanced oxygen evolution reaction (OER) kinetics in basic electrolyte. Moreover, an alkaline electrolyzer assembled by V-Ni3S2@NiO/NF simultaneously functioning as both anode and cathode only needs an extremely small voltage of 1.52 V to yield 10 mA cm–2 and retains this activity for over 55 h. This work provides a new train of thought and tactics for the development of high-efficiency electrocatalysts for overall water splitting.