Improved Electrocatalytic Performance of Core-shell NiCo/NiCoOx with amorphous FeOOH for Oxygen-evolution Reaction

Hierarchical NiCo/NiCoOx with amorphous FeOOH electrocatalysts have been fabricated by a low temperature hydrogenation treatment of Ni/Co bimetallic carbonate hydroxide nanowire arrays on Ni foam and subsequent chemical bath deposition process. The NiCo/NiCoOx composites consisted of NiCo alloy core and nickel cobalt oxide shell with the thickness of around 5 nm exhibits excellent electrocatalytic activity for hydrogen-evolution reaction (HER) in 1 M KOH due to the enhanced conductivity and the large defect-rich interface. However, the electrocatalytic activity for oxygen-evolution reaction (OER) is boosted by ultrathin, amorphous and interconnected FeOOH nanosheets grown on the hierarchical NiCo/NiCoOx composites because of the promoted conductivity and electron transfer ability of the metallic NiCo core and the suitable interaction of NiCoOx and FeOOH with OH− groups. In oxygen evolution process, a low overpotential of 278 mV is required to achieve a current density of 10 mA cm−2 for NiCo/NiCoOx@FeOOH samples, and the Tafel slope is only 47.5 mV dec−1. When integrated NiCo/NiCoOx with NiCo/NiCoOx@FeOOH in an alkaline electrolyzer, a full water splitting current density of 10 mA cm−2 and high electrochemical stability can be obtained at 1.65 V.