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. (C) 2017 Published by Elsevier Ltd.