Hybrid Ni(OH)2/FeOOH@NiFe Nanosheet Catalysts toward Highly Efficient Oxygen Evolution Reaction with Ultralong Stability over 1000 Hours

Developing advanced electrocatalysts with low overpotential and long lifetime toward oxygen evolution reaction (OER) is essential and challengeable for the storage and conversion of renewable energy on a large scale. Herein, novel hybrid Ni(OH)2/FeOOH@NixFey (x:y = 2:1, 1:1, and 1:2) nanosheet catalysts were rationally designed and synthesized for improving OER performance via a scalable sputtering–alloying–dealloying–activation strategy. The hybrid nanosheets directly grown on the stainless steel mesh possess flexible, composition-adjustable, and binder-free characteristics. Especially, the Ni(OH)2/FeOOH@Ni2Fe1 nanosheet catalyst displays incredible OER activity, with an extraordinarily low overpotential of 216 mV at 10 mA cm–2 in a 1 M KOH electrolyte, superior to that of the state-of-the-art NiFe-based electrocatalysts. Significantly, the electrode went through an ultralong durability test over 1000 h (>40 days) without obvious attenuation, exceeding most of the advanced electrocatalysts. Through a series of characterizations (microstructural, spectroscopic, and electrochemical), the improved OER performance of the hybrid electrode can be ascribed to the synergistic effect of hybridization between Ni(OH)2 and FeOOH, the optimal Ni:Fe ratio, the ultrathin nanosheet structure, large electrochemical surface area, and low activation energy.