In Situ Derived Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH/NiFe/Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH Nanotube Arrays from NiFe Alloys as Efficient Electrocatalysts for Oxygen Evolution

Herein, Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH/NiFe/Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH sandwich-structured nanotube arrays (SNTAs) supported on carbon fiber cloth (CFC) (Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH/NiFe/Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH SNTAs–CFC) have been developed as flexible high-performance oxygen evolution reaction (OER) catalysts by a facile in situ electrochemical oxidation of NiFe metallic alloy nanotube arrays during oxygen evolution process. Benefiting from the advantages of high conductivity, hollow nanotube array, and porous structure, Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH/NiFe/Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH SNTAs–CFC exhibited a low overpotential of ∼220 mV at the current density of 10 mA cm<sup>–2</sup> and a small Tafel slope of 57 mV dec<sup>–1</sup> in alkaline solution, both of which are smaller than those of most OER electrocatalysts. Furthermore, Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH/NiFe/Ni<sub><i>x</i></sub>Fe<sub>1–<i>x</i></sub>OOH SNTAs–CFC exhibits excellent stability at 100 mA cm<sup>–2</sup> for more than 30 h. It is believed that the present work can provide a valuable route for the design and synthesis of inexpensive and efficient OER electrocatalysts.