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The development of advanced electrode materials with high performance and low-cost for energy conversion and storage techniques, such as water splitting and application as a supercapacitor, is significant in terms of future renewable energy systems. In this work, a unique NiOOH-decorated α-FeOOH nanosheet array (ASF) has been fabricated, with the help of alkaline oxidative etchant solution (AOES), using sintered 316L stainless steel felt (SF) as substrate, which can be viewed as a “pancake”, while the α-FeOOH nanosheet, as well as the other elements uniformly embedded in it, acts as the skeleton. The formation mechanism of the ASF was discussed in detail based on X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, scanning transmission electron microscopy, and density functional theory calculations. The results indicate that the oriented growth of α-FeOOH was influenced by the surface adsorption for reducing the surface energy of the facet and electrostatic repulsion effect, to form the unexpected nanosheet structure. The 2-dimensional nanosheets could afford large specific surface area, and the active components (including Fe and Ni elements) distributed uniformly on the α-FeOOH nanosheets, enabling the sufficient exposure of electrochemical active sites and facilitating the effective contact between them and the electrolyte. As a consequence, the ASF shows an outstanding oxygen evolution reaction (OER, the overpotential is only 256 mV at 10 mA cm–2, with low Tafel slope of 45 mV dec–1) and supercapacitor performance (the specific capacity is 748.13 mF cm–2 at 1.5 mA cm–2 (554.17 F g–1, 1.1 A g–1), with good rate capacity and cyclic stability) performances.

A CoOOH/NF ultrathin nanoflake array is fabricated by a facile two-step method. Furthermore, an asymmetric supercapacitor was assembled with CoOOH/NF and reduced graphene oxide, displaying excellent properties as energy storage devices.

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