High valence state metal-ion doped Fe–Ni layered double hydroxides for oxygen evolution electrocatalysts and asymmetric supercapacitors

Abstract

The delicate design of nanostructures consisting of multiple components is important for dual-function electrode materials for energy storage. In this work, cobalt-doped nickel–iron layered double hydroxide (Fe–Ni₃Co₂ LDH) assembled from one-dimensional (1D) nanoneedle subunits and FeSe₂/C is synthesized via a facile, one-pot self-template method. FeNi₃Co₂ LDH exhibits remarkable activity for catalyzing the oxygen evolution reaction with a low onset overpotential of 224 mV and a low Tafel slope of 73 mV dec⁻¹, much better than those of FeNi LDH. Significantly, the Fe–Ni₃Co₂ LDH//FeSe₂/C asymmetric supercapacitor (ASC) delivers an ultra-high energy density (22.3 μW h cm⁻²), high power density (2.07 mW cm⁻²), and outstanding cycling stability (84.8% capacitance retention after 5000 galvanostatic charge–discharge cycles at 0.3 mA). The density functional theory (DFT) calculation reveals that the high electrochemical activity of Fe–NiCo LDHs is mainly attributed to cobalt doping which can modify the electronic structure and narrow the bandgap, thereby bringing enhanced conductivity, facile electron transfer, and abundant active sites. Our work could provide new insight into the synthesis of novel multifunctional nanomaterials.