A triple-layered PPy@NiCo LDH/FeCo2O4 hybrid crystalline structure with high electron conductivity and abundant interfaces for supercapacitors and oxygen evolution

Abstract

A rational structural design of electrodes with high electron conductivity, sufficient material interfaces/defects and a regulated charge transfer pathway can be applied in broad practical electrochemical application fields. A triple-layered PPy@NiCo LDH/FeCo₂O₄ hybrid with a tri-metal hybrid nanowire and conductive PPy coating layer is fabricated via a one-step hydrothermal reaction and in situ polymerization. NiCo LDH/FeCo₂O₄ nanowire arrays with a layered crystalline structure are synthesized via an in situ dissolution-growth method, where the partially etched nickel foam substrate subsequently acts as the Ni source. The NiCo LDH/FeCo₂O₄ nanowire arrays together with the ultrathin PPy coating layer can form bi-continuous conductive networks, numerous crystalline edges and structural interfaces to increase the electron transfer rate and the active/adsorption sites, which can further promote the energy storage and electrocatalytic activity. The bi-functional PPy@NiFeCo/NF-4 electrode exhibits a high areal capacitance (9.24 F cm⁻² at 5 mA cm⁻²) and excellent rate capability (90.5% retention from 5 to 30 mA cm⁻²) as a supercapacitor and achieves a small overpotential (244 mV at 50 mA cm⁻²) and Tafel slope (64.39 mV dec⁻¹) as an electrocatalytic OER electrode.