One-step fabrication of NiO_x-decorated carbon nanotubes-NiCo₂O₄ as an advanced electroactive composite for supercapacitors

Tailoring of battery-type NiCo₂O₄ with carbon-based materials for supercapacitors usually involves several steps, which require prolonged syntheses at high temperatures. Here, a facile one-step strategy is presented for the fabrication of a binder-free composite, made of NiO_x decorated multi-walled carbon nanotubes (CNTs) and NiCo₂O₄ nanoparticles on nickel foam to form a stable supercapacitor with high specific capacity. The process is based on the electrophoretic co-deposition of carboxylated-CNTs and NiCo₂O₄ NPs, which were positively charged using Ni²⁺. The latter played a double role by stabilizing the nanomaterials and improving the electrochemical performance by decorating the nanomaterials with NiO_x species. The well-dispersed NiCo₂O₄ NPs in the highly conductive porous matrix of CNTs provide efficient electron transfer, high surface area and superior electrochemical performance, such as high charge storage, high rate delivery and good cycling stability. The nanocomposite film exhibited high specific capacitance of 1363 F gr⁻¹ at 2 A gr⁻¹, while retaining 82% of the capacitance at higher current density (20 A gr⁻¹). The straightforward fabrication process and the excellent electrochemical activity are of generic nature and can be applied for assembling other well-structured carbon-based composites.