NiCo2S4 Nanotube Decorated on Tea-Waste Derived Porous Carbon: A Dual-Purpose Nanocomposite for High-Performance Flexible Asymmetric Supercapacitor and Oxygen Evolution Reaction

Abstract

Water splitting is one of the cleanest ways to produce H₂, considered a reliable, next-generation fuel, and supercapacitors are one of the most efficient energy devices for myriad technologies. Herein, we designed and synthesized NiCo₂S₄ nanotubes-porous carbon (NCS-PC_TW) nanocomposite. Porous carbon was synthesized from abundant and cheap tea leaf waste (i. e., tea leaves obtained after brewing). The performances of NCS-PC_TW nanocomposite have been assessed for two applications: (i) as an active cathode material in an all-solid-state flexible asymmetric supercapacitor (ASC) device and (ii) as an electrocatalyst for oxygen evolution reaction (OER). The asymmetric supercapacitor NCS-PC_TW//PC_TW device exhibited its high performance, such as a specific capacitance of 188.75 F g⁻¹ at 1 A g⁻¹, a high energy density of 72.4 W h kg⁻¹ at a power density of 863 W kg⁻¹, and a long cyclic stability. NCS-PC_TW nanocomposite also demonstrated its excellent efficiency as an electrocatalyst for OER with a low onset potential of 1.48 V, low overpotential of 267 mV at 10 mA cm⁻², a Tafel slope of 82.53 mV dec⁻¹, and stability till 20 h at 50 mA cm⁻². This work illustrates the great potential of NiCo₂S₄-porous carbon nanocomposite in clean energy generation and efficient energy storage technologies.