Phase-controlled preparation of cubic facet zeolitic imidazole framework-8-derived carbon using supercritical-CO2 medium: A solitary carbon material for symmetric supercapacitor

Abstract

The preparation of nitrogen-rich carbon from zeolitic imidazole framework-8 (ZIF-8-C) has inspired considerable attention as electrode materials for advanced energy storage applications. Various dopants and composites have been employed to enhance energy storage performance; nevertheless, these approaches often entail high materials costs and expensive preparation methods. In the pursuit of more efficient ZIF-8-C electrodes, this study introduces a fresh preparation avenue using a supercritical-CO2 method (SC-ZIF-8-C) without any additives/surfactants. A comparison study is employed using the conventional method (C-ZIF-8-C). The prepared materials are examined through physical characterization to elucidate their phase purity, surface morphology, and functionalities. The electrochemical performance of the supercapacitor application is assessed using standard electro-analytical techniques. The SC-ZIF-8-C electrode possessed a low charge transfer resistance of 2.51 Ω and a high specific capacitance of 292.15 F/g at 0.75 A/g. In addition, the SC-ZIF-8-C is constructed as a symmetric sandwich-type device, which shows higher energy and power densities of 16.87 Wh/kg and 449.99 W/kg, respectively. The practical demonstration of a series-connection of devices remains capable of emitting a glow of light, even after 3 min. Thereby, the respectable performance of single carbon material and its eco-friendly synthesis approach establishes a route towards sustainable and green energy storage devices.