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

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 electroanalytical techniques. The SC-ZIF-8-C electrode possessed a low charge transfer resistance of 2.51 Omega 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.