Novel preparation of metal-free carbon xerogels under acidic conditions and their performance as high-energy density supercapacitor electrodes

Abstract

The development of metal-free supercapacitor electrodes with a high energy density is a crucial requirement in the global shift towards sustainable energy sources and industrial pursuit of an optimal supercapacitor. Indeed, from an industrial perspective, time assumes a paramount role in the manufacturing process. A majority of synthesis methods employed for the fabrication of carbon xerogel-based supercapacitor electrodes are characterized by prolonged durations, and result in relatively poor energy and power density. These limitations hinder their practical applications and impede their widespread manufacturing capabilities. In this study, carbon xerogel-based supercapacitor electrodes were made in the shortest time ever reported by making the condition highly acidic with hydrochloric acid (HCl). Furthermore, the investigation of the effect of HCl concentrations (0.1 M, 0.05 M, and 0.01 M) on the morphology and electrochemical behavior of the prepared samples is reported herein. Interestingly, the highest concentration of HCl developed the highest BET surface area, 1032 m² g⁻¹, which enforced the capacitive behavior to deliver a specific capacitance of 402 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 80.8% at a current density of 2 A g⁻¹ in an electrolyte containing 0.5 M H₂SO₄ + 0.5 M Na₂SO₄. Moreover, an impressive energy density of 45 W h kg⁻¹ at a power density of 18.2 kW kg⁻¹ was achieved. Interestingly, as the HCl concentration increased, the equivalent series resistance decreased to 3.9 W with carbon xerogel 0.1 M HCl (CX0.1). The superior performance of CX0.1 may be attributed to its enlarged BET surface area, pore volume, pore diameter, and smaller particle size. This work provides a facile approach for the large-scale production of metal-free carbon supercapacitor electrodes with improved performance and stability and opens novel horizons to explore the impacts of many types of catalysts during the carbon xerogel preparation.