Dual functional superhydrophobic and superorganophilic porous graphene carbon nanocomposite electrodes for Unprecedented High-Voltage supercapacitor with superior rate capability

Abstract

Supercapacitors utilizing organic electrolytes derived from biomass face significant challenges due to their low energy density, a consequence of their limited operating voltage window of 2.7–3.0 V. This limitation restricts their utility in high-performance energy storage applications such as electric vehicles. By employing advanced techniques to meticulously control water contamination through rigorous drying processes and incorporating superhydrophobic functionality, researchers can enhance the performance and durability of organic electrolyte-based supercapacitors. To address these challenges, we present a ground breaking approach featuring a dual-functional porous graphene carbon nanocomposite electrode with superhydrophobic and superorganophilic properties, paired with a TEABF₄-acetonitrile electrolyte. This innovative design achieves a significant extension of the operational voltage to 3.4 V. The porous graphene nanocomposite is produced sustainably using hydrothermal and KOH-activation processes, resulting in a high surface area (2100 m²/g) and a bi-modal pore size distribution. This optimized structure enhances wettability and facilitates rapid ion transport, delivering superior rate capability even at elevated voltages. The asymmetric supercapacitor design resolves disparities in ionic size, promoting efficient ion transport and rapid diffusion. This advancement results in a remarkable 33 % increase in gravimetric energy density for the porous graphene carbon nanocomposite (PGCN) compared to the commercial YP-50F electrode. To further explore ionic behaviour and diffusion within the porous electrode, Nyquist plot analyses were conducted, revealing a significantly higher ion diffusion coefficient (D) for PGCN (∼3.31 × 10⁻⁸ cm²/s) compared to YP-50F (∼2.29 × 10⁻¹⁰ cm²/s). This substantial improvement is attributed to the exceptional superorganophilic nature of the PGCN carbon surface. This pioneering research establishes a new paradigm in supercapacitor technology, enabling devices with wider operating voltages suitable for high-voltage energy storage applications, including electric vehicles and other demanding systems.