Graphene-Like Carbon Fibres Derived from Cotton Waste for High-Performance Supercapacitors: Computational and Experimental Investigation

Abstract

Graphene-like carbon fibres (GLCFs) demonstrated their excellence for supercapacitors (SCs) due to their physical and structural properties. However, the complex synthesis routes for GLCFs hinder their widespread use in SCs. Therefore, we report a facile route for synthesizing GLCFs from a waste cotton, using a two-step synthesis approach to obtain high-quality GLCFs. The synthesized GLCFs exhibited a high-quality graphitic skeleton, as evidenced by Raman analysis, with a 2D band indicative of a graphene-like structure. FESEM images of GLCFs showed a well-established 3D network of folded graphene layers, making them suitable for faster charge-carrier transport in supercapacitor devices. To understand the electronic behaviour of these GLCFs for SC applications, we have conducted a detailed density functional theory (DFT) investigation by using the Synopsys QuantumATK framework. As these GLCFs are supposed to consist of graphene nanosheets (GNS), their structural, electrical, and capacitive properties of GNS were examined under bending conditions. The investigation shows that quantum capacitance reaches a maximum under bending conditions, indicating that bending of GNSs is the most favourable condition for attaining energy-storage properties. As GLCFs are composed of bending sheets of GNSs, efficient charge storage properties are expected, as confirmed by our experimental analysis. The GLCFs showed a specific capacitance of 411.24 F/g at a scan rate of 5 mV/s in 1 M H2SO4 in three electrode set-ups, with excellent capacitance retention over 5000 cycles. Further, we also fabricated GLCFs based coin cell (CR-2032) and achieved a maximum gravimetric capacitance of 31.79 F g⁻¹, maximum areal capacitance of 41.28 mF cm⁻², maximum energy density of 8.65 Wh kg⁻¹, and maximum power density of 105.00 W kg⁻¹, confirming its capacitive behavior and reasonable electrochemical performance as a symmetric supercapacitor.