Eco-friendly fabricated nonporous carbon nanofibers with high volumetric capacitance: improving rate performance by tri-dopants of nitrogen, phosphorus, and silicon

Abstract

Development of high volumetric capacitance, high rate performance and low-cost electrode materials for supercapacitors is still a significant challenge. Among the various promising candidates, carbon nanofibers (CNFs) with heteroatom functionalization have attracted increasing attention. Herein, a type of nonporous CNFs combined with a heteroatom functionalization strategy is proposed for high performance supercapacitor electrodes. Tri-heteroatom functionalization of nonporous carbon nanofibers was carried out by tetraethyl orthosilicate (TEOS) and phosphorus (H₃PO₄) activation of polyacrylonitrile (PAN) through electrospinning and subsequent thermal treatment. The optimal electrode material showed a high gravimetric capacitance of 243.7 F g⁻¹ at 0.5 A g⁻¹, superior rate capability with ∼83% retention at rates ranging from 0.5 A g⁻¹ to 30 A g⁻¹ and excellent cycle stability (capacitance retention rate >100% after 8000 cycles at a high current density of 30 A g⁻¹). It is worth noting that the nonporous CNF also possesses a high packing density, which presents a maximum volumetric capacitance of 253.4 F cm⁻³ at 0.5 A g⁻¹ and 209 F cm⁻³ at 30 A g⁻¹. The current synthetic strategy of preparing nonporous carbon architectures with multi-heteroatom doping offers an eco-friendly, feasible, and cost-effective way for constructing high-performance electrode materials employed in supercapacitors.