S/N Self-Co-Doped Graphene Derived from a Coal Precursor via an Ultrafiltration-Assisted Chemi-Thermal Approach for High-Performance Supercapacitors

Graphene and its derivatives, along with their scalable synthesis, are poised to play a crucial role in advancing future energy technologies. This study presents an ultrafiltration-assisted chemi-thermal approach for synthesizing high-yield sulfur- and nitrogen self-co-doped graphene from coal feedstock, enabling the fabrication of supercapacitor pouch cells for power applications. This scalable four-step process, comprising acid washing, oxidation, ultrafiltration, and thermal reduction, achieves a material yield of approximately 25 wt %. Detailed chemical, structural, and compositional analyses confirm the formation of multilayered (three to four layers) graphene with in situ S/N doping from the coal feedstock. Additionally, the fabricated coal-derived graphene electrode exhibits exceptional performance across various electrolytes, achieving an energy density of 72 Wh kg–1 and a power density of 108 kW kg–1 in 1.5 M TEABF4 electrolyte at a wide potential window of up to 2.7 V. Furthermore, this study also demonstrates the fabrication of supercapacitor pouch cells using the coal-derived graphene, successfully powering a solar-charged LED lamp that maintains illumination for over 15 min at a readable intensity. Thus, this work highlights the potential of a novel, cost-effective, and scalable chemi-thermal approach to graphene synthesis using an inexpensive coal feedstock for the development of advanced graphene-based supercapacitors for energy and power applications.