Low-Grade Coal Feedstock for the Synthesis of High-Valued Graphene Derivatives for Energy Storage Application

Coal has been widely used as a fuel, albeit associated with environmental issues. Therefore, the research on nonfuel applications such as coal to chemicals and materials has been increased to reduce its environmental impacts without forfeiting its economic benefit. In this work, chemically impure and undervalued low-grade coal from the Northeast region (NER) of India is utilized as a carbonaceous precursor for the synthesis of valuable graphene derivatives. The synthetic process consists of a simple chemical approach combined with the ultracentrifugation technique. Electron microscopy of the synthesized graphene derivative reveals the presence of few-layered graphene with an interlayer distance (d-value) of 0.348 nm. The Raman, UV-vis, and FTIR functional group analyses of the products further confirm the graphene formation from such coal. The synthesized graphene derivative was also tested as an electrode material in a supercapacitor cell, where it shows excellent electrochemical behavior with a maximum specific capacitance value of 95.65 F g(-1) at 0.5 A g(-1) current density with a good capacitance retention of 70% at 10 A g(-1). The resultant maximum energy density and power density are 5 Wh kg(-1) and 6.00 kW kg(-1), respectively. This study demonstrates that the low-grade and pollutive coal feedstock can have environmentally green and sustainable utilization as a suitable precursor for valuable graphene derivatives with excellent potential in energy storage and other value-added applications.

Automated summary

Coal, although associated with environmental issues as a fuel, can be utilized as a precursor for valuable graphene derivatives, which have excellent potential in energy storage and other value-added applications. The chemically impure and undervalued low-grade coal from the Northeast region of India was used as a carbonaceous precursor for synthesizing graphene derivatives through a simple chemical method combined with ultracentrifugation. The synthesized graphene derivative exhibited few-layered graphene structure and showed excellent electrochemical behavior as an electrode material in a supercapacitor cell.