Coal Liquefaction Residues Based Carbon Nanofibers Film Prepared by Electrospinning: An Effective Approach to Coal Waste Management

As a major byproduct of direct coal liquefaction, coal liquefaction residue (CLR) waste is environmentally harmful but also valuable. Considering environmental and economic efficiency, exploiting these wastes as electrodes for new generation energy storage devices will increase the economic value and decrease environmental pollution synchronously. In this regard, CLRs are used to prepare carbon nanofibers film for supercapacitors via electrospinning followed by HNO3 preoxidization, air stabilization, and carbonization processes for the first time. The influences of HNO3 preoxidization over the formation of fiber morphology, textural structure, surface chemistry, and electrochemical performance are investigated. Our work demonstrates that HNO3 preoxidization can enhance the content of the heteroatom of the as-spun nanofibers and promote the polymerization of the asphaltene (CLRA) molecular during air stabilization, leading to the changes of the thermal behaviors and thus avoiding the fibers melting successfully. The results show that the obtained sample exhibits a 3D nonwoven network with an average diameter of 200 nm, good flexibility, high content of nitrogen, and large specific surface area. Owing to these merits, the as-obtained sample shows high specific capacitance, excellent rate capability (143 F g(-1) at 100 A g(-1)), and long lifespan (98% of its initial capacitance after 10 000 cycles) as supercapacitor electrode.