Preparation Of Coal Based Carbon Nanofibers And Its Application In Supercapacitor

Xinjiang coal resources are abundant. Hence it is significant for resource conversionstrategy, development of high additional valued carbon materials. Carbon fibers havethe essential properties of carbon material, such as high electric conductivity andthermal conductivity. Besides, they are flexible and light weighted. Carbon fiberelectrode is binder-free and much easier to assemble compared with powderedsamples. The active material in the electrode is hence enhanced. Moreover, higherion-transfer efficiency and higher conductivity are also beneficial to be used aselectrode. This article used organic solvent dissolved acid treated coal to electrospin,and hence prepared coal based carbon nanofiber by following pyrolysis. We studiedthe electrochemical performance of these carbon fibers, and found that the fiber matcan be used as flexible electrode material. This method offered a new way to clean useof coal and new material for supercapacitor electrode.1. Coal was treated with mixed acid H2SO4/HNO3(3:1). Acid treated coal wasobtained after washing. The acid treated coal can well dispersed in polar organicsolvents. The study found that the increase of polarity of the solvent can increasethe solubility of acid treated coal. The acid treatment broke down the aliphatic andether bonds in coal macromolecules, and increased the oxygen-containing groupsat the surface of acid treated coal. In this way can acid treated coal dissolve intopolar organic solvents.2. We used the DMF solution of polyacrylonitrile and acid treated coal as theprecursor of electrospinning, and obtained the electrospun fiber mat. The as-spunfiber mat was pre-oxidized and carbonized and finally turned into a flexible coalbased carbon fiber mat. The carbon fiber has the capacitance of177F g-1. The fibers mat was then activated by water vapor, and the capacitance increased to230F g-1. The cycle retention kept97%after1000cycles at the current density of2Ag-1.3. We used poly (vinyl-alcohol) and acid treated coal NMP as the spinning precursorand electrospun them into a fiber mat. In this study, we used samples withdifferent coal contents and carbonization temperature to do comparison. Theresults showed that the capacitance reached its maximum at600°C, withPVA/coal of2:1. The experiment showed that mixed solvent affected significantlyon the morphology and specific capacitance. The addition of poor solvent canincrease the specific capacitance of the result carbon fiber. The carbon fiber couldreach a capacitance of212F g-1without activation.4. We used the obtained PVA/coal based carbon fiber as the MnO2depositionsubstrate and fabricated MnO2/carbon composite. The capacitances of resultcomposite were194and237F g-1for plasma-treated and untreated samples. Wealso used the chemical vapor deposition to prepare carbon nanotube/carbon fiberas the MnO2deposition substrate. The capacitance of the composite was94F g-1.These results indicate that coal based carbon fibers have promising potential in theapplication of substrate for material with pseudocapacitance.5. We used chemical vapor deposition and ultrasonic spray to fabricate nanomaterials.The results showed that both of the methods are promising however possess thedisadvantage of low carbon yield. We determined that lower temperature duringreaction would be beneficial to the reaction. We intend to lead a way to thefabrication of coal based nanomaterials and provide some references to the futurework.