A win-win method for generating carbon material precursors of carbon nanofibers from coal and CO2 and the associated mechanism

Abstract

Conventional fossil fuel utilization including coal burning process releases a large amount of carbon dioxide (CO2) to the atmosphere each year. Problems of CO2 emission have raised environmental concerns due to the possible link between CO2 and climate change. Thus, finding alternative technologies to utilize coal in an environmentally friendly manner and utilizing the captured CO2 are becoming extremely important. This research aims at fabricating high-value solid materials of carbon nanofibers (CNFs) with decent electrochemical capacitance from an ethanol and supercritical CO2 (EtOH-SCC) extraction method for producing tar from different coals. Tar yields of five coals were received between 26.85% and 37.18%. Gas chromatography-mass spectrometry proved that aliphatic esters comprised the highest percentages in each individual tar sample, ranging from 33.67% to 55.26%. The existence of aromatic structures in the tars were confirmed by Fourier-transform infrared spectra. Surface area of the fabricated carbon nanofiber was as high as 1263 m2 g−1, which significantly contributed to the high capacitance of the associated carbon nanofiber with the highest value to be 290.46F g−1 at 1 A g−1. Moreover, possible reaction mechanisms of ethanol and CO2 with coal were proposed based on the results from 1H NMR, 2H NMR and 13C NMR spectra when using deuterium-labeled ethanol and 13C labeled CO2 as reactants.