Bitumen and asphaltene derived nanoporous carbon and nickel oxide/carbon composites for supercapacitor electrodes

Abstract

Asphaltenes from bitumen are abundant resource to be transformed into carbon as promising supercapacitor electrodes, while there is a lack of understanding the impact from different fractions of bitumen and asphaltenes, as well as the presence of transition metals. Here, nanoporous carbon was synthesized from bitumen, hexane-insoluble asphaltenes and N,N-dimethylformamide (DMF)-fractionated asphaltenes by using Mg(OH)2 nanoplates as the template with in-situ KOH activation, and used as an supercapacitor electrode material. All of the carbon exhibited large surface area (1500–2200 m2 g−1) with a distribution of micro and mesopores except for that derived from the DMF-soluble asphaltenes. The pyrolysis of asphaltenes resulted in the formation of nickel oxide/carbon composite (NiO/C), which demonstrated high capacitance of 380 F g−1 at 1 A g−1 discharge current resulting from the pseudocapacitance of NiO and the electrochemical double layer capacitance of the carbon. The NiO/C composite obtained from the DMF-insoluble portion had low NiO content which led to lower capacitance. Meanwhile, the specific capacitance of NiO/C composite from the DMF-soluble part was lower than the unfractionated asphaltene due to the higher NiO content resulting in lower conductivity. Therefore asphaltenes derived from nickel-rich crude bitumen is suitable for the synthesis of nanoporous NiO/C composite material with high capacitance.