Self-Doped Activated Carbons from Car Exhaust as High-Performance Supercapacitor Electrode Materials for Sustainable Energy Storage System
Akter Hossain Reaz, Hasi Rani Barai, Shimul Saha, Keya Chowdhury, Maharun Negar Mojumder, Shakhawat H. Firoz, Al‐Nakib Chowdhury, Sang Woo Joo, Chanchal Kumar Roy
Abstract
Hydrocarbon based waste materials are emerging as an attractive source of generating activated carbons (ACs), having excellent potential for enormous in-field applications. In this study, it has been demonstrated that the carbon materials collected from the diesel engine exhaust could be a new source for preparing self-doped highly porous AC for high-performance supercapacitor applications. As the diesel engine exhaust carbon (DEEC) itself contains a large number of heteroatoms (O, N, S, and P), simple acid treatment (HCl) of DEEC resulted in a self-doped AC (SDAC_HCl) having contained a high level of heteroatoms as the dopant in it and consequently provided with a large specific surface area of 89 m 2 g −1 . The pyrolytic treatment of DEEC with KOH further resulted in self-doped AC (SDAC_KOH) with an enhanced specific surface area of 549 m 2 g −1 due to the increase in porosity of AC. The supercapacitor performance of the AC materials is evaluated in a symmetric two-electrode cell. The ACs (SDAC_HCl and SDAC_KOH) have shown very high specific capacitance ( C sp ) with aqueous (sodium sulfate, Na 2 SO 4 ), organic (tetraethylammonium tetrafluoroborate/acetonitrile, TEABF 4 /AN) and ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIM][Cl]) electrolytes. The highest C sp of 403 Fg −1 at the current density of 1 Ag −1 is obtained in SDAC_KOH with [BMIM][Cl] electrolyte. The C sp is 193 F g −1 at the high current density of 10 Ag −1 , demonstrating the good compatibility of the electrolyte with the electrode material. The SDAC_KOH with [BMIM][Cl] is able to supply a high energy density of 35.8 Whkg −1 at a power density of 400 Wkg −1 which is very reasonably high compared to other reported AC materials. The SDAC_KOH has shown excellent stability in continuous galvanostatic charge-discharge cycles. The SDAC_KOH has retained 98% of its initial capacitance after 10000 cycles at a high current density of 5 Ag −1 . The facile and effective strategies employed in this study in developing high-performance supercapacitor electrode materials from waste may help design and develop sustainable energy storage systems.