Functionalized activated carbon prepared form petroleum coke with high-rate supercapacitive performance
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Jufeng Huang and Wei Xinga) School of Science, State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, People’s Republic of China
Zifeng Yana) School of Chemical Engineering, State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, People’s Republic of China (Received 31 July 2016; accepted 14 October 2016)
Petroleum coke (PC) is a low-cost and potential carbon source for electrochemical energy storage. To expand the utilization of PC in supercapacitor, PC-based activated carbons (PCACs) with heteroatoms-doped were prepared from PC by KOH chemical activation. The as-prepared carbon exhibited a high surface area (2326.4 m2/g) and hierarchical micro-mesoporous structure, resulting in a high specific capacitance (421 F/g at 1 A/g) and excellent rate performance in KOH electrolyte (217 F/g at 50 A/g). Meanwhile, to improve the high-rate capacitive performance of PCACs in H2SO4 electrolyte, functionalized activated carbon (HQ/PCAC-4) was prepared by physically adsorbing the hydroquinone (HQ) on PCACs. The HQ/PCAC-4 showed an unprecedented capacitance value of 300.2 F/g even at an ultrahigh current density of 50 A/g. In addition, the energy density of HQ/PCAC-4 in H2SO4 electrolyte reached 19.5 W h/kg. The high energy density and excellent rate performance ensured their prosperous application in high-power energy storage system. I. INTRODUCTION
Supercapacitors (SCs), as an important next generation energy storage device, have recently attracted extensive interest.1–3 It is generally accepted that electrode materials are one of dominating factors that influence the capacitive performance of SCs.4 Among various electrode materials, carbon electrode materials represent today more than 80% of the commercially manufactured SCs5 and are considered as the most promising materials for future capacitors with excellent performances. At the same time, the disadvantages of carbon-based SC, including unstable power density at high current density, have been recognized as major challenges for the furtherance of SC technologies.6 So, over the years, significant efforts have been devoted to research the energy storage mechanism of carbon electrode materials and achieved some subversive conclusions. To overcome the obstacle of unstable power density at high current density, the most intensive approach is the building of hierarchical interpenetrating structures. For Contributing Editor: Sung-Yoon Chung a) Address all correspondence to this author. e-mail: [email protected] b) These authors contributed equally to this work. DOI: 10.1557/jmr.2016.405
the mesoporous structures, especially the mesopores with sizes of 2–5 nm,7 numerous studies have already demonstrated that “ion-transferring channels” were formed in the mesopores, which facilitated the ultrafast ion transport during the charge/discharge process. Therefore, the extensive of mesopores resulted in better capability for high-drain-rate operations and led to a good power-output characteristic. To improve energ
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