重庆欢乐生肖走势图 www.jakn.com.cn Journal of Power Sources 195 (2010) 1516–1521
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A doped activated carbon prepared from polyaniline for high performance supercapacitors
Limin Li,Enhui Liu ?,Jian Li,Yanjing Yang,Haijie Shen,Zhengzheng Huang,Xiaoxia Xiang,Wen Li
Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education,College of Chemistry,Xiangtan University,Hunan 411105,PR China
a r t i c l e i n f o Article history:
Received 14July 2009
Received in revised form 3September 2009Accepted 9September 2009
Available online 16 September 2009Keywords:
Doped activated carbon
X-ray photoelectron spectroscopy Electrochemical properties
a b s t r a c t
A novel doped activated carbon has been prepared from H 2SO 4-doped polyaniline which is prepared by the oxypolymerization of aniline.The morphology,surface chemical composition and surface area of the carbon have been investigated by scanning electron microscope,X-ray photoelectron spectroscopy and Brunaner–Emmett–Teller measurement,respectively.Electrochemical properties of the doped activated carbon have been studied by cyclic voltammograms,galvanostatic charge/discharge,and electrochemical impedance spectroscopy measurements in 6mol l ?1KOH.The speci?c capacitance of the carbon is as high as 235F g ?1,the speci?c capacitance hardly decreases at a high current density 11A g ?1after 10,000cycles,which indicates that the carbon possesses excellent cycle durability and may be a promising candidate for supercapacitors.
? 2009 Elsevier B.V. All rights reserved.
In recent years,supercapacitors (also called electrochemical capacitors)have attracted great attention as alternative energy-storage systems,compared to the conventional capacitors,they have higher energy density and broader range of working temper-ature;compared to the secondary battery,they have higher power density,longer cycle life (above 100,000cycles),and shorter charg-ing time [1–3].Two kinds of supercapacitors have been studied:one is the electrical double-layer capacitor (EDLC),in which the capaci-tance arises from the charge separation at the electrode/electrolyte interface,such as carbon;the other is the pseudocapacitor,in which the capacitance arises from faradic reactions occurring at the electrode interface,such as transition-metal oxides [4–7]or electroactive polymers [8–11],etc.In the EDLC,the capacitance is proportional to the surface area of the electrode/electrolyte inter-face,in order to increase the speci?c capacitance,it is necessary to increase the surface area through increasing the micropores of the material,but it leads to the problem of ionic transportation.In pseudocapacitors,noble metal oxides [12–14]show high speci?c capacitance,but their application is limited by their high cost;Elec-troactive polymers also show high speci?c capacitance,but their application is limited by their poor chemical reversibility and short of cycling stability in aqueous electrolytes [15,16].Literally,syn-ergetic effects can be expected if the capacitive charging of the
?Corresponding author.Fax:+8673158292251.E-mail address:[email protected]//www.jakn.com.cn/doc/45a94ef5e2bd960591c67718.html (E.Liu).
double-layer can be combined with a faradaic redox (pseudocapac-itive)reaction in a way that both charge storage mechanisms work in parallel,with the overall capacitance of the electrode being the sum of the double-layer capacitance and the faradaic capacitance.
Introducing some functional groups containing many het-eroatoms (such as oxygen,nitrogen,sulfur and halogen)into a carbon matrix is a good choice.The presence of these func-tionalities gives carbon materials an acid/base character [17,18],which enhances their capacitances by the pseudocapacitive effect.Recently,nitrogen-containing carbon materials have been reported as an interesting route to enhance capacitances [19–24].The results showed that the extent of enhancement depended on the prepara-tion route and electrolyte used.
In this paper,we have prepared a doped activated carbon derived from H 2SO 4-doped polyaniline which is prepared using the oxypolymerization method.Because polyaniline contains about 15wt.%of nitrogen and 79wt.%of carbon,it is commercially available and very cheap,we believe that it is a promising nitrogen-containing carbon material for supercapacitors.To the best of our knowledge,synthesizing such a carbon material for supercapaci-tors by this way has not yet been reported.2.Experimental
2.1.Preparation of polyaniline
Aniline monomer was distilled prior to use,while other chem-icals used were all analytical grade reagents.Distilled water was used in this experiment.A solution of 20ml of aniline in 43ml of
0378-7753/$–see front matter ? 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.jpowsour.2009.09.016