Modified Carbon Papers as Electrode Materials of all-Vanadium Redox Flow Battery
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Modified Carbon Papers as Electrode Materials of all-Vanadium Redox Flow Battery Chih-Hsing Leu1*, Shu-Yuan Chuang1, 2, Kan-Lin Hsueh1, Jia-Ming Huang1, Chia-Chun Chung 1, Chun-Hsing Wu1, Hsiao-Hsuan Hsu1, Yi-Ray Chen1, Wen-Sheng Chang1 1
Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan, Republic of China
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Department of Materials Engineer, Ming Chi University of Technology, Taipei 243, Taiwan, Republic of China
* Corresponding author. Fax: +886-3-5820030, E-mail address: [email protected]
ABSTRACT The electrode materials for VRFB should possess higher electric conductivity, corrosion resistance and hydrophilic properties in sulfuric acid. The characteristics of the electrode materials affect the stability and the energy efficiency of VRFB. Carbon materials are the best suited for VRFB applications. In this study, the calcined treatment, acid treatment and ozone treatment were used to modify the surface of carbon papers. The redox reaction of [VO]2+/[VO2]+ on the modified carbon papers was evaluated by cyclic voltammetry (CV). The surface compositions of carbon materials were analyzed by X-ray photoelectron spectrometry (XPS). The experimental results reveal that three oxidative methods enhance the redox reaction of [VO]2+/[VO2]+. The calcined treatments and acid treatments also enhanced hydrolysis reaction. The mole ratio of O/C apparently increased, but the binding energy of C1s and O1s were not chemically shifted in the acid treatment. The intensity of binding energy of O1s, between 532 eV and 534 eV, apparently increased in the ozone and calcined treatments. The Ox treated samples were more hydrophilic than the Oz treated samples. In the Ox treated samples, the decrease of Rct value indicates that was contributed from the redox reaction of [VO]2+/[VO2]+ and hydrolysis reaction. It does not completely benefit the energy efficiency of VRFB. The 5 x 5 cm2 modified carbon papers were used as electrode materials in the VRFB. The voltage efficiency, coulomb efficiency and energy efficiency reached 93 %, 90 % and 83 %, respectively, at a current density of 12 m$᧪cm-2 at 0.8-1.8 V. Keywords: Modified carbon paper᧷Vanadium redox flow battery᧷Energy storage᧷Electrode materials᧷Treatment 1. INTRODUCTION The practical utilization ratio of renewable energy sources such as solar energy or wind energy
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can be promoted by finding compatible energy storage systems.
All vanadium redox flow
battery (VRFB) is one of potential energy storage technologies due to high energy efficiency, long cycle life and low cost etc. [1-4]. In general, carbon based materials [5-8] are used as the electrode materials of vanadium redox flow battery. Han et al. [9] revealed that carbon base materials were proved to show poor kinetic reversibility.
Therefore, the surface modification of
carbon electrode materials improves the performance of all vanadium redox flow battery. The –OH groups and carbonyl groups were introduced onto carbon materials by different oxidation methods
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