Structure and Electrochemistry of Carbon-Bromine Nanocomposite Electrodes for Electrochemical Energy Storage
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Structure and Electrochemistry of Carbon-Bromine Nanocomposite Electrodes for Electrochemical Energy Storage Prabeer Barpanda and Glenn G Amatucci Energy Storage Research Group (ESRG), Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ 08902, USA. ABSTRACT Activated carbons have been mechanochemically modified by bromine incorporation through high-energy milling route. Varying the milling duration and bromine content, carbonbromine nanocomposites of different compositions were fabricated. The highly reactive and electronegative bromine reacts with host carbon, which can modify its characteristic properties. We have examined the effect of bromination on the structure, chemistry, morphology and electrochemical properties of a mesoporous activated carbon. Bromination leads to possible charge transfer reaction, structural disordering with polybromide formation. Consequently, the non-faradaic capacitance improves and a faradaic pseudocapacitive reaction occurs at 3.1 V and a more traditional bromine reduction at 3.5V. The formation of carbon-bromine nanocomposites was found to deliver improved gravimetric and volumetric capacity. The effect of bromination on physical and electrochemical properties of activated carbons have been presented and contrasted to that of iodine incorporation. INTRODUCTION Electrochemical double layer capacitors (EDLC) (widely referred as supercapacitors) have attracted significant research attention in recent years for application requiring high power density. Activated carbons are widely used for commercial double layer capacitors owing to their high surface area, economic production and safe handling. Such carbons are also applicable to asymmetric hybrid nonaqueous electrochemical cells. The electrochemical capacity of these carbons can be improved by developing their surface morphology, internal space charge and by inception of pseudocapacitive reaction. We have earlier reported about a novel approach to improve the electrochemical capacity of activated carbons by chemical iodine-incorporation method [1,2]. The highly electronegative iodine (gr VII elements) gives rise to manifold improvement in structure and morphology of carbon, which subsequently develops faradaic pseudocapacitive reaction and delivers high capacity. In the current work, we have examined the effect of chemical bromination on the physical and electrochemical properties of activated carbons. Using various characterization techniques, we analyze various properties of carbonbromine nanocomposites to further our understanding on chemical halidation process. EXPERIMENTAL Commercially available activated carbon with trade name ASP (from Timcal Inc) was used as carbon precursor. The ASP carbon was mechanochemically modified by bromineincorporation through high-energy milling using a SPEX 1000 shock type milling machine. The milling process was conducted for 0~60 minutes, using spherical steel milling media of two
different sizes. For bromination, 0~30 we
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