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Abbas, Saleem,Hwang, Jinyeon,Kim, Heejin,Chae, Seen Ae,Kim, Ji Won,Mehboob, Sheeraz,Ahn, Ahreum,Han, Oc Hee,Ha, Heung Yong American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.30
<P>Histidine, inspired by vanadium bromoperoxidase enzyme, has been applied as a homogeneous electrocatalyst to the positive electrolyte of vanadium redox flow battery (VRFB) to improve the performance and stability of VRFB at elevated temperatures. The histidine-containing electrolyte is found to significantly improve the performance of VRFB in terms of thermal stability estimated by the remaining amount of VO<SUB>2</SUB><SUP>+</SUP> in the electrolyte (61 vs 43% of a pristine one), energy efficiency at a high current density of 150 mA cm<SUP>-2</SUP> (78.7 vs 71.2%), and capacity retention (73.2 vs 27.7%) at 60 °C. The mechanism of the catalytic functions of histidine with the chemical species in the electrolyte has been investigated for the first time by multinuclear NMR spectroscopy and first-principles calculations. The analyzed data reveal that histidine improves the kinetics of both charge and discharge reactions through different affinity toward the reactants and products as well as suppresses the precipitation of VO<SUB>2</SUB><SUP>+</SUP> by impeding the polymerization of vanadium ions. These findings are in good agreement with the improved chemical and electrochemical performance of the histidine-containing VRFB. Our results show a new type of chemical/electrochemical mechanism in the improved redox flow battery performance that may be essential in a new research arena for better performance of electrochemical systems.</P> [FIG OMISSION]</BR>
Abbas, Saleem,Lee, Hyuck,Hwang, Jinyeon,Mehmood, Asad,Shin, Hyun-Jin,Mehboob, Sheeraz,Lee, Ju-Young,Ha, Heung Yong Elsevier 2018 Carbon Vol.128 No.-
<P><B>Abstract</B></P> <P>In this work a novel method is unfolded to modify carbon felts (CF) to substantially improve the performance of the electrodes for vanadium redox flow batteries (VRFBs). The carbon felt, a well-known electrode material for VRFB, is catalytically etched by cobalt oxide to form carbon nanorods on the surface of the fibers comprising the CF. Unlike conventional multistep processes to grow nano-structures on carbon felts, this method simply involves a thermal treatment of catalyst-loaded felt in air to produce well aligned nanorods on its fibers. The surface morphology is optimized by etching temperature, treatment time and catalyst type. The catalytically etched CF shows an improved surface wettability and an enlarged specific surface area about two times compared to pristine CF that lead to an improvement of kinetics towards vanadium redox reactions. When used as electrode in all-vanadium redox flow battery, the nanorod-structured CF shows around 35% higher charge/discharge rate capability at 150 mA cm<SUP>−2</SUP> and 80% retained-capacity compared to 48% in case of un-etched CF as confirmed by a long run test with a hundred cycles of charge/discharge operation at 50 mA cm<SUP>−2</SUP>.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Abbas, Saleem,Mehboob, Sheeraz,Shin, Hyun-Jin,Han, Oc Hee,Ha, Heung Yong Elsevier 2019 Chemical Engineering Journal Vol. No.
<P><B>Abstract</B></P> <P>Low energy density of a vanadium redox flow battery (VRFB) due to limited solubility and stability of vanadium ions constrains its wide spread applications and this issue becomes more critical by low active surface areas of electrodes and mass transport limitations of active species on the electrodes that lead to low electrolyte utilization. In this study the issue of low energy density is addressed by improving the electrode performance through modifying the surface properties and morphology of thin (0.19 mm thick) carbon paper electrodes instead of commonly used several millimeters thick carbon felts. Surface functionalization and pore formation of carbon paper are carried out using a catalytic etching method at high temperaturewhere the diameters of nanopores are controlled by tuning the etching conditions. The synergistic effects of thin, nanoporous and functionalized carbon paper result in more effective electrode/electrolyte interaction and the less mass transport resistance. Therefore, the zero-gap VRFB cell employing the nanoporous electrodes displays remarkable performance improvement in terms of electrolyte utilization by 110%, discharge energy density by 155% and energy efficiency by 29% as compared to the one using pristine electrodes at a current density of 50 mA cm<SUP>−2</SUP>. The results imply that the more energy can be harvested by employing nanoporous and functionalized carbon paper electrodes having larger active surface areas.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Issue of low energy density of VRFB is addressed by modifying electrode surface. </LI> <LI> Highly functionalized nanopores are formed on the surface of thin carbon papers. </LI> <LI> Surface area, wettability and electrode/electrolyte contact is highly improved. </LI> <LI> Electrolyte utilization for cell having modified electrodes is improved by 110%. </LI> <LI> 27 Wh L<SUP>−1</SUP> more energy is harvested with 29% higher energy efficiency at 50 mA cm<SUP>−2</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Study of carbon fiber composite-based heat exchanger for icing and de-icing
Saleem Abbas(살림아바스),노세현,김병련,Phuong Nguyen Thanh(응웬탄푸옹),Chan Woo Park(박찬우) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
When heat pumps are utilized in severely cold weather, frost accumulates on the external evaporator fins, reducing thermal efficiency significantly. Carbon fiber reinforced polymer composite can be used as evaporator fins because of their efficient material features and heat resistivity nature. Using resistive heating characteristics, the thermal efficiency of a heat exchanger unit based on CFRP fins was examined.