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RISS 인기검색어
- 검색키워드
- 저자 : Jeong Sanghyun (검색결과 212 건)
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Effect of mesocelluar carbon foam electrode material on performance of vanadium redox flow battery
Jeong, Sanghyun,An, Sunhyung,Jeong, Jooyoung,Lee, Jinwoo,Kwon, Yongchai Elsevier 2015 Journal of Power Sources Vol.278 No.-
<P><B>Abstract</B></P> <P>Languid reaction rate of VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox couple is a problem to solve for improving performance of vanadium redox flow battery (VRFB). To facilitate the slow reaction materials including large pore sized mesocellular carbon foam (MSU-F-C and Pt/MSU-F-C) are used as new catalyst. Their catalytic activity and reaction reversibility are estimated and compared with other catalysts, while cycle tests of charge–discharge and polarization curve tests are implemented to evaluate energy efficiency (EE) and maximum power density (MPD). Their crystal structure, specific surface area and catalyst morphology are measured by XRD, BET and TEM. The new catalysts indicate high peak current ratio, small peak potential difference and high electron transfer rate constant, proving that their catalytic activity and reaction reversibility are superior. Regarding the charge–discharge and polarization curve tests, the VRFB single cells including new catalysts show high EE as well as low overpotential and internal resistance and high MPD. Such excellent results are due to mostly unique characteristics of MSU-F-C having large interconnected mesopores, high surface area and large contents of hydroxyl groups that serve as active sites for VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox reaction and platinums (Pts) supporting the MSU-F-C. Indeed, employment of the catalysts including MSU-F-C leads to enhancement in performance of VRFB by facilitating the slow VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We adopt large pore sized mesocellular carbon foam (MSU-F-C) as a new catalyst for enhancement in VRFB performance. </LI> <LI> The MSU-F-C plays a role in promoting a slow reaction rate of VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox couple. </LI> <LI> Catalysts including MSU-F-C cause improvement in peak current ratio and electron transfer rate constant. </LI> <LI> VRFBs including MSU-F-C show high energy efficiency and maximum power density. </LI> <LI> Better VRFB perfomances are due to high surface area and large contents of hydroxyl groups of MSU-F-C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Effect of nafion membrane thickness on performance of vanadium redox flow battery
Sanghyun Jeong,Yongchai Kwon,Sunhoe Kim,Lae-Hyun Kim 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.11
The performance of vanadium redox ow batteries (VRFBs) using different membrane thicknesses wasevaluated and compared. The associated experiments were conducted with Nafion® 117 and 212 membranes that have175 and 50 µm of thickness, respectively. The charge efficiency (CE) and energy efficiency (EE) of VRFB using Nafion®117 were higher than those of VRFB using Nafion® 212, while power efficiency was vice versa. In terms of amountsof charge and discharge that are measured in different charging current densities, the amounts in VRFB using Nafion®212 are more than that in VRFB using Nafion® 117. To further characterize the effect of membrane thickness on VRFBperformance, electrochemical impedance spectroscopy (EIS) and UV-vis. spectrophotometer (UV-vis) were used. InEIS measurements, VRFB using Nafion® 117 was more stable than that using Nafion® 212, while in UV-vis meas-urements, vanadium crossover rate of VRFB usingNafion® 212 (0.0125 M/hr) was higher than that of VRFB usingNafion® 117 (0.0054M/hr). These results are attributed to high crossover rate of vanadium ion in VRFB using Nafion®212. With these results, vanadium crossover plays more dominant role than electrochemical reaction resistance in de-ciding performance of VRFB in condition of different membranes.
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Jeong, Sanghyun,Choi, Yong Jun,Nguyen, Tien Vinh,Vigneswaran, Saravanamuthu,Hwang, Tae Moon Elsevier 2012 Journal of membrane science Vol.411 No.-
<P><B>Highlights</B></P><P>► Submerged membrane hybrid system (SMHS) with FeCl<SUB>3</SUB> flocculation and/or PAC adsorption. ► Low doses of ferric 0.5mg/L, PAC 0.5g/L removed 72% of DOC, reduced 5 times of UF-MFI. ► Both hydrophobic and hydrophilic compounds were significantly removed by hybrid system. ► 3 membrane fouling models (pore blockage, pore constriction, cake formation) were used. ► Among the 3 models, cake formation was found to be dominant in SMHS.</P> <P><B>Abstract</B></P><P>Three different submerged membrane hybrid systems (SMHSs) namely submerged membrane coagulation hybrid system (SMCHS), submerged membrane adsorption hybrid system (SMAHS), and submerged membrane coagulation–adsorption hybrid system (SMCAHS) were studied as pretreatment systems to seawater reverse osmosis (SWRO). The performances of these SMHSs were compared with that of submerged membrane system (without any coagulation or adsorption) in terms of trans-membrane pressure (TMP) development, critical flux, ultrafilter modified fouling index (UF-MFI), dissolved organic carbon (DOC) removal efficiency, and the removal of detailed organic fractions. The experimental results show that pretreatment by SMCAHS led to the best results in terms of organic removal and critical flux. With the low doses of ferric chloride (FeCl<SUB>3</SUB>) and powder activated carbon (PAC) of 0.5mg of Fe<SUP>3+</SUP>/L and 0.5g of PAC/L, respectively, this hybrid system could remove 72% of DOC and reduce the UF-MFI nearly five times. The initial DOC and UF-MFI of seawater used in this study were 2.53mg/L and 14,165s/L<SUP>2</SUP>, respectively. The application of three different membrane fouling models namely pore blockage, pore constriction, and cake formation models showed that cake formation was the predominant fouling mechanisms causing fouling in SMHSs.</P>
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Jeong, Sanghyun,Cho, Kyungjin,Jeong, Dawoon,Lee, Seockheon,Leiknes, TorOve,Vigneswaran, Saravanamuthu,Bae, Hyokwan Pergamon Press 2017 Water research Vol.124 No.-
<P><B>Abstract</B></P> <P>Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Organic foulants on the RO membrane were also quantified and fractionized. The bacterial community structures in liquid (seawater and effluent) and biofilm (DMF and RO) samples were analyzed using 454-pyrosequencing. The DMF IV fed with the chlorinated seawater demonstrated the highest reductions of DOC including LMW-N as well as AOC among the other DMFs. The DMF IV was also effective in reducing organic foulants on the RO membrane surface. The bacterial community structure was grouped according to the sample phase (i.e., liquid and biofilm samples), sampling location (i.e., DMF and RO samples), and chlorination (chlorinated and non-chlorinated samples). In particular, the biofilm community in the DMF IV differed from the other DMF treatments, suggesting that chlorination exerted as stronger selective pressure than pH adjustment or coagulation on the biofilm community. In the DMF IV, several chemoorganotrophic chlorine-resistant biofilm-forming bacteria such as <I>Hyphomonas</I>, <I>Erythrobacter</I>, and <I>Sphingomonas</I> were predominant, and they may enhance organic carbon degradation efficiency. Diverse halophilic or halotolerant organic degraders were also found in other DMFs (i.e., DMF I, II, and III). Various kinds of dominant biofilm-forming bacteria were also investigated in RO membrane samples; the results provided possible candidates that cause biofouling when DMF process is applied as the pretreatment option for the RO process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Four dual media filters (DMFs) were operated under different engineered conditions. </LI> <LI> DMF with pre-chlorination treatment was effective to reduce organic matter. </LI> <LI> Functional biofilm bacterial structure in DMF and RO membranes were investigated. </LI> <LI> Pre-chlorination acted stronger selective pressure on biofilm community. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Self-Emitting Artificial Cilia Produced by Field Effect Spinning
Jeong, Woohyun,Jeong, Sang-Mi,Lim, Taekyung,Han, Chang-Yeol,Yang, Heesun,Lee, Bo Wha,Park, Sang Yoon,Ju, Sanghyun American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.38
<P>In nature, many cells possess cilia that provide them with motor or sensory functions, allowing organisms to adapt to their environment. The development of artificial cilia with identical or similar sensory functions will enable high-performance and flexible sensing. Here, we investigate a method of producing artificial cilia composed of various polymer materials, such as polyethylene terephthalate, polyurethane, poly(methyl methacrylate), polyvinylpyrrolidone, polystyrene, polyvinyl chloride, and poly (allylamine hydrochloride), using a field effect spinning (FES) method. Unlike wet- or electro-spinning, in which single or multiple strands of fibers are pulled without direction, the FES method can grow fiber arrays vertically and uniformly on a substrate in cilia-like patterns. The lengths and diameters of the vertically grown artificial cilia can be controlled by the precursor polymer concentration in the solution, applied electric current and voltage, and shape and size of the needle tip used for FES. The red, green, and blue emission characteristics of the polymer-quantum dot-based self-emitting artificial cilia prepared in polymer-inorganic nanoparticle hybrid form were determined. In addition, an artificial cilia-based humidity sensor made of the polymer-polymer composite was fabricated.</P> [FIG OMISSION]</BR>
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