The Experts below are selected from a list of 17268 Experts worldwide ranked by ideXlab platform
Yongchai Kwon - One of the best experts on this subject based on the ideXlab platform.
-
nine watt level aqueous organic Redox flow battery stack using anthraquinone and vanadium as Redox Couple
Chemical Engineering Journal, 2020Co-Authors: Wonmi Lee, Gyunho Park, Yong Kim, Dukrye Chang, Yongchai KwonAbstract:Abstract In this study, nine watt (9 W) aqueous organic Redox flow battery (AORFB) stack using vanadium (IV) oxide sulfate hydrate (VOSO4) and anthraquinone-2,7-disulfonic acid (2,7-AQDS) as Redox Couple is developed for the first time. This Redox Couple is dissolved in sulfuric acid with cell voltage of 0.9 V and this is higher than that of other acid based AORFBs. Although this Couple has precipitation and crossover issues of vanadium ions, they are solved by the adoption of two additives, ammonium chloride (NH4Cl) and magnesium sulfate (MgSO4). NH4Cl plays a role in preventing the precipitation problem by enhancing their dispersion capability, while MgSO4 can reduce the crossover problem by keeping the balance of ionic strength between two electrolytes. With that, the effects of concentration of VOSO4, flow rate, and current density on the performances of AORFB single cells using these two additives are evaluated. When the effects are considered, capacity retention is improved and the precipitation and crossover of vanadium ions are suppressed, and these induce a better cycle stability of AORFB. Eventually, the five AORFB single cells are stacked and this AORFB stack shows the excellent maximum power of 9 W at 120 mA·cm−2, while its performance is well preserved for 200 cycles. From this study, we substantiate that the 9 W AORFB stack using organic and vanadium active materials is well achieved by using efficient additives and optimizing the operational factors.
-
performance improvement by novel activation process effect of aqueous organic Redox flow battery using tiron and anthraquinone 2 7 disulfonic acid Redox Couple
Chemical Engineering Journal, 2020Co-Authors: Agnesia Permatasari, Wonmi Lee, Yongchai KwonAbstract:Abstract 4,5- dihydroxybenzene-1,3-disulfonic acid (Tiron) and anthraquinone-2,7-disulfonic acid (AQDS) are proposed as new Redox Couple with sulfuric acid (H2SO4) for aqueous organic Redox flow battery (AORFB). Two-electron Redox reactions of the new Redox Couple induce a fast reaction rate. However, Tiron undergoes transformation by undesirable Michael addition reaction during the first cycle. Additionally, sodium ions contained in Redox Couple lower their solubility in H2SO4. As a result, AORFB capacity loss and AQDS precipitation occur. To alleviate the loss in capacity by the transformation of Tiron, activation process is newly adopted. With the process, Tiron is transformed into reversable and desirable 2,4,5,6-tetrahydroxybenzene-1,3-disulfonic acid before actual operation, and the performance of AORFB operated under the process is similar to that operated without the process although the considerable amount of AQDS is relieved in AORFB operation including activation. In addition, a cation exchange resin, Amberlyst 15, is utilized to transform sodium ions into protons, and a proper increase of H2SO4 concentration provides the appropriate amount of protons for the promotion of Redox reactions. AORFB using optimal process demonstrates the benefit (i) decreasing the volume of AQDS, (ii) increasing the solubility of Tiron and AQDS up to 0.9 M and (iii) preserving the discharge capacity up to 99% after 50 cycles with the maximum possible discharge capacity of 24.4 Ahr L−1.
-
performance evaluation of aqueous organic Redox flow battery using anthraquinone 2 7 disulfonic acid disodium salt and potassium iodide Redox Couple
Chemical Engineering Journal, 2019Co-Authors: Wonmi Lee, Agnesia Permatasari, Byeong Wan Kwon, Yongchai KwonAbstract:Abstract An aqueous organic Redox flow battery (AORFB) using anthraquinone-2,7-disulfonic acid disodium salt (2,7-AQDS) and potassium iodide (KI) as the negative and positive active species is suggested. The active species are dissolved into an aqueous potassium chloride (KCl) solution, while ethylene glycol (EG) and polyvinylpyrrolidone (PVP) are added to improve the solubility of 2,7-AQDS and prevent the side reactions of KI. The aqueous solubility of Redox Couple improved by the utilization of additive plays a role in increasing both capacity and the performance of AORFB, while as kinetic parameters to affect the capacity, electron transfer rate constant (ks) and diffusion coefficient (D) are measured. As a result, when EG is used, the solubility of 2,7-AQDS increases from 0.3 to 0.8 M in KCl solution and PVP acts as a barrier preventing the production of iodine gas that is a product generated by the side reaction of KI. The increase in solubility by the use of EG is because it has two hydroxyl groups and they form hydrogen bonding with the oxygen of sulfonyl or carbonyl group within 2,7-AQDS, while the alkyl group of its backbone that is in non-polar nature interacts with the phenyl group within 2,7-AQDS. In addition, EG increases the Redox activity of KI because this significantly increases the nucleophilic ability of the iodide anion. Regarding the effect of PVP, when PVP is added to the solution containing iodine gas, povidone-iodine complex is formed and this complex impedes the side reaction of KI and maintains iodate that is a reactant for Redox reaction as it is in the system. With that, when the AORFB using the 2,7-AQDS and KI including EG and PVP is run for ten cycle, it shows excellent performances like the discharge capacity of 0.7 AhL−1 and the coulombic and energy efficiencies of 98% and 82%.
-
Mesoporous tungsten oxynitride as electrocatalyst for promoting Redox reactions of vanadium Redox Couple and performance of vanadium Redox flow battery
Applied Surface Science, 2018Co-Authors: Wonmi Lee, Sol Youk, Hun Yong Shin, Jinwoo Lee, Yongjin Chung, Yongchai KwonAbstract:Abstract For enhancing the performance of vanadium Redox flow battery (VRFB), a sluggish reaction rate issue of V 2+ /V 3+ Redox Couple evaluated as the rate determining reaction should be addressed. For doing that, mesoporous tungsten oxide (m-WO 3 ) and oxyniride (m-WON) structures are proposed as the novel catalysts, while m-WON is gained by NH 3 heat treatment of m-WO 3 . Their specific surface area, crystal structure, surface morphology and component analysis are measured using BET, XRD, TEM and XPS, while their catalytic activity for V 2+ /V 3+ Redox reaction is electrochemically examined. As a result, the m-WON shows higher peak current, smaller peak potential difference, higher electron transfer rate constant and lower charge transfer resistance than other catalysts, like the m-WO 3 , WO 3 nanoparticle and mesoporous carbon, proving that it is superior catalyst. Regarding the charge-discharge curve tests, the VRFB single cell employing the m-WON demonstrates high voltage and energy efficiencies, high specific capacity and low capacity loss rate. The excellent results of m-WON are due to the reasons like (i) reduced energy band gap, (ii) reaction familiar surface functional groups and (ii) greater electronegativity.
Licheng Sun - One of the best experts on this subject based on the ideXlab platform.
-
bis 1 1 bis 2 pyridyl ethane copper i ii as an efficient Redox Couple for liquid dye sensitized solar cells
Journal of Materials Chemistry, 2016Co-Authors: Jiayan Cong, Licheng Sun, Erik Gabrielsson, Dominik Kinschel, Quentin Daniel, Majid Safdari, Hong Chen, Per H Svensson, Lars KlooAbstract:A new Redox Couple, [Cu(bpye)2]+/2+, has been synthesized, and applied in dye-sensitized solar cells (DSSCs). Overall efficiencies of 9.0% at 1 sun and 9.9% at 0.5 sun were obtained, which are considerably higher than those obtained for cells containing the reference Redox Couple, [Co(bpy)3]2+/3+. These results represent a record for copper-based complex Redox systems in liquid DSSCs. Fast dye regeneration, sluggish recombination loss processes, faster electron self-exchange reactions and suitable Redox potentials are the main reasons for the observed increase in efficiency. In particular, the main disadvantage of cobalt complex-based Redox Couples, charge-transport problems, appears to be resolved by a change to copper complex Redox Couples. The results make copper complex-based Redox Couples very promising for further development of highly efficient DSSCs.
-
development of an organic Redox Couple and organic dyes for aqueous dye sensitized solar cells
Energy and Environmental Science, 2012Co-Authors: Haining Tian, Licheng Sun, Erik Gabrielsson, Peter W Lohse, Nikolaos Vlachopoulos, Lars Kloo, Anders HagfeldtAbstract:A water-soluble organic Redox Couple (TT−/DTT) and new organic dyes (D45 and D51) have been developed for aqueous dye-sensitized solar cells (DSCs). An optimal efficiency of 3.5% was obtained using the D51 dye and an optimized electrolyte composition. The highest IPCE value obtained was 68% at 460 nm.
-
efficient dye sensitized solar cells based on hydroquinone benzoquinone as a bioinspired Redox Couple
Angewandte Chemie, 2012Co-Authors: Ming Cheng, Xichuan Yang, Licheng Sun, Fuguo Zhang, Jianghua ZhaoAbstract:A hybrid electrolyte involving tetramethylammonium (TMA) hydroquinone/benzoquinone Redox Couple is formulated. This electrolyte is more transparent than the traditional I(-)/I(3)(-) electrolyte and has negligible absorption in the visible region. Dye-sensitized solar cells using the hybrid electrolyte show higher light-to-electricity conversion efficiency. FTO=fluorine-doped tin oxide.
-
efficient dye sensitized solar cells based on an iodine free electrolyte using l cysteine l cystine as a Redox Couple
Energy and Environmental Science, 2012Co-Authors: Ming Cheng, Xichuan Yang, Xiuna Wang, Licheng SunAbstract:A new iodine-free electrolyte based on amino acids L-cysteine/L-cystine as a Redox Couple has been designed and synthesized. DSSCs fabricated with the conventional I−/I3− Redox Couple gave efficiencies of 8.1% and 6.3% under optimized experimental conditions based on ruthenium dye, N719, and metal-free organic dye, TH202, respectively. Based on the same dyes, the DSSCs employing the new L-cysteine/L-cystine Redox Couple showed comparable efficiencies of 7.7% and 5.6%, respectively. However, higher incident-photon-to-electron (IPCE) conversion efficiencies and larger Jsc values were found for devices with the L-cysteine/L-cystine Redox Couple than with I−/I3−. From an electrochemical impedance spectroscopic study, we found that the charge recombination between the conduction band electrons in the TiO2 film and the electrolyte containing the L-cysteine/L-cystine Redox Couple is restrained.
Wonmi Lee - One of the best experts on this subject based on the ideXlab platform.
-
nine watt level aqueous organic Redox flow battery stack using anthraquinone and vanadium as Redox Couple
Chemical Engineering Journal, 2020Co-Authors: Wonmi Lee, Gyunho Park, Yong Kim, Dukrye Chang, Yongchai KwonAbstract:Abstract In this study, nine watt (9 W) aqueous organic Redox flow battery (AORFB) stack using vanadium (IV) oxide sulfate hydrate (VOSO4) and anthraquinone-2,7-disulfonic acid (2,7-AQDS) as Redox Couple is developed for the first time. This Redox Couple is dissolved in sulfuric acid with cell voltage of 0.9 V and this is higher than that of other acid based AORFBs. Although this Couple has precipitation and crossover issues of vanadium ions, they are solved by the adoption of two additives, ammonium chloride (NH4Cl) and magnesium sulfate (MgSO4). NH4Cl plays a role in preventing the precipitation problem by enhancing their dispersion capability, while MgSO4 can reduce the crossover problem by keeping the balance of ionic strength between two electrolytes. With that, the effects of concentration of VOSO4, flow rate, and current density on the performances of AORFB single cells using these two additives are evaluated. When the effects are considered, capacity retention is improved and the precipitation and crossover of vanadium ions are suppressed, and these induce a better cycle stability of AORFB. Eventually, the five AORFB single cells are stacked and this AORFB stack shows the excellent maximum power of 9 W at 120 mA·cm−2, while its performance is well preserved for 200 cycles. From this study, we substantiate that the 9 W AORFB stack using organic and vanadium active materials is well achieved by using efficient additives and optimizing the operational factors.
-
performance improvement by novel activation process effect of aqueous organic Redox flow battery using tiron and anthraquinone 2 7 disulfonic acid Redox Couple
Chemical Engineering Journal, 2020Co-Authors: Agnesia Permatasari, Wonmi Lee, Yongchai KwonAbstract:Abstract 4,5- dihydroxybenzene-1,3-disulfonic acid (Tiron) and anthraquinone-2,7-disulfonic acid (AQDS) are proposed as new Redox Couple with sulfuric acid (H2SO4) for aqueous organic Redox flow battery (AORFB). Two-electron Redox reactions of the new Redox Couple induce a fast reaction rate. However, Tiron undergoes transformation by undesirable Michael addition reaction during the first cycle. Additionally, sodium ions contained in Redox Couple lower their solubility in H2SO4. As a result, AORFB capacity loss and AQDS precipitation occur. To alleviate the loss in capacity by the transformation of Tiron, activation process is newly adopted. With the process, Tiron is transformed into reversable and desirable 2,4,5,6-tetrahydroxybenzene-1,3-disulfonic acid before actual operation, and the performance of AORFB operated under the process is similar to that operated without the process although the considerable amount of AQDS is relieved in AORFB operation including activation. In addition, a cation exchange resin, Amberlyst 15, is utilized to transform sodium ions into protons, and a proper increase of H2SO4 concentration provides the appropriate amount of protons for the promotion of Redox reactions. AORFB using optimal process demonstrates the benefit (i) decreasing the volume of AQDS, (ii) increasing the solubility of Tiron and AQDS up to 0.9 M and (iii) preserving the discharge capacity up to 99% after 50 cycles with the maximum possible discharge capacity of 24.4 Ahr L−1.
-
performance evaluation of aqueous organic Redox flow battery using anthraquinone 2 7 disulfonic acid disodium salt and potassium iodide Redox Couple
Chemical Engineering Journal, 2019Co-Authors: Wonmi Lee, Agnesia Permatasari, Byeong Wan Kwon, Yongchai KwonAbstract:Abstract An aqueous organic Redox flow battery (AORFB) using anthraquinone-2,7-disulfonic acid disodium salt (2,7-AQDS) and potassium iodide (KI) as the negative and positive active species is suggested. The active species are dissolved into an aqueous potassium chloride (KCl) solution, while ethylene glycol (EG) and polyvinylpyrrolidone (PVP) are added to improve the solubility of 2,7-AQDS and prevent the side reactions of KI. The aqueous solubility of Redox Couple improved by the utilization of additive plays a role in increasing both capacity and the performance of AORFB, while as kinetic parameters to affect the capacity, electron transfer rate constant (ks) and diffusion coefficient (D) are measured. As a result, when EG is used, the solubility of 2,7-AQDS increases from 0.3 to 0.8 M in KCl solution and PVP acts as a barrier preventing the production of iodine gas that is a product generated by the side reaction of KI. The increase in solubility by the use of EG is because it has two hydroxyl groups and they form hydrogen bonding with the oxygen of sulfonyl or carbonyl group within 2,7-AQDS, while the alkyl group of its backbone that is in non-polar nature interacts with the phenyl group within 2,7-AQDS. In addition, EG increases the Redox activity of KI because this significantly increases the nucleophilic ability of the iodide anion. Regarding the effect of PVP, when PVP is added to the solution containing iodine gas, povidone-iodine complex is formed and this complex impedes the side reaction of KI and maintains iodate that is a reactant for Redox reaction as it is in the system. With that, when the AORFB using the 2,7-AQDS and KI including EG and PVP is run for ten cycle, it shows excellent performances like the discharge capacity of 0.7 AhL−1 and the coulombic and energy efficiencies of 98% and 82%.
-
Mesoporous tungsten oxynitride as electrocatalyst for promoting Redox reactions of vanadium Redox Couple and performance of vanadium Redox flow battery
Applied Surface Science, 2018Co-Authors: Wonmi Lee, Sol Youk, Hun Yong Shin, Jinwoo Lee, Yongjin Chung, Yongchai KwonAbstract:Abstract For enhancing the performance of vanadium Redox flow battery (VRFB), a sluggish reaction rate issue of V 2+ /V 3+ Redox Couple evaluated as the rate determining reaction should be addressed. For doing that, mesoporous tungsten oxide (m-WO 3 ) and oxyniride (m-WON) structures are proposed as the novel catalysts, while m-WON is gained by NH 3 heat treatment of m-WO 3 . Their specific surface area, crystal structure, surface morphology and component analysis are measured using BET, XRD, TEM and XPS, while their catalytic activity for V 2+ /V 3+ Redox reaction is electrochemically examined. As a result, the m-WON shows higher peak current, smaller peak potential difference, higher electron transfer rate constant and lower charge transfer resistance than other catalysts, like the m-WO 3 , WO 3 nanoparticle and mesoporous carbon, proving that it is superior catalyst. Regarding the charge-discharge curve tests, the VRFB single cell employing the m-WON demonstrates high voltage and energy efficiencies, high specific capacity and low capacity loss rate. The excellent results of m-WON are due to the reasons like (i) reduced energy band gap, (ii) reaction familiar surface functional groups and (ii) greater electronegativity.
Anders Hagfeldt - One of the best experts on this subject based on the ideXlab platform.
-
development of an organic Redox Couple and organic dyes for aqueous dye sensitized solar cells
Energy and Environmental Science, 2012Co-Authors: Haining Tian, Licheng Sun, Erik Gabrielsson, Peter W Lohse, Nikolaos Vlachopoulos, Lars Kloo, Anders HagfeldtAbstract:A water-soluble organic Redox Couple (TT−/DTT) and new organic dyes (D45 and D51) have been developed for aqueous dye-sensitized solar cells (DSCs). An optimal efficiency of 3.5% was obtained using the D51 dye and an optimized electrolyte composition. The highest IPCE value obtained was 68% at 460 nm.
-
high performance phosphide carbon counter electrode for both iodide and organic Redox Couples in dye sensitized solar cells
Journal of Materials Chemistry, 2012Co-Authors: Jin Bai, Liang Wang, Yudi Wang, Anjie Wang, Xiao Lin, Yihua Shen, Zeqing Wang, Anders HagfeldtAbstract:In the present study, molybdenum phosphide (MoP), nickel phosphide (Ni5P4), and carbon-supported Ni5P4 (Ni5P4/C) were proposed for use as counter electrode (CE) catalysts in dye-sensitized solar cells (DSCs) for the regeneration of both the conventional I3−/I− Redox Couple and a new organic T2/T− Redox Couple. For the I3−/I− Redox Couple, the DSCs using MoP and Ni5P4 CE yielded a power conversion efficiency (PCE) of 4.92 and 5.71%, and the DSC using Ni5P4/C showed a high PCE of 7.54%, which was close to that of the DSC using Pt CE (7.76%). For the T2/T− Redox Couple, Ni5P4/C performed much better than Pt and the DSC using Ni5P4/C CE showed a PCE of 4.75%, much higher than the photovoltaic performance of the DSC using Pt CE (3.38%).
-
characterization of surface passivation by poly methylsiloxane for dye sensitized solar cells employing the ferrocene Redox Couple
Journal of Physical Chemistry C, 2010Co-Authors: Sandra M Feldt, Ute B Cappel, Erik M J Johansson, Gerrit Boschloo, Anders HagfeldtAbstract:One-electron outer-sphere Redox Couples, such as ferrocene/ferrocenium, are an interesting alternative to the iodide/triiodide Redox Couple that is normally employed in dye-sensitized solar cells (DSCs) because they should reduce the driving force needed to regenerate the dye. Unfortunately, one-electron Redox Couples also show enhanced recombination with photoinjected electrons, and methods to inhibit this recombination are needed for functioning DSCs. In this study, dye-sensitized titanium dioxide surfaces were passivated by a trichloromethylsilane reaction in order to decrease the fast recombination rates when using the ferrocene Redox Couple. The formation and binding of poly(methylsiloxane) on the dye-sensitized TiO2 surface was verified with infrared spectroscopy and photoelectron spectroscopy. Photoelectrochemical characterization of the silanization method showed that the treatment decreased the recombination rate of photoinjected electrons with ferrocenium and thereby improved the efficiency of t...
-
characteristics of the iodide triiodide Redox mediator in dye sensitized solar cells
Accounts of Chemical Research, 2009Co-Authors: Gerrit Boschloo, Anders HagfeldtAbstract:Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions. The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO2 electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a Redox Couple fills the gap between the electrodes. The Redox Couple is a key component of the DSC. The reduced part of the Couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the Redox Couple because it sets the electrochemical potential at the counter electrode. The Redox Couple also affects the electrochemical potential of the TiO2 electrode through the recombin...
Dan Shan - One of the best experts on this subject based on the ideXlab platform.
-
ferrocyanide ferricyanide Redox Couple induced electrochemiluminescence amplification of carbon dots for ultrasensitive sensing of glutathione
Analytical Chemistry, 2015Co-Authors: Serge Cosnier, Xueji Zhang, Dan ShanAbstract:Here we report a novel solid-state ECL sensor for ultrasensitive sensing of glutathione (GSH) based on ferrocyanide-ferricyanide Redox Couple (Fe(CN)63–/4–) induced electrochemiluminescence (ECL) amplification of carbon dots (C-dots). The electropolymerization of C-dots and (11-pyrrolyl-1-yl-undecyl) triethylammonium tetrafluoroborate (A2) enabled immobilization of the hydrophilic C-dots on the surface of glassy carbon electrode (GCE) perfectly, while the excellent conductivity of polypyrrole was exploited to accelerate electron transfer between them. The Fe(CN)63–/4– can expeditiously convert the C-dots and S2O82– to C-dot•– and SO4•–, respectively. High yields of the excited state C-dots (C-dots*) were obtained, and a ∼10-fold ECL amplification was realized. The C-dots* obtained through the recombination of electron-injected and hole-injected processes may be impeded due to the interference of GSH to K2S2O8. Therefore, the constructed sensor for GSH showed a detection limit down to 54.3 nM (S/N = 3) and...
-
ferrocyanide ferricyanide Redox Couple induced electrochemiluminescence amplification of carbon dots for ultrasensitive sensing of glutathione
Analytical Chemistry, 2015Co-Authors: Wenjun Niu, Serge Cosnier, Xueji Zhang, Ronghui Zhu, Dan ShanAbstract:Here we report a novel solid-state ECL sensor for ultrasensitive sensing of glutathione (GSH) based on ferrocyanide-ferricyanide Redox Couple (Fe(CN)6(3-/4-)) induced electrochemiluminescence (ECL) amplification of carbon dots (C-dots). The electropolymerization of C-dots and (11-pyrrolyl-1-yl-undecyl) triethylammonium tetrafluoroborate (A2) enabled immobilization of the hydrophilic C-dots on the surface of glassy carbon electrode (GCE) perfectly, while the excellent conductivity of polypyrrole was exploited to accelerate electron transfer between them. The Fe(CN)6(3-/4-) can expeditiously convert the C-dots and S2O8(2-) to C-dot(•-) and SO4(•-), respectively. High yields of the excited state C-dots (C-dots*) were obtained, and a ∼10-fold ECL amplification was realized. The C-dots* obtained through the recombination of electron-injected and hole-injected processes may be impeded due to the interference of GSH to K2S2O8. Therefore, the constructed sensor for GSH showed a detection limit down to 54.3 nM (S/N = 3) and a wide linear range from 0.1-1.0 μM with a correlation coefficient of 0.997.