Oxygen(O_(2))is an abundant material with its highly positive redox potential,making it a cost-effective choice for the cathodic active material of aqueous flow batteries(AFBs).However,utilizing O_(2)as an active mate...Oxygen(O_(2))is an abundant material with its highly positive redox potential,making it a cost-effective choice for the cathodic active material of aqueous flow batteries(AFBs).However,utilizing O_(2)as an active material may induce a high overpotential issue for oxygen reduction reaction(ORR).To address this problem,this study proposes a new AFB system employing iron-2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol complex(Fe(BIS-TRIS))and O_(2)as redox couple and cobalt(triisopropanolamine)complex(Co(TiPA))as the redox mediator.Co(TiPA)can mitigate ORR overpotential through a mediated electron transfer(MET)mechanism.More specifically,during the charging step,in the catholyte,Co(II)(TiPA)s are oxidized to Co(III)(TiPA)s at the cathode,while HO_(2)-s are oxidized in the electrolyte tank,producing O_(2).During the discharging step,Co(III)(TiPA)s are reduced to Co(II)(TiPA)s.The resulting Co(II)(TiPA)then chemically reacts with O_(2)in the electrolyte tank,regenerating Co(III)(TiPA).Namely,this cycle ensures that Co(III)(TiPA)is electrochemically reduced to Co(II)(TiPA)at the cathode,while the reduced Co(II)(TiPA)is chemically re-oxidized in the electrolyte tank,effectively mediating electron transfer between electrode and oxygen.This process facilitates ORR without direct electrochemical reaction at the cathode,thereby alleviating its overpotential.UV-Vis spectroscopic analysis verifies that Co(TiPA)spontaneously reacts with O₂and mediates ORR.Fe(BIS-TRIS)-O_(2)AFB maintains 79.1%of its initial capacity over 170 h,demonstrating the feasibility of Co(TiPA)as the redox mediator.However,its structural degradation under oxygen evolution reaction is observed,limiting the long-term stability of Fe(BIS-TRIS)-O_(2)AFB.Thus,its structural modifications or development of alternative redox mediators are required.展开更多
A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bib...A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bibenzimidazole](OPBI)sandwiched between two 20μm thick porous OPBI membranes(p-OPBI)without further lamination steps.The trilayer membrane demonstrates exceptional properties,such as high conductivity and low area-specific resistance(ASR)of 51 mS cm^(−1) and 81mΩ cm^(2),respectively.Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158mΩ cm^(2),while that of Nafion is 193mΩ cm^(2).VO^(2+) permeability is 2.73×10^(-9) cm^(2) min^(−1),about 150 times lower than that of Nafion NR212.In addition,the membrane has high mechanical strength and high chemical stability against VO^(2+).In VRFB,the combination of low resistance and low vanadium permeability results in excellent performance,revealing high Coulombic efficiency(>99%),high energy efficiency(EE;90.8% at current density of 80mA cm^(−2)),and long-term durability.The EE is one of the best reported to date.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.2023R1A2C2002444).
文摘Oxygen(O_(2))is an abundant material with its highly positive redox potential,making it a cost-effective choice for the cathodic active material of aqueous flow batteries(AFBs).However,utilizing O_(2)as an active material may induce a high overpotential issue for oxygen reduction reaction(ORR).To address this problem,this study proposes a new AFB system employing iron-2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol complex(Fe(BIS-TRIS))and O_(2)as redox couple and cobalt(triisopropanolamine)complex(Co(TiPA))as the redox mediator.Co(TiPA)can mitigate ORR overpotential through a mediated electron transfer(MET)mechanism.More specifically,during the charging step,in the catholyte,Co(II)(TiPA)s are oxidized to Co(III)(TiPA)s at the cathode,while HO_(2)-s are oxidized in the electrolyte tank,producing O_(2).During the discharging step,Co(III)(TiPA)s are reduced to Co(II)(TiPA)s.The resulting Co(II)(TiPA)then chemically reacts with O_(2)in the electrolyte tank,regenerating Co(III)(TiPA).Namely,this cycle ensures that Co(III)(TiPA)is electrochemically reduced to Co(II)(TiPA)at the cathode,while the reduced Co(II)(TiPA)is chemically re-oxidized in the electrolyte tank,effectively mediating electron transfer between electrode and oxygen.This process facilitates ORR without direct electrochemical reaction at the cathode,thereby alleviating its overpotential.UV-Vis spectroscopic analysis verifies that Co(TiPA)spontaneously reacts with O₂and mediates ORR.Fe(BIS-TRIS)-O_(2)AFB maintains 79.1%of its initial capacity over 170 h,demonstrating the feasibility of Co(TiPA)as the redox mediator.However,its structural degradation under oxygen evolution reaction is observed,limiting the long-term stability of Fe(BIS-TRIS)-O_(2)AFB.Thus,its structural modifications or development of alternative redox mediators are required.
基金supported by KIST (2E31871 and 2E32591)and Innovation Fund Denmark Denmark (DANFLOW—project#9090-00059)Korea Institute for Advancement of Technology (KIAT)through the International Cooperative R&D program (Project No.P0018437)Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education (2021R1A6A1A03039981).
文摘A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bibenzimidazole](OPBI)sandwiched between two 20μm thick porous OPBI membranes(p-OPBI)without further lamination steps.The trilayer membrane demonstrates exceptional properties,such as high conductivity and low area-specific resistance(ASR)of 51 mS cm^(−1) and 81mΩ cm^(2),respectively.Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158mΩ cm^(2),while that of Nafion is 193mΩ cm^(2).VO^(2+) permeability is 2.73×10^(-9) cm^(2) min^(−1),about 150 times lower than that of Nafion NR212.In addition,the membrane has high mechanical strength and high chemical stability against VO^(2+).In VRFB,the combination of low resistance and low vanadium permeability results in excellent performance,revealing high Coulombic efficiency(>99%),high energy efficiency(EE;90.8% at current density of 80mA cm^(−2)),and long-term durability.The EE is one of the best reported to date.
