Employing cathode materials with multiple redox couples and electrolytes with efficient cation transport kinetics are two effective approaches to improving the electrochemical performance of batteries.In this work,for...Employing cathode materials with multiple redox couples and electrolytes with efficient cation transport kinetics are two effective approaches to improving the electrochemical performance of batteries.In this work,for the first time,we present a design strategy of simultaneously realizing reversible cationic and anionic redox chemistries as well as selective anion/cation transport in the viologen-based COFs(BAVCOF:X,coordinated anions of X=Cl^(-),Br^(-),I^(-),and ClO_(4)^(-))for high-performance Na-ion cathodes.Besides the cationic redox of viologen segments,the different redox activities of anions effectively tune the total capacities of the COFs.Meanwhile,electrochemical analysis and ab-initial molecular dynamics(AIMD)calculation illustrate that the anion/cation transport kinetics of electrolytes caged in the COFs'channels can be selectively tuned by the coordinated anions.As a result,combining high-potential Br-/Br_(2)redox couple,cationic redox of viologen segments,and enhanced Na+transport kinetics,the BAV-COF:Brdemonstrates stable performance with energy densities of 358.7 and 145.2 Wh kg^(-1)at power densities of 116.5 and 2124.1 W kg^(-1),respectively.This study offers new insight into the fabrication of organic cathodes with anionic redox and the advantages of COFs electrode materials in anion/cation transport selectivity for energy storage applications.展开更多
Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide...Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide as flocculant was experimented and evaluated. The results of diaspore and kaolinite single mineral settling tests show that the difference between settlement yield of kaolinite(settling 15 min) and diaspore(settling 3 min) increases from 16% to 60% by adding flocculant at pH=7. Results of selective flocculation experiment of bauxite show that the higher concentrate grade(65.75) and Al-Si ratio(7.34) could be obtained with sodium carbonate as dispersant compared with sodium hexametaphosphate; under the action of flocculating agent, the concentrate grade and Al-Si ratio increase to 67.99 and 9.01. These results could meet the requirements of Bayer production, and the simpler process was expected to cost far less than traditional flotation method and a promising de-silication method of bauxite.展开更多
Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the ad...Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force（LDF） approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.展开更多
Atomically thin two-dimensional membranes are promising for osmotic energy generation.However,the trade-off between permeability and selectivity remains a long-standing bottleneck.Herein,we demonstrate that a cationic...Atomically thin two-dimensional membranes are promising for osmotic energy generation.However,the trade-off between permeability and selectivity remains a long-standing bottleneck.Herein,we demonstrate that a cationic AB-stacking covalent-organic framework(COF)bilayer achieves high ion conductivity and selectivity.Through precise molecular design and the Langmuir-Blodgett(LB)technique,we fabricate an anion-selective COF bilayer(EB-COF)using tetradentate 4,40,400,4000-(porphyrin-5,10,15,20-tetrayl)tetrabenzaldehyde(TFPP)and bidentate ethidium bromide(EB)with a covalently tethered pyridinium moiety.The EB-COF bilayer shows a record-high output power density of 7,174 W m^(-2)(0.5/0.01 M NaCl),significantly outperforming the AA-stacking PDA-COF bilayer constructed with TFPP and neutral p-phenylenediamine(PDA).This exceptional performance stems from highly ordered sub-2-nm nanopores,exceptional pore utilization efficiency,and a large surface charge density of 4.4 mCm^(-2),which together synergistically enhance anion selectivity and ion permeability.This work not only provides fundamental insights into the structure-performance relationship of permselective membranes but also offers a promising strategy for high-efficiency osmotic energy harvesting.展开更多
基金supported by the NSFC/RGC Joint Research Scheme 2020/21(Project No:N_City U104/20)。
文摘Employing cathode materials with multiple redox couples and electrolytes with efficient cation transport kinetics are two effective approaches to improving the electrochemical performance of batteries.In this work,for the first time,we present a design strategy of simultaneously realizing reversible cationic and anionic redox chemistries as well as selective anion/cation transport in the viologen-based COFs(BAVCOF:X,coordinated anions of X=Cl^(-),Br^(-),I^(-),and ClO_(4)^(-))for high-performance Na-ion cathodes.Besides the cationic redox of viologen segments,the different redox activities of anions effectively tune the total capacities of the COFs.Meanwhile,electrochemical analysis and ab-initial molecular dynamics(AIMD)calculation illustrate that the anion/cation transport kinetics of electrolytes caged in the COFs'channels can be selectively tuned by the coordinated anions.As a result,combining high-potential Br-/Br_(2)redox couple,cationic redox of viologen segments,and enhanced Na+transport kinetics,the BAV-COF:Brdemonstrates stable performance with energy densities of 358.7 and 145.2 Wh kg^(-1)at power densities of 116.5 and 2124.1 W kg^(-1),respectively.This study offers new insight into the fabrication of organic cathodes with anionic redox and the advantages of COFs electrode materials in anion/cation transport selectivity for energy storage applications.
基金Project(2005CB623701)supported by the National Key Basic Research Program(973)of China
文摘Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide as flocculant was experimented and evaluated. The results of diaspore and kaolinite single mineral settling tests show that the difference between settlement yield of kaolinite(settling 15 min) and diaspore(settling 3 min) increases from 16% to 60% by adding flocculant at pH=7. Results of selective flocculation experiment of bauxite show that the higher concentrate grade(65.75) and Al-Si ratio(7.34) could be obtained with sodium carbonate as dispersant compared with sodium hexametaphosphate; under the action of flocculating agent, the concentrate grade and Al-Si ratio increase to 67.99 and 9.01. These results could meet the requirements of Bayer production, and the simpler process was expected to cost far less than traditional flotation method and a promising de-silication method of bauxite.
基金the funding of the present study by the German Federation of Industrial Research Associations(AiF)(FKZ VP 2470101RH9)
文摘Perfluorooctane sulfonate（PFOS） has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force（LDF） approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.
基金support from the National Natural Science Foundation of China(grant nos.22125406 and 22074149 for P.Y.,22134002 for L.M.,and 22174146 for Y.J.)the Natural Science Foundation of Beijing(2242028 for W.M.and Z230022 for P.Y.)the National Basic Research Program of China(2022YFA1204500 and 2022YFA1204503)。
文摘Atomically thin two-dimensional membranes are promising for osmotic energy generation.However,the trade-off between permeability and selectivity remains a long-standing bottleneck.Herein,we demonstrate that a cationic AB-stacking covalent-organic framework(COF)bilayer achieves high ion conductivity and selectivity.Through precise molecular design and the Langmuir-Blodgett(LB)technique,we fabricate an anion-selective COF bilayer(EB-COF)using tetradentate 4,40,400,4000-(porphyrin-5,10,15,20-tetrayl)tetrabenzaldehyde(TFPP)and bidentate ethidium bromide(EB)with a covalently tethered pyridinium moiety.The EB-COF bilayer shows a record-high output power density of 7,174 W m^(-2)(0.5/0.01 M NaCl),significantly outperforming the AA-stacking PDA-COF bilayer constructed with TFPP and neutral p-phenylenediamine(PDA).This exceptional performance stems from highly ordered sub-2-nm nanopores,exceptional pore utilization efficiency,and a large surface charge density of 4.4 mCm^(-2),which together synergistically enhance anion selectivity and ion permeability.This work not only provides fundamental insights into the structure-performance relationship of permselective membranes but also offers a promising strategy for high-efficiency osmotic energy harvesting.
