The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ an...The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.展开更多
Graphene-based laminar materials open up to new applications for molecular and ionic separations in aqueous environments due to the atomic thickness, mechanical strength, chemical stability and other fantastic propert...Graphene-based laminar materials open up to new applications for molecular and ionic separations in aqueous environments due to the atomic thickness, mechanical strength, chemical stability and other fantastic properties.Recent advances on controlling the structure and chemical functionality of graphene-based membranes can potentially lead to new classes of tools for desalination, dehydration, toxicant rejection, specific ionic separation and so on. The recent developments of graphene-based membranes prepared by using a concept to form interlayer space between graphene sheets and creating nanoscale or sub-nanoscale pores in a graphene lattice, together with their mass-transfer mechanisms and potential applications in aqueous environments are reviewed. A summary and outlook is further provided on the opportunities and challenges in this arising field.This article is expected to address the intricate details of mass transport through two distinct graphene-based membranes in aqueous environment and to optimize the fabrication of graphene-based membranes as a fascinating separation system for a wide range of applications.展开更多
The ion selectivity of electrodeposited nickel hexacyanoferrate （NiHCF） thin films was investigated using electrochemical impedance spectroscopy （EIS） and cyclic voltammetry （CV）. NiHCF thin films were prepared ...The ion selectivity of electrodeposited nickel hexacyanoferrate （NiHCF） thin films was investigated using electrochemical impedance spectroscopy （EIS） and cyclic voltammetry （CV）. NiHCF thin films were prepared by cathodic deposition on Pt and Al substrates. EIS and CV curves were determined in 1 mol/L （KNO3＋C5NO3） and 1 mol/L （NaNO3＋CsNO3） mixture solutions, which were sensitive to the concentration of Cs^＋ in the electrolytes. Experimental results show that all Nyquist impedance plots show depressed semicircles in the high-frequency range changing over into straight lines at lower frequencies. With increasing amounts of Cs^＋, the redox potentials in CV curves shift toward more positive values and the redox peaks broaden; the semicircle radius in corresponding EIS curves and the charge transfer resistance also increase. EIS combining CV is able to provide valuable insights into the ion selectivity of NiHCF thin films. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
Quaternary ammonium densely functionalized octa-benzylmethyl-containing poly(arylene ether ketone)s(QA-OMPAEKs) with ion exchange capacities(IECs) ranging from 1.23 to 2.21 mmol g^(-1) were synthesized from:(1) Ullman...Quaternary ammonium densely functionalized octa-benzylmethyl-containing poly(arylene ether ketone)s(QA-OMPAEKs) with ion exchange capacities(IECs) ranging from 1.23 to 2.21 mmol g^(-1) were synthesized from:(1) Ullmann coupling extension of tetra-benzylmethyl-containing bisphenol A;(2) condensation polymerization with activated dihalide in the presence of K_2CO_3;(3) selective bromination using N-bromosuccinimide; and(4) quantitative quaternization using trimethylamine. Both smallangle X-ray scattering(SAXS) and transmission electron microscope(TEM) characterizations revealed distinct nano-phase separation in QA-OMPAEKs as a result of the dense quaternization. The QA-OMPAEK-20 with an IEC of 1.98 mmol g^(-1) exhibited a high SO_4^(2-) conductivity of 11.4 mS cm^(-1) and a low VO^(2+) permeability of 0.06×10^(-12) m^2 s^(-1) at room temperature,leading to a dramatically higher ion selectivity than Nafion N212. Consequently, the vanadium redox flow battery(VRFB)assembled with QA-OMPAEK-20 achieved a Coulombic efficiency of 96.9% and an energy efficiency of 84.8% at a current density of 50 mA cm^(-2), which were much higher than those of the batteries assembled with Nafion N212 and a home-made control membrane without distinct nano-phase separation. Therefore, ion segregation is demonstrated to be a strategical route for the design of high performance anion exchange membranes(AEMs) for VRFBs.展开更多
基金Project (20006011) supported by the National Natural Science Foundation of China Project (20021017) by the Natural Science Foundation of Shanxi Province Project (2004-24) by the Scholarship Council Foundation of Shanxi Province
文摘The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.
基金Supported by the National Natural Science Foundation of China(21490582,21506127)
文摘Graphene-based laminar materials open up to new applications for molecular and ionic separations in aqueous environments due to the atomic thickness, mechanical strength, chemical stability and other fantastic properties.Recent advances on controlling the structure and chemical functionality of graphene-based membranes can potentially lead to new classes of tools for desalination, dehydration, toxicant rejection, specific ionic separation and so on. The recent developments of graphene-based membranes prepared by using a concept to form interlayer space between graphene sheets and creating nanoscale or sub-nanoscale pores in a graphene lattice, together with their mass-transfer mechanisms and potential applications in aqueous environments are reviewed. A summary and outlook is further provided on the opportunities and challenges in this arising field.This article is expected to address the intricate details of mass transport through two distinct graphene-based membranes in aqueous environment and to optimize the fabrication of graphene-based membranes as a fascinating separation system for a wide range of applications.
基金the National Natural Science Foundation of China(No.20676089)the Scholar Council Foundation of Shanxi Province,China(No.2004-24).
文摘The ion selectivity of electrodeposited nickel hexacyanoferrate （NiHCF） thin films was investigated using electrochemical impedance spectroscopy （EIS） and cyclic voltammetry （CV）. NiHCF thin films were prepared by cathodic deposition on Pt and Al substrates. EIS and CV curves were determined in 1 mol/L （KNO3＋C5NO3） and 1 mol/L （NaNO3＋CsNO3） mixture solutions, which were sensitive to the concentration of Cs^＋ in the electrolytes. Experimental results show that all Nyquist impedance plots show depressed semicircles in the high-frequency range changing over into straight lines at lower frequencies. With increasing amounts of Cs^＋, the redox potentials in CV curves shift toward more positive values and the redox peaks broaden; the semicircle radius in corresponding EIS curves and the charge transfer resistance also increase. EIS combining CV is able to provide valuable insights into the ion selectivity of NiHCF thin films. 2008 University of Science and Technology Beijing. All rights reserved.
基金supported by the National Natural Science Foundation of China (51503038, 51873037)
文摘Quaternary ammonium densely functionalized octa-benzylmethyl-containing poly(arylene ether ketone)s(QA-OMPAEKs) with ion exchange capacities(IECs) ranging from 1.23 to 2.21 mmol g^(-1) were synthesized from:(1) Ullmann coupling extension of tetra-benzylmethyl-containing bisphenol A;(2) condensation polymerization with activated dihalide in the presence of K_2CO_3;(3) selective bromination using N-bromosuccinimide; and(4) quantitative quaternization using trimethylamine. Both smallangle X-ray scattering(SAXS) and transmission electron microscope(TEM) characterizations revealed distinct nano-phase separation in QA-OMPAEKs as a result of the dense quaternization. The QA-OMPAEK-20 with an IEC of 1.98 mmol g^(-1) exhibited a high SO_4^(2-) conductivity of 11.4 mS cm^(-1) and a low VO^(2+) permeability of 0.06×10^(-12) m^2 s^(-1) at room temperature,leading to a dramatically higher ion selectivity than Nafion N212. Consequently, the vanadium redox flow battery(VRFB)assembled with QA-OMPAEK-20 achieved a Coulombic efficiency of 96.9% and an energy efficiency of 84.8% at a current density of 50 mA cm^(-2), which were much higher than those of the batteries assembled with Nafion N212 and a home-made control membrane without distinct nano-phase separation. Therefore, ion segregation is demonstrated to be a strategical route for the design of high performance anion exchange membranes(AEMs) for VRFBs.
