Based on the difference in tendency to polymerize between tungsten and molybdenum, a new method using D309 resin was propounded. The batch tests indicate that the optimum pH value and contact time for the separation a...Based on the difference in tendency to polymerize between tungsten and molybdenum, a new method using D309 resin was propounded. The batch tests indicate that the optimum pH value and contact time for the separation are 7.0 and 4 h respectively, the maxium separation factor of W and Mo is 9.29. And the experimental resules show that isothermal absorbing tungsten and molybdenum belongs to Langmuir model and Freundlich model respectively, and the absorbing kinetics for tungsten is controlled by intra-particle diffusion. With a solution containing 70 g/L WO3 and 28.97 g/L Mo, the effluent with a mass ratio of Mo to WO3 of 76 and the eluate with a mass ratio of WO3 to Mo of 53.33 are obtained after column test.展开更多
The flotation and adsorption behaviors of dodecyltrimethylammonium chloride(DTAC) and cetyltrimethylammonium chloride(CTAC) on diaspore and kaolinite were studied.Solution depletion methods were used to determine ...The flotation and adsorption behaviors of dodecyltrimethylammonium chloride(DTAC) and cetyltrimethylammonium chloride(CTAC) on diaspore and kaolinite were studied.Solution depletion methods were used to determine adsorption isotherms.Fluorescence probe test along with Zeta potential measurement was also conducted for further investigation into the adsorption of quaternary amines at the mineral-water interface.The results show that the flotation recovery of kaolinite decreases with an increase in pH when DTAC and CTAC are used as collectors,while diaspore is on the contrary.As the carbon chain length of the collectors increases,the flotation recoveries of minerals increase.However,the increment rate of kaolinite is significantly lower than that of diaspore.In the low surfactant concentration range,the cationic surfactants adsorb readily on diaspore surfaces just due to electrostatic interactions.As for kaolinite surfaces,ion exchange process also exists.With a further increase in surfactant concentration,the adsorption was ascribed to the hydrophobic association of chain-chain interactions.Micro-polarity of mineral surfaces study shows that CTAC has a better hydrophobic characteristic than DTAC.Larger aggregates are formed with CTAC on diaspore than on kaolinite in the same solution concentration.The results also indicate that the chain length of cationic surfactants has a greater influence on the adsorption of diaspore than on kaolinite,which is consistent with the flotation result.展开更多
Promising high strangeness dibaryons are studied by the extended quark delocalization and color screeningmodel. It is shown that besides H particle and di-Ω, there might be other dibaryon candidates worth to be searc...Promising high strangeness dibaryons are studied by the extended quark delocalization and color screeningmodel. It is shown that besides H particle and di-Ω, there might be other dibaryon candidates worth to be searchedexperimentally such as NΩ.展开更多
This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle i...This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle in the gas channel and implementing novelly arranged obstacles to improve the PEMFC performance. The effects of velocity distribution,interface reactant concentration and pressure drop on performance are studied. The results show that adding obstacles in the gas channel will produce vertical velocity and can improve output performance,especially in the case of high current density and higher baffle radius. The superiority of the optimized structure in mass transfer capacity is proved,and a mechanism explanation is given for the improvement of performance.展开更多
An anion-exchange-based chromatographic separation approach was developed to selectively recover zinc and copper from the high-chlorine raffinate generated in the process of germanium chlorination distillation using 7...An anion-exchange-based chromatographic separation approach was developed to selectively recover zinc and copper from the high-chlorine raffinate generated in the process of germanium chlorination distillation using 717 resins based on the coordination difference between Zn^(2+)/Cu^(2+)and Cl^(-).The theoretical calculation and spectroscopic analyses suggested that the coordination between Zn^(2+)and Cl^(-)is much stronger than that between Cu^(2+)and Cl^(-),and the Cl-concentration significantly affects Zn(Ⅱ)and Cu(Ⅱ)species.The factors involving Cl-concentration,resin dosage,shaking speed,and temperature were investigated to determine the optimal condition,and the maximum separation factor of Zn/Cu reached as high as 479.2.The results of the adsorption isotherms,adsorption kinetics,SEM,FTIR,and XPS analyses indicated that the process followed the monolayer uniform chemisorption.Through the continuous adsorption experiments,Zn(Ⅱ)and Cu(Ⅱ)in the high-chlorine raffinate were separately recovered,allowing the reuse of residual waste acid and germanium.展开更多
Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a ...Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.展开更多
The effect of background anion on cation exchange reactions, suchas Na-Ca and Na-Cu exchange reac- tions, on montmorillonites has beenstudied, but the results are not always clear and discrepancies existin the literat...The effect of background anion on cation exchange reactions, suchas Na-Ca and Na-Cu exchange reac- tions, on montmorillonites has beenstudied, but the results are not always clear and discrepancies existin the literature. In this study, the exchange of zinc (Zn^2+) forsodium (Na^+) on Wyoming montmorillonite was investigated at 298 deg.K using Cl^-, ClO_4^-, NO_3^-, Oac^-, and SO_4~2- solution media at aconstant total metal charge concentration of 0.02000 mol_c L^-1.Results indicated that the clay CEC values were essential similar forCl^-, ClO_4^-, NO_3^- and SO_4~2- solution media with an average CECof 0.856±0.008 mol_c kg^-1; in an OAc^- solution the clay CEC wasmuch higher than that in other anion media.展开更多
In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U(1) gauge theories. This assumption is that the noneommutative effects start to be visible continuously...In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U(1) gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U(1) gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories.展开更多
The mechanism of cesium exchange on potassium thanium hexacyanoferrate(KTiFC) is described in this paper The dependence of the exchange rate ontemperature, particle granule size, and shaking frequency is studied The r...The mechanism of cesium exchange on potassium thanium hexacyanoferrate(KTiFC) is described in this paper The dependence of the exchange rate ontemperature, particle granule size, and shaking frequency is studied The results showthat ion exchange process is consulled by liquid film diffusion in granule particle. Anexchange reaction occurs mainly betWeen K+ in. the exchanger and Cs+ in the solution.展开更多
A simple and economical chemical process for obtaining high purity neodymium oxide is discussed. The raw material in the form of RE (rare earth) carbonates is produced industrially in Brazil from monazite. Using thi...A simple and economical chemical process for obtaining high purity neodymium oxide is discussed. The raw material in the form of RE (rare earth) carbonates is produced industrially in Brazil from monazite. Using this concentrate as the feed material, ion exchange with a strong cationic resin, commonly used for water treatment, and without the use of retention ions was used for the fractionating of the REE (rare earth elements). The eluent was ammonium salt of EDTA (ethylenediaminetetraacetic acid) at pH 4.0. The complex of EDTA-neodymium was transformed into neodymium oxides via oxalate precipitation. We produced 99.9% pure Nd203 in yields greater than or equal to 80%. Molecular absorption spectrophotometry was used to monitor the neodymium content during the process and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the neodymium oxides. The typical neodymium oxides obtained contained the followings contaminants in micrograms per gram: Sc (4.09); Y (0.39); La (0.78); Ce (5.62); Pr (4.56); Sm (11.10); Eu (1.10); Gd (14.30); Tb (29.3); Dy (4.15); Ho (8.39); Er (13.80); Tm (0.23); Yb (2.29); Lu (0.39). High purity neodymium oxides obtained from this procedure replaced the imported product used in research and development work on rare earth at IPEN/CNEN-SP (Instituto de Pesquisas Energeticas e Nucleares/Comissfio Nacional de Eneergia Nuclear-Sao Paulo).展开更多
Some boundedness results are established in the setting of homogeneous Morrey-Herz spaces for a class of higher order commutators T^mb,l and M^mb,l generated by fractional integral operators Tl and maximal fractional ...Some boundedness results are established in the setting of homogeneous Morrey-Herz spaces for a class of higher order commutators T^mb,l and M^mb,l generated by fractional integral operators Tl and maximal fractional operators Ml with function b(x) in BMO(R^n), respectively.展开更多
High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adeq...High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adequate mechanical properties,and competitive costs.Various molecular moieties,such as benzimidazole,benzothiazole,imide,and ether ether ketone,have been introduced to polymer chain backbones to satisfy the application requirements for HT-PEMs.The most common sulfonated polymers based on the main chain backbones have been employed to improve the rties.Side group/chain engineering,including the introduction of SO_(3)^(-) on the side chain,grafting,branching,and crosslinking,has been widely applied to HTPEMs to further improve their proton conductivity,thermal stability,and mechanical properties.Currently,phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in HT-PEMs.The compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical properties.In this review,the current progress of various membrane materials used for HT-PEMs is summarized.The synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed systemically.Various modification approaches and their deficiencies associated with HT-PEMs are analyzed and clarified.Prospects and future challenges are also presented.展开更多
In order to effectively improve the properties of anion exchange membrane(AEM)materials,a series of novel poly(aryl ether nitrile)s with flexible side-chain-type quaternary phosphonium cations(PAEN-TPP-x)were designed...In order to effectively improve the properties of anion exchange membrane(AEM)materials,a series of novel poly(aryl ether nitrile)s with flexible side-chain-type quaternary phosphonium cations(PAEN-TPP-x)were designed and prepared on the basis of considering the influences of polymer backbone,cationic group species and the connection way between the cations and polymer chains.The synthetic method,structure and ion-exchange capacity,water absorption,swelling,hydroxide conductivity and alkaline stability of the obtained AEMs were studied.A comparative study with other reported AEMs was also performed for further exploration of the relationship between the structure and properties.These AEMs with flexible side-chain-type quaternary phosphonium cations displayed good comprehensive properties.Their water uptakes and swelling ratios were in the range of 11.6%–22.7%and 4.4%–7.8%at 60℃,respectively.They had hydroxide conductivity in the range of 28.6–45.8 mS cm^-1 at 60℃.Moreover,these AEMs also exhibited improved alkaline stability,and the hydroxide conductivity for PAEN-TPP-0.35 could remain 82.1%and 80.6%of its initial value at 60 and 90℃in 2 mol L^-1 NaOH solution for480 h,respectively.展开更多
Platinum-based material is the most efficient and durable electrocatalyst for motivating the hydrogen evolution reaction(HER)in an acidic electrolyte;however,its low abundance and high cost limit its further applicati...Platinum-based material is the most efficient and durable electrocatalyst for motivating the hydrogen evolution reaction(HER)in an acidic electrolyte;however,its low abundance and high cost limit its further application in proton-exchange membrane water electrolysis(PEMWE)technology.Therefore,minimizing the Pt amount while retaining high activity would be desirable.Herein,we use defect-rich W_(18)O_(49)nanowires to anchor well-dispersed,ultrafine Pt species(Pt-W_(18)O_(49))via a freeze-drying method to avoid aggregation,further mediating an efficient and durable HER in acidic water.Density functional theory analyses also demonstrate that the strong electronic interaction between the Pt species and W_(18)O_(49)support greatly improves the HER performance.With a 1/10 Pt loading amount of the commercial 20 wt%Pt/C,the Pt-W_(18)O_(49)catalyst requires the overpotentials of 116 and 743 mV to achieve high current densities of 100 and 1000 mA cm^(−2)in 0.5 mol L^(−1)H_(2)SO_(4),outperforming those of the 20 wt%Pt/C benchmark.More importantly,the Pt-W_(18)O_(49)catalyst can sustain a high-currentdensity HER at 500 mA cm^(−2)for more than 38 h without obvious degradation.This work paves a new avenue for synergistically reducing the Pt amount and retaining high activity for real-world PEMWE.展开更多
The mobility and bioavailability of heavy metals in soils is largely governed by sorption and desorption phenomena.Cu2+ and Pb2+ are among the most potentially toxic heavy metals and they are present,often concomitant...The mobility and bioavailability of heavy metals in soils is largely governed by sorption and desorption phenomena.Cu2+ and Pb2+ are among the most potentially toxic heavy metals and they are present,often concomitantly,in many polluting spills and in agrochemicals.The objective was to assess and compare the competitive sorption and desorption capacities and sorption hysteresis of Cu2+ and Pb2+,as well as their migration through the profiles of four natural soils:a Humic Umbrisol,an Umbric Cambisol,an Endoleptic Luvisol and a Humic Cambisol.In all horizons Pb2+ was invariably sorbed and retained to a greater extent than Cu2+.The sorption and retention of Cu2+ were most in?uenced by pH,e?ective cation exchange capacity(CECe) and Mn oxide content.On the other hand,the fixation capacity of Pb2+ was most in?uenced by pH,CECe,and Mn oxide and organic matter contents.pH and CECe were the individual soil properties most markedly in?uencing Cu2+ and Pb2+ sorption and retention.In all the horizons Pb2+ exhibited greater hysteresis than Cu2+.In each soil the hysteresis in the A horizon was greater than that in the B horizon,except in the Bt horizon of the Endoleptic Luvisol,due to its high pH and vermiculite content.Based on migration indices,Pb2+ was less mobile than Cu2+ in the studied soils.展开更多
基金Project(51174232)supported by the National Natural Science Foundation of China
文摘Based on the difference in tendency to polymerize between tungsten and molybdenum, a new method using D309 resin was propounded. The batch tests indicate that the optimum pH value and contact time for the separation are 7.0 and 4 h respectively, the maxium separation factor of W and Mo is 9.29. And the experimental resules show that isothermal absorbing tungsten and molybdenum belongs to Langmuir model and Freundlich model respectively, and the absorbing kinetics for tungsten is controlled by intra-particle diffusion. With a solution containing 70 g/L WO3 and 28.97 g/L Mo, the effluent with a mass ratio of Mo to WO3 of 76 and the eluate with a mass ratio of WO3 to Mo of 53.33 are obtained after column test.
基金Projects (50974134,50804055) supported by the National Natural Science Foundation of ChinaProject (2005CB623701) supported by the National Basic Research Program of China
文摘The flotation and adsorption behaviors of dodecyltrimethylammonium chloride(DTAC) and cetyltrimethylammonium chloride(CTAC) on diaspore and kaolinite were studied.Solution depletion methods were used to determine adsorption isotherms.Fluorescence probe test along with Zeta potential measurement was also conducted for further investigation into the adsorption of quaternary amines at the mineral-water interface.The results show that the flotation recovery of kaolinite decreases with an increase in pH when DTAC and CTAC are used as collectors,while diaspore is on the contrary.As the carbon chain length of the collectors increases,the flotation recoveries of minerals increase.However,the increment rate of kaolinite is significantly lower than that of diaspore.In the low surfactant concentration range,the cationic surfactants adsorb readily on diaspore surfaces just due to electrostatic interactions.As for kaolinite surfaces,ion exchange process also exists.With a further increase in surfactant concentration,the adsorption was ascribed to the hydrophobic association of chain-chain interactions.Micro-polarity of mineral surfaces study shows that CTAC has a better hydrophobic characteristic than DTAC.Larger aggregates are formed with CTAC on diaspore than on kaolinite in the same solution concentration.The results also indicate that the chain length of cationic surfactants has a greater influence on the adsorption of diaspore than on kaolinite,which is consistent with the flotation result.
基金The project supported by National Natural Science Foundation of China under Grant No.90103018
文摘Promising high strangeness dibaryons are studied by the extended quark delocalization and color screeningmodel. It is shown that besides H particle and di-Ω, there might be other dibaryon candidates worth to be searchedexperimentally such as NΩ.
基金supported by the De-fense Industrial Technology Development Program (No. JCKY2018605B006)the Aviation Science Fund (No. 201928052002)
文摘This study combines the three-dimensional model of the high-temperature proton exchange membrane fuel cell(HT-PEMFC)with theoretical analysis,by optimizing the structure of the fuel cell,adding a semicircular baffle in the gas channel and implementing novelly arranged obstacles to improve the PEMFC performance. The effects of velocity distribution,interface reactant concentration and pressure drop on performance are studied. The results show that adding obstacles in the gas channel will produce vertical velocity and can improve output performance,especially in the case of high current density and higher baffle radius. The superiority of the optimized structure in mass transfer capacity is proved,and a mechanism explanation is given for the improvement of performance.
基金financially supported by the Postdoctoral Research Foundation of Central South University,China(No.140050037)。
文摘An anion-exchange-based chromatographic separation approach was developed to selectively recover zinc and copper from the high-chlorine raffinate generated in the process of germanium chlorination distillation using 717 resins based on the coordination difference between Zn^(2+)/Cu^(2+)and Cl^(-).The theoretical calculation and spectroscopic analyses suggested that the coordination between Zn^(2+)and Cl^(-)is much stronger than that between Cu^(2+)and Cl^(-),and the Cl-concentration significantly affects Zn(Ⅱ)and Cu(Ⅱ)species.The factors involving Cl-concentration,resin dosage,shaking speed,and temperature were investigated to determine the optimal condition,and the maximum separation factor of Zn/Cu reached as high as 479.2.The results of the adsorption isotherms,adsorption kinetics,SEM,FTIR,and XPS analyses indicated that the process followed the monolayer uniform chemisorption.Through the continuous adsorption experiments,Zn(Ⅱ)and Cu(Ⅱ)in the high-chlorine raffinate were separately recovered,allowing the reuse of residual waste acid and germanium.
基金supported through the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical, Biological, and Geosciences Division under DE-SC0010379the support from an ECS Toyota Young Investigator Fellowship
文摘Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.
文摘The effect of background anion on cation exchange reactions, suchas Na-Ca and Na-Cu exchange reac- tions, on montmorillonites has beenstudied, but the results are not always clear and discrepancies existin the literature. In this study, the exchange of zinc (Zn^2+) forsodium (Na^+) on Wyoming montmorillonite was investigated at 298 deg.K using Cl^-, ClO_4^-, NO_3^-, Oac^-, and SO_4~2- solution media at aconstant total metal charge concentration of 0.02000 mol_c L^-1.Results indicated that the clay CEC values were essential similar forCl^-, ClO_4^-, NO_3^- and SO_4~2- solution media with an average CECof 0.856±0.008 mol_c kg^-1; in an OAc^- solution the clay CEC wasmuch higher than that in other anion media.
文摘In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U(1) gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U(1) gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories.
文摘The mechanism of cesium exchange on potassium thanium hexacyanoferrate(KTiFC) is described in this paper The dependence of the exchange rate ontemperature, particle granule size, and shaking frequency is studied The results showthat ion exchange process is consulled by liquid film diffusion in granule particle. Anexchange reaction occurs mainly betWeen K+ in. the exchanger and Cs+ in the solution.
文摘A simple and economical chemical process for obtaining high purity neodymium oxide is discussed. The raw material in the form of RE (rare earth) carbonates is produced industrially in Brazil from monazite. Using this concentrate as the feed material, ion exchange with a strong cationic resin, commonly used for water treatment, and without the use of retention ions was used for the fractionating of the REE (rare earth elements). The eluent was ammonium salt of EDTA (ethylenediaminetetraacetic acid) at pH 4.0. The complex of EDTA-neodymium was transformed into neodymium oxides via oxalate precipitation. We produced 99.9% pure Nd203 in yields greater than or equal to 80%. Molecular absorption spectrophotometry was used to monitor the neodymium content during the process and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the neodymium oxides. The typical neodymium oxides obtained contained the followings contaminants in micrograms per gram: Sc (4.09); Y (0.39); La (0.78); Ce (5.62); Pr (4.56); Sm (11.10); Eu (1.10); Gd (14.30); Tb (29.3); Dy (4.15); Ho (8.39); Er (13.80); Tm (0.23); Yb (2.29); Lu (0.39). High purity neodymium oxides obtained from this procedure replaced the imported product used in research and development work on rare earth at IPEN/CNEN-SP (Instituto de Pesquisas Energeticas e Nucleares/Comissfio Nacional de Eneergia Nuclear-Sao Paulo).
基金the National Natural Science Foundation of China(1057101410571158).
文摘Some boundedness results are established in the setting of homogeneous Morrey-Herz spaces for a class of higher order commutators T^mb,l and M^mb,l generated by fractional integral operators Tl and maximal fractional operators Ml with function b(x) in BMO(R^n), respectively.
基金supported by the National Key Research and Development Program of China(2019YFC1906602)the National Natural Science Foundation of China(U1904171)+3 种基金the Foundation for"Talent Program"the Open Fund of the State Key Laboratory of Biochemical Engineering,Institute of Process Engineering(IPE)Chinese Academy of Sciences(CAS),the Project Fund of Jiangsu Bingcheng Hydrogen Energy Technology Co.,Ltd.the Young Backbone Teachers Training Program Foundation of Henan University of Technology。
文摘High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel cells.The ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adequate mechanical properties,and competitive costs.Various molecular moieties,such as benzimidazole,benzothiazole,imide,and ether ether ketone,have been introduced to polymer chain backbones to satisfy the application requirements for HT-PEMs.The most common sulfonated polymers based on the main chain backbones have been employed to improve the rties.Side group/chain engineering,including the introduction of SO_(3)^(-) on the side chain,grafting,branching,and crosslinking,has been widely applied to HTPEMs to further improve their proton conductivity,thermal stability,and mechanical properties.Currently,phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in HT-PEMs.The compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical properties.In this review,the current progress of various membrane materials used for HT-PEMs is summarized.The synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed systemically.Various modification approaches and their deficiencies associated with HT-PEMs are analyzed and clarified.Prospects and future challenges are also presented.
基金supported by the National Natural Science Foundation of China (21404016)the Key Research Program of Jiangsu Province (BE2017645)+1 种基金the Six Talent Peaks Project of Jiangsu Province (XCL-078)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions of China
文摘In order to effectively improve the properties of anion exchange membrane(AEM)materials,a series of novel poly(aryl ether nitrile)s with flexible side-chain-type quaternary phosphonium cations(PAEN-TPP-x)were designed and prepared on the basis of considering the influences of polymer backbone,cationic group species and the connection way between the cations and polymer chains.The synthetic method,structure and ion-exchange capacity,water absorption,swelling,hydroxide conductivity and alkaline stability of the obtained AEMs were studied.A comparative study with other reported AEMs was also performed for further exploration of the relationship between the structure and properties.These AEMs with flexible side-chain-type quaternary phosphonium cations displayed good comprehensive properties.Their water uptakes and swelling ratios were in the range of 11.6%–22.7%and 4.4%–7.8%at 60℃,respectively.They had hydroxide conductivity in the range of 28.6–45.8 mS cm^-1 at 60℃.Moreover,these AEMs also exhibited improved alkaline stability,and the hydroxide conductivity for PAEN-TPP-0.35 could remain 82.1%and 80.6%of its initial value at 60 and 90℃in 2 mol L^-1 NaOH solution for480 h,respectively.
基金the National Natural Science Foundation of China(21866028)the Development and Innovation Program of Bingtuan(2012QY13)+1 种基金the Program of Science and Technology Innovation Team in Bingtuan(2020CB006)the Achievement Transformation and Technique Popularization Project of Shihezi University(CGZH201910).
文摘Platinum-based material is the most efficient and durable electrocatalyst for motivating the hydrogen evolution reaction(HER)in an acidic electrolyte;however,its low abundance and high cost limit its further application in proton-exchange membrane water electrolysis(PEMWE)technology.Therefore,minimizing the Pt amount while retaining high activity would be desirable.Herein,we use defect-rich W_(18)O_(49)nanowires to anchor well-dispersed,ultrafine Pt species(Pt-W_(18)O_(49))via a freeze-drying method to avoid aggregation,further mediating an efficient and durable HER in acidic water.Density functional theory analyses also demonstrate that the strong electronic interaction between the Pt species and W_(18)O_(49)support greatly improves the HER performance.With a 1/10 Pt loading amount of the commercial 20 wt%Pt/C,the Pt-W_(18)O_(49)catalyst requires the overpotentials of 116 and 743 mV to achieve high current densities of 100 and 1000 mA cm^(−2)in 0.5 mol L^(−1)H_(2)SO_(4),outperforming those of the 20 wt%Pt/C benchmark.More importantly,the Pt-W_(18)O_(49)catalyst can sustain a high-currentdensity HER at 500 mA cm^(−2)for more than 38 h without obvious degradation.This work paves a new avenue for synergistically reducing the Pt amount and retaining high activity for real-world PEMWE.
基金Supported by the Ministry of Science and Innovation of Spain (No.CGL2010-16765/BTE)the FEDER and the Xuntade Galicia in partnership with the University of Vigo through "Angeles Alvarino" and "Parga Pondal" research grants to F. A. Vega and E. F. Covelo,respectively
文摘The mobility and bioavailability of heavy metals in soils is largely governed by sorption and desorption phenomena.Cu2+ and Pb2+ are among the most potentially toxic heavy metals and they are present,often concomitantly,in many polluting spills and in agrochemicals.The objective was to assess and compare the competitive sorption and desorption capacities and sorption hysteresis of Cu2+ and Pb2+,as well as their migration through the profiles of four natural soils:a Humic Umbrisol,an Umbric Cambisol,an Endoleptic Luvisol and a Humic Cambisol.In all horizons Pb2+ was invariably sorbed and retained to a greater extent than Cu2+.The sorption and retention of Cu2+ were most in?uenced by pH,e?ective cation exchange capacity(CECe) and Mn oxide content.On the other hand,the fixation capacity of Pb2+ was most in?uenced by pH,CECe,and Mn oxide and organic matter contents.pH and CECe were the individual soil properties most markedly in?uencing Cu2+ and Pb2+ sorption and retention.In all the horizons Pb2+ exhibited greater hysteresis than Cu2+.In each soil the hysteresis in the A horizon was greater than that in the B horizon,except in the Bt horizon of the Endoleptic Luvisol,due to its high pH and vermiculite content.Based on migration indices,Pb2+ was less mobile than Cu2+ in the studied soils.