The molten mixtures of alkali metal fluorides and aluminum fluoride are applied as aluminum electrolytes or brazing fluxes.However,the presence of Al2F-7^-in such molten systems is disputed.In the present study,MF-AlF...The molten mixtures of alkali metal fluorides and aluminum fluoride are applied as aluminum electrolytes or brazing fluxes.However,the presence of Al2F-7^-in such molten systems is disputed.In the present study,MF-AlF3(M=K,Cs)systems with molar ratios<1 were studied by in-situ Raman spectroscopy and molecular simulation.The results show that,in addition to AlF6^(3-),AlF5^(2-),and AlF4^-,the systems also contained Al2F-7^-.The characteristic bands in the Raman spectra belonging to Al2F-7^-were located at about 225 cm^-1,315 cm^-1,479 cm^-1,and 720 cm^-1.There are two possible structures of Al2F-7^-,which belong to the D3d and D3hpoint groups.Both of these structures are linear,and their single-point energies were found to differ by only 0.31 kcal/mol.展开更多
A series of Pd/AlF3 catalysts was prepared by an impregnation method and tested for vapor-phase dehy- drofluorination of 1,1,1,3,3-pentafluoropropane（HFC-245fa） to synthesize 1,3,3,3-tetrafluoropropene（HFO-1234ze）...A series of Pd/AlF3 catalysts was prepared by an impregnation method and tested for vapor-phase dehy- drofluorination of 1,1,1,3,3-pentafluoropropane（HFC-245fa） to synthesize 1,3,3,3-tetrafluoropropene（HFO-1234ze）. The highest activity was obtained over Pd/AIF3 catalyst containing 1.0%（mass fraction） of Pd, with an HFC-245fa conversion of 79.5% and an HFO-1234ze selectivity of 99.4% after the reaction at 300 ℃ for 100 h. The reactivity was related to the surface acidity, as AlF3 provided active sites for the reaction. With the addition of Pd, the catalyst stability could be significantly improved. Raman spectroscopic and thermal-gravimetric analysis results reveal that there was less carbon deposit on spent Pd/AlF3 catalyst surface because Pd could effectively pyrolyse it. Thus, Pd/AlF3 catalysts were bi-functional for dehydrofluorination of HFC-245fa.展开更多
The ’shuttle effect’ of polysulfide causing rapid capacity fade and low coulo mbic efficiency of high ene rgy storage lithium-sulfur(Li-S) batteries.Herein,a sandwich structure of bamboo charcoal/sulfur coating by a...The ’shuttle effect’ of polysulfide causing rapid capacity fade and low coulo mbic efficiency of high ene rgy storage lithium-sulfur(Li-S) batteries.Herein,a sandwich structure of bamboo charcoal/sulfur coating by aluminum fluoride(BC@S@AlF3) composites is designed and fabricated for the first time.The as-designed cathode exhibited excellent electrochemical properties and stable capacity retention.The initial capacity reaches 1119 mA h/g and the capacity after 100 cycles is 869 mA h/g at 0.5 C,which is much stable than that of composite materials without bamboo charcoal or AlF3 coating.Moreover,the BC@S@AlF3 cathode presents excellent long-term capacity stability with a capacity decay of 0.073% per cycle during 500 charge/discharge cycles at 1 C,offering a potential for use in high energy Li-S batteries.The physical confinement,chemical ancho ring,and catalysis conversion for active sulfur are achieved simultaneously with the AlF3 coating and bamboo charcoal core with porous structure.展开更多
基金the National Natural Science Foundation of China(grant no.51474060)the National Key R&D Program of China(grant no.2017 YFC0805100)+1 种基金the National Natural Science Foundation of Liaoning Province(China)(grant no.2019-MS-129)the Fundamental Research Funds for the Central Universities of China(grant no.N162502002).
文摘The molten mixtures of alkali metal fluorides and aluminum fluoride are applied as aluminum electrolytes or brazing fluxes.However,the presence of Al2F-7^-in such molten systems is disputed.In the present study,MF-AlF3(M=K,Cs)systems with molar ratios<1 were studied by in-situ Raman spectroscopy and molecular simulation.The results show that,in addition to AlF6^(3-),AlF5^(2-),and AlF4^-,the systems also contained Al2F-7^-.The characteristic bands in the Raman spectra belonging to Al2F-7^-were located at about 225 cm^-1,315 cm^-1,479 cm^-1,and 720 cm^-1.There are two possible structures of Al2F-7^-,which belong to the D3d and D3hpoint groups.Both of these structures are linear,and their single-point energies were found to differ by only 0.31 kcal/mol.
基金Supported by the National Natural Science Foundation of China（No.21373186）.
文摘A series of Pd/AlF3 catalysts was prepared by an impregnation method and tested for vapor-phase dehy- drofluorination of 1,1,1,3,3-pentafluoropropane（HFC-245fa） to synthesize 1,3,3,3-tetrafluoropropene（HFO-1234ze）. The highest activity was obtained over Pd/AIF3 catalyst containing 1.0%（mass fraction） of Pd, with an HFC-245fa conversion of 79.5% and an HFO-1234ze selectivity of 99.4% after the reaction at 300 ℃ for 100 h. The reactivity was related to the surface acidity, as AlF3 provided active sites for the reaction. With the addition of Pd, the catalyst stability could be significantly improved. Raman spectroscopic and thermal-gravimetric analysis results reveal that there was less carbon deposit on spent Pd/AlF3 catalyst surface because Pd could effectively pyrolyse it. Thus, Pd/AlF3 catalysts were bi-functional for dehydrofluorination of HFC-245fa.
基金This work was supported by the National Natural Science Foundation of China(Grant No.11602213)the Natural Science Foundation of Hunan province,China(Grant No.2019JJ50578)。
文摘The ’shuttle effect’ of polysulfide causing rapid capacity fade and low coulo mbic efficiency of high ene rgy storage lithium-sulfur(Li-S) batteries.Herein,a sandwich structure of bamboo charcoal/sulfur coating by aluminum fluoride(BC@S@AlF3) composites is designed and fabricated for the first time.The as-designed cathode exhibited excellent electrochemical properties and stable capacity retention.The initial capacity reaches 1119 mA h/g and the capacity after 100 cycles is 869 mA h/g at 0.5 C,which is much stable than that of composite materials without bamboo charcoal or AlF3 coating.Moreover,the BC@S@AlF3 cathode presents excellent long-term capacity stability with a capacity decay of 0.073% per cycle during 500 charge/discharge cycles at 1 C,offering a potential for use in high energy Li-S batteries.The physical confinement,chemical ancho ring,and catalysis conversion for active sulfur are achieved simultaneously with the AlF3 coating and bamboo charcoal core with porous structure.
