The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their perform...The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.展开更多
The effect of curing regime on the distribution ofAl3＋ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning （MAS） nuclear magnetic resonance（NMR） with deconvo...The effect of curing regime on the distribution ofAl3＋ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning （MAS） nuclear magnetic resonance（NMR） with deconvolution technique. The results indicate that the tetrahedral coordination Al3＋ incorporated in C-S-H structure mainly originate from the AP＋ incorporated in the alite and belite phases in the Portland cement. The curing regime of constant temperature of 20 ℃ is beneficial to the octahedral coordination Al3＋ transforming to tetrahedral coordination AP＋ incorporated in C-S-H structure. However, at curing regime of variable temperature, the temperature rising process is more advantageous to the transformation from ettringite to monosulphate, substitution of Al3＋ for Si4＋ in the C-S-H structure and the formation of the third aluminate hydrate （TAH） than that at constant temperature of 20 ℃. The high temperature of 60 ℃ in the holding temperature process promotes the decomposition of ettringite, and enhances the consumption of the Al3＋ incorporated in C-S-H phases and the Al3＋ in TAH for the monosulphate forming. The temperature decreasing promotes the transformation from monosulphate to ettringite, and increases the consumption of the Al3＋ incorporated in C-S-H phases, and then increases the quantity of the TAH.展开更多
We present a comprehensive investigation into the superconducting properties of L_(a3)Al,a La-based metal with a kagome structure.L_(a3)Al crystallizes in a Ni_(3)Sn-type crystal structure(space group P63/mmc),where t...We present a comprehensive investigation into the superconducting properties of L_(a3)Al,a La-based metal with a kagome structure.L_(a3)Al crystallizes in a Ni_(3)Sn-type crystal structure(space group P63/mmc),where the La atoms form a kagome lattice.Resistivity measurements reveal superconducting transition with T_(c)^(onset)=6.37 K and Tczero=6.18 K.In magnetic susceptibility measurements,the superconducting transition is observed at 6.16 K.The lower and upper critical fields are determined to be 22.17 mT and 6.69 T,respectively.Heat capacity measurements confirm the bulk superconductivity,showing a normalized specific heat change of△Ce/(_(γ)T_(c))=2.16 and an electron-phonon coupling strength ofλ_(ep)=0.92.DFT calculations reveal the intricate band structure of La_(3)Al.The notable specific heat jump,coupled with the electron-phonon coupling strengthλ_(ep),indicates that La_(3)Al exhibits characteristics of an intermediately coupled type-Ⅱsuperconductor.展开更多
The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of cat...The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+sites(penta-coordinated Al3+,denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+pentain Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3,which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.展开更多
A novel metal-organic coordination polymer,[Pb2（NO3）3（Hmppdc）（CH3OH）2]n（1,H2mppdc=2,6-dimethyl-4-phenylpyridine-3,5-dicarboxylic acid）,was synthesized from the reaction of H2mppdc,Pb（NO3）2 and CH3OH under so...A novel metal-organic coordination polymer,[Pb2（NO3）3（Hmppdc）（CH3OH）2]n（1,H2mppdc=2,6-dimethyl-4-phenylpyridine-3,5-dicarboxylic acid）,was synthesized from the reaction of H2mppdc,Pb（NO3）2 and CH3OH under solvothermal conditions.X-ray single-crystal diffraction reveals that 1 crystallizes in monoclinic,space group P21/n,with a=10.9883（13）,b=7.3603（10）,c=31.165（3）A,β=96.918（2）,V=2502.2（5）A^3,Z=4,Mr=934.75,Dc=2.481 Mg/m^3,F（000）=1736,the final R=0.0676 and wR=0.1310（I〉2σ（I））.Compound 1 contains two distinct 1-D polynuclear metal-oxygen chains（（PbO5）n and（PbO6）n）,which are bridged by ligands to build up 2-D metal-organic layers,and such layers are further connected to form a 3-D supramolecular network.The new compound exhibits strong photoluminescence in the solid state at room temperature.展开更多
A novel coordination polymer, [Co3（bta）2（dpe）3（H2O）2]·2H2O （1, H3bta = benzene-1,3,5-triacetic acid, and dpe = 1,2-di（pyridin-4-yl）ethene）, has been hydrothermally prepared and characterized by IR spect...A novel coordination polymer, [Co3（bta）2（dpe）3（H2O）2]·2H2O （1, H3bta = benzene-1,3,5-triacetic acid, and dpe = 1,2-di（pyridin-4-yl）ethene）, has been hydrothermally prepared and characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The crystal is of triclinic system, space group P , with a = 9.5687（15）, b = 11.2470（17）, c = 13.686（2） , α = 78.262（3）, β = 89.271（4）, γ = 81.292（3）°, V = 1425.2（4） 3, C60H56N6O16Co3, Mr = 1293.90, Dc = 1.508 g/cm3, F（000） = 667, μ = 0.940 mm-1 and Z = 1. The final R = 0.0707 and wR = 0.1413 for 4950 observed reflections （I 2σ（I））. In the title complex, the bta ligand acts as a four-dentate bridging ligand to link up cobalt atoms into lamellar frameworks which are further interlinked by the dpe ligands to generate a trinodal （3,4,6）-connected （4.62）2（42.68.83.102）（64.82） net.展开更多
5-（Hydroxymethyl） isophthalic acid （H2HIA） as a novel organic ligand was prepared from 3,5-bis（methoxycarbonyl）benzoic acid by a two-step method. And then, a 3D helical coor- dination polymer with a 3-fold inter...5-（Hydroxymethyl） isophthalic acid （H2HIA） as a novel organic ligand was prepared from 3,5-bis（methoxycarbonyl）benzoic acid by a two-step method. And then, a 3D helical coor- dination polymer with a 3-fold interpenetration structure, namely [Zn1/2（HIA）1/2（DPEE）1/2]n （1）, was hydrothermally synthesized at 160 ℃, using H2HIA ligands to assemble with DPEE ligands and Zn2＋ ions. Complex 1 crystalizes in orthorhombic system, space group Pnna, with a = 8.2118（5）, b = 17.1698（7）, c =14.9922（7） ？, V = 2113.82（18） ？3, μ = 1.194 mm-1, Z = 4 and S = 0.967. Moreover, some physical characteristics of complex 1, such as powder X-ray diffraction （PXRD）, thermogravimetry analyses （TGA） and photoluminescent properties, were also investigated.展开更多
Two N-donor ligands mediated Cd（Ⅱ） coordination polymers, namely,[Cd（L）（dmpz）2]n （1） and {[Cd（L）（atr）05（H20）]（H2O）}n （2） （H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate, dmpz = 3,5-dimethy...Two N-donor ligands mediated Cd（Ⅱ） coordination polymers, namely,[Cd（L）（dmpz）2]n （1） and {[Cd（L）（atr）05（H20）]（H2O）}n （2） （H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate, dmpz = 3,5-dimethylpyrazole, and atr= 4-amino-l,2,4-triazole）, havebeen produced. Their structures were characterized by single-crystal X-ray diffraction analysis,elemental analyses and infrared spectra. Compound 1 possesses a one-dimensional （1D） chainstructure and is finally extended into a three-dimensional （3D） supramolecular architecturethough hydrogen bonding interactions. Compound 2 features a two-dimensional （2D） networkwith 4-connected sql topology based on dinuclear Cd（Ⅱ） clusters as nodes, which is alsoassembled into a 3D supramolecular architecture through hydrogen bonding interactions.Furthermore, compounds 1 and 2 exhibit high thermal stabilities and intense fluorescent emissionin the solid, and can be explored as potential luminescent materials.展开更多
A new three-dimensional coordination polymer {[Co（BPTC）0.5（bix）]′（H2O）}n （1, H4BPTC = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid, bix = 1,3-bis（imidazol-l-ylmethyl）-benzene） has been synthesized by the...A new three-dimensional coordination polymer {[Co（BPTC）0.5（bix）]′（H2O）}n （1, H4BPTC = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid, bix = 1,3-bis（imidazol-l-ylmethyl）-benzene） has been synthesized by the hydrothermal method and characterized by IR, elemental analysis, and single-crystal X-ray analysis. The crystal is of orthorhombic, space group Pbcn with a = 13.2975（10）, b = 13.8424（12）, c = 22.6367（17） A, CoC22H19N4Os, Mr = 478.34, V = 4166.7（6） A3, Dc = 1.525 g/cm^3, F（000） = 1968,μ = 0.867 mm^-1, S = 1.023 and Z = 8. The final R = 0.0683 and wR = 0.1529 for 3655 observed reflections with I 〉 20（I）. In the title complex, the 2D Co-BPTC layer is formed through self-assembly of Co（II） ions and bridging BPTC4-ligands in a molar ratio of 2：1. The metal-organic lattice layers are further united together through the second bridging ligand bix to form a 3D metal-organic framework. The thermal stability of the title complex was studied by thermal gravimetric （TG） and differential thermal analysis （DTA）.展开更多
基金financially National Natural Science Foundation of China (22288102, 22172134, U1932201, U2032202)Science and Technology Planning Project of Fujian Province (2022H0002)support from the EPSRC (EP/W03784X/1)。
文摘The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.
基金Funded by the Major State Basic Research Development Program of China(973 Program)(No.2009CB623201)
文摘The effect of curing regime on the distribution ofAl3＋ coordination in hardened cement pastes within 28 d were investigated by 29Si and 27Al magic angle spinning （MAS） nuclear magnetic resonance（NMR） with deconvolution technique. The results indicate that the tetrahedral coordination Al3＋ incorporated in C-S-H structure mainly originate from the AP＋ incorporated in the alite and belite phases in the Portland cement. The curing regime of constant temperature of 20 ℃ is beneficial to the octahedral coordination Al3＋ transforming to tetrahedral coordination AP＋ incorporated in C-S-H structure. However, at curing regime of variable temperature, the temperature rising process is more advantageous to the transformation from ettringite to monosulphate, substitution of Al3＋ for Si4＋ in the C-S-H structure and the formation of the third aluminate hydrate （TAH） than that at constant temperature of 20 ℃. The high temperature of 60 ℃ in the holding temperature process promotes the decomposition of ettringite, and enhances the consumption of the Al3＋ incorporated in C-S-H phases and the Al3＋ in TAH for the monosulphate forming. The temperature decreasing promotes the transformation from monosulphate to ettringite, and increases the consumption of the Al3＋ incorporated in C-S-H phases, and then increases the quantity of the TAH.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52272268 and 52250308)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant No.XDB33010100)+1 种基金the Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF0102)the Synergetic Extreme Condition User Facility(SECUF)。
文摘We present a comprehensive investigation into the superconducting properties of L_(a3)Al,a La-based metal with a kagome structure.L_(a3)Al crystallizes in a Ni_(3)Sn-type crystal structure(space group P63/mmc),where the La atoms form a kagome lattice.Resistivity measurements reveal superconducting transition with T_(c)^(onset)=6.37 K and Tczero=6.18 K.In magnetic susceptibility measurements,the superconducting transition is observed at 6.16 K.The lower and upper critical fields are determined to be 22.17 mT and 6.69 T,respectively.Heat capacity measurements confirm the bulk superconductivity,showing a normalized specific heat change of△Ce/(_(γ)T_(c))=2.16 and an electron-phonon coupling strength ofλ_(ep)=0.92.DFT calculations reveal the intricate band structure of La_(3)Al.The notable specific heat jump,coupled with the electron-phonon coupling strengthλ_(ep),indicates that La_(3)Al exhibits characteristics of an intermediately coupled type-Ⅱsuperconductor.
基金the National Natural Science Foundation of China(No.21676195)the China Postdoctoral Science Foundation(2016M601347)。
文摘The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+sites(penta-coordinated Al3+,denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+pentain Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3,which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.
基金supported by the Key Project of the Chinese Ministry of Education (No 208116)the Scientific and Technological Project of CQEC (No KJ080829)the Chongqing Normal University Scientific Research Foundation Project (No 06XLY016)
文摘A novel metal-organic coordination polymer,[Pb2（NO3）3（Hmppdc）（CH3OH）2]n（1,H2mppdc=2,6-dimethyl-4-phenylpyridine-3,5-dicarboxylic acid）,was synthesized from the reaction of H2mppdc,Pb（NO3）2 and CH3OH under solvothermal conditions.X-ray single-crystal diffraction reveals that 1 crystallizes in monoclinic,space group P21/n,with a=10.9883（13）,b=7.3603（10）,c=31.165（3）A,β=96.918（2）,V=2502.2（5）A^3,Z=4,Mr=934.75,Dc=2.481 Mg/m^3,F（000）=1736,the final R=0.0676 and wR=0.1310（I〉2σ（I））.Compound 1 contains two distinct 1-D polynuclear metal-oxygen chains（（PbO5）n and（PbO6）n）,which are bridged by ligands to build up 2-D metal-organic layers,and such layers are further connected to form a 3-D supramolecular network.The new compound exhibits strong photoluminescence in the solid state at room temperature.
基金supported by the National Natural Science Foundation of China (No. 20971004)the Natural Science Foundation of Anhui Province (No. 11040606M45)
文摘A novel coordination polymer, [Co3（bta）2（dpe）3（H2O）2]·2H2O （1, H3bta = benzene-1,3,5-triacetic acid, and dpe = 1,2-di（pyridin-4-yl）ethene）, has been hydrothermally prepared and characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The crystal is of triclinic system, space group P , with a = 9.5687（15）, b = 11.2470（17）, c = 13.686（2） , α = 78.262（3）, β = 89.271（4）, γ = 81.292（3）°, V = 1425.2（4） 3, C60H56N6O16Co3, Mr = 1293.90, Dc = 1.508 g/cm3, F（000） = 667, μ = 0.940 mm-1 and Z = 1. The final R = 0.0707 and wR = 0.1413 for 4950 observed reflections （I 2σ（I））. In the title complex, the bta ligand acts as a four-dentate bridging ligand to link up cobalt atoms into lamellar frameworks which are further interlinked by the dpe ligands to generate a trinodal （3,4,6）-connected （4.62）2（42.68.83.102）（64.82） net.
基金supported by the Natural Science Foundation of Guizhou Province(20122344)125 program of Guizhou Education Department(2012015)the Doctoral Scientific Fund of Zunyi Normal College(2012BSJJ12)
文摘5-（Hydroxymethyl） isophthalic acid （H2HIA） as a novel organic ligand was prepared from 3,5-bis（methoxycarbonyl）benzoic acid by a two-step method. And then, a 3D helical coor- dination polymer with a 3-fold interpenetration structure, namely [Zn1/2（HIA）1/2（DPEE）1/2]n （1）, was hydrothermally synthesized at 160 ℃, using H2HIA ligands to assemble with DPEE ligands and Zn2＋ ions. Complex 1 crystalizes in orthorhombic system, space group Pnna, with a = 8.2118（5）, b = 17.1698（7）, c =14.9922（7） ？, V = 2113.82（18） ？3, μ = 1.194 mm-1, Z = 4 and S = 0.967. Moreover, some physical characteristics of complex 1, such as powder X-ray diffraction （PXRD）, thermogravimetry analyses （TGA） and photoluminescent properties, were also investigated.
基金supported by the National Natural Science of Foundation of China(No.21671094)
文摘Two N-donor ligands mediated Cd（Ⅱ） coordination polymers, namely,[Cd（L）（dmpz）2]n （1） and {[Cd（L）（atr）05（H20）]（H2O）}n （2） （H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate, dmpz = 3,5-dimethylpyrazole, and atr= 4-amino-l,2,4-triazole）, havebeen produced. Their structures were characterized by single-crystal X-ray diffraction analysis,elemental analyses and infrared spectra. Compound 1 possesses a one-dimensional （1D） chainstructure and is finally extended into a three-dimensional （3D） supramolecular architecturethough hydrogen bonding interactions. Compound 2 features a two-dimensional （2D） networkwith 4-connected sql topology based on dinuclear Cd（Ⅱ） clusters as nodes, which is alsoassembled into a 3D supramolecular architecture through hydrogen bonding interactions.Furthermore, compounds 1 and 2 exhibit high thermal stabilities and intense fluorescent emissionin the solid, and can be explored as potential luminescent materials.
基金supported by the International Technology Cooperation Project of Science and Technology Department of Henan Province (No. 124300510050)
文摘A new three-dimensional coordination polymer {[Co（BPTC）0.5（bix）]′（H2O）}n （1, H4BPTC = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid, bix = 1,3-bis（imidazol-l-ylmethyl）-benzene） has been synthesized by the hydrothermal method and characterized by IR, elemental analysis, and single-crystal X-ray analysis. The crystal is of orthorhombic, space group Pbcn with a = 13.2975（10）, b = 13.8424（12）, c = 22.6367（17） A, CoC22H19N4Os, Mr = 478.34, V = 4166.7（6） A3, Dc = 1.525 g/cm^3, F（000） = 1968,μ = 0.867 mm^-1, S = 1.023 and Z = 8. The final R = 0.0683 and wR = 0.1529 for 3655 observed reflections with I 〉 20（I）. In the title complex, the 2D Co-BPTC layer is formed through self-assembly of Co（II） ions and bridging BPTC4-ligands in a molar ratio of 2：1. The metal-organic lattice layers are further united together through the second bridging ligand bix to form a 3D metal-organic framework. The thermal stability of the title complex was studied by thermal gravimetric （TG） and differential thermal analysis （DTA）.
