The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SC...The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SCR)of nitrogen oxides(NO_(x)).Conventional Cu-SSZ-39(Cu-SSZ-39-T)exhibits excellent hydrothermal stability but limited low-temperature activity(150–225℃)due to a low concentration of Al in 8-membered rings(8MRs)that inhibits the formation of active[Cu(OH)]^(+)-Z species.Herein,an SSZ-39 zeolite synthesized with potassium ions(SSZ-39-K)achieved a significantly higher 8MR Al fraction(37.6%).Density functional theory calculations and H_(2)-temperature-programmed reduction analyses confirmed that the increased 8MR Al population facilitated the formation of[Cu(OH)]^(+)-Z species.Aged Cu-SSZ-39-K exhibited nearly twice the NO_(x)conversion of aged Cu-SSZ-39-T in the 150–225℃range while maintaining comparable high-temperature activity(250–550℃)under a gas hourly space velocity of 250,000 h^(-1).Enhanced low-temperature performance is particularly beneficial for mitigating NO_(x)emissions during cold-start phase.Moreover,SSZ-39-K was synthesized with a high crystallization yield(~65%),nearly double the highest yield(33%)reported for direct synthesis routes.This work establishes a robust strategy for tailoring Al distributions in SSZ-39 zeolites,offering an effective pathway to improve low-temperature NH_(3)-SCR performance and promote practical implementation.展开更多
A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of th...A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.展开更多
制备了不同Al含量的Al-MCM-41试样,其中Si/Al比值最小为3,即最高含铝量xAl=0.303.X射线粉末衍射（XPD）分析表明样品具有MCM-41的特征结构,氮气吸附研究表明,样品呈现Ⅳ型吸附等温线,具有孔径分布均一的中孔结构.文中还利用27Al MAS NM...制备了不同Al含量的Al-MCM-41试样,其中Si/Al比值最小为3,即最高含铝量xAl=0.303.X射线粉末衍射（XPD）分析表明样品具有MCM-41的特征结构,氮气吸附研究表明,样品呈现Ⅳ型吸附等温线,具有孔径分布均一的中孔结构.文中还利用27Al MAS NMR研究了试样中Al的化学环境,结果表明,即使在高铝含量的情况下,样品中的铝原子仍以四配位结合在MCM-41的硅骨架上,未能检测出骨架外六配位铝的存在.文中还就Al含量对孔结构的影响以及Al-MCM-41形成机理作了讨论.展开更多
Metal-organic framework（MOF） material MIL-53（A1） with high thermal stability was prepared by a solvothermal method,serving as a support material of cerium doped copper catalyst（Ce-Cu）/MIL-53（A1） material for C...Metal-organic framework（MOF） material MIL-53（A1） with high thermal stability was prepared by a solvothermal method,serving as a support material of cerium doped copper catalyst（Ce-Cu）/MIL-53（A1） material for CO oxidation with high catalytic activity.The catalytic performance between the（CuCe）/MIL-53（A1） and the Cu/MIL-53（A1） catalytic material was compared to understand the catalytic behavior of the catalysts.The catalysts were characterized by thermogravimetric-differential scanning calorimetry（TGDSC）,N2 adsorption- desorption,X-ray diffraction（XRD）,and transmission electron microscopy（TEM）.The characterization results showed that MIL-53（A1） had good stability and high surface areas,the（Ce-Cu）nanoparticles on the MIL-53（A1） support was uniform.Therefore,the heterogeneous catalytic composite materials（Ce-Cu）/MIL-53（A1） catalyst exhibited much higher activity than that of the Cu/MIL- 53（A1） catalyst in CO oxidation test,with 100%conversion at 80 ℃.The results reveal that（Cu-Ce）/MIL-53（A1） is the suitable candidate for achieving low temperature and higher activity CO oxidation catalyst of MOFs.展开更多
为探究磷酸铝溶胶对分子筛的破坏作用,通过剖析磷酸铝溶胶与其他黏结剂的区别,锁定pH值、磷物种以及二者协同作用为研究变量,采用XRD、BET、TEM、27 Al MAS NMR、29 Si MAS NMR、FTIR和XPS等表征手段分析了这些因素对分子筛晶体结构、...为探究磷酸铝溶胶对分子筛的破坏作用,通过剖析磷酸铝溶胶与其他黏结剂的区别,锁定pH值、磷物种以及二者协同作用为研究变量,采用XRD、BET、TEM、27 Al MAS NMR、29 Si MAS NMR、FTIR和XPS等表征手段分析了这些因素对分子筛晶体结构、孔结构、骨架结构及表面元素分布的影响。结果表明:pH值、磷物种以及二者协同作用对分子筛破坏程度由高到低的顺序为:pH值和磷物种的协同作用>磷物种的作用>pH值的作用;磷酸铝溶胶中的H^(+)和磷物种会相互促进彼此对Y型分子筛的破坏作用,H^(+)使分子筛骨架脱铝,同时磷物种会与分子筛表面的铝物种反应生成磷铝化合物,破坏孔道的同时加剧了骨架铝的脱除,甚至导致骨架硅的脱除,进而造成Y型分子筛骨架结构坍塌。而ZSM-5分子筛受上述因素的影响并不显著,这是由于ZSM-5分子筛较高的骨架硅/铝比使其骨架铝脱除量减少,从而阻碍了该破坏作用的发生,表明常规磷酸铝溶胶不适用于低硅/铝比分子筛的黏结。展开更多
人工智能(AI)对教师教育行业带来了新的活力,也对教师的综合素质提出了更高的要求。为帮助全球教师适应快速发展的人工智能技术,并利用这些技术来提升教学效果和教育质量,联合国教科文组织发布了AI Competency Framework for Teachers(...人工智能(AI)对教师教育行业带来了新的活力,也对教师的综合素质提出了更高的要求。为帮助全球教师适应快速发展的人工智能技术,并利用这些技术来提升教学效果和教育质量,联合国教科文组织发布了AI Competency Framework for Teachers(《教师AI能力框架》)。文章基于该框架的要点,归纳总结世界各国在教师AI能力培养方面的成功经验,分析了中国教师AI能力发展面临的挑战,并提出建议:建立AI系统信任评估清单,加强教师AI能力培训,推动AI资源均衡化,建立教师AI能力考核机制,关注伦理与安全教育,加强国际合作与交流。展开更多
文摘The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SCR)of nitrogen oxides(NO_(x)).Conventional Cu-SSZ-39(Cu-SSZ-39-T)exhibits excellent hydrothermal stability but limited low-temperature activity(150–225℃)due to a low concentration of Al in 8-membered rings(8MRs)that inhibits the formation of active[Cu(OH)]^(+)-Z species.Herein,an SSZ-39 zeolite synthesized with potassium ions(SSZ-39-K)achieved a significantly higher 8MR Al fraction(37.6%).Density functional theory calculations and H_(2)-temperature-programmed reduction analyses confirmed that the increased 8MR Al population facilitated the formation of[Cu(OH)]^(+)-Z species.Aged Cu-SSZ-39-K exhibited nearly twice the NO_(x)conversion of aged Cu-SSZ-39-T in the 150–225℃range while maintaining comparable high-temperature activity(250–550℃)under a gas hourly space velocity of 250,000 h^(-1).Enhanced low-temperature performance is particularly beneficial for mitigating NO_(x)emissions during cold-start phase.Moreover,SSZ-39-K was synthesized with a high crystallization yield(~65%),nearly double the highest yield(33%)reported for direct synthesis routes.This work establishes a robust strategy for tailoring Al distributions in SSZ-39 zeolites,offering an effective pathway to improve low-temperature NH_(3)-SCR performance and promote practical implementation.
基金supported by the National Natural Science Foundation of China(No.21501015)the Hunan Provincial Natural Science Foundation,China(No.2022JJ30604)Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation,China(No.2022CL01)。
文摘A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.
文摘制备了不同Al含量的Al-MCM-41试样,其中Si/Al比值最小为3,即最高含铝量xAl=0.303.X射线粉末衍射（XPD）分析表明样品具有MCM-41的特征结构,氮气吸附研究表明,样品呈现Ⅳ型吸附等温线,具有孔径分布均一的中孔结构.文中还利用27Al MAS NMR研究了试样中Al的化学环境,结果表明,即使在高铝含量的情况下,样品中的铝原子仍以四配位结合在MCM-41的硅骨架上,未能检测出骨架外六配位铝的存在.文中还就Al含量对孔结构的影响以及Al-MCM-41形成机理作了讨论.
基金Funded by the Guiding Research Project of Hubei Province Department of Education(No.B2016098)
文摘Metal-organic framework（MOF） material MIL-53（A1） with high thermal stability was prepared by a solvothermal method,serving as a support material of cerium doped copper catalyst（Ce-Cu）/MIL-53（A1） material for CO oxidation with high catalytic activity.The catalytic performance between the（CuCe）/MIL-53（A1） and the Cu/MIL-53（A1） catalytic material was compared to understand the catalytic behavior of the catalysts.The catalysts were characterized by thermogravimetric-differential scanning calorimetry（TGDSC）,N2 adsorption- desorption,X-ray diffraction（XRD）,and transmission electron microscopy（TEM）.The characterization results showed that MIL-53（A1） had good stability and high surface areas,the（Ce-Cu）nanoparticles on the MIL-53（A1） support was uniform.Therefore,the heterogeneous catalytic composite materials（Ce-Cu）/MIL-53（A1） catalyst exhibited much higher activity than that of the Cu/MIL- 53（A1） catalyst in CO oxidation test,with 100%conversion at 80 ℃.The results reveal that（Cu-Ce）/MIL-53（A1） is the suitable candidate for achieving low temperature and higher activity CO oxidation catalyst of MOFs.
文摘为探究磷酸铝溶胶对分子筛的破坏作用,通过剖析磷酸铝溶胶与其他黏结剂的区别,锁定pH值、磷物种以及二者协同作用为研究变量,采用XRD、BET、TEM、27 Al MAS NMR、29 Si MAS NMR、FTIR和XPS等表征手段分析了这些因素对分子筛晶体结构、孔结构、骨架结构及表面元素分布的影响。结果表明:pH值、磷物种以及二者协同作用对分子筛破坏程度由高到低的顺序为:pH值和磷物种的协同作用>磷物种的作用>pH值的作用;磷酸铝溶胶中的H^(+)和磷物种会相互促进彼此对Y型分子筛的破坏作用,H^(+)使分子筛骨架脱铝,同时磷物种会与分子筛表面的铝物种反应生成磷铝化合物,破坏孔道的同时加剧了骨架铝的脱除,甚至导致骨架硅的脱除,进而造成Y型分子筛骨架结构坍塌。而ZSM-5分子筛受上述因素的影响并不显著,这是由于ZSM-5分子筛较高的骨架硅/铝比使其骨架铝脱除量减少,从而阻碍了该破坏作用的发生,表明常规磷酸铝溶胶不适用于低硅/铝比分子筛的黏结。
文摘人工智能(AI)对教师教育行业带来了新的活力,也对教师的综合素质提出了更高的要求。为帮助全球教师适应快速发展的人工智能技术,并利用这些技术来提升教学效果和教育质量,联合国教科文组织发布了AI Competency Framework for Teachers(《教师AI能力框架》)。文章基于该框架的要点,归纳总结世界各国在教师AI能力培养方面的成功经验,分析了中国教师AI能力发展面临的挑战,并提出建议:建立AI系统信任评估清单,加强教师AI能力培训,推动AI资源均衡化,建立教师AI能力考核机制,关注伦理与安全教育,加强国际合作与交流。
