Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the T...Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.展开更多
Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the sol...Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the soluble lithium polysulfides(LiPSs)as well as the slow reaction kinetics of LiPSs which may make shuttling effect even worse.Herein,we report a strategy to address this issue by in-situ transformation of Co−N_(x) coordinations in cobalt polyphthalocyanine(CoPPc)into Co nanoparticles(Co NPs)embedded in carbon matrix and mono-dispersed on graphene flakes.The Co NPs can provide rich binding and catalytic sites,while graphene flakes act as ideally LiPSs transportation and electron conducting platform.With a remarkable enhanced reaction kinetics of LiPSs via these merits,the sulfur host with a sulfur content up to 70 wt%shows a high initial capacity of 1048 mA∙h/g at 0.2C,good rate capability up to 399 mA·h/g at 2C.展开更多
文摘目的探讨缺血性卒中患者和健康人在进行双任务步行(dual-taskwalking,DTW)时,不同认知任务对步态和认知-运动干扰(cognitive-motor interference,CMI)的影响。方法选取24例急性缺血性卒中患者为卒中组,并选取与卒中组性别、年龄、受教育程度相匹配的16例健康志愿者为对照组。所有被试者依次完成坐姿下两项认知单任务(single-task,ST),包括连续减法任务(serial subtraction,SS)和单词生成任务(word list generation,WLG)。然后完成单任务步行(single-taskwalking,STW)、连续减法时双重任务步行(SS-DTW)和单词生成时双重任务步行(WLGDTW)。使用Codamotion三维动作捕捉系统采集步态参数,包括步速、步频、跨步长和跨步时间,记录认知任务正确反应数量。比较两组在DTW时步行和认知任务的双重任务成本差异。结果(1)在STW和两种DTW时,卒中组步速、跨步长和步频明显低于对照组,跨步时间长于对照组,差异有统计学意义(P<0.05)。与STW相比,卒中组在不同DTW时步速降低、步频减慢且跨步时间延长,在SS-DTW时跨步长变短,差异有统计学意义(P<0.05);对照组在不同DTW时步速降低、步频减慢、跨步长变短和跨步时间延长,差异有统计学意义(P<0.05)。(2)与认知ST相比,卒中组在两种DTW中,认知任务正确次数均减少(P<0.05);对照组仅在SS-DTW时,认知任务正确次数减少,差异有统计学意义(P<0.05)。结论执行双重任务(dual-task,DT)会导致缺血性卒中患者和健康者步态表现下降,卒中患者在DTW时更易出现步态障碍。工作记忆任务和语义记忆任务对步态的干扰程度是相似的。DTW更能反映日常生活活动能力,关于DTW时CMI模式的探索可为评估实际步行功能和DT训练效果提供理论依据。
文摘Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.
基金Project(21905220) supported by the National Natural Science Foundation of ChinaProject(BK20201190) supported by the Jiangsu Provincial Department of Science and Technology,China+2 种基金Projects(2018ZDXM-GY-135,2021JLM-36) supported by the Key Research and Development Plan of Shaanxi Province,ChinaProject(HG6J003) supported by the Fundamental Research Funds for “Young Talent Support Plan” of Xi’ an Jiaotong University,ChinaProject supported by the “1000-Plan program” of Shaanxi Province,China。
文摘Lithium-sulfur(Li-S)batteries have been considered as the next generation high energy storage devices.However,its commercialization has been hindered by several issues,especially the dissolution and shuttle of the soluble lithium polysulfides(LiPSs)as well as the slow reaction kinetics of LiPSs which may make shuttling effect even worse.Herein,we report a strategy to address this issue by in-situ transformation of Co−N_(x) coordinations in cobalt polyphthalocyanine(CoPPc)into Co nanoparticles(Co NPs)embedded in carbon matrix and mono-dispersed on graphene flakes.The Co NPs can provide rich binding and catalytic sites,while graphene flakes act as ideally LiPSs transportation and electron conducting platform.With a remarkable enhanced reaction kinetics of LiPSs via these merits,the sulfur host with a sulfur content up to 70 wt%shows a high initial capacity of 1048 mA∙h/g at 0.2C,good rate capability up to 399 mA·h/g at 2C.
