利用水热法制备了粒径为90-130 nm的多孔硬碳球,并通过浸渍与煅烧的方法制备了硬碳球均匀负载纳米氧化镍颗粒(~10 nm)复合材料.硬碳球的表面官能团和内部的微孔保证了氧化镍颗粒在硬碳上的均匀分布.在100 m Ah·g^(-1)的电流密度下...利用水热法制备了粒径为90-130 nm的多孔硬碳球,并通过浸渍与煅烧的方法制备了硬碳球均匀负载纳米氧化镍颗粒(~10 nm)复合材料.硬碳球的表面官能团和内部的微孔保证了氧化镍颗粒在硬碳上的均匀分布.在100 m Ah·g^(-1)的电流密度下,复合材料电极首次充电比容量高达764 m Ah·g^(-1);在100 mAh·g^(-1)的电流密度下循环100个周期后电极充电比容量保持在777 mAh·g^(-1),容量保持率为101%;800 mAhg^(-1)电流密度下电极的充电比容量达380 mAh·g^(-1),显示复合材料电极具有优异的循环性能和倍率性能.硬碳的表面官能团和内部微孔为氧化镍提供了优先形核位点,保证了二者的牢固结合,使复合材料获得了'协同效应',从而使复合电极具备更短的锂离子扩散路径、更高的电导率和更多的锂离子脱嵌位点.这种方法还可用于制备硬碳/其他金属氧化物复合材料.展开更多
Functional-group-transfer strategies that avoid the use of unsustainable chemicals are attractive for the development of green methodologies.Chlorofluorocarbons(CFCs)not only contribute to the depletion of the stratos...Functional-group-transfer strategies that avoid the use of unsustainable chemicals are attractive for the development of green methodologies.Chlorofluorocarbons(CFCs)not only contribute to the depletion of the stratospheric ozone layer,but their gaseous nature also poses a serious threat in scientific laboratories.Hence,the design of effective and sustainable alternatives to CFCs is highly desirable.Herein,a practical CFC transfer platform for the addition of both a fluoroalkyl group and a chlorine substituent across alkenes by a photomediated redox-neutral manifold using bench-stable and easy-to-handle oxime-based surrogates is reported.The distinct reactivity of these tunable reagents allows for their single-electron reduction to trigger fragmentation driven by benzonitrile formation and loss of carbon dioxide.The other fragments released in that step,namely an electrophilic fluoroalkyl radical and a nucleophilic chloride anion,are subsequently transferred onto alkenes by a radical-ionic mechanism to deliver the desired chlorofluorocarbon products.展开更多
基金by the Alexander von Humboldt Foundation(postdoctoral fellowship to M.Z.,2021-2023)in part by the Deutsche Forschungsgemeinschaft(grant no.Oe 249/26-1)is gratefully acknowledged+1 种基金M.Z.is also grateful for financial support from the University of Science and Technology of China(grant no.KY9990000197)M.O.is indebted to the Einstein Foundation Berlin for an endowed professorship.
文摘Functional-group-transfer strategies that avoid the use of unsustainable chemicals are attractive for the development of green methodologies.Chlorofluorocarbons(CFCs)not only contribute to the depletion of the stratospheric ozone layer,but their gaseous nature also poses a serious threat in scientific laboratories.Hence,the design of effective and sustainable alternatives to CFCs is highly desirable.Herein,a practical CFC transfer platform for the addition of both a fluoroalkyl group and a chlorine substituent across alkenes by a photomediated redox-neutral manifold using bench-stable and easy-to-handle oxime-based surrogates is reported.The distinct reactivity of these tunable reagents allows for their single-electron reduction to trigger fragmentation driven by benzonitrile formation and loss of carbon dioxide.The other fragments released in that step,namely an electrophilic fluoroalkyl radical and a nucleophilic chloride anion,are subsequently transferred onto alkenes by a radical-ionic mechanism to deliver the desired chlorofluorocarbon products.
