We describes a controllable synthesis procedure for growing a-Ee2O3 and Ee3O4 nanowires. High magnetic hematite a-Fe2O3 nanowires are successfully grown on Fe0.5Ni0.5 alloy substrates via an oxide assisted vapor-solid...We describes a controllable synthesis procedure for growing a-Ee2O3 and Ee3O4 nanowires. High magnetic hematite a-Fe2O3 nanowires are successfully grown on Fe0.5Ni0.5 alloy substrates via an oxide assisted vapor-solid process. Experimental results also indicate that previous immersion of the substrates in a solution of oxalic acid causes the grown nanowires to convert gradually into magnetite （Fe3O4） nanowires. Additionally, the saturated state of Fe3O4 nanowires is achieved as the oxalic acid concentration reaches 0.75 mol/L. The average diameter and length of nanowires expands with an increasing operation temperature and the growth density of nanowires accumulates with an increasing gas flux in the vapor-solid process. The growth mechanism of a-Fe2O3 and Fe3O4 nanowires is also discussed. The results demonstrate that the entire synthesis of nanowires can be completed within 2 h.展开更多
We report a facile, two-step hydrothermal synthesis of a novel Co304/a-Fe2O3 branched nanowire heterostructure, which can serve as a good candidate for lithium-ion battery anodes with high Li＋ storage capacity and st...We report a facile, two-step hydrothermal synthesis of a novel Co304/a-Fe2O3 branched nanowire heterostructure, which can serve as a good candidate for lithium-ion battery anodes with high Li＋ storage capacity and stability. The single-crystalline, primary C0304 nanowire trunk arrays directly grown on Ti substrates allow for efficient electrical and ionic transport. The secondary a-Fe2O3 branches provide enhanced surface area and high theoretical Li＋ storage capacity, and can also serve as volume spacers between neighboring Co3O4 NW arrays to maintain electrolyte penetration as well as reduce the aggregation during Li＋ intercalation, thus leading to improved electrochemical energy storage performance.展开更多
Fiber-shaped energy storage devices are indispensable parts of wearable and portable electronics.Aqueous rechargeable Ni/Fe battery is a very appropriate energy storage device due to their good safety without organic ...Fiber-shaped energy storage devices are indispensable parts of wearable and portable electronics.Aqueous rechargeable Ni/Fe battery is a very appropriate energy storage device due to their good safety without organic electrolytes, high ionic conductivity, and low cost. Unfortunately, the low energy density,poor power density and cycling performance hinder its further practical applications. In this study, in order to obtain high performance negative iron-based material, we first synthesized a-iron oxide(α-Fe2O3) nanorods(NRs) with superstructures on the surface of highly conductive carbon nanotube fibers(CNTFs), then electrically conductive polypyrrole(PPy) was coated to enhance the electron, ion diffusion and cycle stability. The as-prepared α-Fe2O3@PPy NRs/CNTF electrode shows a high specific capacity of 0.62 Ah cm-3 at the current density of 1 A cm-3. Furthermore, the Ni/Fe battery that was assembled by the above negative electrode shows a maximum volumetric energy density of 15.47 mWh cm-3 with228.2 mW cm-3 at a current density of 1 A cm-3. The cycling durability and mechanical flexibility of the Ni/Fe battery were tested, which show good prospect for practical application. In summary, these merits make it possible for our Ni/Fe battery to have practical applications in next generation flexible energy storage devices.展开更多
High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts,special optical,electrical and magnetic devices.But the hig...High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts,special optical,electrical and magnetic devices.But the high surface energy of the high-index facets usually drives them to grow faster than the other facets and finally disappear during the crystal growth,which leads the synthesis of nanocrystals with high-indexed facets exposed to be a great challenge.Herein,we introduced two routes to control the synthesis of-Fe2O3polyhedrons with different sets of high-index facets,one using different metal ions(Ni2+,Cu2+or Zn2+)as structure-directing agents and the other applying polymer surfactant sodium carboxymethyl cellulose(CMC)as additive.The growth process of high-index-Fe2O3polyhedrons was also discussed and possible growth mechanism was proposed.展开更多
文摘We describes a controllable synthesis procedure for growing a-Ee2O3 and Ee3O4 nanowires. High magnetic hematite a-Fe2O3 nanowires are successfully grown on Fe0.5Ni0.5 alloy substrates via an oxide assisted vapor-solid process. Experimental results also indicate that previous immersion of the substrates in a solution of oxalic acid causes the grown nanowires to convert gradually into magnetite （Fe3O4） nanowires. Additionally, the saturated state of Fe3O4 nanowires is achieved as the oxalic acid concentration reaches 0.75 mol/L. The average diameter and length of nanowires expands with an increasing operation temperature and the growth density of nanowires accumulates with an increasing gas flux in the vapor-solid process. The growth mechanism of a-Fe2O3 and Fe3O4 nanowires is also discussed. The results demonstrate that the entire synthesis of nanowires can be completed within 2 h.
文摘We report a facile, two-step hydrothermal synthesis of a novel Co304/a-Fe2O3 branched nanowire heterostructure, which can serve as a good candidate for lithium-ion battery anodes with high Li＋ storage capacity and stability. The single-crystalline, primary C0304 nanowire trunk arrays directly grown on Ti substrates allow for efficient electrical and ionic transport. The secondary a-Fe2O3 branches provide enhanced surface area and high theoretical Li＋ storage capacity, and can also serve as volume spacers between neighboring Co3O4 NW arrays to maintain electrolyte penetration as well as reduce the aggregation during Li＋ intercalation, thus leading to improved electrochemical energy storage performance.
基金This work was supported by the National Natural Science Foundation of China (51972162 and 51703241)the Postdoctoral Foundation of Jiangsu Province (2019Z203 and 2019K001)the Science and Technology Project of Nanchang (2017-SJSYS008)
文摘Fiber-shaped energy storage devices are indispensable parts of wearable and portable electronics.Aqueous rechargeable Ni/Fe battery is a very appropriate energy storage device due to their good safety without organic electrolytes, high ionic conductivity, and low cost. Unfortunately, the low energy density,poor power density and cycling performance hinder its further practical applications. In this study, in order to obtain high performance negative iron-based material, we first synthesized a-iron oxide(α-Fe2O3) nanorods(NRs) with superstructures on the surface of highly conductive carbon nanotube fibers(CNTFs), then electrically conductive polypyrrole(PPy) was coated to enhance the electron, ion diffusion and cycle stability. The as-prepared α-Fe2O3@PPy NRs/CNTF electrode shows a high specific capacity of 0.62 Ah cm-3 at the current density of 1 A cm-3. Furthermore, the Ni/Fe battery that was assembled by the above negative electrode shows a maximum volumetric energy density of 15.47 mWh cm-3 with228.2 mW cm-3 at a current density of 1 A cm-3. The cycling durability and mechanical flexibility of the Ni/Fe battery were tested, which show good prospect for practical application. In summary, these merits make it possible for our Ni/Fe battery to have practical applications in next generation flexible energy storage devices.
基金supported by the National Basic Research Program of China(2011CB935800)the National Natural Science Foundation of China(21071076,21021062 and 51172106)
文摘High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts,special optical,electrical and magnetic devices.But the high surface energy of the high-index facets usually drives them to grow faster than the other facets and finally disappear during the crystal growth,which leads the synthesis of nanocrystals with high-indexed facets exposed to be a great challenge.Herein,we introduced two routes to control the synthesis of-Fe2O3polyhedrons with different sets of high-index facets,one using different metal ions(Ni2+,Cu2+or Zn2+)as structure-directing agents and the other applying polymer surfactant sodium carboxymethyl cellulose(CMC)as additive.The growth process of high-index-Fe2O3polyhedrons was also discussed and possible growth mechanism was proposed.
