摘要：Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic *** this study,hierarchical NiO/Ni nanosheets with a tuneable phase and morphology supported on a carbon fiber substrate(CF@NiO/Ni)were fabricated using a hydrothermal approach and post-annealing *** the annealing temperature increases,more metallic Ni is formed,and an apparent porosity appears on the sheet *** from the advantages of a three-dimensional(3D)conducting network,hierarchical porous structure,reinforced dipole/interface polarization,multiple scattering,and good impedance matching,the CF@NiO/Ni-500 composite exhibits an excellent microwave absorption performance even at a filling rate of only 3wt%.Specifically,its minimal reflection loss is-43.92 dB,and the qualified bandwidth is up to 5.64 *** addition,the low radar cross-section area of the CF@NiO/Ni composite coating confirms its strong ability to suppress electromagnetic wave *** expect that this work could contribute to a deeper understanding of the phase and morphology evolution in enhancing microwave absorption.

摘要：调控催化剂表面的化学键来平衡表面水分子的吸附和分解对于碱性溶液中水分解至关重要.本研究提出一种通过原位界面工程来设计与合成表面具有丰富的Ni-W金属键的Ni2W4C-W3C Janus异质结构的简便策略.预先将金属离子均匀分散在纳米纤维中,在碳化过程中,以电纺纤维为反应器,金属盐首先被还原成Ni和W3C.在持续分解的过程中,Ni原子原位插入W3C晶体中形成新的Ni2W4C相,得到Ni2W4C-W3C Janus异质结构.这使得W3C中原本惰性的W原子成为Ni2W4C中的活性位点.Ni2W4C-W3C/碳纳米纤维可以直接作为电极材料,其在碱性电解液中析氢活性达到10 m A/cm^2的电流密度需要63 m V过电位,析氧活性达到30 m A/cm^2的电流密度需要270 m V的过电位.若同时用作阴极和阳极进行全解水性能研究,其电池电压分别需要1.55和1.87 V就达到10和100 m A/cm^2.密度泛函理论结果表明,Ni与W之间的强相互作用增强了W原子的局域电子态.Ni2W4C为H-OH键的裂解提供了活性位点,W3C促进了Hads中间体与H2分子的结合.原位电化学拉曼光谱的结果表明该材料对水分子和羟基具有很强的吸收能力,W原子是真正的反应活性位点.该方法为构建高效电解水催化材料提供了另一种思路.

摘要：本文通过调节烧结温度设计构筑了一种纳米多面体颗粒堆积的中空球状Li Ni0.5Mn1.5O4材料,并进一步通过碳纳米管(CNT)的改性来提高材料的循环性能和高倍率性能.纳米中空结构不仅减少了锂离子的扩散路径,也保证了电解液和正极材料的充分接触,三维网状CNT的改性提高了材料的电子导电率,从而明显改善了材料的循环和高倍率性能.最终得到的LNMO-850/CNT材料在5 C的电流密度下初始容量为127 m A h g-1,500次循环后容量保持在104 m A h g-1.而在20 C的高电流密度下容量仍达到121 m A h g-1,体现了材料优异的循环和高倍率性能.