Insights into High Conductivity of the Two-Dimensional Iodine-Oxidized sp2-c-COF.
Insights into High Conductivity of the Two-Dimensional Iodine-Oxidized sp2-c-COF.
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DOI：
10.1021/acsami.8b14446
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发表时间：
2018-11
影响因子：
9.5
通讯作者：
Qiuju Zhang;M. Dai;H. Shao;Ziqi Tian;Yichao Lin;Liang Chen;X. Zeng
中科院分区：
文献类型：
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作者：
Qiuju Zhang;M. Dai;H. Shao;Ziqi Tian;Yichao Lin;Liang Chen;X. Zeng
最近的一项实验[金，E.；Science 2017,357,673-676]表明，经碘氧化处理后，二维(2D)碳杂化的π共价有机骨架(sp2-c-COF)的电导率可以提高多达12个数量级。为了理解电导率如此巨大增长的物理机制，我们进行了多尺度计算，发现碘氧化的2D COF的高电导率可以归因于2D COF中的空穴转移和离子转移。计算的价带最大值对应的主要电荷分布表明，离域的π电子主要出现在活性反应中心。计算的活性中心的低电离能进一步支持了二维COF在碘氧化过程中倾向于失去电子，生成阳离子COF和阴离子三碘离子I3-。互补经典分子动力学模拟表明，阴离子电导率较高，为13.63×10-2 S m-1，与实验测得的高电导率(7.1×10-2 S m-1)一致。同时，我们还发现，2DCOF中的阳离子还可以引起费米能级的位移，使空穴迁移率增加到86.75cm2·V~(-1)·S~(-1)。为了提出高导电性的高导电性二维SP2-c-COF的潜在应用，我们设计了一个二维螺旋绕线式锂离子电池的原型模型，发现它比典型的电解液材料表现出更高的稳定性。
A recent experiment [ Jin , E. ; Science 2017 , 357 , 673 - 676 ] shows that the conductivity of a two-dimensional (2D) sp2-carbon-hybridized π-conjugated covalent organic framework (sp2-c-COF) can be enhanced by as much as 12 orders of magnitude after iodine oxidation processing. To understand the physical mechanism underlying such a huge increase in the conductivity, we perform multiscale computations and find that the high conductivity of the iodine-oxidized 2D COF can be attributed to both hole transfer and ion transfer within the 2D COF. The computed dominant charge distribution corresponding to the valence band maximum (VBM) suggests that the delocalized π electrons occur mostly at the active reaction sites. The computed low ionization energy at the active reaction sites further supports that the 2D COF tends to lose electrons during iodine oxidation and to yield cationic COF and anionic triiodide I3-. Complementary classical molecular dynamics simulation shows a relatively high anion conductivity of 13.63 × 10-2 S m-1, consistent with the high conductivity measured from the experiment (7.1 × 10-2 S m-1). Meanwhile, we find that the cations in 2D COF can also induce a shift of the Fermi level to cross the valence band, thereby enhancing the hole mobility to 86.75 cm2 V-1 s-1. For proposing a potential application of the highly conductive iodine-oxidized 2D sp2-c-COF, we design a prototypical model of the 2D spirally wound lithium-ion battery and find that it exhibits enhanced stability than a typical electrolyte material.