Insights into the effect of the interlayer spacings of bilayer graphene on the desolvation of H+, Li+, Na+, and K+ ions with water as a solvent: a first-principles study
Insights into the effect of the interlayer spacings of bilayer graphene on the desolvation of H+, Li+, Na+, and K+ ions with water as a solvent: a first-principles study
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深入了解双层石墨烯的层间距对以水为溶剂的 H、Li、Na 和 K 离子去溶剂化的影响：第一性原理研究
DOI：
10.1039/c9cp02922b
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发表时间：
2019
影响因子：
3.3
通讯作者：
Shuwei Tang
中科院分区：
文献类型：
--
作者：
Xu Zhang;Shaobin Yang;Xueying Shan;Sinan Li;Shuwei Tang
离子的去溶效应在超级电容器的容量调节中起着重要的作用，发现后引起了人们的极大关注。本文用第一性原理计算了不同层间距(D)的双层石墨烯(BG)中离子、水和水合离子的反应能，并探讨了H+、Li+、Na+和K+离子的脱溶行为。计算结果表明，在AA堆积的BG中，H+只以H3O+的形式存在，而在AB堆积的BG中，H+只以H30+的形式存在。在AB堆积体系中，H+离子的完全退溶尺寸达到5.6？，这是所研究的四种离子中最大的退溶尺寸。随着离子半径的增大，Li+、Na+和K+在AA-和AB-堆积的BG层中的临界退溶尺寸急剧增加。然而，三种离子的完全退溶尺寸都在4-5ä范围内，并且随着离子半径的增加，完全退溶尺寸呈现相反的趋势。AB堆积BG中Na+的完全解溶尺寸略大于AA堆积BG。进一步的分析表明，H+、Li+、Na+和K+离子的离子半径对脱溶临界尺寸起主导作用。我们的结果为通过调整碳材料的孔结构来精确匹配孔结构和电解液来提高超级电容器的容量提供了有用的信息。
The desolvation effect of ions plays an important role in adjusting the capacity of supercapacitors and has attracted considerable attention after its discovery. Here, first-principles calculations were conducted to calculate the reaction energies of ions, water, and hydrated ions in bilayer graphene (BG) with different interlayer spacings (d) and to explore the desolvation behaviors of H+, Li+, Na+, and K+ ions. The calculated results showed that H+ can only exist in the state of H3O+ in AA-stacking BG, and desolvation exists only in the case of AB-stacking BG. The complete desolvation size for H+ ions in the AB-stacking system reached 5.6 Å, which was the largest desolvation size of the four ions studied. The critical desolvation sizes of Li+, Na+, and K+ in the BG layers of AA- and AB-stacking increased sharply as a consequence of the increasing ionic radius. However, the complete desolvation sizes of all three ions were in the range of 4–5 Å and with the increase in ionic radius, the complete desolvation sizes showed a reverse tendency. The complete desolvation size of Na+ in AB-stacking BG was slightly larger than that in AA-stacking BG. Further analysis presented that the ionic radii of H+, Li+, Na+, and K+ ions make a dominant contribution to the critical size of desolvation. Our present results provide useful information for improving the capacity of supercapacitors by precisely matching the pore structure and electrolyte through the adjustment of the pore structure of carbon materials.