Iamprasertkun Pawin, Hirunpinyopas Wisit, Keerthi Ashok, Wang Bin, Radha Boya, Bissett Mark A, Dryfe Robert A W
School of Chemistry , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom.
National Graphene Institute , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom.
J Phys Chem Lett. 2019 Feb 7;10(3):617-623. doi: 10.1021/acs.jpclett.8b03523. Epub 2019 Jan 28.
Carbon materials are ubiquitous in energy storage; however, many of the fundamental electrochemical properties of carbons are still not fully understood. In this work, we studied the capacitance of highly ordered pyrolytic graphite (HOPG), with the aim of investigating specific ion effects seen in the capacitance of the basal plane and edge-oriented planes of the material. A series of alkali metal cations, from Li, Na, K, Rb, and Cs with chloride as the counterion, were used at a fixed electrolyte concentration. The basal plane capacitance at a fixed potential relative to the potential of zero charge was found to increase from 4.72 to 9.39 μF cm proceeding down Group 1. In contrast, the edge-orientated samples display capacitance ca. 100 times higher than those of the basal plane, attributed to pseudocapacitance processes associated with the presence of oxygen groups and largely independent of cation identity. This work improves understanding of capacitive properties of carbonaceous materials, leading to their continued development for use in energy storage.
碳材料在能量存储中无处不在；然而，碳的许多基本电化学性质仍未被完全理解。在这项工作中，我们研究了高度有序热解石墨（HOPG）的电容，旨在研究该材料基面和边缘取向平面电容中所观察到的特定离子效应。在固定的电解质浓度下，使用了一系列碱金属阳离子，包括Li、Na、K、Rb和Cs，并以氯离子作为抗衡离子。相对于零电荷电位，在固定电位下的基面电容随着第一主族元素的向下排列从4.72 μF/cm增加到9.39 μF/cm。相比之下，边缘取向的样品显示出的电容比基面电容高约100倍，这归因于与氧基团存在相关的赝电容过程，并且在很大程度上与阳离子种类无关。这项工作增进了对碳质材料电容特性的理解，推动了它们在能量存储领域的持续发展。
