Capacitive versus Pseudocapacitive Storage in MXene
Capacitive versus Pseudocapacitive Storage in MXene
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DOI：
10.1002/adfm.202000820
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发表时间：
2020-05-08
影响因子：
19
通讯作者：
Otani, Minoru
中科院分区：
文献类型：
--
作者：
Ando, Yasunobu;Okubo, Masashi;Otani, Minoru
电化学电容器中的MXene电极具有独特的行为，即根据电解液的不同，同时具有电容和伪电容的行为。在这项工作中，为了更好地了解它们的电化学机理，采用了基于密度泛函理论和隐式溶剂化模型的第一性原理计算(称为3D参考相互作用位模型)。从它们的电子态来看，水化壳层阻止了MXene与插层离子之间的轨道耦合，从而导致了双电层的形成和电容行为。然而，一旦阳离子被部分脱水并吸附到Mxene表面，由于阳离子状态与Mxene状态的轨道耦合，特别是对于表面端基，发生电荷转移并导致假电容行为。
MXene electrodes in electrochemical capacitors have a distinctive behavior that is both capacitive and pseudocapacitive depending on the electrolyte. In this work, to better understand their electrochemical mechanism, first-principles calculations based on the density functional theory combined with the implicit solvation model are used (termed as 3D reference-interaction-site model). From the viewpoint of their electronic states, the hydration shell prevents orbital coupling between MXene and the intercalated ions, which leads to the formation of an electric-double layer and capacitive behavior. However, once the cations are partially dehydrated and adsorbed onto the MXene surface, because of orbital coupling of the cation states with the MXene states, particularly for surface-termination groups, charge transfer occurs and results in a pseudocapacitive behavior.