Brady Alexander, Liang Kun, Vuong Van Quan, Sacci Robert, Prenger Kaitlyn, Thompson Matt, Matsumoto Ray, Cummings Peter, Irle Stephan, Wang Hsiu-Wen, Naguib Michael
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, United States.
ACS Nano. 2021 Feb 23;15(2):2994-3003. doi: 10.1021/acsnano.0c09301. Epub 2021 Jan 29.
Layered titanium carbide (TiCT) MXene is a promising electrode material for use in next-generation electrochemical capacitors. However, the atomic-level information needed to correlate the distribution of intercalated cations with surface redox reactions, has not been investigated in detail. Herein we report on sodium preintercalated MXene with high sodium content (up to 2Na per TiCT formula) using a solution of Na-biphenyl radical anion complex ( ≈ -2.6 SHE). Multiple sodiation sites and formation of a two-dimensional sodium domain structure at interfaces/surfaces is identified through combined computational simulations with neutron pair distribution function analysis. The induced layer charges and the redox process characterized by the density-functional tight-binding method on a local scale are found to greatly depend on the location of sodium ions. Electrochemical testing of the pre-sodiated MXene as an electrode material in a sodium-ion capacitor shows excellent reversibility and promising performance, indicating the feasibility of chemical preintercalation as an approach to prepare MXene electrodes for ion capacitors.
层状碳化钛（TiCT）MXene是一种很有前景的电极材料，可用于下一代电化学电容器。然而，将插层阳离子的分布与表面氧化还原反应相关联所需的原子级信息尚未得到详细研究。在此，我们报道了使用Na-联苯自由基阴离子络合物溶液（≈ -2.6 SHE）制备的高钠含量（每个TiCT化学式高达2Na）的钠预插层MXene。通过结合计算模拟和中子对分布函数分析，确定了多个钠化位点以及在界面/表面形成的二维钠域结构。发现局部尺度上以密度泛函紧束缚方法表征的诱导层电荷和氧化还原过程在很大程度上取决于钠离子的位置。将预钠化的MXene作为钠离子电容器的电极材料进行电化学测试，显示出优异的可逆性和良好的性能，表明化学预插层作为一种制备用于离子电容器的MXene电极的方法是可行的。
