Lounasvuori Mailis, Zhang Teng, Gogotsi Yury, Petit Tristan
Nanoscale Solid-Liquid Interfaces, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany.
A.J. Drexel Nanomaterials Institute and Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States.
J Phys Chem C Nanomater Interfaces. 2024 Feb 14;128(7):2803-2813. doi: 10.1021/acs.jpcc.4c00247. eCollection 2024 Feb 22.
The local microenvironment has recently been found to play a major role in the electrocatalytic activity of nanomaterials. Modulating the microenvironment by adding alkali metal cations into the electrolyte can be used to either suppress hydrogen or oxygen evolution, thereby extending the electrochemical window of energy storage systems, or to tune the selectivity of electrocatalysts. MXenes are a large family of two-dimensional transition metal carbides, nitrides, and carbonitrides that have shown potential for use in electrochemical energy storage applications. Due to their negatively charged surfaces, MXenes can accommodate cations and water molecules between the layers. Nevertheless, the nature of the aqueous microenvironment in the MXene interlayer space is poorly understood. Here, we apply Fourier transform infrared spectroscopy (FTIR) to probe the hydrogen bonding of intercalated water in TiCT as a function of intercalated cation and relative humidity. Substantial changes in the FTIR spectra after cation exchange demonstrate that the hydrogen bonding of water molecules confined between the MXene layers is strongly cation-dependent. Furthermore, the IR absorbance of the confined water correlates with resistivity estimated by 4-point probe measurements and interlayer distance calculated from XRD patterns. This work demonstrates that cation intercalation strongly modulates the confined microenvironment, which can be used to tune the activity or selectivity of electrochemical reactions in the interlayer space of MXenes in the future.
最近发现，局部微环境在纳米材料的电催化活性中起着主要作用。通过向电解质中添加碱金属阳离子来调节微环境，可用于抑制析氢或析氧，从而扩展储能系统的电化学窗口，或调节电催化剂的选择性。MXenes是一大类二维过渡金属碳化物、氮化物和碳氮化物，已显示出在电化学储能应用中的潜力。由于其带负电的表面，MXenes可以在层间容纳阳离子和水分子。然而，人们对MXene层间空间中水性微环境的性质了解甚少。在这里，我们应用傅里叶变换红外光谱（FTIR）来探测TiCT中插层水的氢键，它是插层阳离子和相对湿度的函数。阳离子交换后FTIR光谱的显著变化表明，限制在MXene层间的水分子的氢键强烈依赖于阳离子。此外，受限水的红外吸光度与通过四点探针测量估计的电阻率以及根据XRD图谱计算的层间距离相关。这项工作表明，阳离子插层强烈调节受限微环境，未来可用于调节MXenes层间空间中电化学反应的活性或选择性。
