Yazdanparast Sanaz, Soltanmohammad Sina, Fash-White Annika, Tucker Garritt J, Brennecka Geoff L
Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401, United States.
Department of Mechanical Engineering, Colorado School of Mines, Golden, Colorado 80401, United States.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):20129-20137. doi: 10.1021/acsami.0c03181. Epub 2020 Apr 15.
MXenes are emerging two-dimensional (2D) materials for energy-storage applications and supercapacitors. Their surface chemistry, which determines critical properties, varies due to different synthesis conditions. In this work, we synthesized TiVC solid-solution MXenes by two different synthesis methods and investigated their surface functional groups. We performed etching of the TiVAlC MAX phase using two different solutions, a highly concentrated HF (50 wt % ≈ 29 M) and a mixture of LiF and HCl (1.9 M LiF/12 M HCl). Large-scale delamination of TiVCT to produce single-flake suspension was achieved by further intercalation of the resultant MXene from LiF/HCl with tetrabutylammonium hydroxide (TBAOH). X-ray diffraction indicates a large interlayer spacing of 2.18 nm for TiVCT MXene flakes. To investigate the structural stability and adsorption energy of different functional groups on TiVC MXenes, density functional theory (DFT) calculations were performed and supported with X-ray photoelectron spectroscopy (XPS) measurements. A higher concentration of ═O and a lower concentration of -F were achieved on the TiVC synthesized by LiF/HCl, both of which provide a more favorable surface chemistry for energy-storage applications. Our results provide the first systematic study on the effect of synthesis conditions on the surface chemistry of solid-solution TiVC MXenes.
MXenes是用于能量存储应用和超级电容器的新兴二维（2D）材料。其决定关键性能的表面化学性质因合成条件不同而有所变化。在本工作中，我们通过两种不同的合成方法合成了TiVC固溶体MXenes，并研究了它们的表面官能团。我们使用两种不同的溶液对TiVAlC MAX相进行蚀刻，一种是高浓度的HF（50 wt%≈29 M），另一种是LiF和HCl的混合物（1.9 M LiF/12 M HCl）。通过用氢氧化四丁基铵（TBAOH）对由LiF/HCl所得的MXene进行进一步插层，实现了TiVCT的大规模分层以产生单片悬浮液。X射线衍射表明TiVCT MXene薄片的层间距为2.18 nm。为了研究不同官能团在TiVC MXenes上的结构稳定性和吸附能，进行了密度泛函理论（DFT）计算并用X射线光电子能谱（XPS）测量进行了佐证。通过LiF/HCl合成的TiVC上实现了更高浓度的═O和更低浓度的-F，这两者都为能量存储应用提供了更有利的表面化学性质。我们的结果首次对合成条件对固溶体TiVC MXenes表面化学性质的影响进行了系统研究。
