量热法测定MAX和MXene相的热力学稳定性,The Journal of Physical Chemistry C

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量热法测定MAX和MXene相的热力学稳定性
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-12-05 00:00:00 , DOI: 10.1021/acs.jpcc.6b10241
Geetu Sharma ₁ , Michael Naguib ₂ , Dawei Feng ₁ , Yury Gogotsi ₃ , Alexandra Navrotsky ₁

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MXenes是具有令人兴奋特性的分层二维材料，可用于多种能源应用。它们通过浸提从陶瓷（MAX相）中衍生而来，其性能反映出它们所形成的复杂组成，包括嵌入的阳离子，阴离子和水。它们的热力学稳定性可能与这些官能团有关，但尚未通过定量实验测量得到解决。我们报告了在25°C时元素的焓，这些元素是使用高温氧化物熔融溶液量热法对分层的Ti–Al–C MAX相和相应的基于Ti–C的MXene测量的。Ti ₃ C ₂ T _x MXene（T _x代表阴离子表面部分，并通过计算MAX相（理想组成Ti ₃ AlC ₂）形成MXene的反应焓来评估嵌入的阳离子。反应的极高的放热焓证实了MXene在水性环境中的稳定性。化学吸附在表面上并插入中间层中的表面末端（O，OH和F）和阳离子（Li）在MXene的热力学稳定中起主要作用。这些发现通过表征在合成过程中以及在储能，水脱盐和其他应用中与MXene表面结合的物种的能量特征，有助于理解并潜在地改善性能和性能。

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Calorimetric Determination of Thermodynamic Stability of MAX and MXene Phases

MXenes are layered two-dimensional materials with exciting properties useful to a wide range of energy applications. They are derived from ceramics (MAX phases) by leaching, and their properties reflect their resulting complex compositions which include intercalating cations and anions and water. Their thermodynamic stability is likely linked to these functional groups but has not yet been addressed by quantitative experimental measurements. We report enthalpies of formation from the elements at 25 °C measured using high temperature oxide melt solution calorimetry for a layered Ti–Al–C MAX phase, and the corresponding Ti–C based MXene. The thermodynamic stability of the Ti₃C₂T_x MXene (T_x stands for anionic surface moieties, and intercalated cations) was assessed by calculating the enthalpy of reaction of the MAX phase (ideal composition Ti₃AlC₂) to form MXene. The very exothermic enthalpy of reaction confirms the stability of MXene in an aqueous environment. The surface terminations (O, OH, and F) and cations (Li) chemisorbed on the surface and intercalated in the interlayers play a major role in the thermodynamic stabilization of MXene. These findings help in understanding and potentially improving properties and performance by characterizing the energetics of species binding to MXene surfaces during synthesis and in energy storage, water desalination, and other applications.

更新日期：2016-12-05

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