α-Al2O3(0001) 表面的结构和反应性：Al-I 和类三水铝石端接如何相互转换？,The Journal of Physical Chemistry C

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α-Al2O3(0001) 表面的结构和反应性：Al-I 和类三水铝石端接如何相互转换？
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2022-07-28 , DOI: 10.1021/acs.jpcc.2c03743
Yanhua Yue ₁ , Giacomo Melani ₂ , Harald Kirsch ₁ , Alexander Paarmann ₁ , Peter Saalfrank ₂ , R. Kramer Campen _{1,

3} , Yujin Tong _{1,

3}

Affiliation

α-Al ₂ O ₃ (0001) 表面因其在基础研究和应用中的重要性而被广泛研究。先前的工作表明，在超高真空 (UHV) 中，在没有水的情况下，所谓的 Al-I 终端在热力学上是有利的，而在环境中，与液态水接触，会产生类似三水铝石的层。而从α-Al ₂ O ₃ (0001)/H ₂O(l) 界面在理论上看起来相对清晰，该系统的实验表征导致了表面酸度的估计，即等电点，其相差 4 个 pH 单位和在一些报告中具有非氢键表面铝醇的表面结构(Al-OH) 基团和其他基团没有。在这项研究中，我们采用振动和频谱 (VSFS) 和密度泛函理论 (DFT) 模拟来研究UHV 和环境中不同端接的 α-Al ₂ O ₃ (0001) 表面的表面声子模式。我们发现，无论是在 UHV 中对 Al-I 进行加水，还是在环境中对三水铝石样进行热诱导脱羟基，表面都不会相互转换。这一观察结果为先前关于 α-Al ₂ O ₃ (0001)/液态水界面的工作中的分歧提供了新的解释——不同的制备方法可能会产生不相互转换的表面——并表明表面声子光谱响应提供了一种新的探针界面氢键结构。

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Structure and Reactivity of α-Al2O3(0001) Surfaces: How Do Al–I and Gibbsite-like Terminations Interconvert?

The α-Al₂O₃(0001) surface has been extensively studied because of its significance in both fundamental research and application. Prior work suggests that in ultra-high-vacuum (UHV), in the absence of water, the so-called Al–I termination is thermodynamically favored, while in ambient, in contact with liquid water, a Gibbsite-like layer is created. While the view of the α-Al₂O₃(0001)/H₂O(l) interface appears relatively clear in theory, experimental characterization of this system has resulted in estimates of surface acidity, i.e., isoelectric points, that differ by 4 pH units and surface structure that in some reports has non-hydrogen-bonded surface aluminol (Al–OH) groups and in others does not. In this study, we employed vibrational sum frequency spectroscopy (VSFS) and density functional theory (DFT) simulation to study the surface phonon modes of the differently terminated α-Al₂O₃(0001) surfaces in both UHV and ambient. We find that, on either water dosing of the Al–I in UHV or heat-induced dehydroxylation of the Gibbsite-like in ambient, the surfaces do not interconvert. This observation offers a new explanation for disagreements in prior work on the α-Al₂O₃(0001)/liquid water interface─different preparation methods may create surfaces that do not interconvert─and shows that the surface phonon spectral response offers a novel probe of interfacial hydrogen bonding structure.

更新日期：2022-07-28

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