Carbonation of Wollastonite(001) Competing Hydration: Microscopic Insights from Ion Spectroscopy and Density Functional Theory
Carbonation of Wollastonite(001) Competing Hydration: Microscopic Insights from Ion Spectroscopy and Density Functional Theory
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DOI：
10.1021/am508313g
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发表时间：
2015-03-04
影响因子：
9.5
通讯作者：
Thissen, Peter
中科院分区：
文献类型：
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作者：
Longo, Roberto C.;Cho, Kyeongjae;Thissen, Peter
本文报道了水的化学势对硅灰石(CaSiO_3)作为水泥和混凝土模型表面碳化反应的影响。基于密度泛函理论的总能量计算结合基于微动弹性带方法的动能垒预测表明，无水硅灰石表面暴露在CO2中导致了无障碍碳化。二氧化碳与表面的氧反应，形成碳酸盐(CO32-)络合物，并对表面进行重大重建。在形成一个碳酸盐单分子膜后，反应就停止了。如果一个水单分子层覆盖在硅灰石表面，碳化作用不再是无障碍的，但以局部单层结束。在多层水的覆盖下，由于金属-质子交换反应(也称为早期水化)，硅灰石的热力学基态完全改变，Ca~(2+)离子部分从固相中转移到H_2O/硅灰石界面。流动的Ca~(2+)与CO_2再次反应形成碳酸盐络合物，最终形成离域层。通过高分辨率飞行时间二次离子质谱图，我们证实了水合作用可以导致钙离子在硅灰石表面的部分离域。最后，我们通过低能离子散射光谱的意义，结合对碳化和水合的竞争反应的仔细讨论，评估了我们的模型表面结果的影响。
In this paper, we report about the influence of the chemical potential of water on the carbonation reaction of wollastonite (CaSiO3) as a model surface of cement and concrete. Total energy calculations based on density functional theory combined with kinetic barrier predictions based on nudge elastic band method show that the exposure of the water-free wollastonite surface to CO2 results in a barrier-less carbonation. CO2 reacts with the surface oxygen and forms carbonate (CO32-) complexes together with a major reconstruction of the surface. The reaction comes to a standstill after one carbonate monolayer has been formed. In case one water monolayer is covering the wollastonite surface, the carbonation is no more barrier-less, yet ending in a localized monolayer. Covered with multilayers of water, the thermodynamic ground state of the wollastonite completely changes due to a metal-proton exchange reaction (also called early stage hydration) and Ca2+ ions are partially removed from solid phase into the H2O/wollastonite interface. Mobile Ca2+ reacts again with CO2 and forms carbonate complexes, ending in a delocalized layer. By means of high-resolution time-of-flight secondary-ion mass spectrometry images, we confirm that hydration can lead to a partially delocalization of Ca2+ ions on wollastonite surfaces. Finally, we evaluate the impact of our model surface results by the meaning of low-energy ion-scattering spectroscopy combined with careful discussion about the competing reactions of carbonation vs hydration.