活性氧化镁基水泥中MgO和Mg（OH）2的水化和碳酸化机理探讨
Exploring Mechanisms of Hydration and Carbonation of MgO and Mg(OH)2 in Reactive Magnesium Oxide-based Cements
摘要：
活性氧化镁（MgO）基水泥（RMC）可以在碳捕获过程中发挥关键作用。然而，知识的驱动力，控制程度的碳酸化和水化和反应速率在这个系统中仍然有限。在这项工作中，密度泛函理论为基础的模拟被用来调查在环境条件下的RMCs的制造过程中发生的反应的物理性质。参数指标，如吸附能，电荷转移，电子局域化功能，吸附/解离能垒和H2O和CO2分子与MgO和水镁石（Mg（OH）2）团簇的相互作用机制被认为是。评价以下与RMC相关的水合和碳酸化相互作用：i）MgO的碳酸化，ii）MgO的水合，水合MgO的碳酸化，iii）Mg（OH）2的碳酸化，iv）Mg（OH）2的水合和v）碳酸化Mg（OH）2的水合。这些机制的能垒和反应途径的比较表明，MgO的碳酸化是阻碍了H2O分子的存在，而Mg（OH）2的碳酸化是阻碍了初始碳酸盐和水合物层的形成，以及过量的H2O分子的存在。为了将这些发现与大块矿物表面进行比较，研究了CO2和H2O分子与MgO（001）和Mg（OH）2（001）表面的相互作用。因此，这项工作对水合碳酸镁生产中涉及的反应的物理性质和机制提出了深刻的见解，这可能有利于其发展。
英文摘要：
Reactive magnesium oxide (MgO)-based cement (RMC) can play a key role in carbon capture processes. However, knowledge on the driving forces that control the degree of carbonation and hydration and rate of reactions in this system remains limited. In this work, density functional theory-based simulations are used to investigate the physical nature of the reactions taking place during the fabrication of RMCs under ambient conditions. Parametric indicators such as adsorption energies, charge transfer, electron localization function, adsorption/dissociation energy barriers and the mechanisms of interaction of H2O and CO2 molecules with MgO and brucite (Mg(OH)2) clusters are considered. The following hydration and carbonation interactions relevant to RMCs are evaluated i) carbonation of MgO, ii) hydration of MgO, carbonation of hydrated MgO, iii) carbonation of Mg(OH)2, iv) hydration of Mg(OH)2 and v) hydration of carbonated Mg(OH)2. A comparison of the energy barriers and reaction pathways of these mechanisms shows that the carbonation of MgO is hindered by presence of H2O molecules, while the carbonation of Mg(OH)2 is hindered by the formation of initial carbonate and hydrate layers as well as presence of excessed H2O molecules. To compare these finding to bulk mineral surfaces, the interactions of the CO2 and H2O molecules with the MgO(001) and Mg(OH)2 (001) surfaces are studied. Therefore, this work presents deep insights into the physical nature of the reactions and the mechanisms involved in hydrated magnesium carbonates production that can be beneficial for its development.
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