Institute for Soil Research, University of Natural Resources and Life Sciences , Peter-Jordan-Strasse 82, A-1190 Vienna, Austria.
School of Pharmaceutical Sciences and Technology, Tianjin University , Tianjin 300072, P. R. China.
ACS Appl Mater Interfaces. 2017 Jul 19;9(28):24290-24297. doi: 10.1021/acsami.7b05372. Epub 2017 Jul 7.
Density functional theory (DFT) calculations were performed to examine exothermic surface chemistry between alumina and four fluorinated, fragmented molecules representing species from decomposing fluoropolymers: F, HF, CHF, and CF. The analysis has strong implications for the reactivity of aluminum (Al) particles passivated by an alumina shell. It was hypothesized that the alumina surface structure could be transformed due to hydrogen bonding effects from the environment that promote surface reactions with fluorinated species. In this study, the alumina surface was analyzed using model clusters as isolated systems embedded in a polar environment (i.e., acetone). The conductor-like screening model (COSMO) was used to mimic environmental effects on the alumina surface. Four defect models for specific active -OH sites were investigated including two terminal hydroxyl groups and two hydroxyl bridge groups. Reactions involving terminal bonds produce more energy than bridge bonds. Also, surface exothermic reactions between terminal -OH bonds and fluorinated species produce energy in decreasing order with the following reactant species: CF > HF > CHF. Additionally, experiments were performed on aluminum powders using thermal equilibrium analysis techniques that complement the calculations. Consistently, the experimental results show a linear relationship between surface exothermic reactions and the main fluorination reaction for Al powders. These results connect molecular level reaction kinetics to macroscopic measurements of surface energy and show that optimizing energy available in surface reactions linearly correlates to maximizing energy in the main reaction.
采用密度泛函理论（DFT）计算研究了氧化铝与四种代表分解氟聚合物的碎片氟化物之间的放热表面化学：F、HF、CHF 和 CF。该分析对被氧化铝壳钝化的铝（Al）颗粒的反应性有很强的影响。假设氧化铝表面结构可能由于环境中的氢键效应而发生转变，从而促进与氟化物物种的表面反应。在这项研究中，使用模型簇作为孤立系统嵌入在极性环境（即丙酮）中，分析氧化铝表面。使用导体相似屏蔽模型（COSMO）模拟环境对氧化铝表面的影响。研究了四种特定活性 -OH 位点的缺陷模型，包括两个末端羟基和两个羟基桥基团。涉及末端键的反应比桥键产生更多的能量。此外，末端 -OH 键与氟化物物种之间的表面放热反应产生的能量按以下反应物的顺序递减：CF > HF > CHF。此外，使用热平衡分析技术对铝粉进行了实验，这些实验补充了计算。一致地，实验结果表明铝粉表面放热反应与主要氟化反应之间存在线性关系。这些结果将分子水平的反应动力学与表面能的宏观测量联系起来，并表明优化表面反应中可用的能量与最大化主要反应中的能量呈线性相关。
