期刊
ACS APPLIED MATERIALS & INTERFACES
卷 9, 期 28, 页码 24290-24297出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b05372
关键词
DFT calculations; modified alumina structures; implicit solvent model; alumina; catalysis; fluoropolymer reactions; aluminum combustion; fluorides
资金
- Army Research Office [W911NF-14-1-0250]
- Robert Welch Foundation [D-0005]
- Vienna Scientific Cluster [70544]
- NSF Major Research Instrumentation Program Award [0421032]
- Div Of Biological Infrastructure
- Direct For Biological Sciences [0421032] Funding Source: National Science Foundation
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, CH3F, and CF4. 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: CF4 > HF > CH3F. 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.
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