First-Principles Study of the Degradation of Perfluorooctanesulfonate and Perfluorobutanesulfonate on a Magnéli Phase Ti4O7 Anode,ACS ES&T Water

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First-Principles Study of the Degradation of Perfluorooctanesulfonate and Perfluorobutanesulfonate on a Magnéli Phase Ti4O7 Anode
ACS ES&T Water ( IF 4.8 ) Pub Date : 2021-07-28 , DOI: 10.1021/acsestwater.1c00086
Lei Li ₁ , Yaye Wang ₁ , Qingguo Huang ₁

Affiliation

The anodic degradation of perfluorooctanesulfonate (PFOS) and perfluorobutanesulfonate (PFBS) on a Magnéli phase titanium suboxide (Ti₄O₇) surface was investigated via density functional theory simulations. The adsorption energy on the Ti₄O₇ cluster surface decreases in the following order: OH^• > C₄F₉SO₃^– (PFBS^–) ∼ C₈F₁₇SO₃^– (PFOS^–) > H₂O. This suggests that OH^• formed from water oxidation strongly adsorbs on the Ti₄O₇ cluster surface. C₈F₁₇SO₃^– and C₄F₉SO₃^– adsorbed on a model of an OH^•-bound Ti₄O₇ cluster [Ti₄O₇(OH)] were examined computationally in response to different anodic potentials that were simulated by varying the number of added background charges. This indicates a gradual loss of one electron from C₈F₁₇SO₃^– and C₄F₉SO₃^– as the background charges increase on Ti₄O₇(OH). This is accompanied by elongation and eventual breakage of the C–S bond in PFOS and PFBS. The conversion from C₈F₁₇SO₃^– to C₈F₁₇SO₃^• by direct electron transfer involves the largest barrier energy (1.21 eV) in the process of PFOS degradation, while the breakage of the C–S bond in C₄F₉SO₃^• is the rate-limiting step of PFBS^– degradation (1.49 eV). The first-principles computation here in combination with experimental measurements elucidated the elementary steps involved in the degradation of perfluoroalkyl acids (PFAAs) on a Ti₄O₇ anode and its dependence on the molecular structures of PFAAs.

中文翻译：

全氟辛烷磺酸和全氟丁烷磺酸在 Magnéli 相 Ti4O7 阳极上降解的第一性原理研究

通过密度泛函理论模拟研究了全氟辛烷磺酸 (PFOS) 和全氟丁烷磺酸 (PFBS) 在 Magnéli 相低氧化钛 (Ti ₄ O ₇ ) 表面上的阳极降解。Ti ₄ O ₇簇表面的吸附能按以下顺序降低：OH ^• > C ₄ F ₉ SO ₃^– (PFBS ^– ) ∼ C ₈ F ₁₇ SO ₃^– (PFOS ^– ) > H ₂ O。这表明由水氧化形成的OH ^•强烈吸附在 Ti 上₄ O ₇簇表面。C ₈ F ₁₇ SO ₃^–和 C ₄ F ₉ SO ₃^–吸附在一个 OH ^•结合的 Ti ₄ O ₇簇 [Ti ₄ O ₇ (OH)] 的模型上，以响应不同的阳极电位进行计算检查通过改变添加的背景电荷的数量来模拟。这表明 C ₈ F ₁₇ SO ₃^–和 C ₄ F ₉ SO ₃^–逐渐失去一个电子随着 Ti ₄ O ₇ (OH)上的背景电荷增加。这伴随着 PFOS 和 PFBS 中 C-S 键的伸长和最终断裂。^•通过直接电子转移从 C ₈ F ₁₇ SO ₃^–转化为 C ₈ F ₁₇ SO ₃^•在全氟辛烷磺酸降解过程中涉及最大的势垒能（1.21 eV），而 C _{4 中}C-S 键的断裂F ₉ SO ₃^•是 PFBS 的限速步骤^–退化 (1.49 eV)。此处的第一性原理计算与实验测量相结合，阐明了在 Ti ₄ O ₇阳极上降解全氟烷基酸 (PFAA) 所涉及的基本步骤及其对 PFAA 分子结构的依赖性。

更新日期：2021-08-13

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