Hydration of Hexafluoroacetone on Ice

We unravel the fate of hexafluoroacetone (HFA), a PFAS
degradation
product, on ice by combining surface science and DFT. Temperature-programmed
desorption (TPD) and X-ray photoelectron spectroscopy (XPS) experimentally
show that HFA diffuses into the ice film and readily and completely
reacts to form the diol (1,1,1,3,3,3-hexafluoropropane-2,2-diol).
Desorption energies were measured for HFA from the underlying substrate
(Pt(111)) for the desorption of the ice film and for the diol as 44,
52, and 62 kJ/mol, respectively. Calculations show that the formation
of the diol is favorable on the ice surface by at least 29 kJ/mol.
This study is fundamental to better understand the reactivity of HFA
on ice in atmospheric conditions since it clearly demonstrates that
the diol will dominate reactivity with ice in the environment.

本研究结合表面科学与密度泛函理论（Density Functional Theory, DFT），阐明了全氟和多氟烷基物质（Per- and Polyfluoroalkyl Substances, PFAS）的降解产物六氟丙酮（hexafluoroacetone, HFA）在冰面的归趋。程序升温脱附（Temperature-programmed desorption, TPD）与X射线光电子能谱（X-ray photoelectron spectroscopy, XPS）实验结果显示，HFA可扩散进入冰膜，并快速完全反应生成二醇产物1,1,1,3,3,3-六氟丙烷-2,2-二醇（1,1,1,3,3,3-hexafluoropropane-2,2-diol）。本研究分别测得HFA从基底铂(111)晶面脱附、冰膜脱附以及该二醇脱附的脱附能依次为44、52和62 kJ/mol。计算结果表明，冰表面生成该二醇的反应热力学优势至少为29 kJ/mol。本研究明确了环境中冰面介导的反应以该二醇为主导，可为深入理解大气条件下HFA在冰面的反应活性提供重要基础支撑。