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.