Decomposition pathway for model fluorinated ethers on the clean iron surface

Polymeric perfluoroalkylethers (PFAE) are being considered for use as lubricants in high temperature applications, but in the presence of certain metals these molecules show enhanced decomposition. X-ray photoelectron spectroscopy (XPS) was used to explore the pathways for decomposition of three model fluorinated ethers on clean iron surfaces. The decomposition reaction, in vacuum, was observed to proceed at remarkably low temperatures, 155 K and below, via defluorination of the carbon-oxygen backbone, with formation of iron fluoride. The reactivity of iron toward perfluoroalkylether decomposition, when compared to other metals, is due to the strength of the iron fluoride bond. The remarkably low temperature threshold for the decomposition reflects a low activation barrier for C-F scission due to the strong electron donating ability of metallic iron.