Fundamental studies of electrochemical fluorination

Progress toward gaining a better understanding of fundamental aspects of Simons electrochemical fluorination (ECF), including the nature of the electrocatalytic interface and detailed mechanistic pathways, has been significantly hampered by difficulties associated with the safe handling and high reactivity of anhydrous hydrogen fluoride (AHF), the hazardous medium in which this important technological process is carried out.; Novel procedures were developed and implemented in this laboratory, which allow specimens to be exposed to AHF environments in an auxiliary ultrahigh vacuum (UHV) compatible chamber.; Electrochemical fluorination of hexafluorobutanol (HFB) in AHF has been carried out on clean Ni surfaces characterized by X-ray photoelectron spectroscopy (XPS) and transferred to the electrochemical cell without exposure to the ambient atmosphere. Perfluorobutyryl fluoride (PBF), the expected electrofluorination product, was detected with a quadrupole mass spectrometer attached directly to an ECF UHV-compatible chamber. Subsequent XPS/depth profiling analysis of Ni anode surfaces revealed the formation of a NiF₂ layer of a thickness varying between 15 and ca. 200 monolayers.; XPS and electrochemistry were used in combination to examine the behavior of clean and oxidized copper surfaces in HFB/AHF solutions. After exposure of oxidized Cu surfaces to pure liquid AHF, no oxygen could be detected in the XPS spectra indicating that fluorine replaces oxygen quantitatively in the film. Much thicker layers of CuF₂ were observed for Cu surfaces polarized in HFB/AHF electrolytes at potentials positive to the prominent peak found in the voltammetry. Within experimental error, the potential of zero current for Cu in HFB/AHF as measured vs. a formal Cu/CuF₂ reference electrode in voltammetric measurements was found to be 0 V, supporting the view that the Cu/CuF₂ redox couple is indeed responsible for controlling the potential of the reference electrode.; Finally, comparative cyclic voltammetry and XPS studies examined fundamental aspects of the electrochemistry of clean Ni, Au, Ag and Pt in AHF/HFB.