Polarization, passivation, intercalation, and generation: an examination of In-Situ and Ex-Situ analytical techniques for the study of carbon anode materials for the electrochemical generation of elemental fluorine.
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The field of industrial fluorine generation has not made significant progress in the past 60 years due to the difficulty and hazards surrounding the use of hydrofluoric acid (HF) and fluorine gas. This work examines various carbon materials for their use as electrodes in the electrochemical generation of elemental fluorine. An experimental apparatus was designed and constructed to melt and maintain the temperature of the KF·2HF electrolyte in a suitable range for electrochemical measurements. An electrochemical cell was designed and tested for operations in a highly corrosive atmosphere at elevated temperatures. The importance of safe operating procedures surrounding HF is outlined in this work. Various in-situ electrochemical techniques were used to study the ability of the different carbon anode materials in their ability to carry out the fluorine discharge reaction (FDR) as well as study the growth of passivating film. Ex-situ analytical techniques were used to examine the microstructure and composition of the carbon materials before and after electrochemical polarization. The results suggest that the level of non-carbon impurities had the most significant effect on the ability of the carbon material to carry out the FDR efficiently at most potentials tested. The results show that multiple analytical techniques are required to obtain a better understanding of a chemical system, and that no single method can be used to fully explain a single set of results.