Electrochemical oxidation of perfluorobutane sulfonate using boron-doped diamond film electrodes

This research investigated oxidation of perfluorobutane sulfonate (PFBS) at a boron-doped diamond (BDD) film anode. PFBS oxidation produced carbon dioxide, sulfate, fluoride, and trace amounts of trifluoroacetic acid (TFA). Rate constants for PFBS oxidation as a function of current density and temperature were measured using a rotating disk electrode (RDE) reactor. Reaction rates in the RDE reactor were zeroth order with respect to PFBS concentration, which is indicative of a reaction limited by the availability of reactive sites. The apparent electron transfer coefficient and apparent activation energy were used to evaluate the rate-limiting step for PFBS oxidation. Density functional simulations were used to calculate the reaction energies and activation barriers for PFBS oxidation by hydroxyl radicals and by direct electron transfer. Simulation results indicated that the experiments were performed at sufficiently high overpotentials that the rate-limiting step was an activationless direct electron transfer reaction.