Activation Parameters for Oxygen Reduction Kinetics in Trifluoromethane Sulfonic Acid Systems

The kinetics of electroreduction on Pt in concentrated trifluoromethane sulfonic acid (TFMSA) have been investigated at elevated temperatures up to ∼90°C, using microelectrode technique, and the results compared with those previously obtained by similar measurements in concentrated . The activation energies for the reaction in ∼9.5M, 6.0M, and 3.0M TFMSA were, respectively, 17 kJ mol−1, 20 kJ mol−1, and 29 kJ mol−1, as compared to the value of ∼66 kJ mol−1 in 98 weight percent (w/o) . The exchange current densities and the diffusion‐limiting current densities in concentrated TFMSA solutions were, respectively, three and two orders of magnitude higher than the corresponding quantities obtained in 98 w/o . The solubilities and diffusion coefficients of in TFMSA solutions have been evaluated, and their role in the current‐potential behavior for reduction in these electrolytes is discussed.