Charging of a redox catalyst for O2 evolution

Heterogeneous catalysis in solution. Part 24.—Kinetics of a redox system exhibiting three separate diffusion-controlled regions: the iron(III)+ iodide reaction at a rotating platinum disc catalyst

“…In the work on the oxidation of water, whose concentration cannot of course be varied, the activation energies were found to be 17.2 kJ mol-' in 0.5 mol dm-3 H2S04 43 and 22 kJ mol-' in 1 mol dm-3 HClO, + 0.035 mol dm-' H,SO,. 42 In the latter medium, where the formal electrode potentials of the Ce4+/Ce3+ and O,/H,O couples are well separated, the rate was also independent of the Ce3+ concentration. Diffusion of Ce4+ ions to the catalyst surface was therefore thought to be the ratedetermining step.…”