Effect of the Platinum Mass Content in a Catalyst and the State of the Support Surface on the Path of the Oxygen Reduction Reaction in Alkaline Electrolyte

The effect of the support nature and the mass of platinum on the stability, electrochemical characteristics of monoplatinum catalysts, and the reaction path of electrochemical oxygen reduction in alkaline electrolyte is studied. Catalysts with the Pt mass content of 10, 20, 40, 60 wt % are synthesized by the polyol method on carbon nanotubes functionalized in NaOH and doped with nitrogen. The activity, the percentage of hydrogen peroxide formed, and the number of electrons participating in the oxygen reduction reaction are determined from the data obtained by the rotating ring-disk electrode method. For catalysts synthesized on the nitrogen-doped carbon nanotubes, the highest selectivity in the reaction of oxygen reduction to water is observed; the higher Pt surface area at the electrode, the greater is the selectivity, because the contribution of the support surface to the total oxygen reduction reaction decreased. Both the presence of hydrogen peroxide and a decrease in stability result from the decrease in the platinum content in the catalyst.