Influence of the composition and preparation of the rotating disk electrode on the performance of mesoporous electrocatalysts in the alkaline oxygen reduction reaction

We report a systematic study of the influence of the composition and preparation method of the electrocatalyst layer deposited on the rotating (ring) disk electrodes (RDE/RRDE) employed in the alkaline oxygen reduction reaction (ORR). To investigate and rationalize the generally underestimated role of these factors on the ORR performance of mesoporous electrocatalysts, we studied the activity and selectivity of nitrogen-doped ordered mesoporous carbon as a function of the loading of electrocatalyst and of binder, of the type of binder, and of the addition order of the components onto the electrode. The use of an anion-exchange polymer (Fumion FAA-3®) as the binder instead of the commonly employed Nafion® increased the selectivity towards H2O2 and led to a lower kinetic current density. In addition, higher selectivity towards H2O was observed when increasing the loading of the catalyst and of the binder, although the latter resulted in a decreased kinetic current density. These results prove the crucial effect of the composition and preparation method of the layer deposited on the electrode on the ORR performance of the mesoporous electrocatalyst and can provide useful guidelines in view of the translation of the results of RDE studies to an alkaline fuel-cell setup.