Electrocatalytic Measurement Methodology of Oxide Catalysts Using a Thin-Film Rotating Disk Electrode

Abstract

Transition-metal oxides can exhibit high electrocatalytic activity for reactions such as the oxygen reduction reaction (ORR) in alkaline media. It is often difficult to measure and compare the activities of oxide catalysts on either per mass or per surface area basis, because of the poorly defined oxygen transport to and within porous oxide electrodes of several tens of micrometers thickness. In this study, a methodology was developed to compare the ORR activities of submicrometer-sized transition-metal oxides. Thin films of LaNiO[subscript 3], LaCu[subscript 0.5]Mn[subscript 0.5]O[subscript 3], and La[subscript 0.75]Ca[subscript 0.25]FeO[subscript 3] oxide particles were bonded to glassy carbon via an ion-exchanged Nafion binder, and their mass and specific ORR activities were extracted from rotating disk electrode measurements. We found that the specific activity of LaNiO[subscript 3] was much higher than that of La[subscript 0.75]Ca[subscript 0.25]FeO[subscript 3] and LaCu[subscript 0.5]Mn[subscript 0.5]O[subscript 3]. The projection of LaNiO[subscript 3] in the actual fuel cell cathode was presented, which was shown to be competitive with current platinum-based cathodes.