Reactions catalyzed by supported metals are deemed structure sensitive if the reaction rate, normalized by exposed surface site, varies with the average size of the metal particles. That is the case for the title reaction, as was shown three decades ago by Peuckert, et al., who noted that the turnover rate per exposed Pt for oxygen reduction by Pt/C cathodes decreased by a factor of 20 as the particle size of the Pt particles decreased from 4 nm to less than 1 nm. However, when the population of surface sites is attributed to a Rayleigh distribution of particle sizes, the turnover rate appears constant when normalized to the number of sites that vary roughly with the square of particle diameter, e.g., basal (1 1 1) sites. The reanalysis emphasizes the importance of reporting the particle size distribution in addition to the mean particle size.

Structure sensitivity of the electrochemical reduction of oxygen revisited

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