The effect of particle proximity on the oxygen reduction rate of size-selected platinum clusters

Abstract

The diminished surface-area-normalized catalytic activity of highly dispersed Pt nanoparticles compared with bulk Pt is particularly intricate, and not yet understood. Here we report on the oxygen reduction reaction (ORR) activity of well-defined, size-selected Pt nanoclusters; a unique approach that allows precise control of both the cluster size and coverage, independently. Our investigations reveal that size-selected Pt nanoclusters can reach extraordinarily high ORR activities, especially in terms of mass-normalized activity, if deposited at high coverage on a glassy carbon substrate. It is observed that the Pt cluster coverage, and hence the interparticle distance, decisively influence the observed catalytic activity and that closely packed assemblies of Pt clusters approach the surface activity of bulk Pt. Our results open up new strategies for the design of catalyst materials that circumvent the detrimental dispersion effect, and may eventually allow the full electrocatalytic potential of Pt nanoclusters to be realized.

Application of Au–Cu nanowires fabricated by laser ablation in superfluid helium as catalysts for CO oxidation

“…Unlike the reference catalysts (Figs. 3, 4, and 5), all the particles in these chains are as close as possible to one another, which facilitate the positive role in the reaction of different particles mutual interaction already observed in [36].…”

Oxygen Reduction Reaction Catalyzed by Noble Metal Clusters

“…Such performance variation between the Pt nanoparticles and ultra-small Pt clusters was further verified by Angelopoulos' group, who observed mass activities of about 48 A/g for the single crystals and 74 A/g for the atomic clusters with less than 20 Pt atoms [49]. In 2013, a particle proximity effect for ORR was discovered by Arenz's group [78]. In this study, three different Pt nanocluster sizes were investigated, and the specific activity (SA) and mass activity are presented in Figure 1a,b.…”

“…That is, when the edge-to-edge interparticle distance is sufficiently small, ORR activities approaching the bulk Pt surface can be achieved for Pt clusters (Pt >46 ). As a result, mass activity on Pt clusters up to six-times that of Pt/C catalysts was obtained [78]. Interestingly, such performance variation is also reflected in the change of the reaction mechanism, which can be experimentally extrapolated from the Tafel plots.…”

“…Surprisingly, no apparent correlation between the SA and nanocluster size is observed, and Pt >46 , but not Pt 20 , exhibits the highest activity. This is because even Pt 20 is extremely small, so the number of adsorption sites is relatively low [78]. Figure 1c shows that the measured SA value depends on the edge-to-edge distance.…”

The colloidal tool-box approach for fuel cell catalysts: Systematic study of perfluorosulfonate-ionomer impregnation and Pt loading

“…We proposed the increase in SA with increasing Pt wt.% as a result of the so-called particle proximity effect, i.e. by lowering the interparticle distance between neighboring particles an increase in SA for ORR can be observed [20,41].…”