High oxygen reduction activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we fabricate Pt nanoparticles with optimal size for the efficient oxygen reduction reaction (ORR) in proton‐exchange‐membrane fuel cells. Optimal nanoparticle sizes are predicted near ~1, 2, and 3 nm by computational screening. To corroborate our computational results, we have addressed the challenge of ~1 nm sized Pt nanoparticle synthesis with a metal‐organic framework template approach. The electrocatalyst was characterized by high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy and its ORR activity was measured using a rotating disk electrode setup. The observed mass activities (0.87±0.14 A/mgPt) are close to the computational prediction (0.99 A/mgPt). We report the highest up to date mass activity among pure Pt catalysts for the ORR within similar size range. The specific (1.49 mA/cm2) and mass activities were twice as high as the Tanaka commercial Pt/C (0.61 mA/cm2 and 0.42 A/mgPt).     «

High oxygen reduction activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we fabricate Pt nanoparticles with optimal size for the efficient oxygen reduction reaction (ORR) in proton‐exchange‐membrane fuel cells. Optimal nanoparticle sizes are predicted near ~1, 2, and 3 nm by computational screening. To corroborate our computational results, we have addressed the challenge of ~1 nm sized Pt nanoparticle synthesis with a m...     »