High oxygen reduction (ORR) activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we prepare Pt nanoparticles with optimal size for the efficient ORR in proton-exchange-membrane fuel cells.O ptimal nanoparticle sizes are predicted near 1, 2, and 3nmb yc omputational screening.T oc orroborate our computational results,w eh ave addressed the challenge of approximately 1nms ized Pt nanoparticle synthesis with am etal-organic framework (MOF) template approach. The electrocatalyst was characterized by HR-TEM, XPS,a nd its ORR activity was measured using ar otating disk electrode setup.T he observed mass activities (0.87 AE 0.14 Amg Pt À1)a re close to the computational prediction (0.99 Amg Pt À1 ). We report the highest to date mass activity among pure Pt catalysts for the ORR within similar sizerange.The specific and mass activities are twice as high as the Tanaka commercial Pt/C catalysis.

The generation and matrix stabilization of ligand-free, small platinum nanoclusters (NCs) Pt12±x is presented. The metal–organic framework-template approach is based on encapsulating CO-ligated, atom-precise Pt9 Chini clusters [{Pt3(CO)6}3]2– into the zeolitic imidazolate framework ZIF-8. The selective formation of the air-stable inclusion compound [NBu4]2[{Pt3(CO)6}4]@ZIF-8 of defined atomicity Pt12 and with Pt loadings of 1–20 wt % was monitored by UV/vis and IR spectroscopy and was confirmed by high-resolution transmission electron microscopy (HR-TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (PXRD). Thermally induced decarbonylation at 200 °C yields the composite material Pt n @ZIF-8 with a cluster atomicity n close to 12, irrespective of the Pt loading. The PtNCs retain their size even during annealing at 300 °C for 24 h and during catalytic hydrogenation of 1-hexene at 25 °C in the liquid phase. The Pt n @ZIF-8 material can conveniently be used for storing small PtNCs and their further processing. Removal of the protective ZIF-8 matrix under acidic conditions and transfer of the PtNCs to carbon substrates yields defined aggregation to small Pt nanoparticles (1.14 ± 0.35 nm, HR-TEM), which have previously shown exceptional performance in the electrocatalytic oxygen reduction reaction (ORR).

Eine Aktivitätserhçhung der Sauerstoffreduktion (ORR) gilt als der Schlüssel zu zahlreichen Energieanwendungen. Durch die Kombination von Theorie und Experiment werden Pt-Nanopartikel mit optimaler Grçße fürdie effiziente ORR in Protonenaustauschmembran-Brennstoffzellen hergestellt. Optimale Nanopartikelgrçßen werden durchr echnergestütztes Screening in der Nähe von 1, 2und 3nmvorhergesagt. Um die Ergebnisse der Rechnungen zu bestätigen, synthetisierten wir ca. 1nmg roße Pt-Nanopartikel mit einem Templatansatz basierend auf Metall-organischen Gerüsten. Der Elektrokatalysator wurde durch HR-TEM und XPS charakterisiert, und seine Aktivitäti nd er ORR wurdeu nter Verwendung einer rotierenden Scheibenelektrode gemessen. Die beobachtete Massenaktivitätl iegt nahe an der rechnerischen Vorhersage.W ir verzeichnen die aktuell hçchste Massenaktivitätu nter reinen Pt-Katalysatoren fürd ie ORR im vergleichbaren Grçßenbereich. Die Massen-sowie die spezifische Aktivitätw aren zweimal so hochw ie die des kommerziellen Tanaka-Katalysators.