Homogeneous alloy nanoparticles as excellent catalysts. Spherical polyelectrolyte brushes can be used to generate Au‐Pt alloy nanoparticles (see figure) that exhibit properties widely differing from the properties of the respective bulk alloys. The alloy nanoparticles are shown to be homogeneous solid solutions. Moreover, they are effective catalysts for the selective oxidation of alcohols to aldehydes and ketones.

The gas-phase loading of [Zn(4)O(btb)(2)](8) (MOF-177; H(3)btb=1,3,5-benzenetribenzoic acid) with the volatile platinum precursor [Me(3)PtCp'] (Cp'=methylcyclopentadienyl) was confirmed by solid state (13)C magic angle spinning (MAS)-NMR spectroscopy. Subsequent reduction of the inclusion compound [Me(3)PtCp'](4)@MOF-177 by hydrogen at 100 bar and 100 degrees C for 24 h was carried out and gave rise to the formation of platinum nanoparticles in a size regime of 2-5 nm embedded in the unchanged MOF-177 host lattice as confirmed by transmission electron microscopy (TEM) micrographs and powder X-ray diffraction (PXRD). The room-temperature hydrogen adsorption of Pt@MOF-177 has been followed in a gravimetric fashion (magnetic suspension balance) and shows almost 2.5 wt % in the first cycle, but is decreased down to 0.5 wt % in consecutive cycles. The catalytic activity of Pt@MOF-177 towards the solvent- and base-free room temperature oxidation of alcohols in air has been tested and shows Pt@MOF-177 to be an efficient catalyst in the oxidation of alcohols.

Thermosensitive core-shell microgels can be used as ''nanoreactors'' for the immobilization of metal nanoparticles. The microgels consist of a polystyrene core and a network made of poly(Nisopropylacrylamide) (PNIPA) cross-linked by N,N 0 -methylenebisacrylamide. The cross-linked PNIPA shell undergoes a volume transition at around 30 C in which most of the water is expelled. The microgel particles exhibit a weak positive charge due to the cationic initiator. Metal nanoparticles (such as Au, Rh and Pt) with high catalytic activity can be homogeneously embedded into such a network. The oxidation of alcohols to the corresponding aldehydes or ketones has been chosen as a test reaction to probe the catalytic activity of such metal-microgel nanocomposite particles

Model Pt(n)/glassy carbon electrodes (Pt(n)/GCE) were prepared by deposition of mass-selected Pt(n)(+) (n ≤ 11) on GCE substrates in ultrahigh vacuum. Electrocatalysis under conditions appropriate for the oxygen reduction reaction (ORR) was studied, for samples both in situ with no exposure to laboratory air and with air exposure prior to electrochemical measurements. Of the small clusters, only a few cluster sizes show the expected ORR activity, and in those cases, the activity per Pt atom is similar to that seen under identical conditions with a conventionally prepared electrode with Pt nanoparticles grown on a GCE. For other small Pt(n) on GCE, any ORR signal is overwhelmed by large oxidative currents attributed to catalysis of carbon oxidation by water. If the samples are exposed to air prior to electrochemistry, both ORR and carbon oxidation signals are absent, and instead only small capacitive currents or currents attributed to redox chemistry of adventitious organic adsorbates are observed, indicating that air exposure results in passivation of the small Pt clusters.

Understanding the factors that control electrochemical catalysis is essential to improving performance. We report a study of electrocatalytic ethanol oxidation - a process important for direct ethanol fuel cells - over size-selected Pt centers ranging from single atoms to Pt14. Model electrodes were prepared by soft-landing of mass-selected Ptn(+) on indium tin oxide (ITO) supports in ultrahigh vacuum, and transferred to an in situ electrochemical cell without exposure to air. Each electrode had identical Pt coverage, and differed only in the size of Pt clusters deposited. The small Ptn have activities that vary strongly, and non-monotonically with deposited size. Activity per gram Pt ranges up to ten times higher than that of 5 to 10 nm Pt particles dispersed on ITO. Activity is anti-correlated with the Pt 4d core orbital binding energy, indicating that electron rich clusters are essential for high activity.