Thiol monolayer-protected Au clusters (MPCs) were prepared using dendrimer templates, deposited onto a high-surface-area titania, and then the thiol stabilizers were removed under H2/N2. The resulting Au catalysts were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy of adsorbed CO. The Au catalysts prepared via this route displayed minimal particle agglomeration during the deposition and activation steps. Structural data obtained from the physical characterization of the Au catalysts were comparable to features exhibited from a traditionally prepared standard Au catalyst obtained from the World Gold Council (WGC). A differential kinetic study of CO oxidation catalysis by the MPC-prepared Au and the standard WGC catalyst showed that these two catalyst systems have essentially the same reaction order and Arrhenius apparent activation energies (28 kJ/mol). However, the MPC-prepared Au catalyst shows 50% greater activity for CO oxidation. Using a Michaelis−Menten approach, the oxygen binding constants for the two catalyst systems were determined and found to be essentially the same within experimental error. To our knowledge, this kinetic evaluation is the first experimental determination of oxygen binding by supported Au nanoparticle catalysts under working conditions. The values for the oxygen binding equilibrium constant obtained from the Michaelis−Menten treatment (ca. 29−39) are consistent with ultra-high-vacuum measurements on model catalyst systems and support density functional theory calculations for oxygen binding at corner or edge atoms on Au nanoparticles and clusters.

A study of the synergistic tuning of nitrogen-doped carbon nanotubes (NCNTs) as support- and size-monodisperse platinum nanoparticles templated from G4-NH2 dendrimers (Pt-DEN's) as catalysts targeted toward oxygen reduction is reported. UV-vis spectroscopy, adsorption isotherms, TGA, TEM, and voltammetry were used to characterize the loading and activity of Pt-DENs immobilized on CNT and NCNT supports. The facile uptake of Pt-DENs was found to be influenced by the number of edge plane sites on the NCNT support with higher adsorption rates observed for NCNTs with increased nitrogen content. Pt-DEN/NCNT composites exhibit high activity with a mass-transport-limited current density and mass activity of 2.3 mA cm(-2) and 0.05 mA g(-1), respectively, for the oxygen reduction reaction (ORR).

Mixed molybdenum tungsten trioxide films of varying stoichiometry (MoxW1 - xO3, 0 < x < 1) were prepared by cathodic electrodeposition on indium tin oxide (ITO)-coated glass substrates from aqueous peroxo-polymolybdotungstate solutions. Electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, and chronocoulometry were used to gain insight into the electrodeposition mechanism. The compositional and structural properties were characterized for MoxW1 - xO3 films deposited at intermediate potentials (-0.35 V vs Ag/AgCl) and sintered at 250 degrees C using energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. These studies reveal that films consist of homogeneously mixed MoxW1 - xO3, with an enriched Mo content ranging in composition from 0.4 < x < 0.7 depending upon the mol % Mo present in the deposition solution. Chronoamperometry and spectroelectrochemical measurements were conducted to estimate lithium ion diffusion coefficients and coloration efficiencies for the mixed metal oxide films in 1 M LiClO4/propylene carbonate. The subtle interplay between structural and compositional properties due to the uniform mixing of Mo and W oxide components shows that electrochromic and lithium ion transport properties are moderately enhanced relative to those of single-component WO3 and MoO3 and demonstrate improved structural stability over pure MoO3 polymorphs during electrochemical cycling.

New bimetallic Ni-Au supported nanoparticle catalysts were prepared by using dendrimer templated nanoparticles. Amine-terminated generation 5 polyamidoamine (PAMAM) dendrimers were anchored to a commercial silica with a siloxane linked anhydride. The dendrimer was then alkylated and used to template Ni-Au nanoparticles, which were subsequently extracted into organic solution as thiol monolayer protected clusters (MPCs). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) indicated bimetallic nanoparticles of about 2 nm in size. Nanoparticles were deposited onto P-25 TiO 2 , and the capping thiol ligands were removed under flowing H 2 . DRIFTS infrared spectra of adsorbed CO showed only Au on the catalyst surface; no bands attributable to Ni or NiO were observed. Density functional theory (DFT) calculations showed that Au is substantially more stable than Ni on the surface of model slabs. DFT calculations also indicated that the incorporation of Ni into Au slabs results in stronger adsorption of O and CO on Au surfaces. Catalysts were evaluated with low-temperature CO oxidation. Kinetics studies indicated a substantial modification of Au catalysis through Ni incorporation. Apparent activation energies decreased by more than 50% and O 2 reaction orders increased from 0.2 to 0.9. These results are placed in the context of the available literature regarding support effects for Au catalysts. The observed changes to Au chemistry in the current work are substantially larger than previous reports have attributed to support effects. A Michaelis-Menten (enzyme) treatment of the kinetics data indicated that the O 2 reactivity constant increased by a factor of 40 for catalysts with high Ni content. This was in good qualitative agreement with the DFT calculations. At the same time, the introduction of Ni reduced the relative number of catalytically active sites.