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4 results for: All records
Author ORCID ID is 0000000265150988
Full Text and Citations
  1. Bimetallic and multi-component catalysts often exhibit superior activity and selectivity compared with their single-component counterparts. To investigate the origin of the composition dependence observed in the catalytic activities of CoPd bimetallic catalysts, the compositional and structural evolution of monodisperse CoPd alloy nanoparticles (NPs) were followed under catalytic CO oxidation conditions using ambient pressure X-ray spectroscopy (AP-XPS) and transmission electron microscopy (TEM). It was found that the catalysis process induced a reconstruction of the catalysts, leaving CoOx on the NP surface. The synergy between Pd and CoOx coexisting on the surface promotes the catalytic activity of the bimetallic catalysts. Such synergisticmore » effects can be optimized by tuning the Co/Pd ratios in the NP synthesis and reach a maximum at compositions near Co 0.26Pd 0.74, which exhibits the lowest temperature for complete CO conversion. Our combined AP-XPS and TEM studies provide a direct observation of the bimetallic NPs surface evolution under catalytic conditions and its correlation to catalytic properties.« less
  2. Here, we studied the structure of the copper–cobalt (CuCo) surface alloy, formed by Co deposition on Cu(110), in dynamic equilibrium with CO. Using scanning tunneling microscopy (STM), we found that, in vacuum at room temperature and at low Co coverage, clusters of a few Co atoms substituting Cu atoms form at the surface. At CO pressures in the Torr range, we found that up to 2.5 CO molecules can bind on a single Co atom, in carbonyl-like configurations. Based on high-resolution STM images, together with density functional theory calculations, we determined the most stable CuCo cluster structures formed with boundmore » CO. Such carbonyl-like formation manifests in shifts in the binding energy of the Co core-level peaks in X-ray photoelectron spectra, as well as shifts in the vibrational modes of adsorbed CO in infrared reflection absorption spectra. The multiple CO adsorption on a Co site weakens the Co–CO bond and thus reduces the C–O bond scission probability. Our results may explain the different product distribution, including higher selectivity toward alcohol formation, when bimetallic CuCo catalysts are used compared to pure Co.« less
  3. Early–late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt 3Y—targeted as a prototypical example of an early–late intermetallic—has been synthesized as nanoparticles approximately 5–20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt 3BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used.more » Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt 3Sc, Pt 3Lu, Pt 2Na, and Au 2Y.« less

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