Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid-phase catalytic reactions (e.g., hydrogenation of biomass-derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid-phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X-ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ-Al2 O3 . Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under-coordinated copper atoms on the nanoparticle surface.

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Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO.

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The reaction site time yields (STYs, normalized to CO chemisorption sites) and product selectivity were measured for a series of bimetallic, multiwalled carbon nanotube supported PtCo catalysts with varying Pt/Co ratios for aqueous phase glycerol reforming. The STYs for all products increased by factors of around 2 for PtCo 1:0.5 and 1:1, and a factor of 4 for PtCo 1:5 relative to a monometallic Pt catalyst. The PtCo catalysts had similar hydrogen selectivity (>85%) at glycerol conversions up to 60%. X-ray absorption spectroscopy and scanning transmission electron microscopy characterization revealed that PtCo catalysts adopt monometallic Pt, mixed PtCo alloy, and Pt shell/Co core particle configurations. A linear correlation between the fraction of mixed PtCo alloy particles and the STY was found, indicating that higher Co loading resulted in a higher fraction of mixed PtCo alloy particles (the promoted phase) that provided the STY increase.