The existing literature suggests it is particularly difficult to access the catalytically relevant, and relatively complex, intermetallic γ-brass crystal structure through traditional nanoparticle (NP) synthesis techniques. We introduce a simple and rational approach to access this phase in M-Zn (M = Pd, Cu, Ni) systems as silica-supported single-phase nanocrystals. This hybrid approach involves the initial synthesis of supported M/SiO2 through traditional approaches (dry impregnation and strong electrostatic adsorption) followed by heating to high temperatures in the presence of a stoichiometric amount of metallic Zn in an evacuated closed system for several hours. We demonstrate the generality of this method with three different catalytically important bimetallic systems: Pd-Zn, Ni-Zn and Cu-Zn. Of these three, Pd-Zn is by the far the most popular in terms of catalytic applications and yields the smallest particle size (∼8 nm). We tested the influence of various synthesis parameters on phase purity and particle size distribution in case of the synthesized γ-brass Pd-Zn/SiO2 supported catalysts and provide general guidelines towards optimization of synthesis. Upon transformation of Pd/SiO2 to γ-brass Pd-Zn/SiO2, a precipitous drop in CO adsorption and a 25 kJ/mol increase in the ethylene hydrogenation barrier is observed, indicating the catalytic active sites are significantly modified as a result of alloying. We anticipate these catalysts may find applications in various Pd-catalyzed chemistries.
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