Respuesta :
According to the available literature, standard nanoparticle (NP) production processes make it especially challenging to reach the catalytically important and highly complicated intermetallic -brass crystal structure.
We present a straightforward and logical method for obtaining this phase in M-Zn (M = Pd, Cu, Ni) systems as silica-supported single-phase nanocrystals. This hybrid technique begins with the synthesis of supported M/SiO2 using typical methods (dry impregnation and strong electrostatic adsorption), followed by several hours of heating to high temperatures in the presence of a stoichiometric quantity of metallic Zn in an evacuated closed system.
Catalytically important bimetallic systems:
Pd-Zn is by far the most common in catalytic applications and produces the smallest particle size (8 nm). We investigated the effect of various synthesis parameters on phase purity and particle size distribution in the case of synthesized -brass Pd-Zn/SiO2 supported catalysts and provided general guidelines for synthesis optimization.
Pd/SiO2 is transformed to -brass Pd-Zn/SiO2, resulting in a precipitous drop in CO adsorption and a 25 kJ/mol increase in the ethylene hydrogenation barrier, indicating that the catalytic active sites are significantly modified as a result of alloying. We anticipate that these catalysts will find use in a variety of Pd-catalyzed chemistries.
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