Combining metals to form bimetallic nanoparticles allows for tuning the activity and selectivity of nanoscale catalysts.  For Fischer-Tropsch synthesis, cobalt-copper composites improve the formation of oxygenated products without compromising the catalyst activity. However, copper and cobalt are not miscible on the macroscale.At the nanoscale, cobalt and copper can be intimately mixed by preparing core-shell structures, although morphology evolution of these advanced structures has scarcely been studied. Here, monodisperse core-shell Cu-Co nanoparticles were exposed to syngas at 250C. Morphology evolution was studied with STEM-EDS and HRTEM. These techniques showed an unexpected segregation of the two metals during the reaction, giving rise to copper-rich and cobalt-rich nanoparticles. This phenomenon was explained using in-situ core-level spectroscopy (ambient-pressure XPS and high-pressure XAS) conducted at the Advanced Light Source. It highlighted the synergistic role of carbon monoxide (as a strong ligand) and hydrogen (as a reductant) in the segregation process.

Morphology evolution of copper-cobalt core-shell nanoparticles under syngas exposure

245th National Meeting (2013)

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