Improving the Catalytic Performances of Cu–Co Bimetallic Nanoparticles through Carbon Coating

Abstract

In this study, we describe an easy-to-implement procedure to encapsulate CuCo bimetallic nanoparticles within carbon shells of variable thicknesses in the range of ca. 1–5 nm. The resulting nanostructures were thoroughly characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂ physisorption, bright-field transmission electron microscopy (BFTEM), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). All results agreed to show that the particles are individually coated with a relatively regular shell of carbon and a well-crystallized alloyed metal core, while the isotropic morphology and the mean size of the particles were preserved after the carbon deposition process. The catalytic properties of the carbon-coated particles were first evaluated for the liquid-phase acceptorless dehydrogenation of alcohols, and the results were compared to those of the uncoated parent materials. The results show that the carbon protective layer is not detrimental to catalytic activity and allows obtaining excellent stability even after four consecutive tests (about 100 h reaction time) at 185 °C. The carbon-coated particles have further been implemented for the gas-phase hydrogenation reactions of acetone and CO₂, where they performed stably at elevated temperatures and exhibited pronounced selectivities toward the desired products.