Hybrid Au/CuO Nanoparticles: Effect of Structural Features for Selective Benzyl Alcohol Oxidation

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Hybrid Au/CuO NPs supported on carbon (Vulcan-XC72) with different Au/Cu molar ratios (i.e., 13/1, 4/1, 1/1, and 1/17) were synthesized by the solvated metal atom dispersion approach. High-resolution transmission electron microscopy, scanning transmission electron microscopy–electron energy loss spectroscopy maps, and extended X-ray absorption fine structure measurements showed the presence of a Au/CuO core–shell heterostructure having narrow size distributions (mean diameter < 4.7 nm) regardless of their composition. The role of their structure and composition was evaluated for catalytic liquid-phase selective benzyl alcohol oxidation with respect to their monometallic counterparts. As a result, a strong synergistic effect of Au/CuO heterostructures was revealed, which is strictly dependent on the CuO coverage degree of the Au-rich core and thus to the Au/Cu molar ratio. Highest catalytic activity was observed when the CuO shell only partially covers the Au–NP surface (i.e., at high Au/Cu molar ratios: 13/1, 4/1). On the other hand, at high Cu loadings (i.e., Au/Cu molar ratios: 1/1 and 1/17), the CuO shell wraps the Au core completely, inhibiting the catalytic activity.