High Efficiency Cu-ZnO Hydrogenation Catalyst: The Tailoring of Cu-ZnO Interface Sites by Molecular Layer Deposition

This paper describes a molecular layer deposition (MLD)-assisted route for the preparation of Cu-ZnO catalysts used in the hydrogenation of levulinic acid to produce γ-valerolactone. A Cu precursor supported on multiwalled carbon nanotubes was coated with Zn-polyurea organic-inorganic hybrid films via MLD first, and the catalyst was obtained after calcination and reduction under mild conditions. The produced catalysts exhibited remarkably enhanced selectivity, efficiency, and stability due to the created Cu-ZnO interface sites (Cu⁰Zn) and the cooperative effect between Cu⁰Zn and Cu⁺. The ratio of Cu⁰Zn sites could be simply modified by changing the MLD cycle number. The correlation between catalytic activity and the ratio of different Cu species (Cu⁰Zn, Cu⁰, and Cu⁺) suggests that Cu⁰Zn is the main active site and responsible for the remarkably enhancing catalytic activity and low apparent activation energy.