Preparation, microstructure characterization and catalytic performance of Cu/ZnO and ZnO/Cu composite nanoparticles for liquid phase methanol synthesis

Stearate@Cu/ZnO nanocomposite particles with molar ratios of ZnO?∶?Cu = 2 and 5 are synthesized by reduction of the metal-organic Cu precursor [Cu{(OCH(CH(3))CH(2)N(CH(3))(2))}(2)] in the presence of stearate@ZnO nanoparticles. In the case of ZnO?∶?Cu = 5, high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) combined with electron-energy-loss-spectroscopy (EELS) as well as attenuated total reflection Fourier transform infrared (ATR-IR) spectroscopy are used to localize the small amount of Cu deposited on the surface of 3-5 nm sized stearate@ZnO particles. For ZnO?∶?Cu = 2, the microstructure of the nanocomposites after catalytic activity testing is characterized by HAADF-STEM techniques. This reveals the construction of large Cu nanoparticles (20-50 nm) decorated by small ZnO nanoparticles (3-5 nm). The catalytic activity of both composites for the synthesis of methanol from syn gas is evaluated.