Cu2O-Au Nanocomposites with Novel Structures and Remarkable Chemisorption Capacity and Photocatalytic Activity

The decomposition of Cull nanoparticles in aqueous solution has been successfully developed as a novel method for the preparation of Cu2O nanoparticles. In particular, we found that the decomposition of Cull nanoparticles in aqueous solution could be catalyzed by Au colloids, forming CU2O-Au nanocomposites. The composition and structure of the resulting Cu2O-Au nanocomposites have been characterized in detail by inductively coupled plasma atomic emission spectroscopy, powder X-ray diffraction, N2 adsorption-desorption isotherms, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Their visible-light-driven photocatalytic activity toward various dye molecules has also been investigated. Depending on the Au：Cu ratio, Cu20-Au nanocomposites exhibit different novel nanostructures including a beautiful flower-like nanostructure that consists of polycrystalline Cu2O, amorphous Cu2O and Au colloids. We propose that the rapidly-generated bubbles of H2 during the course of the catalytic decomposition reaction drive the simultaneously-formed Cu2O to form amorphous curved thin foils and might also act as a template to assemble curved thin foils of amorphous Cu2O, polycrystalline Cu2O and Au colloids into uniform nanostructures. A Cu2O-Au nanocomposite with a Cu：Au ratio of 40 exhibits remarkable chemisorption capacity and visible-light-driven photocatalytic activity towards methyl orange and acid orange 7 and is a promising chemisorption-photocatalysis integrated catalyst. The catalytic decomposition of the metal hydride might open up a new approach for the fabrication of other metal/metal oxide nanocomposites with novel nanostructures and properties.

Reaction heat-driven CO2 desorption during CO oxidation on Au(997) at low temperatures

Adsorption and reaction of CO and CO2 were studied on oxygen-covered Au（997） surfaces by means of temperature- programmed desorption/reaction spectroscopy. Oxygen atoms （O（a）） on Au（997） enhances the CO2 adsorption and stabilizes the adsorbed COe（a）, and the stabilization effect also depends on the CO2（a） coverage and involved Au sites. CO2（a） desorp- tion is the rate-limiting step for the CO＋O（a） reaction to produce CO2 on Au（997） at 105 K and exhibits complex behaviors, including the desorption of CO2（a） upon CO exposures at 105 K and the desorption of O（a）-stabilized CO2（a） at elevated temperatures. The desorption of CO2（a） from the surface upon CO exposures at 105 K to produce gaseous CO2 depends on the surface reaction extent and involves the reaction heat-driven CO2（a） desorption channel. CO＋O（a） reaction proceeds more easily with weakly-bound oxygen adatoms at the （111） terraces than strongly-bound oxygen adatoms at the （111） steps. These re- sults reveal complex rate-limiting COe（a） desorption behaviors during CO＋O（a） reaction on Au surfaces at low temperatures which provide novel information on the fundamental understanding of Au catalysis.