Facile Microwave-Assisted Hydrothermal Synthesis of CuO Nanomaterials and Their Catalytic and Electrochemical Properties

Copper oxides have been widely used as catalysts, gas sensors, adsorbents, and electrode materials. In this work, CuO nanomaterials were synthesized via a facile microwave-assisted hydrothermal process in Cu(CH(3)C00)(2)(0.1 M)/urea(0.5 M) and Cu(NO3)(2)(0.1 M)/urea(0.5 M) aqueous systems at 150 degrees C for 30 min. The formation processes of copper oxides were investigated, and their catalytic activities were evaluated by the epoxidation of alkenes and the oxidation of CO to CO2. Their electrochemical properties were compared as supercapacitor electrodes using cyclic voltammetry. Experimental results indicated that copper acetate solution could be hydrolyzed to form urchin-like architectured CuO, and the addition of urea accelerated this transformation. CuO nanoparticles were formed and aggregated into spheroidal form (CuO-1) in Cu(CH3COO)(2)/urea aqueous solution. Cu-2(OH)(2)CO3 was formed as an intermediate, and then thermally decomposed into CuO nanorods (CuO-2) in the Cu(NO3)(2)/urea aqueous system. The synthesized copper oxide nanomaterials exhibited excellent catalytic activities for the epoxidation of alkenes, the oxidation of CO, and pseudocapacitance behavior in potassium hydroxide solution. The increase of specific surface area promoted the catalytic activities and conversions for olefins and CO. CO was oxidized to CO2 when the applied temperature was higher than 115 degrees C, and conversion of 100% was obtained at 130 degrees C. CuO-1 showed higher catalytic activities and capacitance values than those of CuO-2 likely due to the former having a larger specific surface area. This work facilitates the preparation of nanosized CuO materials with excellent catalytic and electrochemical performance.