CuO: Synthesis in a Highly Excited Oxygen-Copper Plasma and Decoration of ZnO Nanorods for Enhanced Photocatalysis

Semiconductor-based heterogeneous photocatalysis has received much attention. A plasma-assisted method for synthesizing CuO was developed and used to decorate ZnO nanorods. High quality monoclinic CuO was synthesized in a highly excited oxygen-copper plasma generated by electron cyclotron resonance microwave discharge of O2 gas and pulsed laser ablation of a Cu target. The plasma and the CuO synthesis process were spectroscopically characterized by optical emission measurement. In the oxygen-copper plasma, surface decoration of hydrothermally grown ZnO nanorods with CuO was achieved. The CuO-decorated ZnO nanorods were systematically characterized for morphology, structure, photoexcitation, and light emission by field emission scanning electron microscopy, X-ray diffraction, Raman scattering spectroscopy, Fourier-transform infrared spectroscopy, light absorption, and photoluminescence measurements. Using the prepared samples as photocatalysts, degradation of organic rhodamine B dye was performed under ultraviolet or violet light illumination, showing that the CuO-decorated ZnO nanorods exhibit much higher photocatalytic activity than pure CuO films and bare ZnO nanorods. A Z-scheme electron transfer mechanism was proposed for the enhanced photocatalytic activity of nanostructured ZnO/CuO heterogeneous composites.