P-N Junction Oxide Nanoparticle as a Novel Photocatalyst for Solar Applications

Due to the spectral limitation of popular photocatalysts (PC) TiO2 and ZnO, there is quest for modification of the existing PC to enhance their photocatalytic performance. It has been demonstrated that the coupled nanostructured semiconductors in the form of nanocomposites (NC) enhance the performance by the mutual charge transfer of carriers between each semiconductor components with compatible chemical and electrical properties. ZnO (Bg: 3.37 eV) n-type semiconductor, is most important PC because of its high photosensitivity and stability. CuO (Bg: 1.85 eV), a p-type semiconductor, can be used in conjunction with ZnO to further improve its photocatalytic activity (PCA). Herein, a p-n junction oxide photocatalyst was synthesized by using a simple ball milling technique. The structural, optical and surface properties of the p-n junction photocatalyst CuO/ZnO were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy, Zetasizer Nano ZS (Malvern). The PCA of the photocatalyst was evaluated by photocatalytic oxidation of Methylene Blue (MB). Our study demonstrates a novel p-n junction oxide photocatalyst CuO (wt. 10%)/ZnO having superior PCA for the degradation of model dye under the illumination of UV-Vis light. The MB solution was degraded by 100% within 15 min by the use of CuO (wt. 10%)/ZnO photocatalyst. The enhanced PCA is anticipated from many micro p-n junction formed between ZnO-CuO upon ball milling, which helps in efficient electron/hole pair charge separation upon excitation

Preparation and photocatalytic activity study of p-CuO/n-ZnO composites

In this paper, efficacy of p-n junction p-CuO/n-ZnO composite is assessed as a potential photocatalyst by monitoring degradation of methylene blue (MB) in the presence of UV light. The p-n junction photocatalyst, p-CuO/n-ZnO, was prepared by ball milling of ZnO and CuO in water. The structural properties of p-CuO/n-ZnO composite were characterized by x-ray diffractometer and surface charge properties via zeta potential measurement. The degradation of MB in the presence of composite powder was monitored via UV-vis spectrometer. Various studies affecting the degradation rate of MB were conducted as a function of weight fraction of CuO in the composite and ball milling time. The highest degradation rate of MB was achieved in CuO (10 Wt.%)/ZnO for which high negative zeta potential was recorded. The MB degradation efficiency was found to decrease with the samples ball milled for time longer than 12 hours due to increased agglomeration of particles. The mechanisms that influence the photocatalytic activity of p-CuO/n-ZnO are discussed based on the p-n junction principle. © 2012 Materials Research Society