Photocatalytic Activity of CoO/ZnO Nanocrystalline for Dye Wastewater Treatment under UV Light

Abstract

CoO nanocrystal is well-known photocatalyst for overall water splitting. However it suffers from a very short lifetime of only 1 h. The poor stability is derived from carrier recombination-induced thermal oxidation. This research will provide information about synthesis of CoO/ZnO nanocrystalline that can potentially enhance photocatalysts. CoO has been synthesized first under hydrothermal method, followed by calcination process. Thereafter, CoO has been used to produce CoO/ZnO under precipitation method. The samples were characterized using XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), and UV-VIS (UV–Visible Spectroscopy) to analyze their composition, chemical functional group, optical absorption, and band gap. The XRD spectrum showed that CoO/ZnO had cubic spinel and hexagonal phase structure with crystallite size of 69.0, 46.4, 32.8, and 32,4 nm. The bands in obtained FTIR spectrum at 586.36, 671.23, and 410-429 cm−1 were correlated with vibrations of the Co3+ in octahedral hole, the Co2+ in tetrahedral hole, and Zn-O, respectively. The band gap energy of CoO, CoO/ZnO with variation of 1:1 and 1:3 were 4.39, 4.14, and 3.65 eV, respectively. The photocatalytic activities of CoO/ZnO were confirmed by methylene blue dyes photodegradation of 663 nm under UV light irradiation in aqueous solution. The 22.4% methylene blue can be removed within 3 h. Overall, these findings reveal the potential of CoO/ZnO for practical application.