Photocatalytic activity of ZnO-MnO₂ core shell nanocomposite in degradation of RhB dye

Abstract

Purpose The purpose of this study is to synthesize a semiconductor photocatalyst which responds to both UV light and visible light in removal of organic dyes. Design/methodology/approach ZnO nanoparticles were pre-synthesised via sol-gel method using zinc nitrate tetrahydrate and methanamine at 90°C for 20 h. Subsequently, the as-synthesised ZnO nanoparticles were filtered, washed and dried. To synthesize ZnO-MnO 2 core shell nanocomposites (CSNs), 2:3 M ratio of KMnO 4 and MnSO 4 solution was stirred for an hour. Next, ZnO nanoparticles were added into the solution. The solution was heated at 160°C for 3 h for the formation of ZnO-MnO 2 CSNs. The structural, optical and photocatalytic properties of ZnO-MnO 2 CSNs were characterised by field emission scanning electron microscope, transmission electron microscopy (TEM), X-ray diffractometer and PL spectroscopy, respectively. Findings The photodegradation efficiencies of rhodamine B (RhB) dye by ZnO-MnO 2 CSNs as photocatalysts are 87.1 per cent under UV irradiation and 76.6 per cent under visible light irradiation, respectively. Their corresponding rate constants are 0.016 min −1 under UV irradiation and 0.013 min −1 under visible light irradiation. It can be concluded that N-deethylation was the dominant step during the photodegradation of RhB dye as compared to cycloreversion. The ZnO-MnO 2 CSNs demonstrated good photostability after three consecutive runs. Originality/value ZnO-MnO 2 CSN photocatalyst which could response to UV and visible light in degradation of RhB dye was synthesised using sol-gel method. The analysis shows that N-deethylation was the key photodegradation mechanism of RhB by ZnO-MnO 2 CSN.