Efficiency enhancement of photocatalytic activity under UV and visible light irradiation using ZnO/Fe3O4 heteronanostructures

ZnO/Fe3O4 heteronanostructures (HNSs) have attracted great attention due to their possibility of removing organic pollutants in aqueous solutions, then detaching from aqueous solutions by magnetic fields. However, there is a lack of research on their photocatalytic performance under visible light irradiation and the mechanism for the degradation process is still arguable. We present here the enhancement in the photocatalytic activity of ZnO/Fe3O4 HNSs, synthesized by a facile hydrothermal technique, under both Ultraviolet (UV) and visible light irradiation. Particularly, the methylene blue (MB) degradation efficiency exhibited a great enhancement of up to 99.7% and 79.7% for HNSs with different ZnO:Fe3O4 mole ratios of 16:1 and 8:1 under UV and visible light, respectively. It could be explained by the transfer of electrons (i) from the conduction band (CB) of ZnO to that of Fe3O4 or/and (ii) from the CB of Fe3O4 to new defect states (e.g., Fe2+/Fe3+ levels) below the CB of ZnO. Additionally, ZnO/Fe3O4 HNSs show great stability in their photocatalytic activities when remained 95.1% and 92.1% after 5-reused cycles under UV and visible light irradiation, respectively. Therefore, the fabricated ZnO/Fe3O4 HNSs show great potential for enhancing the MB degradation efficiency under both UV and visible light.