Intimate coupling of 3D MnFe2O4 cubes on 1D ZnO nanorods for sustainable photocatalysis under visible light: Computational analysis of reactive sites and degradation pathway

Background: In recent times, the discharge of wastewater containing aromatic compounds has serious effects on human health and the environment. Thus the fabrication of an efficient and visible light-active nano photocatalyst offers an optimum and sustainable solution. Method: In this study, ZnO/MnFe2O4 nanocatalyst was fabricated by the ultrasonication mediated reflux method. The fabricated nanomaterials were characterized with SEM, TEM, XRD, XPS, UV-visible DRS, BET, EIS, PL, ESR analysis. The ensued nanocomposite (NCs) was employed for the photocatalytic removal of methylene blue (MB) dye. Significant findings: The photocatalytic efficiency of ZnO/MnFe2O4 NCs for the removal of MB was 85% which was higher than the efficiency of both the individual semiconductors ZnO (63%) and MnFe2O4 (69%). The rate constant for the photocatalytic removal of MB by ZnO/MnFe2O4 NCs (0.07 min-1) was 12 times higher than the ZnO (0.006 min-1) and 1.75 times higher than MnFe2O4 (0.04 min-1). The boosted photocatalytic performance of ZnO/MnFe2O4 was attributed to the higher surface area (204.559 m2/g) with more active sites compared to ZnO (188.212 m2/g) and MnFe2O4 (106.893 m2/g). The as-fabricated ZnO/MnFe2O4 NCs possess excellent stability as affirmed by recycle test and the analysis of reused XRD. The major part of the degradation of MB was performed by center dot OH- radicals which was confirmed by scavenging test. The overall results suggest that the fabricated ZnO/MnFe2O4 is an active material for photocatalytic applications.