▎ 摘　　要

Hierarchical spinel NiCo2O4 anchored with reduced graphene oxide (NiCO2O4-rGO) nanoflake composites was prepared by using a chemical route for a high-performance photocatalyst. Xray diffractometry, field emission scanning electron microscopy and Fourier transform infrared spectroscopy were employed to study the structure, morphology and functional groups of the as-prepared NiCO2O4-rGO nanoflake composites. The UV-vis diffusive reflectance spectroscopy revealed the reduction of optical bandgap from 1.32 to 1.20 eV compared with pristine spinel NiCo2O4 nanoflakes. NiCO2O4-rGO nanoflake composites exhibited improved photocatalytic efficiency when compared with that of pristine NiCo2O4 nanoflakes. We verified that 100% degradation of MB in 40 min was observed under natural sunlight irradiation. The photocatalytic degradation efficiency was found to retain 97% of its original value after 6 cycles. The superior photocatalytic efficiency of NiCO2O4-rGO nanoflake composites over pristine NiCo2O4 nanoflakes is attributed to not only its enhanced surface area providing more active sites for light adsorption but also a heterojunction created between rGO and NiCo2O4. Addition of rGO greatly improves charge separation efficiency hence decreasing electron hole pair recombination. Overall, this work revealed that synthesis of NiCo2O4-rGO nanoflake composites may be a promising candidate for the removal of inorganic pollutant from waste water at industrial level under natural sunlight irradiation. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).