Visible-Light Photocatalytic Water Splitting and Norfloxacin Degradation by Reduced Graphene Oxide-Coupled MnON Nanospheres

Photocatalytic water splitting has gained considerable attention owing to the sustainable nature of hydrogen as a clean energy source alternative to fossil fuels. In this study, nanocomposites consisting of manganese oxynitride and reduced graphene oxide were synthesized by the combined involvement of a solvothermal process and Hummer's method and examined for their photocatalytic applications for water splitting hydrogen production and degradation of norfloxacin as a model pollutant. Spectroscopic and structural analyses showed successful formation of the stable composite in which manganese oxynitride nanoparticles are decorated on graphene sheets. With increasing content of graphene oxide in the composite, it showed the enhanced photocatalytic efficiency in water splitting hydrogen evolution. This is well explained by the large surface area, more light absorption, and interfacial charge transfer in the composite photocatalyst. The hydrogen evolution rates of MnON nanoparticles and MnON/RGO composites of mass ratios 1:1, 1:2, and 1:3 were measured as 250.1, 456.2, 543.6, and 708.5 μmol g^-1min^-1, respectively, and the oxygen evolution rates were measured as 129.0, 229.4, 273.4, and 354.6 μmol g^-1min^-1, respectively, suggesting the important roles of reduced graphene oxide. The photocatalysts also demonstrated enhanced stability and recyclability after multiple uses.