Surface decoration of MnWO4 nanoparticles with g-C3N4 nanosheets to build hetero-structure and its structural, optical and enhanced visible light photocatalytic activity

In this study, we report the synthesis of manganese tungstate (MnWO₄)/graphitic carbon nitrides (g-C₃N₄) hybrid photocatalysts by simple hydrothermal method. The prepared photocatalysts have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, photoluminescence spectroscopy (PL) and UV–visible spectroscopy. XRD and TEM results reveal that the both pure and composite samples have monoclinic wolframite structure with spherical nanoparticles, which is decorated on the surface of g-C₃N₄ sheets. A considerable red shift in the absorption and narrowing the band gap (3.02–2.55 eV) energy was observed in the MnWO₄/g-C₃N₄ composite samples. The photocatalytic measurements exhibit that the optimized photocatalyst (15 wt%-MnWO₄/g-C₃N₄) show high degradation efficiency (98%) and long-term stability towards rhodamine (RhB) dye under visible light irradiation. The J-V characteristics reveal that MnWO₄/g-C₃N₄ photoanode show high photo-conversion efficiency (PCE%) of 7.15%, which is higher than that of pure MnWO₄ (2.34%). The significant enhancement in the photocatalytic behavior is due to the coactions between the g-C₃N₄ nanosheets and MnWO₄ nanoparticles.