Layer structured Na2Ni(MoO4)2 particles as a visible-light-driven photocatalyst for degradation of methylene blue

A new visible-light-driven photocatalyst of Na2Ni(MoO4)2 particle was prepared by the modified Pechini method. The crystal structure was measured by X-ray diffraction (XRD) and the structural refinement. The sample was investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), and UV-vis absorption spectrum measurements. The average size of Na2Ni(MoO4)2 particle is about 180 nm. Na2Ni(MoO4)2 particle have an efficient optical absorption in the UV-visible light wavelength region with a direct allowed electronic transition of 2.06 eV. The effective photodegradation of methylene blue (MB) dye was demonstrated, which benefits from the special crystal structure of Na2Ni(MoO4)2 particle. This crystal lattice has two infinite chains formed by (Ni,Na)O6 and MoO4 polyhedra standing in lines alone with the inner wall of the hexagonal tunnels. This results in the efficient optical absorption and provides more chances for electron-hole separations, which can further react with dye molecules to oxidize the dye pollutant into non-toxic products.