Controllable synthesis of WO₃/Co_1-δWO₄ composite nanopowders for photocatalytic degradation of methylene blue (MB)

Systematical design and controllable synthesis of nanometer heterogeneous structure have attracted much attention in the photocatalytic field. The tungsten oxide/cobalt tungstate (WO₃/Co_1-δWO₄) nanoparticles with heterogeneous interface were synthesized by co-precipitation process. The XRD pattern shows shifts of diffraction peaks of CoWO₄ to lower angle side, implying the deficient of Co²⁺ in the lattice. The internal field across the heterogeneous structure transfers the photon-generated electrons from the conduction band of WO₃ to that of Co_1-δWO₄. The enhancement of the electron density greatly improves the photoluminescence emission intensity at a magnitude of around 2 × 10⁶ in comparison with that of pure WO₃ or CoWO₄. The photocatalytic efficiency was inspected by exposing the methylene blue (MB) mixing with 1% WO₃/Co_1-δWO₄ nanopowders to the visible light for degradation. The main optical absorption band of MB at 664 nm decays from 2.35 to 0.04 cm⁻¹ after photo-degradation for 3.5 h, suggesting excellent photocatalytic performance.