Adsorption and visible-light-driven photocatalytic properties of Ag3PO4/WO3 composites: A discussion of the mechanism

The debated photocatalytic mechanism in the photocatalyst composite Ag 3 PO 4 /WO 3 is explored by analyzing the electron flow direction between Ag 3 PO 4 and WO 3 . Cubic phase WO 3 nanosheets with a thickness of 10–20 nm are prepared using the sintering method at 200 °C and decorated by cubic Ag 3 PO 4 particles using a practical deposition-precipitation method. Pure WO 3 shows a strong adsorption activity for rhodamine B (RhB) and methylene blue (MB), but no adsorption activity for methyl orange (MO) and it shows no photocatalytic activity on these three dye molecules. Pure Ag 3 PO 4 has no adsorption activity on RhB but shows a strong photocatalytic activity on RhB under visible light irradiation. As-prepared AW-x composites with different weight ratios show no adsorption activity but a high photocatalytic activity. However, after heat-treatment at 200 °C for 24 h, the composite catalysts show both a strong adsorption and photocatalytic activities on RhB. The results provide an indirect evidence that the electron flow direction is from WO 3 to Ag 3 PO 4 , which thus supports the Z-scheme photocatalytic mechanism.