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

The debated photocatalytic mechanism in the photocatalyst composite Ag3PO4/WO3 is explored by analyzing the electron flow direction between Ag3PO4 and WO3. Cubic phase WO3 nanosheets with a thickness of 10-20 nm are prepared using the sintering method at 200 degrees C and decorated by cubic Ag3PO4 particles using a practical deposition-precipitation method. Pure WO3 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 Ag3PO4 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 degrees 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 WO3 to Ag3PO4, which thus supports the Z-scheme photocatalytic mechanism.