Enhanced photocatalytic activity of Pt/WO3 photocatalyst combined with TiO2 nanoparticles by polyelectrolyte-mediated electrostatic adsorption

An electrostatic adsorption approach was used to realize a composite structure in which larger metal oxide crystalline particles were surrounded by metal oxide nanoparticles. Poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) were alternately adsorbed onto crystalline tungsten trioxide (WO3) particles (ca. 200 nm) via a layer-by-layer assembly, followed by adsorption of TiO2 particles (ca. 6 nm) on the surfaces covered by PDDA. After calcination to remove the adsorbed polymer layers, Pt particles were dispersed on the composite structure by photodeposition. The resulting Pt/WO3-TiO2 composite photocatalyst showed a higher rate of activity towards the photocatalytic decomposition of gaseous acetone under visible light irradiation (lambda > 420 nm) compared with that of Pt/WO3. Pt/WO3-TiO2 also converted acetone to CO2 almost completely, whereas the amount of CO2 produced over Pt/WO3 was much smaller than that expected for the complete oxidation of acetone. The enhanced activity of Pt/WO3-TiO2 was ascribed to hole transfer from the valence band of WO3 to that of TiO2, which likely suppressed electron-hole recombination and enabled the oxidation reaction to take place on the surface of the TiO2 particles.