Enhanced photocatalytic activity of Pt/WO 3 photocatalyst combined with TiO 2 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 (WO 3 ) particles ( ca. 200 nm) via a layer-by-layer assembly, followed by adsorption of TiO 2 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/WO 3 –TiO 2 composite photocatalyst showed a higher rate of activity towards the photocatalytic decomposition of gaseous acetone under visible light irradiation ( λ > 420 nm) compared with that of Pt/WO 3 . Pt/WO 3 –TiO 2 also converted acetone to CO 2 almost completely, whereas the amount of CO 2 produced over Pt/WO 3 was much smaller than that expected for the complete oxidation of acetone. The enhanced activity of Pt/WO 3 –TiO 2 was ascribed to hole transfer from the valence band of WO 3 to that of TiO 2 , which likely suppressed electron–hole recombination and enabled the oxidation reaction to take place on the surface of the TiO 2 particles.