Drop-cast tungsten trioxide semiconducting films in Photoelectrocatalysis

Abstract

Polycrystalline, monoclinic, uniform WO 3 films of up to 2.5 μm thickness were prepared by drop casting onto F:SnO 2 /glass using as precursor peroxo-tungstic acid and polyethylene glycol in water, and firing in air at 520 °C. The n-type WO 3 layers produced photocurrents in junctions with aqueous electrolytes. Under depletion conditions, IPCEs (incident photon to current efficiencies) of up to 0.7 at 365 nm and 0.2 at 405 nm were obtained. The photosensitivity of WO 3 thin films extended into the visible range up to 470 nm. The photoelectrocatalytic activity of such layers was examined using the azo-dye “acid orange 7” (AO7) as a model pollutant. Degradation of AO7 was carried out under backside UVA broadband illumination of electrodes of 62 cm 2 active surface area, in a parallel plate flow-through reactor equipped with a stainless steel counter electrode under electrical bias of 1.1–1.3 V. Rapid recirculation of the electrolyte was maintained in order to derive true kinetic parameters. During illumination, the concentration of AO7 (initial value 1 mM) decreased exponentially. At the beginning of a degradation experiment the Faradaic efficiency, f 0 , was 0.48. • Polycrystalline WO 3 films of up to 2.5 μm thickness were prepared by drop casting onto F:SnO 2 /glass peroxo-tungstic acid and polyethylene glycol in water, and firing in air at 520 °C. • The n-type WO 3 layers produced photocurrents up to 470 nm in junctions with aqueous electrolytes. • Photoelectrocatalytic activity of such layers was examined using the azo-dye “acid orange 7” (AO7) under backside UVA illumination of electrodes of 62 cm 2 active surface area, in a parallel plate flow-through reactor under electrical bias of 1.1–1.3 V. • During UVA illumination, the concentration of AO7 (initial value 1 mM) decreased exponentially. The initial Faradaic efficiency, f 0 , was 0.48.