Tungsten trioxide film photoanodes prepared by aerosol pyrolysis for photoelectrochemical applications

Abstract

The present work describes the preparation of tungsten trioxide photoanodes by aerosol pyrolysis on FTO/glass substrates. WO3 layers were characterised by profilometry, XRD, SEM and photoelectrochemistry (linear voltammetry and chronoamperometry under illumination). Optimal deposition conditions to obtain a relatively thick layer were found to be: 11 mm nozzle diameter, 2.5 cm nozzle to substrate distance, and 105 cm/s airflow velocity. A deposition temperature of at least 450 °C was necessary to obtain γ-monoclinic WO3. The as-deposited layers had loose particles on the surface; however, these particles could be removed by scotch tape with no influence on the roughness and photoactivity of the layer. The highest photocurrent was achieved by annealing the layers at 450 °C; however, such layers were not photoelectrochemically stable. To obtain superior long-term stability, an annealing temperature of 550 °C was necessary. The highest, stable photocurrent of ∼ 990 μA/cm2 (E = 0.9 V vs. Ag/AgCl, 1 sun) was achieved for a layer thickness of 3.8 µm.