Photoelectrochemical performance of W-doped BiVO4 thin films deposited by spray pyrolysis

Abstract

The effects of tungsten doping and hydrogen annealing on the PEC performance of BiVO4 photoanodes for solar water splitting were studied. Thin films of BiVO4 were deposited on ITO-coated glass slides by ultrasonic spray pyrolysis of an aqueous solution containing bismuth nitrate and vanadium oxysulfate. Tungsten doping was achieved by adding either silicotungstic acid or ammonium metatungstate to the precursor. The 1.7-2.2 um thick films exhibited a highly porous microstructure. Undoped films that were reduced at 375 C in 3% H2 exhibited the largest photocurrent densities under 0.1 W cm^-2 AM 1.5 illumination, where photocurrent densitites of up to 1.3 mA cm^-2 at 0.5 V with respect to Ag/AgCl were achieved. Films doped with 1% or 5% (atomic) tungsten from either STA or AMT exhibited reduced PEC performance and greater sample-to-sample performance variations. PXRD data indicated that the films continue to crystallize in the monoclinic polymorph at low doping levels but crystallize in the tetragonal scheelite structure at higher doping. It is surmised that the phase and morphology differences promoted by the addition of W during the deposition process reduced the PEC performance as measured by photovoltammetry.