BiVO4/CuWO4 heterojunction photoanodes for efficient solar driven water oxidation

Abstract

BiVO₄/CuWO₄ heterojunction electrodes were prepared using spray deposition of a highly porous bismuth vanadate film onto the surface of an electrodeposited three dimensional network connected copper tungstate. Bilayer BiVO₄/CuWO₄/fluorine doped tin oxide glass (FTO) electrodes demonstrated higher photocurrent magnitudes than either with BiVO₄/FTO or CuWO₄/FTO electrodes in 1.0 M Na₂SO₄ electrolyte buffered at pH 7. The photocurrent is enhanced by the formation of the heterojunction that aids charge carrier collection brought about by the band edge offsets. When the pH 7 buffered electrolytes contained 1.0 M bicarbonate is employed instead of 1.0 M sulfate, the charge transfer resistance was decreased. This led to nearly 1.8 times the photocurrent density at 1.0 V vs. Ag/AgCl. The photocurrent was stable over 24 hours in bicarbonate electrolyte.