BiVO4/CuWO4 heterojunction photoanodes for efficient solar driven water oxidation

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.