Investigation of the origin of the enhanced photoelectrochemical performance of gradient W-doped bismuth vanadate (BiVO₄) photoanodes

Gradient W-doped Bismuth vanadate (BiVO4) photoanodes were fabricated to figure out the main factor improving the photoelectrochemical (PEC) performance, achieved by the gradient doping. We found that the film in which the concentration of W in the bulk was higher than that in the surface showed the highest photocurrent density, compared to those of other samples, which could be mainly attributed to the improvement of the charge transfer efficiency. It means that W existing on the surface of BiVO4 played a crucial role in the enhancement of the water splitting efficiency and the charge separation achieved by the built-in electric field modestly contributed to the improvement of the performance.