Nanostructured WO₃/BiVO₄ heterojunction films for efficient photoelectrochemical water splitting

We report on a novel heterojunction WO₃/BiVO₄ photoanode for photoelectrochemical water splitting. The heterojunction films are prepared by solvothermal deposition of a WO₃ nanorod-array film onto fluorine-doped tin oxide (FTO) coated glass, with subsequent deposition of a low bandgap, 2.4 eV, visible light responding BiVO₄ layer by spin-coating. The heterojunction structure offers enhanced photoconversion efficiency and increased photocorrosion stability. Compared to planar WO ₃/BiVO₄ heterojunction films, the nanorod-array films show significantly improved photoelectrochemical properties due, we believe, to the high surface area and improved separation of the photogenerated charge at the WO₃/BiVO₄ interface. Synthesis details are discussed, with film morphologies and structures characterized by field emission scanning electron microscopy and X-ray diffraction.