WO(3)/BiVO(4) Photoanodes: Facets Matching at the Heterojunction and BiVO(4) Layer Thickness Effects

[Image: see text] Photoelectrochemical solar energy conversion offers a way to directly store light into energy-rich chemicals. Photoanodes based on the WO(3)/BiVO(4) heterojunction are most effective mainly thanks to the efficient separation of photogenerated charges. The WO(3)/BiVO(4) interfacial space region in the heterojunction is investigated here with the increasing thickness of the BiVO(4) layer over a WO(3) scaffold. On the basis of X-ray diffraction analysis results, density functional theory simulations show a BiVO(4) growth over the WO(3) layer along the BiVO(4) {010} face, driven by the formation of a stable interface with new covalent bonds, with a favorable band alignment and band bending between the two oxides. This crystal facet phase matching allows a smooth transition between the electronic states of the two oxides and may be a key factor ensuring the high efficiency attained with this heterojunction. The photoelectrochemical activity of the WO(3)/BiVO(4) photoanodes depends on both the irradiation wavelength and the thickness of the visible-light-absorbing BiVO(4) layer, a 75 nm thick BiVO(4) layer on WO(3) being best performing.