BiVO4-TiO2 composite photocatalysts for dye degradation formed using the SILAR method - open data

Composite photocatalyst films have been fabricated by depositing BiVO4 upon TiO2 via a sequential ionic layer adsorption reaction (SILAR) method. The photocatalytic materials were investigated by XRD, TEM, UV-vis diffuse reflectance, ICP-OES, XPS, photoluminescence and Mott-Schottky analyses. SILAR processing was found to deposit monoclinic-scheelite BiVO4 nanoparticles onto the surface, giving successive improvements in the films’ visible light harvesting. Electrochemical and valence band XPS studies revealed that the prepared heterojunctions have a type II band structure, with the BiVO4 conduction band and valence band lying cathodically shifted from those of TiO2. The photocatalytic activity of the films was measured by the decolourisation of the dye rhodamine 6G using λ > 400 nm visible light. It was found that 5 SILAR cycles was optimal, with a pseudo 1st order rate constant of 0.004 min-1. As a reference material the same SILAR modification has been made to an inactive wide band gap ZrO2 film, where the mismatch of conduction and valence band energies disallows charge separation. The photocatalytic activity of the BiVO4-ZrO2 system was found to be significantly reduced, highlighting the importance of charge separation across the interface. The mechanism of action of the photocatalysts has also been investigated, in particular the effect of self-sensitisation by the model organic dye and the ability of the dye to inject electrons into the photocatalysts conduction band.