Bi2O3–WO3 compounds for photocatalytic applications by solid state and viscous processing

Water-splitting photoelectrochemical cells utilising photocatalysts have the potential to become a significant hydrogen source for fuel cells. Historically, the photocatalytic properties of TiO2 and other compounds have been carefully investigated, but they suffer from poor energy conversion efficiencies for solar radiation. Inspired by the low bandgaps and high electrical conductivities of WO3 and Bi2O3, this study investigates the suitability of compounds within this binary system as efficient photocatalysts. The structure and optical absorption spectra of these compounds have been determined via X-ray diffraction and UV–vis spectroscopy over the range of 300–900 nm. The semiconductor bandgaps of Bi2O3, WO3 and Bi2WO6 were found to be 0.2 eV, in agreement with previously reported results. Two sample preparation techniques have been considered—solid-state processing and viscous processing techniques. A custom-built, computerised micro-coextrusion system has been used to prepare intermediate compounds from the WO3–Bi2O3 binary oxide system and the design and optimisation of this technique are discussed.