Synthesis of Bi2WO6 photoanode on transparent conducting oxide substrate with low onset potential for solar water splitting

Abstract

To enable water splitting in photoelectrochemical cells, the conduction-band (CB) and valence-band edges must straddle the hydrogen-reduction and water-oxidation potentials; however, the CB edge potential of many photoanodic semiconductors is insufficient. Here, we demonstrate the nanostructured Bi₂WO₆ for photoanodic application, which has a high, flat-band potential of 0.15 V vs. RHE. Single-phase, orthorhombic Bi₂WO₆ nano-structures were successfully grown on an FTO substrate through a two-step hydrothermal synthesis with subsequent thermal treatment at 600 °C. The synthesized Bi₂WO₆ photoanode shows a lower onset potential and improved photocurrents which were enhanced further by a factor of three by coating the surface with Co-Pi. The low onset potential of the Bi₂WO₆/Co-Pi photoanode results in a higher operating photocurrent in a p/n photodiode cell combined with a p-Si/n-Si/Pt photocathode.