Band Edge Engineering in BiVO4/TiO2 Heterostructure: Enhanced Photoelectrochemical Performance through Improved Charge Transfer

The efficient separation of photogenerated electron hole pairs and stability against corrosion are critical preconditions for a photoelectrode to achieve a high photoelectrochemical performance. In this work it is shown how both criteria can be met by employing a heterostructure of bismuth vanadate (BiVO4) and titanium dioxide (TiO2) as the photocatalyst. Using electronic structure calculations, an alteration of the band alignment is predicted at the heterojunction from type I to type II by hydrogen treatment of the top TiO2 layer. Guided by this idea, we have fabricated heterostructures of BiVO4 and TiO2 and studied the effect of hydrogen treatment. The achieved band engineering results in a significant improvement in photocurrent density, up to 4.44 mA cm(-2) at 1.23 V vs RHE, and a low onset potential, -0.14 V vs RHE, under visible light illumination. The enhanced photoelectrochemical performance originates in facilitated hole transport to the electrode surface and enhanced photoabsorption in the TiO2 layer. This work is an example of how hydrogenation can be used to tailor the properties of BiVO4/H:TiO2 heterostructures and provides valuable insights for the further development of similar material combinations.