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 (BiVO 4 ) and titanium dioxide (TiO 2 ) 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 TiO 2 layer. Guided by this idea, we have fabricated heterostructures of BiVO 4 and TiO 2 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 TiO 2 layer. This work is an example of how hydrogenation can be used to tailor the properties of BiVO 4 /H:TiO 2 heterostructures and provides valuable insights for the further development of similar material combinations.