Activating a TiO₂/BiVO₄ Film for Photoelectrochemical Water Splitting by Constructing a Heterojunction Interface with a Uniform Crystal Plane Orientation

The construction of a heterojunction has been considered one of the most effective strategies to improve the photoelectrochemical (PEC) performance of photoanodes; however, most researchers only focus on the design and preparation of a novel and efficient heterojunction photoelectrode, and the investigation on the effect of the heterojunction interface structure on PEC performance is ignored. In this work, a TiO2/BiVO4 photoanode with a uniform crystal plane orientation in the heterojunction interface (TiO2-110/BiVO4-202) was prepared by an in situ transformation method. We found that the PEC activity of the TiO2/BiVO4 photoanode can be activated by constructing such a heterojunction interface. Compared with a TiO2/BiVO4 photoanode with a random crystal plane orientation prepared by a simple soaking–calcining method (S-TiO2/BiVO4, 0.04 mA/cm2 at 1.23 VRHE), the TiO2/BiVO4 photoanode prepared by the in situ transformation method (I-TiO2/BiVO4) exhibits a significantly better PEC performance, and the photocurrent density of I-TiO2/BiVO4 is about 2.2 mA/cm2 at 1.23 VRHE under visible light irradiation without a cocatalyst. This is mainly attributed to the fact that I-TiO2/BiVO4 has a faster electron transfer rate in the heterojunction interface according to the results of PEC analysis. Furthermore, density functional theory (DFT) calculations show that the BiVO4-202 surface has a higher Fermi energy level, thereby expediting the photogenerated carrier transport in the heterojunction interface. This work corroborates and strengthens the view that the heterojunction interface structure has a significant effect on the PEC performance.