Understanding the synergistic effect of WO₃-BiVO₄ heterostructures by impedance spectroscopy

WO₃-BiVO₄ n-n heterostructures have demonstrated remarkable performance in photoelectrochemical water splitting due to the synergistic effect between the individual components. Although the enhanced functional capabilities of this system have been widely reported, in-depth mechanistic studies explaining the carrier dynamics of this heterostructure are limited. The main goal is to provide rational design strategies for further optimization as well as to extend these strategies to different candidate systems for solar fuel production. In the present study, we perform systematic optoelectronic and photoelectrochemical characterization to understand the carrier dynamics of the system and develop a simple physical model to highlight the importance of the selective contacts to minimize bulk recombination in this heterostructure. Our results collectively indicate that while BiVO₄ is responsible for the enhanced optical properties, WO₃ controls the transport properties of the heterostructured WO₃-BiVO₄ system, leading to reduced bulk recombination.