Triple Layer Heterojunction WO₃/BiVO₄/BiFeO₃ Porous Photoanode for Efficient Photoelectrochemical Water Splitting

Storing sunlight into chemical bonds for further use as a photoelectrochemical (PEC) water splitting is one of the most promising methods to fulfill the human interminable energy desire. In this research, a triple heterojunction WO3/BiVO4 (BVO)/BiFeO3 (BFO) porous photoanode is synthesized through a sol–gel method and its PEC performance is compared to those of WO3/BVO as well as pristine films. The triple layer heterojunction photoanode is comprised of three interdiffused layers of each component with interconnected pores, thickness of 340 nm, and absorption edge slightly red-shifted compared to pristine layers. Although WO3/BVO junction demonstrates enhanced PEC performance, introduction of BFO on WO3/BVO dramatically improves the overpotential and charge transfer resistance. Not only the appropriate band alignment between WO3 and BVO but also the self-polarization behavior as well as p–n junction formation by BFO top layer entirely improves the PEC performance of the triple layer heterojunction photoanode. This photoanode also shows promising photostability and electron lifetime thanks to its enhanced charge separation compared to WO3/BVO and pristine components.