Efficient photoelectrocatalytic performances using a WO3/BiVO4 heterojunction photoanode: applied bias-promoted photoinduced charge transfer and separation†

Combining tungsten trioxide (WO₃) with bismuth vanadate (BiVO₄) to form a heterojunction photoanode offers a promising solution to achieving highly efficient photoelectrocatalytic (PEC) performances. In this work, we successfully fabricated the WO₃/BiVO₄ heterojunction on tungsten (W) foil via a hydrothermal route, followed by a successive ionic layer adsorption and reaction (SILAR) process. The PEC performances for synergetic H₂ evolution and organic pollutant degradation were significantly enhanced after the BiVO₄ nanoparticles were loaded on the WO₃ photoanode. The PEC performance with the WO₃/BiVO₄ heterojunction as the photoanode was demonstrated to be much more dependent on the applied bias potential (V_ab) than that with pristine WO₃ as the photoanode. Based on the various photoelectrochemical features and fundamental theory of semiconductor heterojunctions, it was well elucidated that, under the applied bias potential, the gradual diminishment and eventual reversal of the energy band bending at the heterojunction interface could achieve the efficient transfer and separation of more photogenerated charges, thereby enhancing overall PEC performances. This work highlights the roles of the evolution of the band bending in the WO₃/BiVO₄ heterojunction interface by applied bias in promoting the efficient transfer and separation of photogenerated charges.