Interfacial Engineering of BiVO4/Bi2Mo2O9 Heterojunction Toward Photogenerated Carriers Anisotropic Transfer

Developing an advanced strategy to decrease the charge recombination of BiVO₄ is a vital requirement to boost charge transfer for photoelectrochemical water oxidation. Herein, a type II BiVO₄/Bi₂Mo₂O₉ heterojunction is successfully synthesized on fluorine-doped tin oxide substrate by successive ionic layer adsorption and reaction method. Thanks to the Fermi-level energy difference of 275 mV between BiVO₄ and Bi₂Mo₂O₉, an outward built-in electric filed pointing from Bi₂Mo₂O₉ to BiVO₄ is induced, which accelerates the directional flowing of photogenerated electron and hole. Such a unique design structure fastens the electron migration from BiVO₄ to Bi₂Mo₂O₉, and the holes will transfer to the surface to participate in water oxidation. The longer lifetime (9.2 ns) by time-resolved transient photoluminescence signifies that the Bi₂Mo₂O₉ can boost interfacial carriers’ anisotropic migration; the surface charge transfer rate of BiVO₄/Bi₂Mo₂O₉ is up to 387.6 s⁻¹ (1.4 V vs reversible hydrogen electrode (RHE)). The BiVO₄/Bi₂Mo₂O₉ heterojunction exhibits a remarkable charge separation efficiency of 64% and outstanding photocurrent density of 0.9 mA cm⁻² at 1.23 V versus RHE.