Construction of a Bi2MoO6:Bi2Mo3O12 heterojunction for efficient photocatalytic oxygen evolution

In this study, two different crystallographic phases of bismuth molybdate, alpha-Bi2Mo3O12 and gamma-Bi2MoO6 were synthesized hydrothermally. A series of Bi2Mo3O12/Bi2MoO6 heterostructures with different phase ratios were readily prepared by tuning the concentration of the molybdenum precursor while retaining the same bismuth precursor concentration. The Bi2Mo3O12/Bi2MoO6 heterojunction was found to substantially enhance the photocatalytic water oxidation capability relative to neat Bi2Mo3O12 and Bi2MoO6. The Bi2MoO6 and Bi2Mo3O12 were found to possess a complementary band alignment between which enabled the charge transfer process across the heterojunction interface. Ag and MnOx photodeposition was conducted on the heterostructures to affirm the charge transfer direction between the two crystal phases. Under visible light irradiation, photo-generated holes transfer from the active Bi2MoO6 phase to the inactive Bi2Mo3O12, suggesting efficient charge separation occurs between the two components, explaining the better photocatalytic performance.