Z-scheme heterojunctions with double vacancies semiconductors MoO3−x and Fe-doped W18O49 for photocatalytic nitrogen fixation

Ammonia gas has important application value in many fields. However, a large amount of energy is consumed to prepare ammonia by the Haber-Bosch process. A cleaner catalytic way to prepare ammonia has become a common goal of human beings. In this paper, Z-scheme heterojunction MoO3−x/Fe-W18O49 was prepared by two-step solvothermal method. The prepared MoO3−x is a flower-like structure formed by the stacking of nanosheets, which can be applied as the attachment carrier of Fe-W18O49 nanowires to effectively inhibit the aggregation of nanowires. Therefore, Fe-W18O49 nanowires will have more oxygen vacancies (OVs) on the surface of the catalyst as the active center of the reaction. MoO3-x containing OVs has LPSR effect, which can enlarge the light absorption range of the heterojunction. In addition, the vacancies contained in MoO3−x can promote the recombination of weak reducing electrons and weak oxidation holes. The catalyst MoO3−x/Fe-W18O49 exhibits strong redox capacity, which is conducive to the occurrence of nitrogen fixation reaction. Under the simulated sunlight condition, the ammonia production rate reached 137.5 µmol g−1 h−1 without any sacrificial reagent. MoO3−x/Fe-W18O49 has good catalytic performance and stability. This work has a certain reference value for the construction of efficient heterojunction catalyst for photocatalytic nitrogen fixation.