Synthesis of BiFeO3/Bi25FeO40 heterojunction structure and precise adjustment of forbidden band width

An effective strategy to enhance the performance of perovskite oxides is to precise adjust their sizes and forbidden bandwidth. However, it is challenging to synthesize perovskites with the desired morphology and structure because perovskites typically require harsh synthesis conditions, such as high pressure and high temperature. Herein, we designed and synthesized BiFeO3/Bi25FeO40 heterojunction nanoparticles with adjustable energy-band structure using the simple sol-gel method by adjusting the concentration of Fe3+ and calcination temperature. As a result, the BiFeO3/Bi25FeO40 heterojunction exhibits a lower band gap than BiFeO3, Bi2Fe4O9, Bi25FeO40, and BiFeO3/Bi2Fe4O9. The reduced band gap of BiFeO3/Bi25FeO40 is due to the formation of heterojunction structure. Meanwhile, the three strategies of heterojunction construction, temperature controlling, and Fe3+ doping can precise regulate the band gap structure of bismuth ferrite (BFO). These findings not only provide guidance for the construction of perovskite heterostructures but also promote the application of BFO in photocatalytic and other redox reactions.