Construction of a homologous bimetallic oxide Bi2Fe4O9@Bi25FeO40 heterostructure to boost supercapacitor performance†

Herein, a Bi₂Fe₄O₉@Bi₂₅FeO₄₀ heterostructure with a high specific surface area of 30.07 m² g⁻¹ and abundant heterogeneous interfaces was successfully fabricated and applied to supercapacitors for the first time. The Bi₂Fe₄O₉@Bi₂₅FeO₄₀ electrode exhibits a high specific capacity (550.8 F g⁻¹ at 1.0 A g⁻¹) and good cycling stability (75% capacitance retention and 92.3% coulombic efficiency after 3000 cycles at 5.0 A g⁻¹), significantly outperforming the pure Bi₂Fe₄O₉ or Bi₂₅FeO₄₀ electrode. This work proposes an effective interfacial engineering strategy to enhance supercapacitor performance.