Probing Photo‐Assisted Charge Storage Mechanism Using Bi‐Fe Perovskite Oxide Electrode for Solar Supercapacitor

Abstract In this study, the rhombohedral crystalline pure phase BiFeO ₃ (BFO) of irregularly shaped spherical particles of ≈100 nm and energy bandgap of ≈2.31 eV are synthesized by sol–gel auto‐combustion method and explored as electrode material for photo‐assisted supercapacitor. The electronic structure studies revealed that the coexistence of heterovalent Bi and Fe elements accelerated the electrochemical redox kinetics and photo‐assisted charge storage properties. The resonant photoemission studies confirmed that near the Fermi level, the valence band spectra comprised the Fe3d and O2p hybridized states. The Fe‐O hybridized state felicitates the charge transfer transitions (O2p (h ⁺ ) + hυ ↔ Fe ³⁺ + e ⁻ ↔ Fe ²⁺ ), which assists the intercalation/de‐intercalation process of OH ⁻ anions. Therefore, BFO has delivered 26.77% photo efficiency and the enhanced specific capacity of 21 Cg ⁻¹ at 2 Ag ⁻¹ in aq. 3 m KOH under illumination, which is attributed to the accelerated photo‐generated charge carrier separation and storage with surface polarization effect. BFO also delivered capacitance retention of 77.5% even after 1000 continuous GCD cycles under visible light irradiation.