Low-temperature-synthesized Mn-doped Bi2Fe4O9 as an efficient electrode material for supercapacitor applications

Abstract

Micro-rectangle-shaped manganese-doped bismuth ferrite (Mn-doped Bi₂Fe₄O₉) was prepared at a very low temperature by a cost-efficient hydrothermal technique. Manganese was doped in bismuth ferrite at three different concentrations of 1.5 mmol (BFMO1), 2.5 mmol (BFMO2), and 3.5 mmol (BFMO3). BFMO1 showed excellent electrochemical performance based on its structural, morphological, and electrochemical properties. Physicochemical characterization was carried out using XRD, Raman, XPS, FESEM, TEM, and BET analyses. The XRD peaks revealed the doping of Mn at a lower concentration in Bi₂Fe₄O₉ rather than forming a new phase in BFMO1. The different vibration modes in the Raman spectra also proved the presence of Mn-doped Bi₂Fe₄O₉ in BFMO1. The micro-rectangle-shaped particles with a length of 1.8 μm and breadth of 1.6 μm, along with spherical-shaped nanoparticles, were noticed in FE-SEM images of BFMO1. On increasing the concentration of manganese, the micro-rectangle particles broke down into small flakes. The surface area of BFMO1 was 17.06 m² g⁻¹, as measured using BET analysis. The micro-rectangular Mn-doped Bi₂Fe₄O₉ (BFMO1) showed the highest specific capacitance of 487 F g⁻¹ at the current density of 1 A g⁻¹ with 3 M aq. NaOH in a three-electrode configuration compared with the other composites. The symmetric-type BFMO1 supercapacitor device showed the specific capacitance of 81.57 F g⁻¹ at a current density of 0.5 A g⁻¹, with an energy density of 19 W h kg⁻¹ and power density of 325 W kg⁻¹. The BFMO1 symmetric device possessed excellent cyclic stability up to 5000 cycles with 87.7% capacitance retention.