Phase- and Crystal Structure-Controlled Synthesis of Bi₂O₃, Fe₂O₃, and BiFeO₃ Nanomaterials for Energy Storage Devices

Abstract

Controlling the phase and crystal structure of nanomaterials is a challenging mission in a wet chemical method and has remarkable importance to the materials properties. Herein, we demonstrate a facile sol−gel method to synthesize Bi 2 O 3 , Fe 2 O 3 , BiFeO 3 , Bi 36 Fe 2 O 57 , secondary phase, and mixed phase of BiFeO 3 (Bi 25 FeO 40 and Bi 2 Fe 4 O 9 ) by tailoring the parameters such as molar concentration, calcination temperature, and duration. Further, all the electrode materials were demonstrated for supercapacitor (SC) application. The pure-phase BiFeO 3 nanoparticles show a highest specific capacitance of 253 F/g at a current density of 1 A/g compared to all other electrodes under a 3 M KOH electrolyte. The higher specific capacitance of BiFeO 3 nanoparticles is ascribed to their higher surface area, pure ABO 3 structure, and lower charge-transfer resistance. Moreover, the BiFeO 3 nanoparticles were also tested under a neutral electrolyte (1 M Na 2 SO 4 ) and found to have 3.7 times lower specific capacitance compared to the alkaline electrolyte (3 M KOH). The electrokinetic study of the as-synthesized active electrodes illustrates the maximum capacitive involvement to store the overall charge. The BiFeO 3 nanoparticles display outstanding stability with a retention rate of 99.02% after 1100 consecutive galvanostatic charge−discharge cycles at various current densities. Moreover, a solid-state symmetric SC device (SSD) was fabricated using BiFeO 3 nanoparticles. The device delivered a maximum energy density of 17.01 W h/kg at a current density of 1 A/g and a power density of 7.2 kW/kg at a current density of 10 A/g. The BiFeO 3 SSD showed an excellent capacitive retention rate of 88% after 5000 cycles, suggesting that it could be a promising electrode material for practical application in energy storage devices.

Blossoming of Multivalent Iron Phosphate Microplatelets Grown on Multiwall Carbon Nanotube Frameworks: Investigation of Supercapacitive Performance through Symmetric and Asymmetric Configurations

“…This result supports the calculated “ b ” value from the CV curve conforming to the pseudocapacitive nature of the CNT/FPO electrode. “ C 1 ” and “ C 2 ” represent the mass capacitances and R L indicates the leakage resistance. , …”

“…"C 1 " and "C 2 " represent the mass capacitances and R L indicates the leakage resistance. 52,53 According to the Bode plot (Figure 9e), the phase angle is −82°(close to 90°), which indicates outstanding capacitive performance. Given that resistive impedances and capacitances are equal at a phase angle of −45°, the relaxation time characteristic at that specific phase may be calculated using the formula τ o = 1/f o and is shown to be 0.2 s, agreeing with the findings of the preceding conclusion.…”

Facile Solvothermal Synthesis of NiO/g-C3N4 Nanocomposite for Enhanced Supercapacitor Application

“…Peak currents in CV curves fluctuate with the scan rate that is regulated by diffusive and capacitive processes mediated by a redox reaction. Several approaches for denoising diffusive and capacitive control processes for pseudocapacitive electrodes have been reported [60,61]. Brezesinski et al, in particular, proposed a generalized equation for electrokinetic studies employing CV studies at various sweep rates.…”

Exploring morphological variation in bismuth ferrite nanostructures by pulsed laser deposition: synthesis, structural and electrochemical properties

“…Supercapacitors have several advantages over other storage devices, such as a higher power density, rapid charge/discharge, extended lifetime, and they are environmentally friendly. In recent years, researchers have proposed various designs of supercapacitors [6][7][8]. However, the demand for those with high performance and low cost remains high [9].…”