Phase-selective formation of γ-Fe2O3 in PANI nanocomposites for supercapacitors with structural and electrochemical comparison to α-Fe2O3

Abstract

Phase engineering of inorganic fillers offers an effective route to tune interfacial charge transport in polymer nanocomposites. α-Fe2O3 nanoparticles were prepared by a standard nitrate-citrate combustion process, while phase selective γ-Fe2O3 nanoparticles were synthesized via phytochemical-assisted nitrate-citrate combustion route using Morinda citrifolia fruit extract. Structural and magnetic analyses confirmed the formation of rhombohedral α-Fe2O3 exhibiting antiferromagnetic behavior and cubic spinel γ-Fe2O3 with ferrimagnetic ordering. Both nanoparticles were subsequently integrated into a polyaniline (PANI) matrix through in-situ polymerization. Influence of magnetic ordering and phase-dependent magnetic behavior among α-Fe2O3/PANI and γ-Fe2O3/PANI reveals the uniqueness of γ-Fe2O3 in electrochemical studies. Electrical and electrochemical measurements demonstrate that γ-Fe2O3/PANI nanocomposite exhibits enhanced conductivity, less charge-transfer resistance and higher supercapacitive performance in comparison to α-Fe2O3/PANI. The γ-Fe2O3/PANI electrode delivers specific capacitance 287.71 Fg−1, energy density 25.55 Wh kg−1 and power density 418 W kg−1 at 1 Ag−1 and retains 89.32% of specific capacitance after 2000 cycles. The comparative investigation of magnetic ordering and phase dependent magnetic behavior in α-Fe2O3/PANI and γ-Fe2O3/PANI nanocomposites reveals the distinctive electrochemical advantages of the γ-Fe2O3 phase. These findings highlight the significance of magnetic phase engineering as a viable strategy for tailoring interfacial charge-transfer processes in polymer-based nanocomposite electrodes, thereby providing a rational pathway for development of front-line energy-storage devices.