Electropolymerized polyaniline/manganese iron oxide hybrids with an enhanced color switching response and electrochemical energy storage

Polyaniline (PANI) nanocomposites embedded with manganese iron oxide (MnFe₂O₄) nanoparticles were prepared as thin films by electropolymerizing aniline monomers onto indium tin oxide (ITO) glass slides pre-spin-coated with MnFe₂O₄ nanoparticles. The shift of the characteristic peaks of PANI/MnFe₂O₄ in UV-visible absorption spectra and Fourier transform infrared (FT-IR) spectra indicates the formation of composite films and the chemical interaction between the PANI matrix and MnFe₂O₄ particles. A coloration efficiency of 92.31 cm² C^-1 was obtained for the PANI/MnFe₂O₄ nanocomposite film, higher than that of the pristine PANI film, 80.13 cm² C^-1, suggesting a synergistic effect between the MnFe₂O₄ particles and the PANI matrix. An enhanced areal capacitance of 4.46 mF cm^-2 was also achieved in the PANI/MnFe₂O₄ nanocomposite film compared with 3.95 mF cm^-2 in the pristine PANI film by CV at a scan rate of 5 mV s^-1. The enhanced performances of the composite films were attributed to the pseudocapacitive properties of MnFe₂O₄ and rougher morphology caused by the embedment of MnFe₂O₄ particles into the PANI matrix. Finally, the sulfuric acid (H₂SO₄) concentration and temperature effects on the supercapacitive behavior of the pristine PANI and PANI/MnFe₂O₄ nanocomposite films were studied, suggesting the positive effects of decreasing H₂SO₄ concentration and increasing temperature in a low temperature range; higher temperatures can destroy the PANI structure and cause the degradation of PANI.