Three-dimensional core-shell Fe₃O₄/Polyaniline coaxial heterogeneous nanonets: Preparation and high performance supercapacitor electrodes

Although polyaniline (PANI) demonstrates a great potential as high performance pseudocapacitor materials for supercapacitors, poor cycle stability due to structural instability is the major hurdle for practical applications. Therefore, designing PANI-based supercapacitors with structure matching performances is highly desirable. In this study, three-dimensional (3D) core-shell Fe₃O₄/PANI coaxial heterogeneous nanonets were rationally fabricated via magnetic field induced self-assembly and in situ polymerization. The as-prepared Fe₃O₄/PANI nanonets were successfully employed as supercapacitor electrode materials. With the magnetic field derived nanochains from Fe₃O₄ microspheres as the framework for PANI growth and strain buffer support and the PANI nanofibers as the electrochemically active part, these nanonets realized high specific capacitance, long cycling life, and good rate capability. To be more specific, Fe₃O₄/PANI nanonets displayed a specific capacitance of 620 F g^-1 at 1.0 A g^-1 in 1.0 M H₂SO₄ solution and capacitance retention of 85% after 2000 cycles at 2.0 A g^-1. Compared to other Fe₃O₄/PANI hybrids, the obtained better electrochemical performances of these Fe₃O₄/PANI nanonets were a result of the complementary contributions of both componential structures in the designed composite electrode. The strategy renders a possibility for using metallic oxide as the favorable support for conducting polymers to effectively store energy.