Synthesis and properties of Fe3O4/polyaniline and its tiny magnetic field functions during oxygen transfer processes

The promotion of oxygen transfer by tiny magnetic fields has a great theoretical and practical significance in the improvement of fuel cell performance. In the present study, a Fe3O4/polyaniline (PANI) material is prepared via sol-gel and in situ polymerization. The structures of Fe3O4, PANI, and Fe3O4/PANI are characterized via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometry, and differential thermal analysis. A three-electrode electrochemical device and zinc air fuel cells (ZAFC) are used to investigate the functions of Fe3O4/PANI during the oxygen transfer process. The conductivity of Fe3O4/PANI is 0.30S cm(-1), the intrinsic coercivity is 10.18 kA m(-1), and the remanent magnetization is 5.27 A m(2) kg(-1). At a low Fe3O4/PANI load density, the tiny magnetic field can promote oxygen transfer, increase the electric double-layer capacitance, lower the charge-transfer resistance, and improve the ZAFC discharge performance. At a high load density of 7.11 mg cm(-2), the tiny magnetic field can inhibit oxygen transfer because of the interactions between the different magnetic poles. Fe3O4/PANI can also improve the ZAFC discharge performance under nonmagnetic conditions because of its higher electrochemical reduction activities. (C) 2012 Elsevier B.V. All rights reserved.