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 0.30 S cm−1, the intrinsic coercivity is 10.18 kA m−1, and the remanent magnetization is 5.27 A m2 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.

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► The performance of fuel cells can become better in tiny magnetic field.
► The efficiency of tiny magnetic field is related with Fe3O4/PANI load densities.
► Tiny magnetic field can decrease charge transfer resistance at lower load densities.
► Magnetic particles’ interactions disrupt oxygen transfer at larger load densities.
► To improve Fe3O4/PANI load density can increase electric double-layer capacitance.