Fuel Cell Oxygen Electrode Spinel Oxide Catalytic Materials

Oxygen electrode is an important issue in the development of fuelcells, and the most critical factor affacting their performances is thecatalysis of the oxygen reduction reaction (ORR). In this thesis work,investigations were carried out in following fields: (1) spinel Co₃O₄,CoFe₂O₄, NiCo₂O₄, MnCo₂O₄ and perovskite La_0.6Ca_0.4CoO₃ wereprepared by conventional heating method; (2) MnCo₂O₄ was synthesizedwith microwave (MW) irradiation technology; (3) X-ray diffraction(XRD) and scanning electronic micorograph (SEM) were employed tocharacterize the catalysts prepared; (4) The air diffusion electrodes(ADEs) were prepared with the synthesized oxides as catalysts, thepolarization curve technique and electrochemical impedencespectroscopy (EIS) methodes were used to study the electrocatalyticperformaces of the prepared oxides for ORR in alkaline medium; (5) Thepreparing factors influencing the performances of the ADEs were alsoinvestigated.The results showed that: (1) In all of the oxides synthesized byconventional heating, Co₃O₄ displayed the best catalytic performance forOER in alkaline medium meanwhile MnCo₂O₄ exhibited best in ORR,with the former giving a current density of 50 mA.cm^-2 at the potential of0.4 V (vs Hg/HgO) and the latter 80 mA.cm^-2 at -0.2 V (vs Hg/HgO); (2)The optimum conditions for synthesizing MnCo₂O₄ by microwave (MW)were obtained. The MnCo₂O₄ particles synthesized under these conditionsshowed nano-crystalline with high purity and a diameter of 10～20 nm.The ORR current density of the ADE with MnCo₂O₄ as catalyst reached96 mA·cm^-2 in air atmosphere at room temperature; (3) Compared toconventional heat treatment, MW method is significantly advantageous insynthesizing nanoparticles with uniformity diameter; (4) The ADEsprepared with the catalytic layer of 0.5 mm in thickness, and withVulcan-XC 72 as catalyst support, and a proportion of 20wt% for PTFEin active layer, showed the best performances.