The Preparation And Applicati On Of Perovskitetype Oxide Catalst In Air Electrode

Air electrode is extensively equipped in fuel cell and metal-air battery, settled between the electrolyte and air, employed to be cathode in discharging procedure. In this article, the approaches to enhancing the air electrode performance were examined, namely preparing the more effective oxygen reduction catalysts to lessen the electrochemical polarization and improving the electrode structure to decrease the material diffusion resistance.Ten kinds of perovskite-type oxides were synthesized by the calcination of amorphous citric acid complex precursors. The thermal decomposition behavior of the precursor was examined by means of thermogravimetry (TG). X-ray diffraction verified the catalyst materials with obvious characteristic diffraction peaks and perfect crystalline phases.In the experiment of H2O2 catalytic decomposition, the catalytic decomposition activity of La0.8Sr0.2MnO3 was high and that of LaCoOs reached the highest among ten kinds of perovskite-type oxide catalysts. By measuring the curve of steady-state polarization and AC impedance , the electrochemical activity of catalyst was investigated. The results showed that La0.8Sr0.2MnO3 exhibits the highest electrochemical activity among all of the catalysts. It suggested that the higer the activity of H2O2 catalytic decomposition the higher the electrochemical activity with the exception of LaCoOs presumably for inherent instability. The study on AA'BOs and ABB'O3 showed that the partial substitution of A-site or B-site ion could always obtain new catalysts with good catalytic activity.Combined with the investigation of mass transfer on the surface of air electrode, the semi-hydrophobic and porous gas diffusion electrodes were fabricated by use ofas catalyst. Then employing Hg/HgO elecreode as reference electrode and nickel screen as counter electrode, a semi-cell model was made. The optimum conditions for air electrode preparation were shown as follow: 20% PTFE in active layer, thickness of active layer 0.2~0.35mm, diffusion layer 0.3mm, compacting pressure 20MPa and layers sequence D|S|A layout. The air electrode exhibited good performance that current was as high as 378mA at -0.6V ( Vs Hg/HgO ).The mathematical process of polarization curve revealed that the fabrication technique of air electrode was steady and prone to bring high electrode performance.