Fe Metals Phthalocyanines As Oxygen Reduction Catalysts

Gas diffusion electrodes, which are widely used in alkaline fuel cells and air batteries, have a great effect on the performance of batteries. But the oxygen reduction reaction (ORR) on electrode critically obstructs the development of those batteries due to small reversible characteristics and difficult process. The most effective factor on gas diffusion electrodes is dependent on catalyzer. Metals in Platinum group are the most effective catalyst for ORR because of its high electrocatalytic activity and chemical stability. However, These metals are very expensive and limited in their commercial application. Therfore, how to advance the activity of gas diffusion electrode is most important for alkaline fuel cells and air batteries.In this paper, the synthesis of FePc and bi-FePc and their heat treatment under flowing argon atmosphere at different temperatures is reported. The physics phasic speciality were characterized by UV-vis spectrum,IR spectrum,granularity and element analysis. The heat stability of the two materials was tested by TG/DTG. The gas diffusion electrodes were prepared and the effects of FePc and bi-FePc before and after heat treatment on ORR in alkaline medium were investigated using polarization curves, Tafel curves and electrochemical impedance spectroscopy (EIS).It is shown that the temperature of heat treatment to FePc and bi-FePc had obviously effect on ORR. EIS simulation exposed that FePc and bi-FePc after heat treatment had different impact on each part of ORR (R_ct-electrode intrinsic resistance between the interfaces of electrode and electrolyte and R_c-charger transfer resistance of electrochemical reaction). It is found that FePc and bi-FePc after heating at 600℃had the best catalysis due to minimum R_c+R_ct. The characteristic of two semi-circles on all the gas diffusion electrodes was present on the EIS Nyquist plot. The equivalent circuit for ORR was present to explain this characteristic. A discussion on the possible catalysing mechanism for ORR on FePc and bi-FePc electrodes was made.