Preparation Of Metallo-polyphthalocyanine And Application In The Magnesium Air Fuel Cell

Metal-air cells are fuel cells, which they are promising power sources because of their high theoretical voltage, high specific energy, low cost, light weight, and environmental compatibility. The cathode reaction of a metal-air fuel cell involves an oxygen reduction reaction (ORR) process. Thus, the electrocatalyst in the cathode is an important factor in determining cathode performance.Because monomer phthalocyanine catalysts have low activity and poor selectivity, we designed and synthesized metallo-polyphthalocyanine (MPPc) catalysts. The polymer is characterized systematically by a variety of means such as UV-Vis, FT-IR and1H NMR. The results confirm the structure of MPPc. The result of TG shows that MPPc is stable below500℃. The PPcM/C is prepared by dispersing metallo-polyphthalocyanine a high surface area carbon powder (Vulcan XC-72), and then heat-treated in Ar atmosphere. The electrocatalytic properties of catalysts have been evaluated by RDE measurements. The best heat-treatment temperature of the catalysts is400℃and the best proportion of PPcFe and C is1:1, whose initial potential for oxygen reduction in O2-saturated H2SO4is0.80V. The kinetic parameters confirm that PTPPFe/C catalyzes O2reduction mainly through a4-electron pocess. Linear sweep voltammetry and chronoamperometry tests were performed in order to observe the catalyst stability in different conditions. Almost no performance deficiency is observed after200potentiometric cycles and60h of chronoamperometry test. SEM, EDX, XRD and XPS are used to characterize elementary composition, microstructure and micromorphology. The results show that the active site of MPPc/C was M-N4in phthalocyanine ring, and the MPPc was dispersed homogeneously on the surface of XC-72.Magnesium air fuel cell (MAFC) single cells are assembled and the discharge performances are tested. The optimal anode materials are magnesium-manganese alloy doped with rare earth elements; the optimal thickness of gas diffusion layer is2mm; the poly-tetrafluoro-ethylene (PTFE) content of gas diffusion layer is50%; the optimal pore-forming material is anhydrous sodium sulfate (Na2SO4); the optimal pore-forming material content of gas diffusion layer is33%; the optimal thickness of catalyst layer is0.1mm; the optimal ratio of compositions of catalyst is activated carbon:acetylene carbon black:PTFE=2:1:3; The optimal pore-forming material content of catalyst layer is25%; the optimal distance between anode and cathode is6mm. In the condition of optimal preparation technology, the performance of MAFC single cell with PPcFe and Pt/C is tested. The result show at high current density, the PPcFe/C catalyst is close to the Pt/C catalyst. The discharge curves of single MAFC with different catalysts is carried out at constant current density of20mAcm-2for more than11h. It is seen that MAFC single cell shows an excellent stability over the entire test duration.