The Study Of Enriched Oxygen Materials For Cathodic Catalyst Of PEMFC

Savings in fossil fuel, due to high efficiency of energy conversion, low pollution level, low noise and low maintenance costs render fuel cells preferable over other energy conversion devices and premier candidates as portable source of power for light duty vehicles and buildings and as replacement for rechargeable batteries. In reality, air instead of pure oxygen is used as cathode oxidant. However, the lower oxygen particle pressure which is only about 0.021MPa in air and much inert gas which remains in catalyst layer will result in a cathode voltage loss for several tens of mill volts. It seems reasonable to expect that if oxygen storage materials are incorporated into the catalyst layer of PEFMC cathode, local oxygen concentration will be increased, which can in turn enhance the fuel cell performance.In this paper, CeO₂ and MnO₂ have been studied as enriched oxygen materials for catalysts. In consideration of chemical characteristic of each material CeO₂ is incorporated into Pt/C catalyst layer by sol-gel method and MnO₂ is deposited into catalyst layer by chemical oxidation. The compound catalysts appearance and the particles size disperser situation are measured by XRD and TEM physical methods. The electrochemical performance of electrode prepared by compound catalysts is investigated by using the CV, galvanostatic discharge method. The result of compound catalysts analysis show that enriched oxygen materials CeO₂ and MnO₂ can enhance oxygen redox in catalyst layer of electrode in spite of reducing active area of Pt/C catalyst because of materials covering. It is fond that 2%wt CeO₂ and 4%wt MnO₂ are the best incorporated mass in the Pt/C catalyst comparing with the others. Consequently, performance of PEMFC which use compound catalysts as cathode catalyst is better than the one without enriched oxygen materials.Finally, kinetic parameters of electrode with compound catalysts are calculated by CV, Tafel and electrochemical impedance spectroscopy analysis. The analysis show that compound catalysts and Pt/C have the same two electrons reaction principle of oxygen atoms on Pt in electrode, but electrode polarization resistance is reduced in compound catalysts meanwhile the bigger exchange current density i₀ indicates that high capable of oxygen deoxidize. Through the simple analysis battery dynamic response, the compound catalyst can reduce fuel cell voltage loss.