Preparation And Performance Of Proton Exchange Membrane Materials At High Temperature

Proton exchange membrane fule cells(PEMFC)have attracted more attentions,because of high energy conversion rate,low pollution,start quickly,designed simply.In order to realize the industrialization development of proton exchange membrane fuel cells,there is need to improve the working temperature,reduce the use amount of the platinum.As a result of the limitation of the electrolyte,the PEMFC can operate just under 200?.Therefore,research about electrolyte of high temperature proton exchange fuel cells is the current tendency of PEMFC.Polybenzimidazole(PBI)have advantages of thermal stability,high mechanical strength.Oxidation is formed after its polymer in the gain and loss of hydrogen proton,and are able to produce some cross linking.Meanwhile,PBI form a continuous hydrogen bonds between the molecules,making it possible to deliver hydrogen proton.Pure PBI are insulators at room temperature,so it is necessary to modify PBI.We can improve the conductivity of the PBI by doping conducting ion.The current mainstream method is to use PBI film immerse into phosphoric acid.But under the condition of high temperature,phosphoric acid with high temperature erosion,resulting in a loss of proton conductivity.So the working temperature of PBI electrolyte is at 170?.It is necessary to find to rarely rely on proton conductors of the phosphoric acid as electrolyte.This paper tries to use solid phase respectively the CeP2O7/BPO4,CeP2O7/BPO4/GO,CeP2O7,Ce3+ doped CeP2O7,SnP2O7,mesoporous SnP2O7 electrolyte,testing their electrochemical performance.The full conclusion is as follows:Here,we report promising candidates for inorganic composite membranes for PEMFCs using solid CeP207/BPO4 and CeP2O7/BPO4/GO(without a liquid phase)by solid state reaction method at temperatures between 200? and 300?,through pressing sintering electrolytes.The structure and phase stability of the membranes are analysed by X-ray diffraction,Fourier transform infrared(FTIR)and thermos-gravimetric analysis(TGA),and the microstructure morphology is analysed by scanning electron microscopy(SEM).The electrical conductivity of CeP2O7/BPO4/GO composite electrolyte,temperature from 200? to 250?,increasing conductivity from 0.09 to 0.14 S·cm-1,but at the 300? conductivity reduce to 0.08 S·cm-1,higher than CeP2O7/BPO4 conductivity at the same temperature.Doped GO indeed can improve the conductivity of composite membrane.CeP2O7/BPO4/GO reached the highest at 250? power density of 240 mW·cm-2,significantly higher than the same temperature CeP2O7/BPO4 125 mW·cm-2.Showing CeP2O7/BPO4/GO composite electrolyte even under the condition of high temperature and low humidity,still has a high electrical conductivity and battery performance.By doping CeCl3,after reaction of CeO2 and H3PO4,we prepare Ce0.9Ce0.1P2O7,CeP2O7 powder.XRD analysis results show CeP2O7,Ce0.9Ce0.1P2O7 as cubic phase.By testing X-ray photoelectron spectroscopy,Fourier infrared analyzer analysis,the results can prove that low state of Ce3+ has been successfully added to the CeP2O7 lattice.Using the thermos-gravimetric analysis test the thermal stability of the powder.Ac impedance method is used to test the electrical conductivity of the electrolyte.Ce0.9Ce0.1P2O7 conductivity in 160? to 200?,from 0.006 S·cm-1 to 0.01 S·cm-1,but after 200?,as the temperature rises,the conductivity will be reduced,but the conductivity is still higher than that of pure CeP2O7.Ce0.9Ce0.1P2O7 single battery with better electrochemical performance of electrolyte,reached the highest at 200? of power density of 26.6 mW·cm-2,compared with only 18 mW·cm-2 with CeP2O7 highest power density.The results show that Ce0.9Ce0.1P2O7 is can be used as a potential electrolyte materials for high temperature proton exchange membrane fuel cell.Mesoporous SnO2 was synthesized by soft template method,and SnP2O7,mesoporous SnP2O7 powder and its corresponding electrolyte were respectively prepared.The structure and phase stability of the membranes are analysed by X-ray diffraction(XRD)and thermos-gravimetric analysis(TGA).The distribution of holes can be obtained by the BJH model,and SnP2O7 average particle is about 255 nm,the average pore diameter of about 4 nm,accordind with the standard size of mesoporous(IUPA).The microstructure morphology of SnP2O7 particles and pellets is analysed by transmission electron microscope(TEM)and scanning electron microscopy(SEM).The obtained particles and pores size of Meso-SnP2O7 are characterized by the ETA and BET.The electrical conductivity of mesoporous SnP2O7 increased from 180?to 220?,0.015 S·cm-1 at 220? and 0.0029 S cm-1 for non-mesoporous SnP2O7.However,as the temperature rises,the conductivity is significantly reduced.Mesoporous SnP2O7 has better electrochemical performance compared to nonporous SnP2O7,reaching 15 mW·cm-2 at 220?.At the same temperature of the non-mesoporous SnP2O7,the power density of non-mesoporous SnP2O7 only reach 4.1 mW·cm-2.