Study On Composite Proton Exchange Membrane Based On Prussian Blue Analogue

Fuel cell is a clean energy conversion device that converts chemical energy of hydrogen into electricity,and the reaction product is only water.At present,proton exchange membrane fuel cell（PEMFC）technology is one of the most mature commercial applications and has become the focus of research and development in recent years.However,severe proton exchange membranes（PEMs）dehydration usually occurs under high temperature and low humidity conditions,resulting in a significant decline in the actual performance of fuel cells.Previous optimization strategies tend to design and control the morphology structure of water absorption or hydrophilic domains in PEMs,while proton transport type（Grotthuss or Vehicle type）as a basic mechanism is rarely paid attention to,resulting in a lack of significant improvement.In this work,a new way to improve the performance of PEMs under low relative humidity conditions is proposed by using Cu^II[Fe^III（CN）₆]_2/3 Prussian blue analogue（Cu Fe-PBA）as packing additive.Although the filler’s internal frame is hydrophobic,due to the appropriate lattice length of Cu Fe-PBA,the lattice water molecules contained in the framework may form a well-connected hydrogen bond network that helps facilitate Grotthuss type proton transport even at low relative humidity.Therefore,in this study,Cu Fe-PBA containing lattice water was creatively developed as PEMs filler,and sulfonated polysulfone（SPSf,Sulfonation Degree 60%）with excellent thermal and mechanical stability was used as polymer matrix.Uniform solid Cu Fe-PBA nanoparticles were synthesized by simple aqueous phase precipitation.SPSf composite PEMs containing Cu Fe-PBA were prepared by solution casting method.We focus on the internal correlation between water molecule deployment and proton transport,and characterize the lattice water content of Cu Fe-PBA framework.The composite membranes containing 0.5 wt%,1.0 wt%,1.5 wt%and 2 wt%PBA fillers were fabricated to compare with the pristine SPSf membrane.The effects of different contents of Cu Fe-PBA fillers on the microstructure and basic properties of the membranes were investigated,and the mechanism of swelling inhibition and proton transfer promotion was discussed.The improvement effect of Cu Fe-PBA on PEM and fuel cell performance under high temperature and low humidity conditions was verified and compared.The results show that among the SPSf/Cu Fe-PBA composite PEMs,the membrane by doping 1.5 wt%Cu Fe-PBA in the SPSf matrix shows significantly optimized performance in both out of situ and in situ evaluation,especially at low relative humidity,which is comparable to commercial Nafion 212.Based on the primary work mentioned above,the performance of composite membranes based on Prussian blue analogues（PBAs）of different additives were explored,and the general rule of PBAs affecting the performance of composite membranes was summarized to further prove its universal applicability.Ni Fe-PBA and Mn Co-PBA nanoparticles and the resulting composite membranes were prepared by the same method.The results showed that the three different PBAs composite films had similar performances in compatibility,mechanical properties,water absorption and swelling behavior.The hybridization of Ni Fe-PBA and Mn Co-PBA fillers also effectively improved the proton conductivity,and the trend was consistent with that of Cu Fe-PBA,e.g.the best proton conductivity of each occurred at 1.5 wt%addition.Under the same conditions,the conductivity of the composite membranes is always in the order of SPSf/Cu Fe-PBA>SPSf/Ni Fe-PBA>pristine SPSf membrane,and the electrical conductivity of SPSf/Mnco-PBA composite film increases slowly and is only higher than that of SPSf pure film at low humidity.Therefore,Cu Fe-PBA filler has the best performance in improving the proton conductivity of the membranes.SPSf/Mn Co-PBA composite membranes showed resistance to chemical degradation over accelerated test,which is related to the use of manganese ions as free radical scavenger.The difference of the PBA-based additives in improving membrane performance is mainly due to the different content of water in PBA,the proportion of water molecule in Cu Fe-PBA is the highest,probably due to the degree of defects in their respective frame structures,leading to better proton transport behavior.