Performance Analysis of Phytic Acid-loaded Metal Organic Framework-Polybenzimidazole Composite Membrane in High Temperature Proton Exchange Membrane Fuel Cell
Adding additional proton conductors into polybenzimidazole(PBI)is an effective strategy to improve proton conductivity.In this study,the metal-organic framework MIL-101(Cr)was used to effectively load phytic acid and evenly distribute it in the PBI membrane to construct an additional proton transport pathway.The loading process of phytic acid did not destroy the original crystal structure of MIL-101(Cr).The composite membrane prepared has a higher phosphoric acid(PA)doping level,better thermal stability and stronger acid retention ability than the original PBI membrane.In addition,the MIL-101(Cr)particles loaded with phytic acid limited the movement of the PBI chain and improved the mechanical properties of the membrane.MIL-101(Cr)loaded with phytic acid constructed additional proton conduction pathways and high-density hydrogen bond networks in the PBI membrane to further increase the conductivity of the composite membrane.The conductivity of the PA-doped composite membrane can reach 0.0744 S·cm-1 at 160 ℃ under anhydrous conditions,while that of the PA-PBI membrane is only 0.0398 S·cm-1.In addition,the single cell performance at 160 ℃ without additional humidification and back pressure was tested.The maximum output power density of the composite membrane is 178 mW·cm-2,which is 38 mW·cm-2 higher than that of the PBI membrane.