The Preparation And Charactrizations Of MOFs Based Proton Exchange Membranes

In the20th century, fuel cells have attracted extensive attention as a new way of generating electricity on the tide of nuclear power. The basic principle of fuel cells is different from that of thermal power in which it converts chemical energy of fuel into electrical energy through redox reactions without burning. The completion of fuel oxidation and oxygen reduction enables the electrochemical electron transfer, and the process has high conversion rate but no noise and pollution. Since the early1960s, the proton exchange membrane fuel cell (PEMFC) has been studied especially the core component proton exchange membrane (PEM). However, the perfluorosulfonic acid membrane such as Nafion(?) is almost the only commercial PEM, despite the high price. Therefore, design and exploitation of high-performance, low-cost proton exchange membrane is of importance to promote the further development and practical of fuel cells.Metal-Organic Frameworks (MOFs) are rapidly emerged as a kind of composite material in recent years which has a three-dimensional pore structure, the metal ions usually acts as the node to link with organic ligand and build the extension of3D structure. In electrochemistry field, especially the application of PEM, MOFs are rarely reported. In this context, our work focuses on developing a novel composite PEM through linking polymer materials with MOFs structure by chemical bonds, the main contents are listed as follows:(1) The Fe-MIL-101-NH2with functional groups was introduced into the SPPO through Hinsberg reaction to form uniform PEM. The membrane exhibited excellent proton conductivity:250mS/cm at90℃,98%RH. This is the first chemically synthetic to integrate MOFs with polymer material for the application of PEM. The proton conduction mechanism was investigated preliminarily, it suggested that MOFs itself and sulfimide provided protons, a complete proton conduction path from SPPO to Fe-MIL-101-NH2was built by, and water served as the carrier in the process.(2)1-(3-aminopropyl)-imidazole as proton receptor was absorbed into the hole of Fe-MIL-101-NH2, taking place of water molecules to be the proton carrier and connecting with SPPO by chemical bonds for preparation of high temperature PEM. The proton conductivity of membrane was40mS/cm at160℃, ambient humidity, and the methanol permeability is one third that of Nafion-115at30℃. In the view of proton conduction paths in the first chapter, Grotthuss mechanism and Vehicle mechanism was coexisted which achieved the proton conduction with heterocyclic nitrogen imidazole molecule as proton carrier.(3) Based on the study of the second chapter, thermostable SPPESK was used as matrix, organic ligand3-amino-1,2,4-triazole was grafted on the matrix to synthesize ZCCH. Nanoscale-orientation high temperature PEM was prepared by electrostatic spinning technique. The proton conductivity of membrane was81mS/cm at160℃, ambient humidity; the methanol permeability was0.7×10-7cm2/s, about6%of Nafion-115at30℃. Grotthuss mechanism played a role in the orientation of nano electrospinning, the high temperature proton conductivity of electrospinning membrane was gradually enhanced by the man-made proton conduction channel of the nanoscale electrospun as sulfimide was the proton donor and triazole was the proton donor and acceptor.(4)The GO/ZCCH were prepared in the system of GO on the basis of previous chapters. This material took advantages of the dual characteristic of GO and MOFs. The high-temperature PEM was obtained by the chemical reaction of GO/MOFs and SPPO. The proton conductivity of GO/ZCCH base membrane was120mS/cm at160℃, ambient humidity; the methanol permeability of GO/Fe-MIL-101-NH2base membrane is7%that of Nafion-115at30℃. The proton conduction was generated by the epoxy group on the surface of GO and the crystalline MOFs embedded in the GO layers that created new proton transfer path, the composite membrane thus achieved multidimensional proton conduction. Meanwhile, the polymer material involved also affected the proton conduction. The water retention of the GO/Fe-MIL-101-NH2base membrane was gradually faded after140℃resulting in the decrease of proton conductivity, but the proton conductivity of GO/ZCCH base membrane still continuously increased as temperature was increased. Such PEM offers promising performance in a wide temperature range (30～60℃), our study will provide a new insight into the applications of MOFs in PEM fuel cells.