Preparation And Characterization Of Triazole Grafting Titanate Nanotube For Elevated Temperature Proton Conductor Application

Proton exchange membrane fuel cell (PEMFC) is considered as the most promising new energy technology because of its special merits. However, high cost caused by the system complexity as well as the application of Pt catalyst has become a great barrier in the process of its commercialization. The increase in operating temperature of PEMFC can effectively decrease the size of the applied radiator because of the simplified heat management and can make the non-Pt catalyst applied possible. In addition, the improved tolerance to impurity of fuels for PEMFC operated at elevated temperature also decreases the price of its applications. However,, the common used perfluoronated membranes for current fuel cell technology, for example Nafion(?) from Dupont, are not suitable for elevated temperature applications because of their strongly humidity-dependent ionic conductivity and relatively low glass transition temperature. Thus, development of elevated temperature electrolyte membranes has become an active area for PEMFCs. One important approach for the development of elevated temperature membranes is to replace water with low-volatile proton solvent in the membrane. Among those developed proton conductors, heterocycles have been demonstrated to be promising candidates as they undergo a very similar behavior toward protons to that of water by nature as well as high boiling temperatures. However, leaching of the heterocycles by water produced during PEMFC operation can both decrease the proton conductivity and poison the catalyst, leading to low or even no performance of assembled fuel cell. Considering the above problems, we develop a technique to immobilize the triazole moieties onto titanate nanotubes for elevated temperature proton conductors. Some conclusions are drawn as followings:(1)The chemical composition of so-formed titanate nanotube is H2Ti3O7, and physical properties were characterized to be about5nm in inner diameter, lnm in tube wall thickness,100nm in length. In addition, it was thermally stable up to268.3℃, indicating its capability to be applied as elevated temperature substrate materials. Based on the microstructure of the synthesized nanotubes, the formation mechanism and the optimized synthetic conditions are analyzed. It has been found that the nanotubes are formed during the process of washing step and the hydrothermal treatment does not affect its structure. The optimized reaction condition for the synthesis of titanate nanotube was to react for48h under150℃. Besides, the morphology of the nanotube could not be affected by the acidity of washing solution, which demonstrated that the nanotube could be stably applied in the acidic environment of PEMFC.(2) The grafting of triazole moieties onto titanate nanotubes have been confirmed by means of element analysis, XPS and solid1H-NMR techniques. The formed triazole grafted titanate nanotube proton conductors are thermally stable up to314℃, and its proton conductivity reaches2.399mScm-1at160℃under anhydrous condition, demonstrating its potential application for elevated temperature proton conductor.