Preparation And Characterization Of Novel Proton Exchange Membrane Based On Nafion

Proton exchange membrane fuel cell(PEMFC) is an electrochemical device which directly converts the chemical energy of the fuel and oxidant into electrical energy,and the fuel of PEMFC is H₂ or methanol.PEMFC has been considered as a promising alternative energy source because of their high efficiency and low environmental impact.The proton exchange membrane is one of the key materials in PEMFC,which plays the roles on separating the fuel from the oxidant ahd conducting proton.The PEMs based on the perfluorosulfonic polymers have been used for practical PEMFC systems.However,further progress in this field has been restricted by the in sufficient performance of these membranes.Due to their high cost,high methanol crossover and dramatic decreasing in the proton conductivity in the high temperatures,these perfluorinated polymer electrolytes could not be used in the Industrial production.In this paper,we focus on modifying drawbacks of Nafion membrane in order to improve capacity of water,reduce methanol permeability and the cost.The innovative achievements obtained are mainly as follows:Novel inorganic-organic composite membranes based on modified Nafion by doping hydrophilic inorganic.Nafion/sodium titanate nanotubes and Nafion/bentonite composite membranes were fabricated firstly.It was shown by SEM and XRD that inorganic distributed uniformly in the membranes and there were no reunion.Study focused on the trend of water uptake of composite membranes with different inorganic contents at different temperature and change of proton conductivity by the impact of water uptake.It was observed that composite membranes had good performance such as the high water-uptake,which improved the proton conductivity significantly at high temperature.Nafion/PVDF blend membranes and Nafion/SPSF blend membranes were fabricated by the methodology of polymer blend.Study focused on the water uptake, swelling degree and the trend of methanol permeability with different polymer contents at different temperature.Methanol permeability was measured by membrane diffusion method.The results showed that compared with Nafion membrane,methanol permeability of blend membranes decreased by about one order of magnitude.It was obvious that the addition of PVDF and SPSF significantly improved the methanol permeability of blend membranes.Novel Nafion/Na₂Ti₃O₇/H-PTFE and Nafion/CNFs composite membranes were fabricated firstly.Study focused on the proton conductivity and mechanical behavior of composite membranes.It was obvious that the addition of reinforcement significantly improved the mechanical properties and anti-swelling capacity of composite membranes, so that objective of reducing costs can be achieved by reducing the dosage of Nafion resin.Proton conductivity of Nafion/CNFs composite membrane was similar with Nafion membrane.There are 57 figures,6 tables and 75 references in this thesis.