| Direct methanol fuel cell (DMFC) is considered to be one of the most promising energy sources in the future, owing to its high power density, simple design and operation, easy fuel storage and transportation. Proton exchange membrane as one of the key components of fuel cell is received more and more attention.This paper aims to prepare high-performance proton exchange membrane by means of the organic-inorganic hybriding approach. Chitosan (CS) and sulfonated polyetheretherketone (SPEEK) with a good methanol-resisting property and a low price were selected as polymer membrane materials and sub-micron spherical titania as the inorganic filler material. To enhance the proton conductivity and the compatibility of organic and inorganic interface, the surface of titania was modified with various functional groups through chemical adsorption method. The modified titania submicrospheres were incorporated into the polymer matrix to prepare a variety of new proton exchange membranes. The membrane performances were systematically investigated.1. Organophosphorylated titania submicrospheres (OPTi) of controlled size (250-875 nm) were synthesized using amino trimethylene phosphonic acid (ATMP) as phosphorylation reagent and then incorporated into a chitosan (CS) matrix to fabricate CS/OPTi hybrid membranes. The additional -PO3H2 groups enhanced the proton conductivity of the hybrid membrane, simultaneously, the presence of OPTi reduced the free volume of membranes and twisted pathway for methanol transport, thus resulting in reduced methanol permeability. Among all of the as-prepared hybrid membranes, the membrane contained 15wt.% OPTi (600 nm) exhibited the highest proton conductivity of 0.011 S cm-1 and a lower methanol permeability of 5.32×10-7 cm2 s-1 at a 2 M methanol feed.2. Titania submicrospheres were sulfonated using 4,5-Dihydroxy- 1,3-benzenedisulfonic acid disodium through a facile chelation method. The obtained TiO2-SO3H was incorporated into SPEEK matrix to fabricate SPEEK/TiO2-SO3H hybrid membranes. The presence of TiO2-SO3H inhibited the SPEEK chain mobility and improved the membrane resistance to dimensional swelling and thermal stability. By comparison with the pure SPEEK and SPEEK/TiO2, the improved interfacial compatibility within the SPEEK/TiO2-SO3H membranes simultaneously enhanced the proton conducting and methanol rejecting property. The SPEEK/TiO2-SO3H-15 membrane showed a proton conductivity of 0.053 S cm-1 and a reduced methanol permeability of 4.19×10-7 cm2 s-1 at a 2 M methanol feed.3. Inspired by the proton conducting mechanism in nature, a series of titania spheres modified with amino, carboxylic, phenyl groups and amino acids were prepared, and then incorporated into SPEEK to fabricate high performance hybrid membranes. It was found that the membrane containing titania modified with amino acids exhibited higher proton conductivity (0.066 S cm-1 at 20 oC). It could be deduced that when the amount of proton donors was abundant, the presence of proton receptor promoted the proton conduction, but when the proton donors were scarce, the presence of proton receptor impeded the proton transfer. Amino acids containing both proton donor (-COOH) and receptor (-NH2) served as a good"buffer"against the fluctuation of the external proton donor-receptor environment and thus exerted a favorable synergistic effect on proton conductivity.
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