Abstract
Polymer electrolyte membranes (PEMs) for direct methanol fuel cell (DMFC) applications were prepared from a graft-copolymer (PSF-g-PSSA) consisting of a polysulfone (PSF) main chain and poly(styrene sulfonic acid) (PSSA) side chains with various average distances between side chains (Lav) and side chain lengths (Lsc). The polymers were synthesized by grafting ethyl p-styrenesulfonate (EtSS) on macro-initiators of chloromethylated polysulfone with different contents of chloromethyl (CM) groups, and by changing EtSS content in the copolymers by using atom transfer radical polymerization (ATRP). The DMFC performance tests using membrane electrode assemblis (MEAs) with the three types of the PEMs revealed that: a PSF-g-PSSA PEM (SF-6) prepared from a graft copolymer with short average distances between side chains (Lav) and medium Lsc had higher DMFC performance than PEMs with long Lav and long Lsc or with short Lav and short Lsc. SF-6 had about two times higher PDmax (68.4 mW/cm2) than Nafion® 112 at 30 wt % of methanol concentration. Furthermore, it had 58.2 mW/cm2 of PDmax at 50 wt % of methanol concentration because of it has the highest proton selectivity during DMFC operation of all the PSF-g-PSSA PEMs and Nafion® 112.
Highlights
Direct methanol fuel cells (DMFCs) using polymer electrolyte membranes (PEMs) represent one of the most attractive power sources because of their stable operation at relatively low temperatures, the high energy density obtained by using highly concentrated methanol solutions as fuel, and their simplicity [1,2]
One of the effective strategies to get both high proton conductivity and low methanol permeability is to develop PEMs prepared from graft copolymers consisting of two chemically different polymer segments: a main chain made from a polymer with low methanol permeability and side chains made from a polymer having proton conductive properties
The methanol permeability (PDMFC ) during DMFC operation was evaluated from the following equation, assuming that the PEM was in contact with the feed methanol solution and feed cathode gas: PDMFC =
Summary
Direct methanol fuel cells (DMFCs) using polymer electrolyte membranes (PEMs) represent one of the most attractive power sources because of their stable operation at relatively low temperatures, the high energy density obtained by using highly concentrated methanol solutions as fuel, and their simplicity [1,2]. One of the effective strategies to get both high proton conductivity and low methanol permeability is to develop PEMs prepared from graft copolymers consisting of two chemically different polymer segments: a main chain made from a polymer with low methanol permeability and side chains made from a polymer having proton conductive properties. Prepared by graft‐atom transfer radical recently reported partially-fluorinated graft copolymers of poly([vinylidene difluoride-copolymerization (g‐ATRP) of styrene from commercial P(VDF‐co‐CTFE). Copolymers the g-ATRP synthesis to prepare a graft copolymer using aromatic is to perform by of methods styrene from. One of the synthesis methods to prepare copolymer using aromatic polymers is to perform of atom transfer radical polymerization [27,28]. To use the chloromethylated as acation‐exchange macro-initiator membranes (CEMs) werepolymerization prepared from(ATRP). Grafting membranes (CEMs) weresulfonic prepared from a graftside copolymer of asynthesized polysulfone by (PSF).
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