Development of Aromatic Polymer Electrolyte Membrane with High Conductivity and Durability for Fuel Cell

Abstract

This report describes a design, preparation and evaluation data of a novel polymer electrolyte membrane, which have been successfully developed for the use in fuel cell vehicles (FCV). This membrane is prepared from the aromatic block copolymer, consisting of alternating stiff sulfonic acid-bearing segments and hydrophobic flexible polymeric sub-units. A bicontinuous microphase-separated morphology of the membrane has been attested, contributing to its excellent water resistance with keeping high proton conductivity. The JSR membrane exhibits actually the same chemical stability as a conventional poly(perfluorosufonic acid) one, while outperforming the latter in power output of the fuel cell, life time and temperature range. In particular, a cold start of FCV have been first demonstrated at À20 C, using this material. A manufacturing of the JSR membrane in the semi-industrial scale is established. This technology has been officially approved for the extension through the public road examination. This SPSJ award is given for developing novel aromatic polymer electrolyte membrane with high performance for the practical use. Fuel cells are widely regarded as promising energy sources due to their high energy efficiency in terms of limiting fossil fuel resources. Among them, polymer electrolyte fuel cells (PEFC) can generate electricity with high power density at moderate temperatures, even at room temperature, to offer a significant advantage to other fuel cell systems, e.g., phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC). Many efforts have been devoted into the research and development of PEFC for transportation and stationary applications, as well as in the design of closely related DMFC (direct methanol fuel cells) for the use in portable devices.PEFC consists of two electrodes, which are separated by the polymer electrolyte membrane. On the anode side, hydrogen dissociates into protons and electrons by the electrochemical reaction with the catalyst on the electrode surface. Protons diffuse through the membrane to the cathode, while electrons are transmitted to the cathode through the electron conductor, creating thereby an electrical current. Polymer electrolyte membrane is a key material governing the power generation of the fuel cell, and it should meet strict requirements as possessing a high proton conductivity closely linked to high power generation ability, high stability and durability in the fuel cell environment, excellent mechanical toughness, high heat endurance, as well as impermeability to fuel gas or liquid.Poly(perfluorosulfonic acid) membranes (Figure 1) have been widely used as benchmark materials in PEFC. However, the operation temperature of this type of membranes is limited within the range from 0 C to 80 C, because of the drop in conductivity below the freezing point of water and the poor thermo-mechanical properties above 80 C. Moreover, the durability of membranes is not sufficient to achieve the practical applications in PEFC. There...

Multiblock Copolymers with Highly Sulfonated Blocks Containing Di‐ and Tetrasulfonated Arylene Sulfone Segments for Proton Exchange Membrane Fuel Cell Applications

“…[15] Still, a number of investigations have recently demonstrated that it is possible to reach high proton conductivities in sulfonated hydrocarbon membranes at low relative humidities (RHs) provided that a percolating phase domain is maintained where the local concentration of acid is kept high. [16,17] This implies that the membrane polymers must carry segments, or blocks, which are highly sulfonated, and that an efficient phase separation between the hydrophilic parts must occur to maintain a high local sulfonic acid concentration in the membrane. At the same time, an excessive water uptake and loss of mechanical strength at high RH must be prevented.…”

Poly(sulfonated phenylene)‐block‐Polyimide Copolymers for Fuel Cell Applications

“…[1][2][3][4] Recently, hydrophilic-hydrophobic aromatic multiblock copolymers have attracted great interest to improve the proton conductivity under low humidity. [5][6][7][8][9][10] Poly( p-phenylene) derivatives bearing sulfonated aromatic side groups have been investigated as PEMs because of their excellent chemical stability based on the fully aromatic structure. [10][11][12][13] Goto et al developed multiblock aromatic copolymers composed of hydrophilic oligo(2-(3-sulfobenzoyl)-1,4-phenylene) segments and hydrophobic aromatic oligomer segments.…”

“…[5][6][7][8][9][10] Poly( p-phenylene) derivatives bearing sulfonated aromatic side groups have been investigated as PEMs because of their excellent chemical stability based on the fully aromatic structure. [10][11][12][13] Goto et al developed multiblock aromatic copolymers composed of hydrophilic oligo(2-(3-sulfobenzoyl)-1,4-phenylene) segments and hydrophobic aromatic oligomer segments. [10] Hydrolytically labile bonds such as imide groups were not incorporated in the hydrophobic aromatic segments.…”

“…[10][11][12][13] Goto et al developed multiblock aromatic copolymers composed of hydrophilic oligo(2-(3-sulfobenzoyl)-1,4-phenylene) segments and hydrophobic aromatic oligomer segments. [10] Hydrolytically labile bonds such as imide groups were not incorporated in the hydrophobic aromatic segments. Their membranes exhibited bicontinuous microphase-separated morphology and as a result had excellent mechanical properties and high proton conductivity, and have been used in fuel cell vehicles.…”

Tetrasulfonated Poly(arylene biphenylsulfone ether) Block Copolymer and Its Composite Membrane Containing Highly Sulfonated Blocks

“…2 Recently, highly sulfonated moieties 3 or sequenced hydrophilic and hydrophobic groups as block copolymers 4 were claimed to improve proton conductivity under high temperature. However, none of these alternative membranes could compete with Nafion membranes.…”