PEM/AEM Junction Design for Bipolar Membrane Fuel Cells

Abstract

The combination of proton exchange membrane (PEM) and anion exchange membrane (AEM) materials to form a bipolar membrane (BPM) is of interest in hybrid electrochemical devices to mitigate the disadvantages of their monopolar counterparts. The PEM-AEM interface is a critical component in bipolar membrane fuel cell operation. In this study, mono-and di-membrane bipolar membranes were fabricated. Interfacial materials with varying conductivities were used in order to control the location of the junction within the di-membrane BPMs. Mono-membrane BPMs were constructed via conversion of a single face of a monopolar membrane (Nafion). The membranes were used in fully functional fuel cells and characterized via electrochemical impedance spectroscopy (EIS). For the di-membrane BPMs, use of a conductive interface consisting of a single ion conductive material resulted in devices with lower interfacial resistance as compared to a neutral interface. When comparing conductive interface materials, anion-conductive materials provided lower total membrane resistance than proton-conductive materials. This decrease is due to positioning the junction closer to the anode and farther from the air-cathode. These results show that the formation of the optimal junction is critically dependent on fabrication technique and location. Polymeric membrane-based fuel cells are a promising candidate to provide clean, efficient, and energy dense power sources. Of the primary types of these fuel cells, proton exchange membrane (PEM) fuel cells have capabilities of producing extremely high power densities, and the materials used as the proton exchange membrane (e.g. Nafion) are thermally and mechanically robust, allowing for long-term operation. Despite these features, there are several drawbacks relating to the operation of these devices under acidic conditions. First, the migration of protons from anode to cathode results in electro-osmotic drag of water (and methanol, where applicable) which can lead to a phenomenon known as "cathode flooding" or a blockage of transport passageways with water. Second, both the catalytic and polymeric materials required to survive the harsh acidic operating environment are expensive to manufacture. Third, both the metal catalyst and its carbon support are subject to corrosion at low pH.One alternative to the PEM fuel cell is the anion exchange membrane (AEM) fuel cell. This configuration addresses many of the shortcomings of the PEM cell simply by operating under alkaline (high pH) conditions. AEM fuel cells potentially address many of the issues inherent with PEM devices. The basic operating environment is much more conducive to the oxygen reduction reaction (ORR), which opens the possibility of using non-platinum based (cheaper) catalysts.1-3 Additionally, anion exchange membranes are typically hydrocarbon based, and as such are less expensive to manufacture than Nafion and other perfluorosulfonic acid (PFSA) membranes used in PEM devices. Another benefit is the reversed direction of ion transport through th...

Synergistic Effect of 2-Acrylamido-2-methyl-1-propanesulfonic Acid on the Enhanced Conductivity for Fuel Cell at Low Temperature

“…Immobile sulfonic acid groups may dissociate and the hydronium ions (e.g., H 3 O + , H 5 O 2 +, and H 9 O 4 + ) were formed via hydrogen bonding around the sulfonic acid groups from sulfonated polymer electrolytes in a hydrated condition [ 30 , 31 ]. In swollen state, free protons easily transport from sulfonated polymer electrolyte membranes along with the hydrogen-bonded ionic network so that the proton conductivity will be clearly enhanced by the water uptake in the membrane matrix.…”

“…The yield of the final SPEES product was 99%. To convert it to sulfonamide form [ 30 , 31 ], the required amount of SPEES was dissolved in DMAc and reacted with SOCl 2 at 80 °C for 5–6 h to form the SPEES-Cl ( Scheme 1 ). The product, SPEES-Cl, stems according to the above method and procedures.…”

“…As an aliphatic polar monomer, AMPS has been recently used for the preparation of polyelectrolyte for a few applications [ 22 , 23 , 24 , 25 ], because of its good thermal, chemical, and flexible properties. Polymerization of ionic liquid-AMPS (IL-AMPS) with a reactive surfactant produced polymers with high ionic conductivity suitable for the sensor, fuel cell, and battery applications [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. The pristine PAMPS derivatives are, however, generally too weak in mechanical strength in water, illustrating hydrogel properties.…”

Bipolar Membranes to Promote Formation of Tight Ice‐Like Water for Efficient and Sustainable Water Splitting

“…Bipolar membranes (BPMs), a laminate of cation and anion exchange membranes with a catalyst layer at the membrane junction, has recently received much attention for use in electrochemical energy conversion systems (e.g., in water splitting, CO 2 reduction for photofuels, and fuel cells) due to its enhanced water dissociation capability and ion-selective transport properties. [1][2][3][4][5][6] At the junction of BPMs, water molecules dissociate to generate H + and OH − ions, and subsequently, the ions are selectively transported through either a cation or anion-exchange membrane, respectively. [7] Furthermore, this unique characteristic of BPMs maintains the pHs of both the catholyte and anolyte, which have been optimized for the catalyst used at each electrode, thus significantly reducing the total overpotential of the cell.…”

Electrochemical Adsorption on Pt Nanoparticles in Alkaline Solution Observed Using In Situ High Energy Resolution X-ray Absorption Spectroscopy

“…As a result, the degradation of the electrolyte does not occur. For these reasons, AEMs have great potential to be utilized in direct methanol fuel cells (DMFCs) [16,17,18,19], direct hydrazine fuel cells (DHFCs) [15,20], and hybrid fuel cells [21,22]. However, since a reaction mechanism mainly based on the ORR on the Pt surface in an acidic solution may not be appropriate, it is necessary to understand the ORR mechanism in an alkaline solution to improve the performance and durability of AEM fuel cells consuming a liquid fuel such as methanol or hydrazine.…”