Polymer electrolyte membrane operational range

In addition to these smaller applications, fuel cells can be used in portable generators, such as those used to provide electricity for portable equipment. Thousands of portable fuel cell systems have been developed and operated worldwide, ranging from 1 watt to 1.5 kilowatts in power. The two primary technologies for portable applications are polymer electrolyte membrane (PEM) and direct methanol fuel cell (DMFC) designs. 

Solutions of DMM, TMM and methanol were evaluated in single cells and a 5-cell stack supplied by Giner, Inc. The cells were operated at temperatures ranging from 25 °C to 90 °C and were heated at the ceil block and the anode fuel reservoir, which was equipped with a condenser to prevent evaporation but allow CO2 rejection from the system. In the present study, the membrane electrode assembly (manufactured by Giner Inc.) consisted of electrocatalytic Pt-Ru (50/50 atom %) and R fine metal powders (surface area 30-70 m /g) bonded to either side of a Nafion -117 polymer electrolyte membrane. The... 

High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) operate in a temperature range of 160 to 180 °C. For the HT-PEMFC the hydraulic system of a house is at any time a heat sink. HT-PEMFC based fuel cells can be used in hydraulic systems of new and existing buildings. Furthermore, the HT-PEMFC requires less effort to cleanup the synthesis gas of the fuel processor. But the HT-PEMFC is only demonstrated in few applications so far and the development status is not so advanced as for the LT PEMFC. 

In addition, the ability to work in a wide range of operative conditions is another key aspect for the development of advanced membranes. Chemical stability is of particular importance when the membrane interfaces are exposed to aggressive solvents, such as in several organic solvent nanofiltration (OSN) applications [21]. Resistance to fouling is also important in water filtration because this phenomenon can threaten the continuous operability of the membrane module [22]. In high-temperature (eg, precombustion CO2 capture from syngas [23] or polymer electrolyte membranes for fuel cells [24]) and high-pressure (eg, reverse osmosis and nanofiltration membranes for... 

Matty PEM fuel cell research projects are being performed by IPHE members. IPHE fuel cell projects include the development of advanced membranes, the application of gradient porous composite MEAs for different types of fuel cells, and the development of novel polymer electrolyte membranes for MEAs capable of operating in the temperature range of <-20°C to 120°C at zero humidification. 

The DMFC design is quite similar to that of a PEFC (Figure 1.10). As in a PEFC, in a DMFC the anode and cathode are separated by a polymer electrolyte membrane, typically Nafion . These cells also operate in the temperature range of 30-90 °C. 

Many different types of fuel-cell membranes are currently in use in, e.g., solid-oxide fuel cells (SOFCs), molten-carbonate fuel cells (MCFCs), alkaline fuel eells (AFCs), phosphoric-acid fuel cells (PAFCs), and polymer-electrolyte membrane fuel cells (PEMFCs). One of the most widely used polymers in PEMFCs is Nalion, which is basically a fluorinated teflon-like hydrophobic polymer backbone with sulfonated hydrophilic side chains." Nafion and related sulfonic-add based polymers have the disadvantage that the polymer-conductivity is based on the presence of water and, thus, the operating temperature is limited to a temperature range of 80-100 °C. This constraint makes the water (and temperature) management of the fuel cell critical for its performance. Many computational studies and reviews have recently been pubhshed," and new types of polymers are proposed at any time, e.g. sulfonated aromatic polyarylenes," to meet these drawbacks. 

The fuel cells are classified based on the fuel, operating temperature, electrolyte type, physical state of fuel cell components and the fabrication technology. The polymer electrolyte membrane fuel cell (PEMFC) operating on a methanol-water mixture as a fuel is called a Direct Methanol Fuel Cell (DMFC). DMFC uses sulphonated fluoropolymer, such as NAFION 117 as the electrolyte membrane. Nafion membranes require high levels of humidification and can operate comfortably only within a narrow temperature range of 25°C... 

Since a polymer electrolyte membrane is interposed between the cathode and the anode, its chemical stability must be such that no undesired chemical reactions occur when the electrodes come into direct contact. In addition, in order to operate in an appropriate temperature range, polymer... 

Clearly, a fundamental understanding of the key strac-ture/property relationships, particularly membrane morphology and conductivity as a function of polymer electrolyte architecture and water content - both in the bulk hydrated membrane and at the various interfaces within the membrane electrode assembly (MEA), can provide guidance in the synthesis of novel materials or MEA manufacturing techniques that lead to the improvement in the efficiency and/or operating range of PEMFCs. 

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