Proton exchange membrane fuel cell solid electrolyte

Note PAFC phosphoric acid fuel cell PEMFC proton exchange membrane fuel cell/polymer electrolyte membrane fuel cell MBFC microbiological fuel cell DMFC direct methanol conversion fuel cell AFC alkaline fuel cell MCFC molten carbonate fuel cell SOFC solid oxide fuel cell ZAFC zinc air fuel cell. 

The polymer electrolyte membrane fuel cell (PEMFC) also known as proton exchange membrane fuel cell, polymer electrolyte fuel cell (PEFC) and solid polymer fuel cell (SPFC) was first developed by General Electric in the USA in the 1960 s for use by NASA in their initial space applications. The electrolyte is an ion conducting polymer membrane, described in more details in Section 2.2. Anode and cathode are bonded to either side of the membrane. This assembly is normally called membrane electrode assembly (MEA) or EMA which is placed between the two flow field plates (bipolar plates) (Section 2.5) to form what is known as stack . The basic operation of the PEMFC is the same as that of an acid electrolyte cell as the mobile ions in the polymer are or proton. 

The most promising fuel cell for transportation purposes was initially developed in the 1960s and is called the proton-exchange membrane fuel cell (PEMFC). Compared with the PAFC, it has much greater power density state-of-the-art PEMFC stacks can produce in excess of 1 kWA. It is also potentially less expensive and, because it uses a thin solid polymer electrolyte sheet, it has relatively few sealing and corrosion issues and no problems associated tvith electrolyte dilution by the product water. 

Membrane-type fuel cells. The electrolyte is a polymeric ion-exchange membrane the working temperatures are 60 to 100°C. Such systems were first used in Gemini spaceships. These fuel cells subsequently saw a rather broad development and are known as (solid) polymer electrolyte or proton-exchange membrane fuel cells (PEMFCs). 

Figure 29. Conductivity of some intermediate-temperature proton conductors, compared to the conductivity of Nafion and the oxide ion conductivity of YSZ (yttria-stabilized zirconia), the standard electrolyte materials for low- and high-temperature fuel cells, proton exchange membrane fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

Proton exchange membrane fuel cell (PEMFC) working at around 70 °C with a polymer membrane electrolyte, such as Nafion, which is a solid proton conductor (conducting by the H + cation). 

According to the electrolyte and working temperature, one distinguishes the low-temperature fuel cell technologies (i) alkaline fuel cell, AFC (70 to 80°C), (ii) proton exchange membrane fuel cell, PEMFC (70 to 80°C), (iii) phosphoric acid cell, PAFC (200°C) from the high-temperature technologies, (iv) molten carbonate fuel cell, MCFC (650 to 700°C), and (v) solid oxide fuel cell, SOFC (1000°C). 

Smith B, Sridhar S, Khan A, (2005). Solid polymer electrolyte membranes for fuel cell applications-a review. Journal of Membrane Science 259 10-26 Sopian K, Wan Daud W, (2006). Challenges and future developments in proton exchange membrane fuel cells. Renewable Energy 31 719-727 Srinivasan S, (2006). Fuel cells From fundamentals to applications. Springer Science and Business Media LLC, New York... 

The membranes in polymeric proton-exchange membrane fuel cells (PEMFC) serve as a solid electrolyte. The membrane s conductivity comes about because in the presence of water it swells, a process leading to the dissociation of the acidic functional groups and formation of protons free to move about throughout the membrane. 

Proton exchange membrane fuel cells, also called polymer electrolyte fuel cell or solid polymer electrolyte fuel cells, use a proton exchange membrane, which acts as a solid electrolyte between the anode and cathode electrodes. Proton exchange membrane fuel cells are favored for use in automobiles, residential power as well as in portable devices such as laptops and cell phones. These fuel cells utilize hydrogen gas and air or oxygen to produce power. 

There exist a variety of fuel cells. For practical reasons, fuel cells are classified by the type of electrolyte employed. The following names and abbreviations are frequently used in publications alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and proton exchange membrane fuel cells (PEMFC). Among different types of fuel cells under development today, the PEMFC, also called polymer electrolyte membrane fuel cells (PEFC), is considered as a potential future power source due to its unique characteristics [1-3]. The PEMFC consists of an anode where hydrogen oxidation takes place, a cathode where oxygen reduction occurs, and an electrolyte membrane that permits the transfer of protons from anode to cathode. PEMFC operates at low temperature that allows rapid start-up. Furthermore, with the absence of corrosive cell constituents, the use of the exotic materials required in other fuel cell types is not required [4]. 

Fuel cells do not use a solid material to store their charge. Instead, low-temperature proton exchange membrane fuel cells use gases such as hydrogen and liquid ethanol (the same form of alcohol found in vodka) or methanol as fuels. These materials are pumped over the surface of the fuel cells, and in the presence of noble-metal catalysts, the protons in these fuels are broken away from the fuel molecule and transported through the electrolyte membrane to form water and heat in the presence of air. The liberated electrons can, just as in the case of batteries, be used to drive an electric motor. Other types of fuel cells, such as molten carbonate fuel cells and solid oxide fuel cells, can use fuels such as carbon in the form of coal, soot, or old rubber tires and operate at 800 degrees Celsius with a very high efficiency. 

The electrolyte can be an aqueous solution, alkaline or acid. It was alkaline fuel cells that generated the necessary electricity on Apollo 11, the first manned spacecraft to the moon. In modern fuel cells a membrane may act as a solid electrolyte. A polymer PEMFC (Proton Exchange Membrane Fuel Cell) is often used. 

Fuel cells are currently at the early commercial stage for some applications. There are increasing numbers of units deployed in field trials for an increasing number of applicahons. The polymer electrolyte membrane (PEM) fuel cell is one of the most common types of fuel cells under development today. (They also are commonly referred to as proton exchange membrane fuel cells based on the key characteristic of the solid electrolyte membrane to transfer protons from the anode to the cathode.) With the experience gained through... 

An electrolyte is an essential component within fuel cells, used to facilitate the selective migration of ions between the electrodes. Fuel cells are typically classified according to the electrolytes used alkaline fuel cell (AFC), polymer electrolyte (or proton exchange membrane) fuel cell (PEMFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell (SOFC). Typical efficiencies, operating temperatures and output voltage for the various types of fuel cells are shown in Table 2.14. It should be noted that none of these fuel cells... 

Proton-exchange membrane fuel cells (PEMFC)—use solid-polymer proton-conducting membrane electrolyte at temperatures generally ranging from ambient to 90°C. Today s technology primarily uses the trifluoromethanesulfonic-acid-based electrolyte membrane, such as DuPont s Nafion . 

The type of the catalyst employed in the fuel cell depends on the type of fuel, the solid electrolyte used, and the operating temperature. Here we will consider the recent trends in catalysis for the two major types of the fuel cells, including low-temperature proton exchange membrane fuel cells and high-temperature SOFCs. Depending on the fuel used, low-temperature PEMFCs fall into two major categories hydrogen and direct methanol fuel cells (DMFCs). 

Since the type of electrolyte material dictates operating principles and characteristics of a fuel cell, a fuel cell is generally named after the type of electrolyte used. For example, an alkaline fuel cell (AFC) uses an alkaline solution such as potassium hydroxide (KOH) in water, an acid fuel cell such as phosphoric acid fuel cell (PAFC) uses phosphoric acid as electrolyte, a solid polymer electrolyte membrane fuel cell (PEMFC) or proton exchange membrane fuel cell uses proton-conducting solid polymer electrolyte membrane, a molten carbonate fuel cell (MCFC) uses molten lithium or potassium carbonate as electrolyte, and a solid oxide ion-conducting fuel cell (SOFC) uses ceramic electrolyte membrane. 

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