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1、文献翻译英文原文：Fuel Cells and Their ProspectsA fuel cell is an electrochemical conversion device. It produces electricity from fuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out
2、of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.Fuel cells are different from electrochemical cell batteries in that they consume reactant from an external source, which must be replenished-a thermodynamicall
3、y open system. By contrast batteries store electrical energy chemically and hence represent a thermodynamically closed system.Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcoh
4、ols. Other oxidants include chlorine and chlorine dioxide. Fuel cell designA fuel cell works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel though a circuit, hence converting them to electrical power. The catalyst typically comp
5、rises a platinum group metal or alloy. Another catalytic process takes the electrons back in, combining them with the protons and oxidant to form waste products (typically simple compounds like water and carbon dioxide).A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. V
6、oltage decreases as current increases, due to several factors: Activation loss Ohmic loss (voltage drop due to resistance of the cell components and interconnects) Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage) To deliver the desired am
7、ount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn. Such a design is called a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.
8、Proton exchange fuel cellsIn the archetypal hydrogenoxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a solid polymer electrolyte fuel cell (SPEFC) in the early 1970s, before the p
9、roton exchange mechanism was well-understood. (Notice that polymer electrolyte membrane and proton exchange mechanism result in the same acronym.)On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants
10、causing them to become what is commonly referred to as multi-facilitated proton membranes (MFPM). The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cat
11、hode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water in this example, the only waste product, either liquid or vapor.In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel,
12、methanol (see: direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.The materials used in fuel cells differ by type. In a typical membrane electrode assembly (MEA), the electrodebipolar plates are
13、 usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.Oxygen ion exchange fuel cellsIn a solid oxide fu
14、el cell design, the anode and cathode are separated by an electrolyte that is conductive to oxygen ions but non-conductive to electrons. The electrolyte is typically made from zirconia doped with yttria.On the cathode side, oxygen catalytically reacts with a supply of electrons to become oxygen ions
15、, which diffuse through the electrolyte to the anode side. On the anode side, the oxygen ions react with hydrogen to form water and free electrons. A load connected externally between the anode and cathode completes the electrical circuit.Fuel cell design issuesCostsIn 2002, typical cells had a cata
16、lyst content of US$1000 per-kilowatt of electric power output. In 2008 UTC Power has 400kw Fuel cells for $1,000,000 per 400kW installed costs. The goal is to reduce the cost in order to compete with current market technologies including gasoline internal combustion engines. Many companies are working on techniques to reduce cost in a variety of ways including reducing the amount of platinum needed in each individual cell. Ballard Pow
