fuel cell
Fuel cell
fuel cell
[′fyül ‚sel]fuel cell
A pollution-free electricity generation technology for electric vehicles. Road testing began at the end of the 20th century, and hydrogen-powered fuel-cell buses have been running since the mid-2000s. Japan has been selling its Mirai fuel-cell automobile since 2014, and Japan along with China and South Korea have all set long-range targets for fuel-cell vehicles (FCVs).From a refueling standpoint, a fuel-cell vehicle is like a car at a gas station rather than an electric vehicle (EV) that plugs into a charger. A fuel cell takes in hydrogen-rich fuel and air (oxygen) and turns them into electricity for the electric motors. The waste product is water, and although not recommended for drinking, one test by Toyota showed fewer organic impurities than a glass of milk.
The Energy Alternative?
Fuel cells compete with lithium-ion batteries as the source of electricity for the electric motors in the vehicle, and there are challenges. While hydrogen can be derived from natural gas, propane, methane or water, it depends on which sources ultimately make the most sense. In addition, hydrogen is difficult to distribute and stockpile, and installing hydrogen pumps in every gas station is a gigantic undertaking. See lithium ion.
Heat and Power the Home
Fuel cells are also expected to provide a pollution-free source of energy for electricity and heat in the home. This combined usage is a major incentive for fuel cell research and development.
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| A Ballard Fuel Cell |
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| Ballard Power in British Columbia is one of the largest makers of fuel cells. Separated by a polymer exchange membrane (PEM), the anode and cathode are coated with a platinum catalyst that causes the hydrogen fuel to separate into free electrons and positive hydrogen ions (protons). The free electrons are the electricity, while the ions migrate through the PEM to the cathode and combine with oxygen and returning electrons to form water and heat. (Image courtesy of Ballard Power Systems.) |
Fuel Cell
the most important component of an electrochemical generator, which directly converts the chemical energy of fuel and oxidant reactants into electricity.
At the heart of a fuel cell are two electrodes separated by a solid or liquid electrolyte (see Figure 1). The fuel and oxidant are introduced into chambers adjacent to the electrodes, and oxidation and reduction reactions occur on the electrolyte-electrode interface in the presence of a catalyst (seeOXIDATION-REDUCTION REACTION). As a result of these reactions, ions A~ and B+ are formed, which later recombine to yield the final reaction product AB, and heat Q is released or absorbed. The electrons liberated by the oxidation of the fuel create an excess negative charge on the corresponding electrode (anode), and an excess positive charge is produced on the cathode as a result of the reduction of the oxidant. When the external circuit is closed, an electric current appears, which performs useful work Euse. The overall reaction is A + B = AB + Q + Euse.
The electrolyte in a fuel cell not only contains substances that participate in the electrochemical reactions, but also substances that provide for the spatial separation of the oxidation and reduction processes. The efficient operation of a fuel cell requires an extensive electrode surface (up to hundreds of square meters per gram of substance), rational organization of the adsorption and
ionization processes and of the conduction of electrons and reaction products, and high purity of the reactants.
The idea of constructing a fuel cell was put forward in the early 19th century by the English physicist W. R. Grove, but it was only in the 1960’s that practical fuel cells were constructed— almost simultaneously in the USSR, USA, France, and Great Britain. By the mid-1970’s, many different types of fuel cells had been developed, differing in operating temperature (from room temperature to 1200°K), type of fuel (hydrogen, hydrogen-bearing substances, and metals), oxidant (oxygen, oxygen-bearing substances, and chlorine), catalyst (platinum, palladium, silver, nickel, and carbon), and electrolyte (alkalies or acids, solid metal oxides, salt melts, and ion-exchange polymers).
Fuel cells in which hydrogen, oxygen, and an alkali (or ion-exchange polymer) are used as fuel, oxidant, and electrolyte, respectively, have proved the most practical. Such fuel cells operate at moderate temperatures (up to 100°C), which ensures a long operating life—up to several thousand hours; their operating voltage is approximately 1 volt. In principle, however, any substance that reacts at the operating temperature with oxygen or halogens may serve as the fuel in a fuel cell. Fuel cells using the direct oxidation of hydrocarbons (propane or gasoline), alcohols, and ammonia also show promise for future development.
One of the major problems hindering the development of fuel cells is the need to develop a theory of catalysis and to devise practical methods for the production of catalysts with sufficient activity, corrosion resistance, and resistance to the poisoning effect of reaction products. (See alsoGROVE CELL.)
REFERENCES
Fetter, K. Elektrokhimicheskaia kinetika. Moscow, 1967. (Translated from German.)Filstich, W. Toplivnye elementy. Moscow, 1968. (Translated from German.)
Muchnik, G. F. “Perspektivy i nauchnye problemy primeneniia metodov neposredstvennogo polucheniia elektroenergii iz khimicheskikh topliv.” Izv. AN SSSR: Energetika i transport, 1973, no. 2.
N. S. LIDORENKO and G. F. MUCHNIK