|
PEMFC
Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle. Science PEMFCs are built out of membrane electrode assemblies (MEA) which include the electrodes, electrolyte, catalyst, and gas diffusion layers. An ink of catalyst, carbon, and electrode are sprayed or painted onto the solid electrolyte and carbon paper is hot pressed on either side to protect the inside of the cell and also act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel Cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came more than a century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell, also known as the Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules. Since then, fuel cells have b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuel Cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came more than a century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell, also known as the Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules. Since then, fuel cells have b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proton-exchange Membrane
A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton-exchange membrane fuel cell or of a proton-exchange membrane electrolyser: separation of reactants and transport of protons while blocking a direct electronic pathway through the membrane. PEMs can be made from either pure polymer membranes or from composite membranes, where other materials are embedded in a polymer matrix. One of the most common and commercially available PEM materials is the fluoropolymer (PFSA) Nafion, a DuPont product. While Nafion is an ionomer with a perfluorinated backbone like Teflon, there are many other structural motifs used to make ionomers for proton-exchange membranes. Many use polyaromatic polymers, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Electrode Assembly
A membrane electrode assembly (MEA) is an assembled stack of proton-exchange membranes (PEM) or alkali anion exchange membrane (AAEM), catalyst and flat plate electrode used in fuel cells and electrolyzers. PEM-MEA The PEM is sandwiched between two electrodes which have the catalyst embedded in them. The electrodes are electrically insulated from each other by the PEM. These two electrodes make up the anode and cathode respectively. The PEM is typically a fluoropolymer (PFSA) proton permeable electrical insulator barrier. Hydrocarbon variants are currently being developed and are expected to succeed fluoropolymers. This barrier allows the transport of the protons from the anode to the cathode through the membrane but forces the electrons to travel around a conductive path to the cathode. The most commonly used Nafion PEMs are Nafion XL, 112, 115, 117, and 1110. The electrodes are heat pressed onto the PEM. Commonly used materials for these electrodes are carbon cloth or carbon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkaline Fuel Cell
The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its British inventor, Francis Thomas Bacon, is one of the most developed fuel cell technologies. Alkaline fuel cells consume hydrogen and pure oxygen, to produce potable water, heat, and electricity. They are among the most efficient fuel cells, having the potential to reach 70%. NASA has used alkaline fuel cells since the mid-1960s, in the Apollo-series missions and on the Space Shuttle. Half Reactions The fuel cell produces power through a redox reaction between hydrogen and oxygen. At the anode, hydrogen is oxidized according to the reaction: \mathrm_2 + \mathrm^- \longrightarrow \mathrm_2\mathrm + \mathrm^- producing water and releasing electrons. The electrons flow through an external circuit and return to the cathode, reducing oxygen in the reaction: \mathrm_2 + \mathrm_2\mathrm + \mathrm^- \longrightarrow \mathrm^- producing hydroxide ions. The net reaction consumes one oxygen molecule and two h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proton Exchange Fuel Cell Diagram
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ratio). Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei). One or more protons are present in the Atomic nucleus, nucleus of every atom. They provide the attractive electrostatic central force which binds the atomic electrons. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol ''Z''). Since each chemical element, element has a unique number of protons, each element has its own unique atomic number, which determines the number of atomic electrons and consequently the chemical characteristics of the element. The word ''proton'' is Greek language, G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SEM Micrograph Of An MEA Cross Section
SEM can refer to: Computing * Search engine marketing, promoting websites by increasing their visibility in search engine results * Security event manager, a security log tool used on data networks Economics and management * Stock Exchange of Mauritius, the principal stock exchange of the island country of Mauritius * Strategic enrollment management, an element of planning for new growth at a university or college Energy * Single Electricity Market, the integration of the electricity sectors of the Republic of Ireland and Northern Ireland in a single market * Strategic energy management, continuous improvement process for energy efficiency based on behavioral change Mathematics and statistics * Structural equation modeling, in data analysis * Simultaneous equations model, in econometrics * Standard error of the mean in statistics Places * Craig Field (Alabama), US airport, IATA code * Sem, Ariège, France * Sem, Norway Science and technology * Scanning ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Current (electricity)
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In an electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons. The SI unit of electric current is the ampere, or ''amp'', which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit. Electric current is measured using a device called an ammeter. Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conduct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen Reduction Reaction
In chemistry, the oxygen reduction reaction refers to the reduction half reaction whereby O2 is reduced to water or hydrogen peroxide. In fuel cells, the reduction to water is preferred because the current is higher. The oxygen reduction reaction is well demonstrated and highly efficient in nature. Stoichiometry The stoichiometries of the oxygen reduction reaction, which depends on the medium, are shown: 4e− pathway in acid medium: O2 + 4 e- + 4H+ -> 2 H2O 2e− pathway in acid medium: O2 + 2e- + 2H+ -> H2O2 4e− pathway in alkaline medium: O2 + 4e- + 2H2O -> 4 OH- 2e− pathway in alkaline medium: O2 + 2e- + H2O -> HO2- + OH- 4e- pathway in solid oxide: O2 + 4e- -> 2 O^2- The 4e− pathway reaction is the cathode reaction in fuel cell especially in proton-exchange membrane fuel cells, alkaline fuel cell and solid oxide fuel cell. While the 2e− pathway reaction is often the side reaction of 4e- pathway or can be used in synthesis of H2O2. Catalysts Biocatalysts The oxyg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Hydrogen Electrode
The standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be at 25 °C, but to form a basis for comparison with all other electrochemical reactions, hydrogen's standard electrode potential (''E''°) is declared to be zero volts at any temperature. Potentials of all other electrodes are compared with that of the standard hydrogen electrode at the same temperature. Nernst equation for SHE The hydrogen electrode is based on the redox half cell corresponding to the reduction of two hydrated protons, 2 H+(aq), into one gaseous hydrogen molecule, H2(g). General equation for a reduction reaction: : \text + z~e^ \rightleftharpoons \text The reaction quotient (') of the half-reaction is the ratio between the chemical activities (''a'') of the reduced form (the reductant, ) and the oxidized form (the oxidant, ). : Q_r = \frac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and ''molecule'' is often used when referring to polyatomic ions. A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O). In the kinetic theory of gases, the term ''molecule'' is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not consid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MEA Fabrication Methods
MEA or Mea may refer to: Education * Minnesota Education Association * MEA Engineering College, Perinthalmanna * Michigan Education Association Fictional characters * Mea (''Popotan''), a maid for three sisters in the visual novel ''Popotan'' * Mea Kurosaki, a transformation weapon in the manga series ''To Love Ru Darkness'' * Mea 3, a representative of planet Eminiar VII in the ''Star Trek'' episode " A Taste of Armageddon" Organizations * Manx Electricity Authority * ME Association, a British organization providing information and support on ME/CFS * Metropolitan Electricity Authority, responsible for supplying the Bangkok Metropolitan Region * Middle East Airlines, the flag carrier airline of Lebanon * Municipal Employees' Association, former British trade union Politics * Multilateral Environmental Agreement * Ministry of External Affairs (other), several Science * ''Mea'' (moth), a genus of moths * Mean electrical axis, in electrocardiography * Mean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
