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The oxygen reduction reaction is an essential reaction for aerobic organisms. Such organisms are powered by the heat of combustion of fuel (food) by O 2.Rather than combustion, organisms rely on elaborate sequences of electron-transfer reactions, often coupled to proton transfer.
Although cellular respiration is technically a combustion reaction, it is an unusual one because of the slow, controlled release of energy from the series of reactions. Nutrients that are commonly used by animal and plant cells in respiration include sugar , amino acids and fatty acids , and the most common oxidizing agent is molecular oxygen ...
Example of a reduction–oxidation reaction between sodium and chlorine, with the OIL RIG mnemonic [1] Redox (/ ˈ r ɛ d ɒ k s / RED-oks, / ˈ r iː d ɒ k s / REE-doks, reduction–oxidation [2] or oxidation–reduction [3]: 150 ) is a type of chemical reaction in which the oxidation states of the reactants change. [4]
Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆G°) must satisfy ∆G° = – z FE°, where z electrons are transferred, and the Faraday constant F is the conversion factor describing Coulombs transferred per mole electrons. Those Gibbs free energy ...
In the electron transport chain, electrons are passed through a series of proteins via oxidation-reduction reactions, with each acceptor protein along the chain having a greater reduction potential than the previous. The last destination for an electron along this chain is an oxygen molecule.
When oxygen is reduced using an electrocatalyst, an unwanted and harmful by-product, hydrogen peroxide, may be produced. Hydrogen peroxide can damage the internal components of a PEM fuel cell, so oxygen-reduction electrocatalysts are engineered in such a way as to limit the amount of peroxide formed.
For example, an enzyme that catalyzed this reaction would be an oxidoreductase: A – + B → A + B – In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor). In biochemical reactions, the redox reactions are sometimes more difficult to see, such as this reaction from glycolysis:
Because of the alkaline chemistry, oxygen reduction reaction (ORR) kinetics at the cathode are much more facile than in acidic cells, allowing use of non-noble metals, such as iron, cobalt, nickel, manganese, or carbon-based nanomaterial at the anode (where fuel is oxidized); and cheaper catalysts such as silver at the cathode, [2] due to the ...