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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.
At the positively charged anode, an oxidation reaction occurs, generating oxygen gas and giving electrons to the anode to complete the circuit. The two half-reactions, reduction and oxidation, are coupled to form a balanced system. In order to balance each half-reaction, the water needs to be acidic or basic.
Reduction of oxygen into oxygen ions occurs at the cathode. These ions can then diffuse through the solid oxide electrolyte to the anode where they can electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons. These electrons then flow through an external circuit where they can do work.
The most popular oxygen electrode materials are lanthanum strontium cobalt ferrite (LSCF) and lanthanum strontium chromite (LSC), perovskite materials able to catalyze oxygen reduction and oxide ion oxidation reactions. [3] The electrolyte is a solid-state layer placed between the two electrodes. It is an electric insulator, it is impermeable ...
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 ...
4H + + 4e − → 2H 2 Reduction (generation of dihydrogen) 2H 2 O → 2H 2 + O 2 Total Reaction Of the two half reactions, the oxidation step is the most demanding because it requires the coupling of 4 electron and proton transfers and the formation of an oxygen-oxygen bond.
The values below are standard apparent reduction potentials (E°') for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution. [1] [2] The actual physiological potential depends on the ratio of the reduced (Red) and oxidized (Ox) forms according to the Nernst equation and the thermal voltage.
The oxygen is rapidly reduced, with two electrons coming from the Fe 2+-cytochrome a 3, which is converted to the ferryl oxo form (Fe 4+ =O). The oxygen atom close to Cu B picks up one electron from Cu +, and a second electron and a proton from the hydroxyl of Tyr(244), which becomes a tyrosyl radical. The second oxygen is converted to a ...