Oxygenevolution is the process of generating molecular oxygen (O2) by a chemical reaction, usually from water. Oxygen evolution from water is effected by oxygenic photosynthesis, electrolysis of water, and thermal decomposition of various oxides. The biological process supports aerobic life. When relatively pure oxygen is required industrially, it is isolated by distilling liquefied air.[1]
Photosynthetic oxygen evolution is the fundamental process by which oxygen is generated in the earth's biosphere. The reaction is part of the light-dependent reactions of photosynthesis in cyanobacteria and the chloroplasts of green algae and plants. It utilizes the energy of light to split a water molecule into its protons and electrons for photosynthesis. Free oxygen, generated as a by-product of this reaction, is released into the atmosphere.[2][3]
Water oxidation is catalyzed by a manganese-containing cofactor contained in photosystem II, known as the oxygen-evolving complex (OEC) or the water-splitting complex. Manganese is an important cofactor, and calcium and chloride are also required for the reaction to occur.[4] The stoichiometry of this reaction is as follows:
2H2O ⟶ 4e− + 4H+ + O2
The protons are released into the thylakoid lumen, thus contributing to the generation of a proton gradient across the thylakoid membrane. This proton gradient is the driving force for adenosine triphosphate (ATP) synthesis via photophosphorylation and the coupling of the absorption of light energy and the oxidation of water for the creation of chemical energy during photosynthesis.[5]
History of discoveryedit
It was not until the end of the 18th century that Joseph Priestley accidentally discovered the ability of plants to "restore" air that had been "injured" by the burning of a candle. He followed up on the experiment by showing that air "restored" by vegetation was "not at all inconvenient to a mouse." He was later awarded a medal for his discoveries that "...no vegetable grows in vain... but cleanses and purifies our atmosphere." Priestley's experiments were further evaluated by Jan Ingenhousz, a Dutch physician, who then showed that the "restoration" of air only worked while in the presence of light and green plant parts.[4]
Water electrolysisedit
Together with hydrogen (H2), oxygen is evolved by the electrolysis of water. The point of water electrolysis is to store energy in the form of hydrogen gas, a clean-burning fuel. The "oxygen evolution reaction (OER) is the major bottleneck [to water electrolysis] due to the sluggish kinetics of this four-electron transfer reaction."[6] All practical catalysts are heterogeneous.
Electrons (e−) are transferred from the cathode to protons to form hydrogen gas. The half reaction, balanced with acid, is:
2 H+ + 2e− → H2
At the positively charged anode, an oxidation reaction occurs, generating oxygen gas and releasing electrons to the anode to complete the circuit:
2 H2O → O2 + 4 H+ + 4e−
Combining either half reaction pair yields the same overall decomposition of water into oxygen and hydrogen:
Overall reaction:
2 H2O → 2 H2 + O2
Chemical oxygen generationedit
Although some metal oxides eventually release O2 when heated, these conversions generally require high temperatures. A few compounds release O2 at mild temperatures. Chemical oxygen generators consist of chemical compounds that release O2 when stimulated, usually by heat. They are used in submarines and commercial aircraft to provide emergency oxygen. Oxygen is generated by the high-temperature decomposition of sodium chlorate:[1]
^ Yano, Junko; Kern, Jan; Yachandra, Vittal K.; Nilsson, Håkan; Koroidov, Sergey; Messinger, Johannes (2015). "Chapter 2 Light-Dependent Production of Dioxygen in Photosynthesis". In Peter M.H. Kroneck and Martha E. Sosa Torres (ed.). Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. Vol. 15. Springer. pp. 13–43. doi:10.1007/978-3-319-12415-5_2. PMC4688042. PMID 25707465.
^ abRaven, Peter H.; Ray F. Evert; Susan E. Eichhorn (2005). Biology of Plants, 7th Edition. New York: W.H. Freeman and Company Publishers. pp. 115–127. ISBN0-7167-1007-2.
^Raval M, Biswal B, Biswal U (2005). "The mystery of oxygen evolution: analysis of structure and function of photosystem II, the water-plastoquinone oxido-reductase". Photosynthesis Research. 85 (3): 267–93. doi:10.1007/s11120-005-8163-4. PMID 16170631. S2CID 12893308.
^Song, Jiajia; Wei, Chao; Huang, Zhen-Feng; Liu, Chuntai; Zeng, Lin; Wang, Xin; Xu, Zhichuan J. (2020). "A Review on Fundamentals for Designing Oxygen Evolution Electrocatalysts". Chemical Society Reviews. 49 (7): 2196–2214. doi:10.1039/C9CS00607A. hdl:10356/153346. PMID 32133479. S2CID 212416753.
Oxygen evolution - Lecture notes by Antony Crofts, UIUC
Evolution of the atmosphere – Lecture notes, Regents of the University of Michigan
How to make oxygen and hydrogen from water using electrolysis
February 15, 2024
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Oxygen evolution is the process of generating molecular oxygen O2 by a chemical reaction usually from water Oxygen evolution from water is effected by oxygenic photosynthesis electrolysis of water and thermal decomposition of various oxides The biological process supports aerobic life When relatively pure oxygen is required industrially it is isolated by distilling liquefied air 1 Contents 1 Oxygen evolution in nature 1 1 History of discovery 2 Water electrolysis 3 Chemical oxygen generation 4 See also 5 References 6 External linksOxygen evolution in nature editMain article Oxygen evolving complex Photosynthetic oxygen evolution is the fundamental process by which oxygen is generated in the earth s biosphere The reaction is part of the light dependent reactions of photosynthesis in cyanobacteria and the chloroplasts of green algae and plants It utilizes the energy of light to split a water molecule into its protons and electrons for photosynthesis Free oxygen generated as a by product of this reaction is released into the atmosphere 2 3 Water oxidation is catalyzed by a manganese containing cofactor contained in photosystem II known as the oxygen evolving complex OEC or the water splitting complex Manganese is an important cofactor and calcium and chloride are also required for the reaction to occur 4 The stoichiometry of this reaction is as follows 2H2O 4e 4H O2The protons are released into the thylakoid lumen thus contributing to the generation of a proton gradient across the thylakoid membrane This proton gradient is the driving force for adenosine triphosphate ATP synthesis via photophosphorylation and the coupling of the absorption of light energy and the oxidation of water for the creation of chemical energy during photosynthesis 5 History of discovery edit It was not until the end of the 18th century that Joseph Priestley accidentally discovered the ability of plants to restore air that had been injured by the burning of a candle He followed up on the experiment by showing that air restored by vegetation was not at all inconvenient to a mouse He was later awarded a medal for his discoveries that no vegetable grows in vain but cleanses and purifies our atmosphere Priestley s experiments were further evaluated by Jan Ingenhousz a Dutch physician who then showed that the restoration of air only worked while in the presence of light and green plant parts 4 Water electrolysis editTogether with hydrogen H2 oxygen is evolved by the electrolysis of water The point of water electrolysis is to store energy in the form of hydrogen gas a clean burning fuel The oxygen evolution reaction OER is the major bottleneck to water electrolysis due to the sluggish kinetics of this four electron transfer reaction 6 All practical catalysts are heterogeneous nbsp Diagram showing the overall chemical equation Electrons e are transferred from the cathode to protons to form hydrogen gas The half reaction balanced with acid is 2 H 2e H2At the positively charged anode an oxidation reaction occurs generating oxygen gas and releasing electrons to the anode to complete the circuit 2 H2O O2 4 H 4e Combining either half reaction pair yields the same overall decomposition of water into oxygen and hydrogen Overall reaction 2 H2O 2 H2 O2Chemical oxygen generation editAlthough some metal oxides eventually release O2 when heated these conversions generally require high temperatures A few compounds release O2 at mild temperatures Chemical oxygen generators consist of chemical compounds that release O2 when stimulated usually by heat They are used in submarines and commercial aircraft to provide emergency oxygen Oxygen is generated by the high temperature decomposition of sodium chlorate 1 2 NaClO3 2 NaCl 3 O2Potassium permanganate also releases oxygen upon heating but the yield is modest 2 KMnO4 MnO2 K2MnO4 O2See also editGreat Oxygenation Event Colonization of MarsReferences edit a b Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 Yano Junko Kern Jan Yachandra Vittal K Nilsson Hakan Koroidov Sergey Messinger Johannes 2015 Chapter 2 Light Dependent Production of Dioxygen in Photosynthesis In Peter M H Kroneck and Martha E Sosa Torres ed Sustaining Life on Planet Earth Metalloenzymes Mastering Dioxygen and Other Chewy Gases Metal Ions in Life Sciences Vol 15 Springer pp 13 43 doi 10 1007 978 3 319 12415 5 2 PMC 4688042 PMID 25707465 Greife Paul Schonborn Matthias Capone Matteo Assuncao Ricardo Narzi Daniele Guidoni Leonardo Dau Holger 2023 The electron proton bottleneck of photosynthetic oxygen evolution Nature 1 6 doi 10 1038 s41586 023 06008 5 a b Raven Peter H Ray F Evert Susan E Eichhorn 2005 Biology of Plants 7th Edition New York W H Freeman and Company Publishers pp 115 127 ISBN 0 7167 1007 2 Raval M Biswal B Biswal U 2005 The mystery of oxygen evolution analysis of structure and function of photosystem II the water plastoquinone oxido reductase Photosynthesis Research 85 3 267 93 doi 10 1007 s11120 005 8163 4 PMID 16170631 S2CID 12893308 Song Jiajia Wei Chao Huang Zhen Feng Liu Chuntai Zeng Lin Wang Xin Xu Zhichuan J 2020 A Review on Fundamentals for Designing Oxygen Evolution Electrocatalysts Chemical Society Reviews 49 7 2196 2214 doi 10 1039 C9CS00607A hdl 10356 153346 PMID 32133479 S2CID 212416753 External links editPlant Physiology Online 4th edition Topic 7 7 Oxygen Evolution Oxygen evolution Lecture notes by Antony Crofts UIUC Evolution of the atmosphere Lecture notes Regents of the University of Michigan How to make oxygen and hydrogen from water using electrolysis Retrieved from https en wikipedia org w index php title Oxygen evolution amp oldid 1180220529, wikipedia, wiki, book, books, library,
