:Electrochemical reduction of carbon dioxide

In carbon fixation, plants convert carbon dioxide into sugars, from which many biosynthetic pathways originate. The catalyst responsible for this conversion, RuBisCO, is the most common protein. Some anaerobic organisms employ enzymes to convert CO₂ to carbon monoxide, from which fatty acids can be made.{{cite journal | vauthors = Fontecilla-Camps JC, Amara P, Cavazza C, Nicolet Y, Volbeda A | title = Structure-function relationships of anaerobic gas-processing metalloenzymes | journal = Nature | volume = 460 | issue = 7257 | pages = 814–22 | date = August 2009 | pmid = 19675641 | doi = 10.1038/nature08299 | bibcode = 2009Natur.460..814F | s2cid = 4421420 }}

In industry, a few products are made from CO₂, including urea, salicylic acid, methanol, and certain inorganic and organic carbonates.Susan Topham, "Carbon Dioxide" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a05_165}} In the laboratory, carbon dioxide is sometimes used to prepare carboxylic acids in a process known as carboxylation. An electrochemical CO2 electrolyzer that operates at room temperature at an industrial scale cell size (15,000cm2) was announced by OCOchem in April 2024 as part of an R&D contract issued by the US Army.  The CO2 electrolyzer was reported as the largest in the world with a cathode surface area of 15,000cm2, 650% larger than nearest alternative, and achieving a sustained 85% Faradaic efficiency.{{Cite news |last=Yahoo News |date=April 25, 2024 |title=OCOchem Advances Hydrogen Formate Electrolyzer Process By 10x To Create World’s Largest Industrial Scale CO2 Electrolyzer Cell |url=https://finance.yahoo.com/news/ocochem-advances-hydrogen-formate-electrolyzer-160000293.html |url-status=live |work=Yahoo Finance}} Elevated temperature solid oxide electrolyzer cells (SOECs) for CO₂ reduction to CO are commercially available. For example, Haldor Topsoe offers SOECs for CO₂ reduction with a reported 6–8 kWh per Nm³Normal Cubic Meter - the quantity of gas that occupies one cubic meter at standard temperature and pressure. CO produced and purity up to 99.999% CO.{{cite web|title= Produce Your Own Carbon Monoxide - on-site and on-demand|publisher= Haldor Topsoe|website= www.topsoe.com|url= https://www.topsoe.com/processes/carbon-monoxide|url-status= live|archive-url= https://web.archive.org/web/20210228151311/https://www.topsoe.com/processes/carbon-monoxide|archive-date= 28 February 2021}}

The electrochemical reduction of carbon dioxide to various products is usually described as:

The redox potentials for these reactions are similar to that for hydrogen evolution in aqueous electrolytes, thus electrochemical reduction of CO₂ is usually competitive with hydrogen evolution reaction.

Electrochemical methods have gained significant attention:

1. at ambient pressure and room temperature;
2. in connection with renewable energy sources (see also solar fuel)
3. competitive controllability, modularity and scale-up are relatively simple.{{cite journal | vauthors = Lee S, Lee J | title = Electrode Build-Up of Reducible Metal Composites toward Achievable Electrochemical Conversion of Carbon Dioxide | journal = ChemSusChem | volume = 9 | issue = 4 | pages = 333–44 | date = February 2016 | pmid = 26610065 | doi = 10.1002/cssc.201501112 | bibcode = 2016ChSCh...9..333L }}

The electrochemical reduction or electrocatalytic conversion of CO₂ can produce value-added chemicals such methane, ethylene, ethanol, etc., and the products are mainly dependent on the selected catalysts and operating potentials (applying reduction voltage). A variety of homogeneous and heterogeneous catalysts{{Cite book | vauthors = Hori Y | chapter = Electrochemical CO2 Reduction on Metal Electrodes | doi = 10.1007/978-0-387-49489-0_3 | title = Modern Aspects of Electrochemistry | volume = 42 | pages = 89–80 | year = 2008 | isbn = 978-0-387-49488-3 }} have been evaluated.

Many such processes are assumed to operate via the intermediacy of metal carbon dioxide complexes.{{cite journal | vauthors = Benson EE, Kubiak CP, Sathrum AJ, Smieja JM | title = Electrocatalytic and homogeneous approaches to conversion of CO2 to liquid fuels | journal = Chemical Society Reviews | volume = 38 | issue = 1 | pages = 89–99 | date = January 2009 | pmid = 19088968 | doi = 10.1039/b804323j | s2cid = 20705539 }} Many processes suffer from high overpotential, low current efficiency, low selectivity, slow kinetics, and/or poor catalyst stability.{{cite book | vauthors = Halmann MM, Steinberg M | title = Greenhouse gas carbon dioxide mitigation: science and technology. | publisher = CRC press | date = May 1998 | isbn = 1-56670-284-4 }}

The composition of the electrolyte can be decisive.{{cite journal |doi=10.1038/s41586-019-1782-2 |title=Molecular tuning of CO2-to-ethylene conversion |year=2020 |last1=Li |first1=Fengwang |display-authors=et al. |journal=Nature |volume=577 |issue=7791 |pages=509–513 |pmid=31747679 |s2cid=208217415 |url=https://resolver.caltech.edu/CaltechAUTHORS:20190917-154117893 }}{{cite journal | vauthors = Rosen BA, Salehi-Khojin A, Thorson MR, Zhu W, Whipple DT, Kenis PJ, Masel RI | title = Ionic liquid-mediated selective conversion of CO₂ to CO at low overpotentials | journal = Science | volume = 334 | issue = 6056 | pages = 643–4 | date = November 2011 | pmid = 21960532 | doi = 10.1126/science.1209786 | bibcode = 2011Sci...334..643R | s2cid = 31774347 | doi-access = free }}{{cite journal | vauthors = Service RF | title = Two new ways to turn 'garbage' carbon dioxide into fuel | journal = Science Magazine | date = 1 September 2017 | url = https://www.science.org/content/article/two-new-ways-turn-garbage-carbon-dioxide-fuel | doi = 10.1126/science.aap8497 | url-access = subscription }} Gas-diffusion electrodes are beneficial.{{Cite journal| vauthors = Thorson MR, Siil KI, Kenis PJ |s2cid=95111100|date=2013|title=Effect of Cations on the Electrochemical Conversion of CO 2 to CO|journal=Journal of the Electrochemical Society|volume=160|issue=1|pages=F69–F74|doi=10.1149/2.052301jes|issn=0013-4651|doi-access=free}}{{cite journal | vauthors = Lv JJ, Jouny M, Luc W, Zhu W, Zhu JJ, Jiao F | title = A Highly Porous Copper Electrocatalyst for Carbon Dioxide Reduction | journal = Advanced Materials | volume = 30 | issue = 49 | pages = e1803111 | date = December 2018 | pmid = 30368917 | doi = 10.1002/adma.201803111 | bibcode = 2018AdM....3003111L | doi-access = | osti = 1712663 | s2cid = 53093014 }}{{cite journal | vauthors = Dinh CT, Burdyny T, Kibria MG, Seifitokaldani A, Gabardo CM, García de Arquer FP, Kiani A, Edwards JP, De Luna P, Bushuyev OS, Zou C, Quintero-Bermudez R, Pang Y, Sinton D, Sargent EH | display-authors = 6 | title = CO₂ electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface | journal = Science | volume = 360 | issue = 6390 | pages = 783–787 | date = May 2018 | pmid = 29773749 | doi = 10.1126/science.aas9100 | doi-access = free }}

Catalysts can be grouped by their primary products.{{cite journal | vauthors = Centi G, Perathoner S | year = 2009 | title = Opportunities and prospects in the chemical recycling of carbon dioxide to fuels | journal = Catalysis Today | volume = 148 | issue = 3–4| pages = 191–205 | doi = 10.1016/j.cattod.2009.07.075 }}{{cite journal | vauthors = Qiao J, Liu Y, Hong F, Zhang J | title = A review of catalysts for the electroreduction of carbon dioxide to produce low-carbon fuels | journal = Chemical Society Reviews | volume = 43 | issue = 2 | pages = 631–75 | date = January 2014 | pmid = 24186433 | doi = 10.1039/c3cs60323g }}{{Cite book |date=2008 |editor-last=Vayenas |editor-first=Constantinos G. |editor2-last=White |editor2-first=Ralph E. |editor3-last=Gamboa-Aldeco |editor3-first=Maria E. |title=Modern Aspects of Electrochemistry |url=https://link.springer.com/book/10.1007/978-0-387-49489-0 |language=en |doi=10.1007/978-0-387-49489-0 |volume=42 |isbn=978-0-387-49488-3 }} Several metal are unfit for CO₂RR because they promote to perform hydrogen evolution instead.{{Cite journal |last1=Lin |first1=Jiayi |last2=Zhang |first2=Yixiao |last3=Xu |first3=Pengtao |last4=Chen |first4=Liwei |date=2023-05-01 |title=CO2 electrolysis: Advances and challenges in electrocatalyst engineering and reactor design |journal=Materials Reports: Energy |series=CO2 Reductions to Fuels and Carbon Feedstocks (Part 2) |volume=3 |issue=2 |pages=100194 |doi=10.1016/j.matre.2023.100194 |issn=2666-9358|doi-access=free }} Electrocatalysts selective for one particular organic compound include tin or bismuth for formate and silver or gold for carbon monoxide. Copper produces multiple reduced products such as methane, ethylene or ethanol, while methanol, propanol and 1-butanol have also been produced in minute quantities.{{cite journal | vauthors = Ting LR, García-Muelas R, Martín AJ, Veenstra FL, Chen ST, Peng Y, Per EY, Pablo-García S, López N, Pérez-Ramírez J, Yeo BS | display-authors = 6 | title = Electrochemical Reduction of Carbon Dioxide to 1-Butanol on Oxide-Derived Copper | journal = Angewandte Chemie | volume = 59 | issue = 47 | pages = 21072–21079 | date = November 2020 | pmid = 32706141 | pmc = 7693243 | doi = 10.1002/anie.202008289 }}

Three common products are carbon monoxide, formate, or higher order carbon products (two or more carbons).{{Cite journal |last1=Mok |first1=Dong Hyeon |last2=Li |first2=Hong |last3=Zhang |first3=Guiru |last4=Lee |first4=Chaehyeon |last5=Jiang |first5=Kun |last6=Back |first6=Seoin |date=2023-11-11 |title=Data-driven discovery of electrocatalysts for CO2 reduction using active motifs-based machine learning |journal=Nature Communications |language=en |volume=14 |issue=1 |pages=7303 |doi=10.1038/s41467-023-43118-0 |issn=2041-1723|doi-access=free |pmid=37952012 |pmc=10640609 }}

Carbon monoxide can be produced from CO₂RR over various precious metal catalysts.{{Cite journal |last1=Marcandalli |first1=Giulia |last2=Monteiro |first2=Mariana C. O. |last3=Goyal |first3=Akansha |last4=Koper |first4=Marc T. M. |date=2022-07-19 |title=Electrolyte Effects on CO 2 Electrochemical Reduction to CO |journal=Accounts of Chemical Research |language=en |volume=55 |issue=14 |pages=1900–1911 |doi=10.1021/acs.accounts.2c00080 |issn=0001-4842 |pmc=9301915 |pmid=35772054}} Gold is known to be the most active, however Ag is also highly active. It is known that the stepped facets of both Au and Ag crystals (e.g. 110 and 211) are over an order of magnitude more active than the planar facets (e.g. 111 and 100). Single site catalysts, usually based on Ni in a graphitic lattice have also shown to be highly selective towards carbon monoxide.

Mechanistically, catalysts that convert CO₂RR to carbon monoxide do not bind strongly to carbon monoxide allowing it to escape from the catalyst. The rate limiting step for CO₂RR to carbon monoxide is the first electron transfer step and this is heavily influenced by the electric field. {{Cite journal |last1=Feaster |first1=Jeremy T. |last2=Shi |first2=Chuan |last3=Cave |first3=Etosha R. |last4=Hatsukade |first4=Toru |last5=Abram |first5=David N. |last6=Kuhl |first6=Kendra P. |last7=Hahn |first7=Christopher |last8=Nørskov |first8=Jens K. |last9=Jaramillo |first9=Thomas F. |date=2017-07-07 |title=Understanding Selectivity for the Electrochemical Reduction of Carbon Dioxide to Formic Acid and Carbon Monoxide on Metal Electrodes |url=https://pubs.acs.org/doi/10.1021/acscatal.7b00687 |journal=ACS Catalysis |language=en |volume=7 |issue=7 |pages=4822–4827 |doi=10.1021/acscatal.7b00687 |osti=1390311 |issn=2155-5435}}

Formic acid is produced as a primary product from CO₂RR over diverse catalysts.{{cite journal |title= Water-Mediated ElectroHydrogenation of CO2 at Near-Equilibrium Potential by Carbon Nanotubes/Cerium Dioxide Nanohybrids |year=2020 | vauthors = Valenti G, Melchionna M, Montini T, Boni A, Nasi L, Fonda E, Criado A, Zitolo A, Voci S, Bertoni G, Bonchio M | display-authors = 6 |journal= ACS Appl. Energy Mater. |volume=3 |issue= 9 |pages=8509–8518 | doi= 10.1021/acsaem.0c01145|doi-access=free |hdl= 11368/2972442 |hdl-access= free }}

Catalysts that promote Formic Acid production from CO₂ operate by strongly binding to both oxygen atoms of CO₂, allowing protons to attack the central carbon. After attacking the central carbon, one proton attaching to an oxygen results in the creation of formate. Indium catalysts promote formate production because the Indium-Oxygen binding energy is stronger than the Indium-Carbon binding energy.{{Cite journal |last1=Guo |first1=Weiwei |last2=Tan |first2=Xingxing |last3=Bi |first3=Jiahui |last4=Xu |first4=Liang |last5=Yang |first5=Dexin |last6=Chen |first6=Chunjun |last7=Zhu |first7=Qinggong |last8=Ma |first8=Jun |last9=Tayal |first9=Akhil |last10=Ma |first10=Jingyuan |last11=Huang |first11=Yuying |last12=Sun |first12=Xiaofu |last13=Liu |first13=Shoujie |last14=Han |first14=Buxing |date=2021-05-12 |title=Atomic Indium Catalysts for Switching CO 2 Electroreduction Products from Formate to CO |url=https://pubs.acs.org/doi/10.1021/jacs.1c00151 |journal=Journal of the American Chemical Society |language=en |volume=143 |issue=18 |pages=6877–6885 |doi=10.1021/jacs.1c00151 |pmid=33856799 |s2cid=233257736 |issn=0002-7863|url-access=subscription }} This promotes the production of formate instead of Carbon Monoxide.

Copper electrocatalysts produce multicarbon compounds from CO₂. These include C₂ products (ethylene, ethanol, acetate, etc.) and even C₃ products (propanol, acetone, etc.){{Cite journal |last1=Kuhl |first1=Kendra P. |last2=Cave |first2=Etosha R. |last3=Abram |first3=David N. |last4=Jaramillo |first4=Thomas F. |date=2012-04-26 |title=New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces |url=https://pubs.rsc.org/en/content/articlelanding/2012/ee/c2ee21234j |journal=Energy & Environmental Science |language=en |volume=5 |issue=5 |pages=7050–7059 |doi=10.1039/C2EE21234J |issn=1754-5706|url-access=subscription }} These products are more valuable than C1 products, but the current efficiencies are low.{{Cite journal |last1=Kong |first1=Qingquan |last2=An |first2=Xuguang |last3=Liu |first3=Qian |last4=Xie |first4=Lisi |last5=Zhang |first5=Jing |last6=Li |first6=Qinye |last7=Yao |first7=Weitang |last8=Yu |first8=Aimin |last9=Jiao |first9=Yan |last10=Sun |first10=Chenghua |date=2023-03-06 |title=Copper-based catalysts for the electrochemical reduction of carbon dioxide: progress and future prospects |journal=Materials Horizons |language=en |volume=10 |issue=3 |pages=698–721 |doi=10.1039/D2MH01218A |issn=2051-6355|doi-access=free |pmid=36601800 }}

• Electromethanogenesis
• Biobattery
• Electrofuel
• Lemon battery
• Photoelectrochemical reduction of carbon dioxide
• Photochemical reduction of carbon dioxide
• Electrolysis of water
• Electrochemical energy conversion
• Bioelectrochemical reactor

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• {{cite book | vauthors = LaConti AB, Molter TM, Zagaja JA | date = May 1986 | title = Electrochemical Reduction of Carbon Dioxide. | url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA169630 | archive-url = https://web.archive.org/web/20120327064123/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA169630 | archive-date = 27 March 2012 | url-status = dead | series = Online: Information for the Defense Industry }}
• {{cite book | vauthors = Fujita E | url = http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=20E4E93014C17486C2D213998D1D56FC?purl=/752152-JsQXqJ/native/ | title = Carbon Dioxide (Reduction) | date = January 2000 | publisher = Brookhaven National Lab. (BNL) | location = Upton, NY (United States) }}
• {{cite web | vauthors = Neelameggham NR | url = http://www.tms.org/pubs/journals/jom/0802/neelameggham-0802.html | title = Carbon Dioxide Reduction Technologies: A Synopsis of the Symposium at TMS 2008 | work = The Minerals, Metals & Materials Society (TMS) }}

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Category:Carbon dioxide

Category:Electrolysis

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Category:Electrochemical engineering