Corresponding Author

Yan-xia CHEN(yachen@ustc.edu.cn)


In this review, we present the major developments in the understanding of the mechanisms of the electrochemical reduction of CO2 from a historical perspective. Most of the work discussed in this review was carried out at copper electrodes, as this is the only material at which hydrocarbons are produced in reasonable quantities. The emphasis focuses on the differentiation of mechanisms for the generation of C1 and C2 products as well as factors and methods for controlling the product selectivity of CO2 reduction. We have highlighted ambiguities, assumptions, and important methodologies, such as differential electrochemical mass spectrometry and electrochemical in-situ infrared spectroscopy, which help greatly to clarify these issues in the literature.

Graphical Abstract


CO2 reduction, mechanism, infrared spectroscopy, differential electrochemical mass spectrometry, Cu electrode

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[1]Yang H Q, Xu Z H, Fan M H , et al. Progress in carbon dioxide separation and capture: A review[J]. Journal of Environmental Sciences, 2008,20(1):14-27.
doi: 10.1016/s1001-0742(08)60002-9 URL pmid: 18572517

[2]Mikkelsen M, Jørgensen M, Krebs F C . The teraton challenge. A review of fixation and transformation of carbon dioxide[J]. Energy & Environmental Science, 2010,3(1):43-81.

[3]Hori Y, Kikuchi K, Murata A , et al. Production of methane and ethylene in electrochemical reduction of carbon dioxide at copper electrode in aqueous hydrogencarbonate solution[J]. Chemistry Letters, 1986,6:897-898.

[4]Kuhl K P, Cave E R, Abram D N , et al. New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces[J]. Energy & Environmental Science, 2012,5(5):7050-7059.

[5]Ting L R L, Yeo B S . Recent advances in understanding mechanisms for the electrochemical reduction of carbon dioxide[J]. Current Opinion in Electrochemistry, 2018,8:126-134.
doi: 10.1021/acs.chemrev.7b00459 URL pmid: 29319300

[6]Raciti D, Wang C . Recent advances in CO2 reduction electrocatalysis on copper[J]. ACS Energy Letters, 2018,3(7):1545-1556.
doi: 10.1021/acs.accounts.9b00496 URL pmid: 31913013

[7]Kortlever R, Shen J, Schouten K J P , et al. Catalysts and reaction pathways for the electrochemical reduction of carbon dioxide[J]. Journal of Physical Chemistry Letters, 2015,6(20):4073-4082.
doi: 10.1021/acs.jpclett.5b01559 URL pmid: 26722779

[8]Tian Z Q, Priest C, Chen L . Recent progress in the theoretical investigation of electrocatalytic reduction of CO2[J]. Advanced Theory and Simulations, 2018,1(5):1800004.

[9]Rendón-Calle A, Builes S, Calle-Vallejo F . A brief review of the computational modeling of CO2 electroreduction on Cu electrodes[J]. Current Opinion in Electrochemistry, 2018,9:158-165.
doi: 10.1016/j.coelec.2018.03.012 URL

[10]Yoo J S, Christensen R, Vegge T , et al. Theoretical insight into the trends that guide the electrochemical reduction of carbon dioxide to formic acid[J]. ChemSusChem, 2016,9(4):358-363.
doi: 10.1002/cssc.201501197 URL pmid: 26663854

[11]Costentin C, Robert M, Saveant J M . Catalysis of the electrochemical reduction of carbon dioxide[J]. Chemical Society Reviews, 2013,42(6):2423-2436.
doi: 10.1039/c2cs35360a URL pmid: 23232552

[12]Qiao J L, Liu Y Y, Hong F , et al. A review of catalysts for the electroreduction of carbon dioxide to produce low-carbon fuels[J]. Chemical Society Reviews, 2014,43(2):631-675.
doi: 10.1039/c3cs60323g URL pmid: 24186433

[13]Kumar B, Brian J P, Atla V , et al. New trends in the development of heterogeneous catalysts for electrochemical CO2 reduction[J]. Catalysis Today, 2016,270:19-30.
doi: 10.1021/la9019475 URL pmid: 19572538

[14]Hori Y . Electrochemical CO2 reduction on metal electrodes[M]//Modern Aspects of Electrochemistry, Vayenas C G, White R E, Gamboa-Aldeco M E (Eds.), Springer, New York, 200:89-189.

[15]Bagger A, Wen Ju, Varela A S , et al. Electrochemical CO2 reduction: A classification problem[J]. ChemPhys-Chem, 2017,18(22):3266-3273.
doi: 10.1002/cphc.201700736 URL pmid: 28872756

[16]Quaino P, Juarez F, Santos E , et al. Volcano plots in hydrogen electrocatalysis uses and abuses[J]. Beilstein Journal of Nanotechnology, 2014,5:846-854.
doi: 10.3762/bjnano.5.96 URL pmid: 24991521

[17]Trasatti S . Work function, electronegativity, and electrochemical behaviour of metals: III. Electrolytic hydrogen evolution in acid solutions[J]. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1972,39(1):163-184.

[18]Sarkar S, Peter S C . An overview on Pd-based electrocatalysts for the hydrogen evolution reaction[J]. Inorganic Chemistry Frontiers, 2018,5(9):2060-2080.

[19]Jung N, Cho Y H, Ahn M , et al. Methanol-tolerant cathode electrode structure composed of heterogeneous composites to overcome methanol crossover effects for direct methanol fuel cell[J]. International Journal of Hydrogen Energy, 2011,36(24):15731-15738.

[20]Chung D Y, Kim H I, Chung Y H , et al. Inhibition of CO poisoning on Pt catalyst coupled with the reduction of toxic hexavalent chromium in a dual-functional fuel cell[J]. Scientific Reports, 2014,4:7450.
doi: 10.1038/srep07450 URL pmid: 25502744

[21]Feaster J T, Shi C, Cave E R , et al. Understanding selectivity for the electrochemical reduction of carbon dioxide to formic acid and carbon monoxide on metal electrodes[J]. ACS Catalysis, 2017,7(7):4822-4827.

[22]Chen Y H, Kanan M W . Tin oxide dependence of the CO2 reduction efficiency on tin electrodes and enhanced activity for tin/tin oxide thin-film catalysts[J]. Journal of the American Chemical Society, 2012,134(4):1986-1989.
doi: 10.1021/ja2108799 URL pmid: 22239243

[23]Baruch M F, Pander J E, White J L , et al. Mechanistic insights into the reduction of CO2 on tin electrodes using in situ ATR-IR spectroscopy[J]. ACS Catalysis, 2015,5(5):3148-3156.
doi: 10.1021/acscatal.5b00402 URL

[24]Luc W, Collins C, Wang S , et al. Ag-Sn bimetallic catalyst with a core-shell structure for CO2 reduction[J]. Journal of the American Chemical Society, 2017,139(5):1885-1893.
doi: 10.1021/jacs.6b10435 URL pmid: 28094994

[25]Lee C H, Kanan M W . Controlling H+ vs. CO2 reduction selectivity on Pb electrodes[J]. ACS Catalysis, 2015,5(1):465-469.

[26]DiMeglio J L, Rosenthal J . Selective conversion of CO2 to CO with high efficiency using an inexpensive bismuth-based electrocatalyst[J]. Journal of the American Chemical Society, 2013,135(24):8798-8801.
doi: 10.1021/ja4033549 URL pmid: 23735115

[27]Zhao S, Jin R X, Jin R C . Opportunities and challenges in CO2 reduction by gold- and silver-based electrocatalysts: from bulk metals to nanoparticles and atomically precise nanoclusters[J]. ACS Energy Letters, 2018,3(2):452-462.

[28]Rosen B A, Salehi-Khojin A, Thorson M R , et al. Ionic liquid-mediated selective conversion of CO2 to CO at low overpotentials[J]. Science, 2011,334(6056):643-644.
doi: 10.1126/science.1209786 URL pmid: 21960532

[29]Hatsukade T, Kuhl K P, Cave E R , et al. Insights into the electrocatalytic reduction of CO2 on metallic silver surfaces[J]. Physical Chemistry Chemical Physics, 2014,16(27):13814-13819.
doi: 10.1039/c4cp00692e URL pmid: 24915537

[30]Kuhl K P, Hatsukade T, Cave E R , et al. Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces[J]. Journal of the American Chemical Society, 2014,136(40):14107-14113.
doi: 10.1021/ja505791r URL pmid: 25259478

[31]Blyholder G . Molecular orbital view of chemisorbed carbon monoxide[J]. Journal of Chemical Physics, 1964,68(10):2772-2777.

[32]Föhlisch A, Nyberg M, Bennich P , et al. The bonding of CO to metal surfaces[J]. Journal of Chemical Physics, 2000,112(4):1946-1958.

[33]Koper M T M, van Santen R A, Wasileski S A , et al. Field-dependent chemisorption of carbon monoxide and nitric oxide on platinum-group (111) surfaces: Quantum chemical calculations compared with infrared spectroscopy at electrochemical and vacuum-based interfaces[J]. Journal of Chemical Physics, 2000,113(10):4392-4407.
doi: 10.1063/1.1288592 URL

[34]Yoshio H, Katsuhei K, Shin S . Production of CO and CH4 in electrochemical reduction of CO2 at metal electrodes in aqueous hydrogencarbonate solution[J]. Chemistry Letters, 1985,14(11):1695-1698.

[35]Wuttig A, Liu C, Peng Q L , et al. Tracking a common surface-bound intermediate during CO2-to-fuels catalysis[J]. ACS Central Science, 2016,2(8):522-528.
doi: 10.1021/acscentsci.6b00155 URL pmid: 27610413

[36]Hori Y, Koga O, Watanabe Y , et al. FTIR measurements of charge displacement adsorption of CO on poly- and single crystal (100) of Cu electrodes[J]. Electrochimica Acta, 1998,44:1389-1395.

[37]Saussey J, Lavalley J C, Lamotte J , et al. I.R. spectroscopic evidence of formyl species formed by CO and H2 Co-adsorption on ZnO and Cu-ZnO[J]. Journal of the Chemical Society, Chemical Communications, 1982,5:278-279.

[38]Hori Y, Takahashi R, Yoshinami Y , et al. Electrochemical reduction of CO at a copper electrode[J]. Journal of Physical Chemistry B, 1997,101(36):7075-7081.
doi: 10.1021/acsami.9b16862 URL pmid: 31815424

[39]Qi L J, Liu S P, Gao W , et al. Mechanistic understanding of CO2 electroreduction on Cu2O[J]. Journal of Physical Chemistry C, 2018,122(10):5472-5480.

[40]Nie X W, Esopi M R, Janik M J , et al. Selectivity of CO2 reduction on copper electrodes: The role of the kinetics of elementary steps[J]. Angewandte Chemie International Edition, 2013,52(9):2459-2462.
doi: 10.1002/anie.201208320 URL pmid: 23345201

[41]Schouten K J P, Kwon Y, van der Ham C J M , et al. A new mechanism for the selectivity to C1 and C2 species in the electrochemical reduction of carbon dioxide on copper electrodes[J]. Chemical Science, 2011,2(10):1902-1909.

[42]Kyriacou G, Anagnostopoulos A . Electroreduction of CO2 on differently prepared copper electrodes: The influence of electrode treatment on the current efficiences[J]. Journal of Electroanalytical Chemistry, 1992,322(1/2):233-246.

[43]Shiratsuchi R, Aikoh Y, Nogami G . Pulsed electroreduction of CO2 on copper electrodes[J]. Journal of The Electrochemical Society, 1993,140(12):3479-3482.
doi: 10.1149/1.2221113 URL

[44]Kimura K W, Fritz K E, Kim J , et al. Controlled selectivity of CO2 reduction on copper by pulsing the electrochemical potential[J]. ChemSusChem, 2018,11(11):1781-1786.
doi: 10.1002/cssc.201800318 URL pmid: 29786966

[45]Wang L, Nitopi S A, Bertheussen E , et al. Electrochemical carbon monoxide reduction on polycrystalline copper: Effects of potential, pressure, and pH on selectivity toward multicarbon and oxygenated products[J]. ACS Ca-talysis, 2018,8(8):7445-7454.
doi: 10.1021/acsnano.8b03513 URL pmid: 30010321

[46]Peterson A A, Abild-Pedersen F, Studt F , et al. How copper catalyzes the electroreduction of carbon dioxide into hydrocarbon fuels[J]. Energy & Environmental Science, 2010,3(9):1311-1315.

[47]Pérez-Gallent E, Figueiredo M C, Calle-Vallejo F , et al. Spectroscopic observation of a hydrogenated CO dimer intermediate during CO reduction on Cu(100) electrodes[J]. Angewandte Chemie International Edition, 2017,129(13):3621-3624.
doi: 10.1002/anie.201700580 URL pmid: 28230297

[48]Schouten K J P, Qin Z, Pérez Gallent E , et al. Two pathways for the formation of ethylene in CO reduction on single-crystal copper electrodes[J]. Journal of the American Chemical Society, 2012,134(24):9864-9867.
doi: 10.1021/ja302668n URL pmid: 22670713

[49]Luo W J, Nie X W, Janik M J , et al. Facet dependence of CO2 reduction paths on Cu electrodes[J]. ACS Catalysis, 2016,6(1):219-229.
doi: 10.1021/acscatal.5b01967 URL

[50]Montoya J H, Shi C, Chan K , et al. Theoretical insights into a CO dimerization mechanism in CO2 electroreduction[J]. Journal of Physical Chemistry Letters, 2015,6(11):2032-2037.
doi: 10.1021/acs.jpclett.5b00722 URL pmid: 26266498

[51]Xiao H, Cheng T, Goddard W A , et al. Mechanistic explanation of the pH dependence and onset potentials for hydrocarbon products from electrochemical reduction of CO on Cu(111)[J]. Journal of the American Chemical Society, 2016,138(2):483-486.
doi: 10.1021/jacs.5b11390 URL pmid: 26716884

[52]Cheng T, Xiao H, Goddard W A . Free-energy barriers and reaction mechanisms for the electrochemical reduction of CO on the Cu(100) surface, including multiple layers of explicit solvent at pH 0[J]. Journal of Physical Chemistry Letters, 2015,6(23):4767-4773.
doi: 10.1021/acs.jpclett.5b02247 URL pmid: 26562750

[53]Goodpaster J D, Bell A T, Head-Gordon M . Identification of possible pathways for C-C bond formation during electrochemical reduction of CO2: New theoretical insights from an improved electrochemical model[J]. Journal of Physical Chemistry Letters, 2016,7(8):1471-1477.
doi: 10.1021/acs.jpclett.6b00358 URL pmid: 27045040

[54]Garza A J, Bell A T, Head-Gordon M . Mechanism of CO2 reduction at copper surfaces: Pathways to C2 products[J]. ACS Catalysis, 2018,8(2):1490-1499.

[55] Dunwell M, Yan Y S, Xu B J . Understanding the influence of the electrochemical double-layer on heterogeneous electrochemical reactions[J]. Current Opinion in Chemical Engineering, 2018,20:151-158.
doi: 10.1021/nn503780b URL pmid: 25211307

[56] Zhu S Q, Jiang B, Cai W B , et al. Direct observation on reaction intermediates and the role of bicarbonate anions in CO2 electrochemical reduction reaction on Cu surfaces[J]. 2017,139(44):15664-15667.

[57] Resasco J, Lum Y, Clark E , et al. Effects of anion identity and concentration on electrochemical reduction of CO2[J]. ChemElectroChem, 2018,5(7):1064-1072.

[58] Akira M, Yoshio H . Product selectivity affected by cationic species in electrochemical reduction of CO2 and CO at a Cu electrode[J]. Bulletin of the Chemical Society of Japan, 1991,64(1):123-127.

[59] Singh M R, Kwon Y, Lum Y , et al. Hydrolysis of electrolyte cations enhances the electrochemical reduction of CO2 over Ag and Cu[J]. Journal of the American Chemical Society, 2016,138(39):13006-13012.
doi: 10.1021/jacs.6b07612 URL pmid: 27626299

[60] Pérez-Gallent E, Marcandalli G, Figueiredo M C , et al. Structure- and potential-dependent cation effects on CO reduction at copper single-crystal electrodes[J]. Journal of the American Chemical Society, 2017,139(45):16412-16419.
doi: 10.1021/jacs.7b10142 URL pmid: 29064691

[61] Resasco J, Chen L D, Clark E , et al. Promoter effects of alkali metal cations on the electrochemical reduction of carbon dioxide[J]. Journal of the American Chemical Society, 2017,139(32):11277-11287.
doi: 10.1021/jacs.7b06765 URL pmid: 28738673

[62] Hori Y, Wakebe H, Tsukamoto T , et al. Adsorption of CO accompanied with simultaneous charge transfer on copper single crystal electrodes related with electrochemical reduction of CO2 to hydrocarbons[J]. Surface Science, 1995,335:258-263.

[63] Li H J, Li Y d, Koper M T M , et al. Bond-making and breaking between carbon, nitrogen, and oxygen in electrocatalysis[J]. Journal of the American Chemical Society, 2014,136(44):15694-15701.
doi: 10.1021/ja508649p URL pmid: 25314268

[64] Shaw S K, Berna A, Feliu J M , et al. Role of axially coordinated surface sites for electrochemically controlled carbon monoxide adsorption on single crystal copper electrodes[J]. Physical Chemistry Chemical Physics, 2011,13(12):5242-5251.
doi: 10.1039/c0cp02064h URL pmid: 21253640

[65] Salimon J, Hernández-Romero R M, Kalaji M . The dynamics of the conversion of linear to bridge bonded CO on Cu[J]. Journal of Electroanalytical Chemistry, 2002,538:99-108.

[66] Gunathunge C M, Ovalle V J, Li Y , et al. Existence of an electrochemically inert CO population on Cu electrodes in alkaline pH[J]. ACS Catalysis, 2018,8(8):7507-7516.
doi: 10.1021/acscatal.8b01552 URL

[67] Baricuatro J H, Kim Y G, Korzeniewski C L , et al. Seriatim ECSTM-ECPMIRS of the adsorption of carbon monoxide on Cu(100) in alkaline solution at CO2-reduction potentials[J]. Electrochemistry Communication, 2018,91:1-4.
doi: 10.1016/j.elecom.2018.04.016 URL

[68] Huang Y, Handoko A D, Hirunsit P , et al. Electrochemical reduction of CO2 using copper single-crystal surfaces: Effects of CO* coverage on the selective formation of ethylene[J]. ACS Catalysis, 2017,7(3):1749-1756.
doi: 10.1021/acscatal.6b03147 URL

[69] Zhang R G, Hao X B, Duan T , et al. Adsorption and activation of CO and H2, the corresponding equilibrium phase diagrams under different temperature and partial pressures over Cu(100) surface: Insights into the effects of coverage and solvent effect[J]. Fuel Processing Technology, 2017,156:253-264.

[70] Hussain A . Beneficial effect of Cu on a Cu-modified Au catalytic surface for CO oxidation reaction: A DFT study[J]. Journal of Physical Chemistry C, 2013,117(10):5084-5094.

[71] Dunwell M, Yang X, Yan Y S , et al. Potential routes and mitigation strategies for contamination in interfacial specific infrared spectroelectrochemical studies[J]. Journal of Physical Chemistry C, 2018,122(43):24658-24664.

[72] Sartin M M, Yu Z Y, Chen W , et al. Effect of particle shape and electrolyte cation on CO adsorption to copper oxide nanoparticle electrocatalysts[J]. Journal of Physical Chemistry C, 2018,122(46):26489-26498.



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