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Wu, Y.; Du, H.; Li, P.; Zhang, X.; Yin, Y.; Zhu, W. Mechanism of Electrochemical Reduction of CO2 to CH4. Encyclopedia. Available online: https://encyclopedia.pub/entry/43738 (accessed on 06 July 2024).
Wu Y, Du H, Li P, Zhang X, Yin Y, Zhu W. Mechanism of Electrochemical Reduction of CO2 to CH4. Encyclopedia. Available at: https://encyclopedia.pub/entry/43738. Accessed July 06, 2024.
Wu, Yugang, Huitong Du, Peiwen Li, Xiangyang Zhang, Yanbo Yin, Wenlei Zhu. "Mechanism of Electrochemical Reduction of CO2 to CH4" Encyclopedia, https://encyclopedia.pub/entry/43738 (accessed July 06, 2024).
Wu, Y., Du, H., Li, P., Zhang, X., Yin, Y., & Zhu, W. (2023, May 04). Mechanism of Electrochemical Reduction of CO2 to CH4. In Encyclopedia. https://encyclopedia.pub/entry/43738
Wu, Yugang, et al. "Mechanism of Electrochemical Reduction of CO2 to CH4." Encyclopedia. Web. 04 May, 2023.
Mechanism of Electrochemical Reduction of CO2 to CH4
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This entry is adapted from the peer-reviewed paper 10.3390/methane2020012

Electrocatalytic CO2 reduction to valued products is a promising way to mitigate the greenhouse effect, as this reaction makes use of the excess CO2 in the atmosphere and at the same time forms valued fuels to partially fulfill the energy demand for human beings. Methane, which is among the products of CO2RR, is regarded as a high-value commodity due to its high energy density of 55.5 MJ/kg. Moreover, the methane produced by the electrochemical reduction of CO2 is not emitted into the atmosphere and contributes to the greenhouse effect as the well-established infrastructure for gas pipelines, allowing for the seamless storage, consumption, and distribution of methane, rendering it a widely utilized component of natural gas. 

carbon dioxide reduction methane electrocatalysts

1. Introduction

Anthropogenic activities, particularly the extensive utilization of fossil fuels, have caused a significant increase in atmospheric CO2 concentrations, exacerbating the ongoing climate change crisis. Increased levels of CO2 lead to a heightened greenhouse effect, resulting in several adverse impacts on the global climate, including an increase in temperatures and sea level, altered precipitation patterns, and an increased frequency and intensity of natural disasters. These phenomena, in turn, have far-reaching ecological, social, and economic consequences, such as habitat destruction, species extinction, displacement of populations, and loss of biodiversity. Therefore, it is imperative to adopt sustainable energy sources and practices that reduce our dependence on fossil fuels to mitigate the detrimental effects of climate change and ensure a sustainable future for the planet and its inhabitants [1][2][3][4][5][6][7]. Thus, the reduction of CO2 to carbon-containing fuels is a promising technology for reducing CO2 emissions and achieving a sustainable future. This approach allows the conversion of intermittent renewable energy into high-energy fuels, providing a pathway to reduce our reliance on fossil fuels. Additionally, integrating CO2 into the global energy cycle through hydrocarbon synthesis allows us to achieve true global carbon neutrality [8][9][10][11][12][13]. At present, the main technologies aimed at reducing CO2 emissions include photo-, electro-, bio-, thermal, and their synergistic catalyses [14][15][16][17][18][19]. Each of these methods has its own set of advantages and limitations. For instance, photocatalysis is easy to perform and has a broad range of applications; however, it suffers from poor catalyst stability and lifespan [20]. Biocatalysis involves using biological enzymes to catalyze CO2 in mild-reaction conditions with good selectivity; however, yields are often low and catalyst deactivation is a common issue [21].
Methane, which is among the products of CO2RR, is regarded as a high-value commodity due to its high energy density of 55.5 MJ/kg. Moreover, the methane produced by the electrochemical reduction of CO2 is not emitted into the atmosphere and contributes to the greenhouse effect as the well-established infrastructure for gas pipelines, allowing for the seamless storage, consumption, and distribution of methane, rendering it a widely utilized component of natural gas. With a composition of 21.4% of total primary energy, methane boasts a high abundance and is an attractive candidate for various energy applications [22][23][24][25][26]. Concomitantly, contemporary technology offers the potential to convert CH4 into fundamental chemicals through various routes, such as the oxidative conversion into syngas or direct conversion into other chemical compounds [27][28][29][30]. Even after the inevitable transition to thermonuclear energy in the distant future, methane remains the most portable, easily stored, and transported fuel and general-purpose chemical raw material [31]. Most importantly, the next generation of rocket fuel will be liquid methane; the in situ production of methane as rocket fuel on alien planets, such as Mars, will become a key technology for human interstellar navigation. Therefore, the development of CO2RR technology to prepare high amounts of CH4 is necessary for this application.

2. Reaction Mechanism

Many research efforts have attempted to discover the mechanism of the electrochemical reduction of CO2 to CH4 from both experimental [32][33][34][35] and computational points of view [35][36][37][38][39][40]. From the pure-thermodynamics point of view, it is possible to reduce carbon dioxide to CH4 at a potential of + 0.17 V vs. reversible hydrogen electrode (RHE) [41] (Table 1). However, numerous studies have shown that CO2 electrochemical reduction to CH4 consists of multiple elementary steps [33][38]. CO2 is firstly absorbed on the catalyst and hydrogenated into *COOH via an electron transfer–proton coupling process [37]. Then, the *COOH is further evolved into *CO, which is the main branch point to determine whether or not to produce oxygen-containing products. In path I, *CO goes through a CHO* intermediate, with the overall path proceeding as:
CO2* → COOH* → CO* → CHO* → CH2O* → CH3O* → CH4 + O* or CH3OH*
(the H+ + e− reactants and H2O product formed were left off).
Table 1. Half reactions and potentials of CO2 electrochemical-reduction reactions.
Half-Reactions Formula Electrode Potential/V (vs. RHE)
CO2 + H2O + 2e− → CO + 2OH− −0.10
CO2 + 2H2O + 2e− → HCOOH + 2OH− −0.20 (pH < 4); −0.20 + 0.059 (pH > 4)
CO2 + 3H2O + 4e− → HCHO + 4OH− −0.07
CO2 + 5H2O + 6e− → CH3OH + 6OH− 0.02
CO2 + 6H2O + 8e− → CH4 + 8OH− 0.17
2CO2 + 8H2O + 12e− → C2H4 + 12OH− 0.08
2CO2 + 9H2O + 12e− → CH3CH2OH + 12OH− 0.09
The step to determine the selectivity is the final CH3O* reduction step. It was found that the production of CH4 had a more favorable reaction-free energy. In path II, *CO goes through a COH* intermediate with the overall path proceeding as:
CO* → COH* → C* → CH* → CH2* → CH3* → CH4*
(the H+ + e− reactants and H2O products formed were left off).
Notably, from Peterson et al.’s work, it is known that the absorption energy of the intermediate is crucial for product distributions [42]. For example, the metals (Au, Ag, and Zn) with weak *CO-bound energy produce little methane because CO experiences priority desorption before any further reductions occur [43][44][45]. Additionally, metals (Pt, Pd, and Ni) with strong *CO-bound energy cannot remove the *CO from the surface because of the highly unfavorable thermodynamic conditions. Thus, CO2 can only be reduced further to CH4 with an exceedingly low Faraday efficiency (FE) on these electrodes [46]. In contrast, the metal Cu is located near the top of the volcano curve of the limit potential. This means that the *CO-adsorption intensity of Cu is suitable for CH4 production via the CO2RR process.
Notably, some details of the reactions may be slightly different from what was mentioned above over different CO2RR catalysts. Dong et al. [47] reported that *CO protonated through a similar bridge configuration on the Cu2O/Cu interface. This conclusion was confirmed by the density functional theory (DFT) calculation. Interestingly, they also found that the Cu2O/Cu interface formed during the electrochemical reaction process played a crucial role in determining the selectivity of methane formation, which may indicate that the crystal plane is not the key factor for the CO2RR to CH4 formation process on reconstructed Cu2O microparticles.
As for the surface-reaction mechanism, two hypotheses were proposed, which are the Eley–Rideal (H comes from the solution) and Langmuir–Hinshelwood (H comes from the surface-adsorbed hydrogen (*H)) mechanisms, respectively. Yogesh and coworkers [48] studied the mechanism of electrochemical CO2 reduced to CH4 on the surface of Cu. They found that the methane production rate was significantly suppressed when increasing the pressure of CO. However, for the Eley–Rideal mechanism, the reaction rate should be positively correlated with the pressure of CO, which was inconsistent with the experimental phenomena. The experimental result thus excludes the Eley–Rideal mechanism and strongly supports the Langmuir–Hinshelwood mechanism, where COads and Hads are in competition with each other for surface sites. The result was also confirmed by Asthagiri and coworkers’ works with the DFT calculation [37].

References

  1. Pearson, P.N.; Palmer, M.R. Atmospheric carbon dioxide concentrations over the past 60 million years. Nature 2000, 406, 695–699.
  2. Liu, L.-X.; Fu, J.; Jiang, L.-P.; Zhang, J.-R.; Zhu, W.; Lin, Y. Highly Efficient Photoelectrochemical Reduction of CO2 at Low Applied Voltage Using 3D Co-Pi/BiVO4/SnO2 Nanosheet Array Photoanodes. ACS Appl. Mater. Interfaces 2019, 11, 26024–26031.
  3. Brady, J.M. Global Climate Change and Human Health. J. PeriAnesthesia Nurs. 2020, 35, 89–90.
  4. Salemdeeb, R.; Saint, R.; Clark, W.; Lenaghan, M.; Pratt, K.; Millar, F. A pragmatic and industry-oriented framework for data quality assessment of environmental footprint tools. Resour. Environ. Sustain. 2021, 3, 100019.
  5. Zhang, D.; Yang, W.; Wang, Z.; Ren, C.; Wang, Y.; Ding, M.; Liu, T. Efficient electrochemical CO2 reduction reaction on a robust perovskite type cathode with in-situ exsolved Fe-Ru alloy nanocatalysts. Sep. Purif. Technol. 2023, 304, 122287.
  6. Yuan, Y.; Lu, J. Demanding energy from carbon. Carbon Energy 2019, 1, 8–12.
  7. Wang, G.; Li, X.; Yang, X.; Liu, L.-X.; Cai, Y.; Wu, Y.; Wang, S.; Li, H.; Zhou, Y.; Wang, Y.; et al. Metal-Based Aerogels Catalysts for Electrocatalytic CO2 Reduction. Chem.-A Eur. J. 2022, 28, e202201834.
  8. De Luna, P.; Hahn, C.; Higgins, D.; Jaffer, S.A.; Jaramillo, T.F.; Sargent, E.H. What would it take for renewably powered electrosynthesis to displace petrochemical processes? Science 2019, 364, aav3506, Erratum in Science 2020, 367, eabb0992.
  9. Liu, Z.; Deng, Z.; He, G.; Wang, H.; Zhang, X.; Lin, J.; Qi, Y.; Liang, X. Challenges and opportunities for carbon neutrality in China. Nat. Rev. Earth Environ. 2022, 3, 141–155.
  10. Shi, X.; Zheng, Y.; Lei, Y.; Xue, W.; Yan, G.; Liu, X.; Cai, B.; Tong, D.; Wang, J. Air quality benefits of achieving carbon neutrality in China. Sci. Total Environ. 2021, 795, 148784.
  11. Salvia, M.; Reckien, D.; Pietrapertosa, F.; Eckersley, P.; Spyridaki, N.-A.; Krook-Riekkola, A.; Olazabal, M.; De Gregorio Hurtado, S.; Simoes, S.G.; Geneletti, D.; et al. Will climate mitigation ambitions lead to carbon neutrality? An analysis of the local-level plans of 327 cities in the EU. Renew. Sustain. Energy Rev. 2021, 135, 110253.
  12. He, M.; Sun, Y.; Han, B. Green Carbon Science: Efficient Carbon Resource Processing, Utilization, and Recycling towards Carbon Neutrality. Angew. Chem. Int. Ed. 2022, 61, e202112835.
  13. Liu, Z.; Sun, T.; Yu, Y.; Ke, P.; Deng, Z.; Lu, C.; Huo, D.; Ding, X. Near-Real-Time Carbon Emission Accounting Technology Toward Carbon Neutrality. Engineering 2022, 14, 44–51.
  14. Wang, Y.; Godin, R.; Durrant, J.R.; Tang, J. Efficient Hole Trapping in Carbon Dot/Oxygen-Modified Carbon Nitride Heterojunction Photocatalysts for Enhanced Methanol Production from CO2 under Neutral Conditions. Angew. Chem. Int. Ed. 2021, 60, 20811–20816.
  15. Ajmal, S.; Yasin, G.; Kumar, A.; Tabish, M.; Ibraheem, S.; Sammed, K.A.; Mushtaq, M.A.; Saad, A.; Mo, Z.; Zhao, W. A disquisition on CO2 electroreduction to C2H4: An engineering and design perspective looking beyond novel choosy catalyst materials. Coord. Chem. Rev. 2023, 485, 215099.
  16. Wei, J.; Yao, R.; Han, Y.; Ge, Q.; Sun, J. Towards the development of the emerging process of CO2 heterogenous hydrogenation into high-value unsaturated heavy hydrocarbons. Chem. Soc. Rev. 2021, 50, 10764–10805.
  17. Lee, W.J.; Li, C.; Prajitno, H.; Yoo, J.; Patel, J.; Yang, Y.; Lim, S. Recent trend in thermal catalytic low temperature CO2 methanation: A critical review. Catal. Today 2021, 368, 2–19.
  18. Navarro-Jaén, S.; Virginie, M.; Bonin, J.; Robert, M.; Wojcieszak, R.; Khodakov, A.Y. Highlights and challenges in the selective reduction of carbon dioxide to methanol. Nat. Rev. Chem. 2021, 5, 564–579.
  19. Shi, D.; Feng, Y.; Zhong, S. Photocatalytic conversion of CH4 and CO2 to oxygenated compounds over Cu/CdS–TiO2/SiO2 catalyst. Catal. Today 2004, 98, 505–509.
  20. Pachaiappan, R.; Rajendran, S.; Senthil Kumar, P.; Vo, D.-V.N.; Hoang, T.K.A. A review of recent progress on photocatalytic carbon dioxide reduction into sustainable energy products using carbon nitride. Chem. Eng. Res. Des. 2022, 177, 304–320.
  21. Becker, J.M.; Lielpetere, A.; Szczesny, J.; Junqueira, J.R.C.; Rodríguez-Maciá, P.; Birrell, J.A.; Conzuelo, F.; Schuhmann, W. Bioelectrocatalytic CO2 Reduction by Redox Polymer-Wired Carbon Monoxide Dehydrogenase Gas Diffusion Electrodes. ACS Appl. Mater. Interfaces 2022, 14, 46421–46426.
  22. Zhao, R.; Ding, P.; Wei, P.; Zhang, L.; Liu, Q.; Luo, Y.; Li, T.; Lu, S.; Shi, X.; Gao, S.; et al. Recent Progress in Electrocatalytic Methanation of CO2 at Ambient Conditions. Adv. Funct. Mater. 2021, 31, 2009449.
  23. Sun, L.; Wang, Y.; Guan, N.; Li, L. Methane Activation and Utilization: Current Status and Future Challenges. Energy Technol. 2020, 8, 1900826.
  24. Lunsford, J.H. Catalytic conversion of methane to more useful chemicals and fuels: A challenge for the 21st century. Catal. Today 2000, 63, 165–174.
  25. De Souza, R.F.B.; Florio, D.Z.; Antolini, E.; Neto, A.O. Partial Methane Oxidation in Fuel Cell-Type Reactors for Co-Generation of Energy and Chemicals: A Short Review. Catalysts 2022, 12, 217.
  26. Divins, N.J.; Braga, A.; Vendrell, X.; Serrano, I.; Garcia, X.; Soler, L.; Lucentini, I.; Danielis, M.; Mussio, A.; Colussi, S.; et al. Investigation of the evolution of Pd-Pt supported on ceria for dry and wet methane oxidation. Nat. Commun. 2022, 13, 5080.
  27. Song, H.; Ye, J. Direct photocatalytic conversion of methane to value-added chemicals. Trends Chem. 2022, 4, 1094–1105.
  28. Kang, Y.; Tian, M.; Huang, C.; Lin, J.; Hou, B.; Pan, X.; Li, L.; Rykov, A.I.; Wang, J.; Wang, X. Improving Syngas Selectivity of Fe2O3/Al2O3 with Yttrium Modification in Chemical Looping Methane Conversion. ACS Catal. 2019, 9, 8373–8382.
  29. Karakaya, C.; Kee, R.J. Progress in the direct catalytic conversion of methane to fuels and chemicals. Prog. Energy Combust. Sci. 2016, 55, 60–97.
  30. Sun, Z.; Russell, C.K.; Whitty, K.J.; Eddings, E.G.; Dai, J.; Zhang, Y.; Fan, M.; Sun, Z. Chemical looping-based energy transformation via lattice oxygen modulated selective oxidation. Prog. Energy Combust. Sci. 2023, 96, 101045.
  31. Arutyunov, V.; Savchenko, V.; Sedov, I.; Arutyunov, A.; Nikitin, A. The Fuel of Our Future: Hydrogen or Methane? Methane 2022, 1, 96–106.
  32. Hara, K.; Kudo, A.; Sakata, T. Electrochemical CO2 reduction on a glassy carbon electrode under high pressure. J. Electroanal. Chem. 1997, 421, 1–4.
  33. Schouten, K.J.P.; Kwon, Y.; van der Ham, C.J.M.; Qin, Z.; Koper, M.T.M. A new mechanism for the selectivity to C1 and C2 species in the electrochemical reduction of carbon dioxide on copper electrodes. Chem. Sci. 2011, 2, 1902–1909.
  34. Yu, P.; Lv, X.; Wang, Q.; Huang, H.; Weng, W.; Peng, C.; Zhang, L.; Zheng, G. Promoting Electrocatalytic CO2 Reduction to CH4 by Copper Porphyrin with Donor–Acceptor Structures. Small 2023, 19, 2205730.
  35. Xuan, X.; Cheng, J.; Yang, X.; Zhou, J. Highly Selective Electrochemical Reduction of CO2 to CH4 over Vacancy–Metal–Nitrogen Sites in an Artificial Photosynthetic Cell. ACS Sustain. Chem. Eng. 2020, 8, 1679–1686.
  36. Hatsukade, T.; Kuhl, K.P.; Cave, E.R.; Abram, D.N.; Jaramillo, T.F. Insights into the electrocatalytic reduction of CO2 on metallic silver surfaces. Phys. Chem. Chem. Phys. 2014, 16, 13814–13819.
  37. Nie, X.; Luo, W.; Janik, M.J.; Asthagiri, A. Reaction mechanisms of CO2 electrochemical reduction on Cu(111) determined with density functional theory. J. Catal. 2014, 312, 108–122.
  38. Dong, H.; Li, Y.; Jiang, D.-E. First-Principles Insight into Electrocatalytic Reduction of CO2 to CH4 on a Copper Nanoparticle. J. Phys. Chem. C 2018, 122, 11392–11398.
  39. Chan, K. A few basic concepts in electrochemical carbon dioxide reduction. Nat. Commun. 2020, 11, 5954.
  40. Ge, L.; Rabiee, H.; Li, M.; Subramanian, S.; Zheng, Y.; Lee, J.H.; Burdyny, T.; Wang, H. Electrochemical CO2 reduction in membrane-electrode assemblies. Chem 2022, 8, 663–692.
  41. Kortlever, R.; Shen, J.; Schouten, K.J.P.; Calle-Vallejo, F.; Koper, M.T.M. Catalysts and Reaction Pathways for the Electrochemical Reduction of Carbon Dioxide. J. Phys. Chem. Lett. 2015, 6, 4073–4082.
  42. Peterson, A.A.; Nørskov, J.K. Activity Descriptors for CO2 Electroreduction to Methane on Transition-Metal Catalysts. J. Phys. Chem. Lett. 2012, 3, 251–258.
  43. Jitaru, M.; Lowy, D.A.; Toma, M.; Toma, B.C.; Oniciu, L. Electrochemical reduction of carbon dioxide on flat metallic cathodes. J. Appl. Electrochem. 1997, 27, 875–889.
  44. Dutta, A.; Morstein, C.E.; Rahaman, M.; Cedeño López, A.; Broekmann, P. Beyond Copper in CO2 Electrolysis: Effective Hydrocarbon Production on Silver-Nanofoam Catalysts. ACS Catal. 2018, 8, 8357–8368.
  45. Du, H.; Fu, J.; Liu, L.-X.; Ding, S.; Lyu, Z.; Chang, Y.-C.; Jin, X.; Kengara, F.O.; Song, B.; Min, Q.; et al. Recent progress in electrochemical reduction of carbon monoxide toward multi-carbon products. Mater. Today 2022, 59, 182–199.
  46. Frese, K.W. Chapter 6—ELECTROCHEMICAL REDUCTION OF CO2 AT SOLID ELECTRODES. In Electrochemical and Electrocatalytic Reactions of Carbon Dioxide; Sullivan, B.P., Ed.; Elsevier: Amsterdam, The Netherlands, 1993; pp. 145–216.
  47. Deng, B.; Huang, M.; Li, K.; Zhao, X.; Geng, Q.; Chen, S.; Xie, H.; Dong, X.a.; Wang, H.; Dong, F. The Crystal Plane is not the Key Factor for CO2-to-Methane Electrosynthesis on Reconstructed Cu2O Microparticles. Angew. Chem. Int. Ed. 2022, 61, e202114080.
  48. Schreier, M.; Yoon, Y.; Jackson, M.N.; Surendranath, Y. Competition between H and CO for Active Sites Governs Copper-Mediated Electrosynthesis of Hydrocarbon Fuels. Angew. Chem. Int. Ed. 2018, 57, 10221–10225.
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Subjects: Green & Sustainable Science & Technology
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Yugang Wu
,
Huitong Du
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Peiwen Li
,
Xiangyang Zhang
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Yanbo Yin
,
Wenlei Zhu
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Update Date: 04 May 2023
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