An industrial perspective on catalysts for low-temperature CO2 electrolysis
Source abstract
Abstract
Electrochemical conversion of CO2 to useful products at temperatures below 100 °C is nearing the commercial scale. Pilot units for CO2 conversion to CO are already being tested. Units to convert CO2 to formic acid are projected to reach pilot scale in the next year. Further, several investigators are starting to observe industrially relevant rates of the electrochemical conversion of CO2 to ethanol and ethylene, with the hydrogen needed coming from water. In each case, Faradaic efficiencies of 80% or more and current densities above 200 mA cm-2 can be reproducibly achieved. Here we describe the key advances in nanocatalysts that lead to the impressive performance, indicate where additional work is needed and provide benchmarks that others can use to compare their results.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: CO2 Reduction Techniques and Catalysts · Ionic liquids properties and applications · Carbon dioxide utilization in catalysis
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (100+)
Show source-provided references
1. Kaczur, J. J., Yang, H., Liu, Z., Sajjad, S. D. & Masel, R. I. A review of the use of immobilized ionic liquids in the electrochemical conversion of CO2. J. Carbon Res. 6, 33 (2020).10.3390/c6020033 ↗
2. Ross, M. B. et al. Designing materials for electrochemical carbon dioxide recycling. Nat. Catal. 2, 648–658 (2019).10.1038/s41929-019-0306-7 ↗
3. Xie, J., Huang, Y., Wu, M. & Wang, Y. Electrochemical carbon dioxide splitting. ChemElectroChem 6, 1587–1604 (2019).10.1002/celc.201801716 ↗
4. Song, J. T., Song, H., Kim, B. & Oh, J. Towards higher rate electrochemical CO2 conversion: from liquid-phase to gas-phase systems. Catalysts 9, 224 (2019).10.3390/catal9030224 ↗
5. Li, F., MacFarlane, D. R. & Zhang, J. Recent advances in the nanoengineering of electrocatalysts for CO2 reduction. Nanoscale 10, 6235–6260 (2018).10.1039/C7NR09620H ↗
6. Nwabara, U. O., Cofell, E. R., Verma, S., Negro, E. & Kenis, P. J. A. Durable cathodes and electrolyzers for the efficient aqueous electrochemical reduction of CO2. ChemSusChem 13, 855–875 (2020).10.1002/cssc.201902933 ↗
7. Lee, M.-Y. et al. Current achievements and the future direction of electrochemical CO2 reduction: a short review. Crit. Rev. Environ. Sci. Technol. 50, 769–815 (2020).10.1080/10643389.2019.1631991 ↗
8. Siemens CO2 for a Clean Performance: Rheticus Research Project Enters Phase 2 https://press.siemens.com/global/en/pressrelease/research-project-rheticus (2019).
9. Krause, R. et al. Industrial application aspects of the electrochemical reduction of CO2 to CO in aqueous electrolyte. Chem. Ing. Tech. 92, 53–61 (2020).10.1002/cite.201900092 ↗
10. Haas, T., Krause, R., Weber, R., Demler, M. & Schmid, G. Technical photosynthesis involving CO2 electrolysis and fermentation. Nat. Catal. 1, 32–39 (2018).10.1038/s41929-017-0005-1 ↗
11. Matthews, T. S. et al. On the route to commercialization of a CO2 electrolyzer: lessons learned from an industry effort to fight climate change. Prepr. Pap. Am. Chem. Soc. Div. Energy Fuels 60, 222–223 (2015).
12. Kaczur, J. J., Yang, H., Liu, Z., Sajjad, S. D. & Masel, R. I. Carbon dioxide and water electrolysis using new alkaline stable anion membranes. Front. Chem. 6, 263 (2018).10.3389/fchem.2018.00263 ↗
13. Yang, H., Kaczur, J. J., Sajjad, S. D. & Masel, R. I. Electrochemical conversion of CO2 to formic acid utilizing Sustainion membranes. J. CO2 Util. 20, 208–217 (2017).10.1016/j.jcou.2017.04.011 ↗
14. Kaczur, J. J., Yang, H., Sajjad, S. D. & Masel, R. I. Method and system for electrochemical production of formic acid from carbon dioxide. US patent 10,047,446 (2018).
15. Yang, H., Kaczur, J. J., Sajjad, S. D. & Masel, R. I. CO2 conversion to formic acid in a three compartment cell with sustainion membranes. ECS Trans. 77, 1425–1431 (2017).10.1149/07711.1425ecst ↗
16. Xia, C. et al. Continuous production of pure liquid fuel solutions via electrocatalytic CO2 reduction using solid-electrolyte devices. Nat. Energy 4, 776–785 (2019).10.1038/s41560-019-0451-x ↗
17. Zhu, Q. et al. Carbon dioxide electroreduction to C2 products over copper–cuprous oxide derived from electrosynthesized copper complex. Nat. Commun. 10, 3851 (2019).10.1038/s41467-019-11599-7 ↗
18. Li, F. et al. Cooperative CO2-to-ethanol conversion via enriched intermediates at molecule–metal catalyst interfaces. Nat. Catal. 3, 75–82 (2020).10.1038/s41929-019-0383-7 ↗
19. García de Arquer, F. P. et al. CO2 electrolysis to multicarbon products at activities greater than 1 A /cm2. Science 367, 661–666 (2020).10.1126/science.aay4217 ↗
20. Wang, X. et al. Efficient electrically powered CO2-to-ethanol via suppression of deoxygenation. Nat. Energy https://doi.org/10.1038/s41560-020-0607-8 (2020).10.1038/s41560-020-0607-8 ↗
21. Zhong, M. et al. Accelerated discovery of CO2 electrocatalysts using active machine learning. Nature 581, 178–183 (2020).10.1038/s41586-020-2242-8 ↗
22. Dinh, C.-T. et al. CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface. Science 360, 783–787 (2018).10.1126/science.aas9100 ↗
23. Vennekoetter, J.-B., Scheuermann, T., Sengpiel, R. & Wessling, M. The electrolyte matters: stable systems for high rate electrochemical CO2 reduction. J. CO2 Util. 32, 202–213 (2019).10.1016/j.jcou.2019.04.007 ↗
24. Romero Cuellar, N. S. et al. Two-step electrochemical reduction of CO2 towards multi-carbon products at high current densities. J. CO2 Utilization 36, 263–275 (2020).10.1016/j.jcou.2019.10.016 ↗
25. Romero Cuellar, N. S., Wiesner-Fleischer, K., Fleischer, M., Rucki, A. & Hinrichsen, O. Advantages of CO over CO2 as reactant for electrochemical reduction to ethylene, ethanol and n-propanol on gas diffusion electrodes at high current densities. Electrochim. Acta 307, 164–175 (2019).10.1016/j.electacta.2019.03.142 ↗
26. Jouny, M., Hutchings, G. S. & Jiao, F. Carbon monoxide electroreduction as an emerging platform for carbon utilization. Nat. Catal. 2, 1062–1070 (2019).10.1038/s41929-019-0388-2 ↗
27. Li, C. W., Ciston, J. & Kanan, M. W. Electroreduction of carbon monoxide to liquid fuel on oxide-derived nanocrystalline copper. Nature 508, 504–507 (2014).10.1038/nature13249 ↗
28. Gurudayal et al. Sequential cascade electrocatalytic conversion of carbon dioxide to C–C coupled products. ACS Appl. Energy Mater. 2, 4551–4559 (2019).10.1021/acsaem.9b00791 ↗
29. Zhang, H., Li, J., Cheng, M.-J. & Lu, Q. CO electroreduction: current development and understanding of Cu-based catalysts. ACS Catal. 9, 49–65 (2019).10.1021/acscatal.8b03780 ↗
30. Ren, S. et al. Molecular electrocatalysts can mediate fast, selective CO2 reduction in a flow cell. Science 365, 367–369 (2019).10.1126/science.aax4608 ↗
31. Wang, Q., Zhang, Y., Lin, H. & Zhu, J. Recent advances in metal–organic frameworks for photo-/electrocatalytic CO2 reduction. Chemistry 25, 14026–14035 (2019).10.1002/chem.201902203 ↗
32. Zhang, E. et al. Bismuth single atoms resulting from transformation of metal–organic frameworks and their use as electrocatalysts for CO2 reduction. J. Am. Chem. Soc. 141, 16569–16573 (2019).10.1021/jacs.9b08259 ↗
33. Jeong, H.-Y. et al. Achieving highly efficient CO2 to CO electroreduction exceeding 300 mA cm−2 with single-atom nickel electrocatalysts. J. Mater. Chem. A 7, 10651–10661 (2019).10.1039/C9TA02405K ↗
34. Zheng, T. et al. Large-scale and highly selective CO2 electrocatalytic reduction on nickel single-atom catalyst. Joule 3, 265–278 (2019).10.1016/j.joule.2018.10.015 ↗
35. Li, J., Zhang, Y. & Kornienko, N. Heterogeneous electrocatalytic reduction of CO2 promoted by secondary coordination sphere effects. New J. Chem. https://doi.org/10.1039/C9NJ05892C (2020).10.1039/C9NJ05892C ↗
36. Ovalle, V. J. & Waegele, M. M. Understanding the impact of N-arylpyridinium ions on the selectivity of CO2 reduction at the Cu/electrolyte interface. J. Phys. Chem. C 123, 24453–24460 (2019).10.1021/acs.jpcc.9b08666 ↗
37. Sinha, S. & Warren, J. J. Unexpected solvent effect in electrocatalytic CO2 to CO conversion revealed using asymmetric metalloporphyrins. Inorg. Chem. 57, 12650–12656 (2018).10.1021/acs.inorgchem.8b01814 ↗
38. Shen, J., Lan, D. & Yang, T. Influence of supporting electrolyte on the electrocatalysis of CO2 reduction by cobalt protoporphyrin. Int. J. Electrochem. Sci. 13, 9847–9857 (2018).10.20964/2018.10.62 ↗
39. Zhao, M. et al. Inhibiting hydrogen evolution using a chloride adlayer for efficient electrochemical CO2 reduction on Zn electrodes. ACS Appl Mater. Interfaces 12, 4565–4571 (2020).10.1021/acsami.9b22811 ↗
40. Yoshida, T. et al. Ionic-caged heterometallic bismuth–platinum complex exhibiting electrocatalytic CO2 reduction. Dalton Trans. 49, 2652–2660 (2020).10.1039/C9DT04817K ↗
41. Suter, S. & Haussener, S. Optimizing mesostructured silver catalysts for selective carbon dioxide conversion into fuels. Energy Environ. Sci. 12, 1668–1678 (2019).10.1039/C9EE00656G ↗
42. Pankhurst, J. R., Guntern, Y. T., Mensi, M. & Buonsanti, R. Molecular tunability of surface-functionalized metal nanocrystals for selective electrochemical CO2 reduction. Chem. Sci. 10, 10356–10365 (2019).10.1039/C9SC04439F ↗
43. Christensen, R., Hansen, H. A. & Vegge, T. Identifying systematic DFT errors in catalytic reactions. Catal. Sci. Technol. 5, 4946–4949 (2015).10.1039/C5CY01332A ↗
44. Yoo, J. S., Christensen, R., Vegge, T., Norskov, J. K. & Studt, F. Theoretical insight into the trends that guide the electrochemical reduction of carbon dioxide to formic acid. ChemSusChem 9, 358–363 (2016).10.1002/cssc.201501197 ↗
45. Studt, F., Abild-Pedersen, F., Varley, J. B. & Nørskov, J. K. CO and CO2 hydrogenation to methanol calculated using the BEEF-vdW functional. Catal. Lett. 143, 71–73 (2013).10.1007/s10562-012-0947-5 ↗
46. Liu, Z., Yang, H., Kutz, R. & Masel, R. I. CO2 electrolysis to CO and O2 at high selectivity, stability and efficiency using Sustainion membranes. J. Electrochem. Soc. 165, J3371–J3377 (2018).10.1149/2.0501815jes ↗
47. Edwards, J. P. et al. Efficient electrocatalytic conversion of carbon dioxide in a low-resistance pressurized alkaline electrolyzer. Appl. Energy 261, 114305 (2020).10.1016/j.apenergy.2019.114305 ↗
48. Masel, R. I., Chen, Q., Liu, Z. & Kutz, R. Catalyst layers and electrolyzers. US patent 9,481,939 (2018).
49. Masel, R. I., Liu, Z., Kutz, R. & Sajjad, S. D. Catalyst layers and electrolyzers. US patent 9,945,040 (2018).
50. Higgins, D., Hahn, C., Xiang, C., Jaramillo, T. F. & Weber, A. Z. Gas-diffusion electrodes for carbon dioxide reduction: a new paradigm. ACS Energy Lett. 4, 317–324 (2019).10.1021/acsenergylett.8b02035 ↗
51. Endrődi, B. et al. Multilayer electrolyzer stack converts carbon dioxide to gas products at high pressure with high efficiency. ACS Energy Lett. 4, 1770–1777 (2019).10.1021/acsenergylett.9b01142 ↗
52. Liu, Z. et al. Electrochemical generation of syngas from water and carbon dioxide at industrially important rates. J. CO2 Util. 15, 50–56 (2016).10.1016/j.jcou.2016.04.011 ↗
53. Ma, C. et al. Carbon nanotubes with rich pyridinic nitrogen for gas phase CO2 electroreduction. Appl. Catal. B 250, 347–354 (2019).10.1016/j.apcatb.2019.03.041 ↗
54. Kutz, R. B. et al. Sustainion imidazolium-functionalized polymers for carbon dioxide electrolysis. Energy Technol. 5, 929–936 (2017).10.1002/ente.201600636 ↗
55. Masel, R. I., Chen, Q. & Liu, Z. Ion-conducting membranes. US patent 9,849,450 (2017).
56. Masel, R. I., Chen, Q., Liu, Z. & Kutz, R. Ion-conducting membranes. US patent 9,370,773 (2016).
57. Landes, H., Sanchis, E. M. F. & Hanebuth, M. Method and device for the electrochemical utilization of carbon dioxide. European patent application EP3414363A1 (2018).
58. Krause, R., Neubauer, S., Reller, C., Schmid, B. & Schmid, G. CO2 electrolysis method. Patent Cooperation Treaty application WO2018050419A1 (2018); https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2018050419
59. Verma, S., Lu, X., Kenis, P. J. A., Ma, S. & Masel, R. I. The effect of electrolyte composition on the electroreduction of CO2 to CO on Ag based gas diffusion electrodes. Phys. Chem. Chem. Phys. 18, 7075–7084 (2016).10.1039/C5CP05665A ↗
60. Salehi-Khojin, A. et al. Nanoparticle silver catalysts that show enhanced activity for carbon dioxide electrolysis. J. Phys. Chem. C 117, 1627–1632 (2013).10.1021/jp310509z ↗
61. Masel, R. I. & Salehi-Khojin, A. Catalysts for electrochemical conversion of carbon dioxide. US patent 9,012,345 (2015).
62. Kim, C. et al. Achieving selective and efficient electrocatalytic activity for CO2 reduction using immobilized silver nanoparticles. J. Am. Chem. Soc. 137, 13844–13850 (2015).10.1021/jacs.5b06568 ↗
63. Zhang, L., Zhao, Z.-J. & Gong, J. Nanostructured materials for heterogeneous electrocatalytic CO2 reduction and their related reaction mechanisms. Angew. Chem. Int. Ed. 56, 11326–11353 (2017).10.1002/anie.201612214 ↗
64. Zhu, W. et al. Monodisperse Au nanoparticles for selective electrocatalytic reduction of CO2 to CO. J. Am. Chem. Soc. 135, 16833–16836 (2013).10.1021/ja409445p ↗
65. Cho, M. et al. Versatile, transferable 3-dimensionally nanofabricated Au catalysts with high-index crystal planes for highly efficient and robust electrochemical CO2 reduction. J. Mater. Chem. A 7, 6045–6052 (2019).10.1039/C8TA12242C ↗
66. Mistry, H. et al. Exceptional size-dependent activity enhancement in the electroreduction of CO2 over Au nanoparticles. J. Am. Chem. Soc. 136, 16473–16476 (2014).10.1021/ja508879j ↗
67. Weekes, D. M., Salvatore, D. A., Reyes, A., Huang, A. & Berlinguette, C. P. Electrolytic CO2 reduction in a flow cell. Acc. Chem. Res. 51, 910–918 (2018).10.1021/acs.accounts.8b00010 ↗
68. Mahyoub, S. A. et al. An overview on the recent developments of Ag-based electrodes in the electrochemical reduction of CO2 to CO. Sustain. Energy Fuels 4, 50–67 (2019).10.1039/C9SE00594C ↗
69. Sun, D. et al. Rational design of Ag-based catalysts for the electrochemical CO2 reduction to CO: a review. ChemSusChem 13, 39–58 (2020).10.1002/cssc.201902061 ↗
70. Rudnev, A. V. et al. Enhanced electrocatalytic CO formation from CO2 on nanostructured silver foam electrodes in ionic liquid/water mixtures. Electrochim. Acta 306, 245–253 (2019).10.1016/j.electacta.2019.03.102 ↗
71. Liu, S.-Q. et al. Hollow porous Ag spherical catalysts for highly efficient and selective electrocatalytic reduction of CO2 to CO. ACS Sustain. Chem. Eng. 7, 14443–14450 (2019).10.1021/acssuschemeng.9b01635 ↗
72. Kottakkat, T. et al. Electrodeposited AgCu foam catalysts for enhanced reduction of CO2 to CO. ACS Appl. Mater. Interfaces 11, 14734–14744 (2019).10.1021/acsami.8b22071 ↗
73. Wang, Y., Niu, C. & Zhu, Y. Copper–silver bimetallic nanowire arrays for electrochemical reduction of carbon dioxide. Nanomaterials 9, 173 (2019).10.3390/nano9020173 ↗
74. Lee, S., Park, G. & Lee, J. Importance of Ag–Cu biphasic boundaries for selective electrochemical reduction of CO2 to ethanol. ACS Catal. 7, 8594–8604 (2017).10.1021/acscatal.7b02822 ↗
75. Hoang, T. T. H. et al. Nanoporous copper–silver alloys by additive-controlled electrodeposition for the selective electroreduction of CO2 to ethylene and ethanol. J. Am. Chem. Soc. 140, 5791–5797 (2018).10.1021/jacs.8b01868 ↗
76. Hjorth, I., Nord, M., Roenning, M., Yang, J. & Chen, D. Electrochemical reduction of CO2 to synthesis gas on CNT supported CuxZn1−xO catalysts. Catal. Today https://doi.org/10.1016/j.cattod.2019.02.045 (2019).10.1016/j.cattod.2019.02.045 ↗
77. Lin, R. et al. PdAg bimetallic electrocatalyst for highly selective reduction of CO2 with low COOH* formation energy and facile CO desorption. Nano Res. 12, 2866–2871 (2019).10.1007/s12274-019-2526-1 ↗
78. Zeng, J. et al. Pd–Ag alloy electrocatalysts for CO2 reduction: composition tuning to break the scaling relationship. ACS Appl. Mater. Interfaces 11, 33074–33081 (2019).10.1021/acsami.9b11729 ↗
79. Larrazabal, G. O., Martin, A. J., Mitchell, S., Hauert, R. & Perez-Ramirez, J. Synergistic effects in silver–indium electrocatalysts for carbon dioxide reduction. J. Catal. 343, 266–277 (2016).10.1016/j.jcat.2015.12.014 ↗
80. Park, H. et al. AgIn dendrite catalysts for electrochemical reduction of CO2 to CO. Appl. Catal. B 219, 123–131 (2017).10.1016/j.apcatb.2017.07.038 ↗
81. Abeyweera, S. C., Yu, J., Perdew, J. P., Yan, Q. & Sun, Y. Hierarchically 3D porous Ag nanostructures derived from silver benzenethiolate nanoboxes: enabling CO2 reduction with a near-unity selectivity and mass-specific current density over 500 A/g. Nano Lett. 20, 2806–2811 (2020).10.1021/acs.nanolett.0c00518 ↗
82. Lee, W. H. et al. Highly selective and scalable CO2 to CO—electrolysis using coral-nanostructured Ag catalysts in zero-gap configuration. Nano Energy https://doi.org/10.1016/j.nanoen.2020.105030 (2020).10.1016/j.nanoen.2020.105030 ↗
83. Jhong, H.-R. M. et al. Gold nanoparticles on polymer-wrapped carbon nanotubes: an efficient and selective catalyst for the electroreduction of CO2. ChemPhysChem 18, 3274–3279 (2017).10.1002/cphc.201700815 ↗
84. Verma, S. et al. Insights into the low overpotential electroreduction of CO2 to CO on a supported gold catalyst in an alkaline flow electrolyzer. ACS Energy Lett. 3, 193–198 (2018).10.1021/acsenergylett.7b01096 ↗
85. Jin, L. et al. Ultrasmall Au nanocatalysts supported on nitrided carbon for electrocatalytic CO2 reduction: the role of the carbon support in high selectivity. Nanoscale 10, 14678–14686 (2018).10.1039/C8NR04322A ↗
86. Hong, S., Lee, S., Kim, S., Lee, J. K. & Lee, J. Anion dependent CO/H2 production ratio from CO2 reduction on Au electrocatalyst. Catal. Today 295, 82–88 (2017).10.1016/j.cattod.2017.05.063 ↗
87. Goyal, A., Marcandalli, G., Mints, V. A. & Koper, M. T. M. Competition between CO2 reduction and hydrogen evolution on a gold electrode under well-defined mass transport conditions. J. Am. Chem. Soc. 142, 4154–4161 (2020).10.1021/jacs.9b10061 ↗
88. Zhang, B. A., Ozel, T., Elias, J. S., Costentin, C. & Nocera, D. G. Interplay of homogeneous reactions, mass transport, and kinetics in determining selectivity of the reduction of CO2 on gold electrodes. ACS Cent. Sci. 5, 1097–1105 (2019).10.1021/acscentsci.9b00302 ↗
89. Yin, Z. et al. An alkaline polymer electrolyte CO2 electrolyzer operated with pure water. Energy Environ. Sci. 12, 2455–2462 (2019).10.1039/C9EE01204D ↗
90. Zhu, W. et al. Active and selective conversion of CO2 to CO on ultrathin Au nanowires. J. Am. Chem. Soc. 136, 16132–16135 (2014).10.1021/ja5095099 ↗
91. Wen, X. et al. A reassembled nanoporous gold leaf electrocatalyst for efficient CO2 reduction towards CO. Inorg. Chem. Front. 5, 1207–1212 (2018).10.1039/C8QI00023A ↗
92. Chen, Y., Li, C. W. & Kanan, M. W. Aqueous CO2 reduction at very low overpotential on oxide-derived Au nanoparticles. J. Am. Chem. Soc. 134, 19969–19972 (2012).10.1021/ja309317u ↗
93. Ismail, A. M., Csapo, E. & Janaky, C. Correlation between the work function of Au–Ag nanoalloys and their electrocatalytic activity in carbon dioxide reduction. Electrochim. Acta 313, 171–178 (2019).10.1016/j.electacta.2019.05.016 ↗
94. Wu, N., Xiao, L. & Zhuang, L. Theoretical search for novel Au or Ag bimetallic alloys capable of transforming CO2 into hydrocarbons. J. Mater. Chem. A 7, 20567–20573 (2019).10.1039/C9TA07929G ↗
95. Xiang, H. et al. Copper–indium binary catalyst on a gas diffusion electrode for high-performance CO2 electrochemical reduction with record CO production efficiency. ACS Appl. Mater. Interfaces 21, 601–608 (2020).10.1021/acsami.9b16862 ↗
96. Chen, D. et al. Tailoring the selectivity of bimetallic copper–palladium nanoalloys for electrocatalytic reduction of CO2 to CO. ACS Appl. Energy Mater. 1, 883–890 (2018).10.1021/acsaem.7b00320 ↗
97. Francke, R., Schille, B. & Roemelt, M. Homogeneously catalyzed electroreduction of carbon dioxide—methods, mechanisms, and catalysts. Chem. Rev. 118, 4631–4701 (2018).10.1021/acs.chemrev.7b00459 ↗
98. Torbensen, K. et al. Molecular catalysts boost the rate of electrolytic CO2 reduction. ACS Energy Lett. 5, 1512–1518 (2020).10.1021/acsenergylett.0c00536 ↗
99. Corbin, N., Zeng, J., Williams, K. & Manthiram, K. Heterogeneous molecular catalysts for electrocatalytic CO2 reduction. Nano Res. 12, 2093–2125 (2019).10.1007/s12274-019-2403-y ↗
100. Sun, L., Reddu, V., Fisher, A. C. & Wang, X. Electrocatalytic reduction of carbon dioxide: opportunities with heterogeneous molecular catalysts. Energy Environ. Sci. 13, 374–403 (2020).10.1039/C9EE03660A ↗