(485g) A Practical Perspective on CO2 Electrolysis in View of Future Net-Zero Energy Systems

Driven by a variety of factors, including the need to stabilize anthropogenic carbon emissions, falling costs of renewable energy, and social pressures, among others, different local, regional, and national governments and companies have committed to reach net-zero carbon emissions in the energy system by 2050¹. Achieving net-zero carbon emissions in energy systems is a daunting task that will require significant efforts to reduce carbon emissions in hard-to-decarbonize energy sectors, e.g., the transportation and industrial sectors^2,3. For instance, globally, achieving a net-zero energy system by 2050 could require the cumulative reduction of 8 Gt CO2 and 6.5 Gt CO2 from 2020 to 2050 in the industrial and transportation sectors, respectively (https://www.iea.org/reports/net-zero-by-2050). Moreover, around 7.6 Gt CO2 would need to be captured and stored or utilized in 2050, including 5.2 Gt CO2 from emitting point sources, i.e., fossil fuel combustion, ammonia and bioethanol plants, and industrial processes, and 1.0 Gt CO2 from air, i.e., via direct air capture (https://www.iea.org/reports/net-zero-by-2050). In this context, CO2 electroreduction to chemicals and fuels could facilitate the pathway towards a net-zero energy system by (i) replacing conventional carbon-emitting fuel and petrochemical processes and (ii) utilizing otherwise emitted CO2 or CO2 from the atmosphere. However, despite recent progress on the fundamental and mechanistic understanding^4-6, catalyst and reactor design^7-10, as well as scale-up and commercialization^11-14 of CO2 electrolysis, large-scale industrial deployment of this technology is not yet imminent. Indeed, technoeconomic analyses suggest that significant capital and operating cost reductions are required for CO2 electrolysis to be profitable or cost-competitive with traditional fossil-based or biocatalytic production processes, particularly for C2+ products, e.g., ethylene and ethanol^15-17.

This presentation provides an overview of CO2 electrolysis in view of net-zero energy systems. First, we provide a detailed description of different figures of merit for CO2 electrolysis as well as proposed industrial benchmarks and the corresponding status quo of the technology, for both low-temperature and high-temperature electrolysis. Additionally, we illustrate how each figure of merit may impact the total system cost for CO2 electrolysis, when possible. Then, an overview of the opportunities and challenges associated with the integration of CO2 capture and CO2 electrolysis is presented. We then summarize recent advances and remaining research gaps in catalysts and membranes for CO2 electrolysis and discuss progress towards practical reactor and process designs. Finally, we discuss the integration pathways for CO2 electrolysis, renewable energy sources, and electricity markets, including a discussion around the variability of renewable power sources, the dynamics of electricity prices, and the flexibility of CO2 electrolyzers.

References

1. United Nations. Net-Zero-Coalition. (2022). Available at: https://www.un.org/en/climatechange/net-zero-coalition. (Accessed: 3rd July 2022)

2. Hepburn, C. et al. The technological and economic prospects for CO2 utilization and removal. Nature 575, 87–97 (2019).

3. Davis, S. J. et al. Net-zero emissions energy systems. Science (80-. ). 360, (2018).

4. Birdja, Y. Y. et al. Advances and challenges in understanding the electrocatalytic conversion of carbon dioxide to fuels. Nat. Energy 4, 732–745 (2019).

5. Ma, W. et al. Electrocatalytic reduction of CO2 and CO to multi-carbon compounds over Cu-based catalysts. Chem. Soc. Rev. 50, 12897–12914 (2021).

6. Zhang, W. et al. Progress and Perspective of Electrocatalytic CO2 Reduction for Renewable Carbonaceous Fuels and Chemicals. Adv. Sci. 5, 1700275 (2018).

7. Lees, E. W., Mowbray, B. A. W., Parlane, F. G. L. & Berlinguette, C. P. Gas diffusion electrodes and membranes for CO2 reduction electrolysers. Nat. Rev. Mater. 7, 55–64 (2022).

8. Wakerley, D. et al. Gas diffusion electrodes, reactor designs and key metrics of low-temperature CO2 electrolysers. Nat. Energy 7, 130–143 (2022).

9. Hauch, A. et al. Recent advances in solid oxide cell technology for electrolysis. Science (80-. ). 370, (2020).

10. Overa, S., Ko, B. H., Zhao, Y. & Jiao, F. Electrochemical Approaches for CO2 Conversion to Chemicals: A Journey toward Practical Applications. Acc. Chem. Res. 55, 638–648 (2022).

11. Sánchez, O. G. et al. Recent advances in industrial CO2 electroreduction. Curr. Opin. Green Sustain. Chem. 16, 47–56 (2019).

12. Chen, C., Khosrowabadi Kotyk, J. F. & Sheehan, S. W. Progress toward Commercial Application of Electrochemical Carbon Dioxide Reduction. Chem 4, 2571–2586 (2018).

13. Burdyny, T. & Smith, W. A. CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions. Energy Environ. Sci. 12, 1442–1453 (2019).

14. Cheng, Y., Hou, P., Wang, X. & Kang, P. CO2 Electrolysis System under Industrially Relevant Conditions. Acc. Chem. Res. 55, 231–240 (2022).

15. Jordaan, S. M. & Wang, C. Electrocatalytic conversion of carbon dioxide for the Paris goals. Nat. Catal. 4, 915–920 (2021).

16. Somoza-Tornos, A., Guerra, O. J., Crow, A. M., Smith, W. A. & Hodge, B.-M. Process modeling, techno-economic assessment, and life cycle assessment of the electrochemical

reduction of CO2: a review. iScience 24, 102813 (2021).

17. Shin, H., Hansen, K. U. & Jiao, F. Techno-economic assessment of low-temperature carbon dioxide electrolysis. Nat. Sustain. 4, 911–919