Barriers and opportunities for the deployment of CO₂ electrolysis in net-zero emissions energy systems

As energy systems across the globe transition toward net-zero emissions, the decarbonization of hard-to-decarbonize sectors, e.g., industry and transportation, is becoming more crucial. Renewable power-driven carbon dioxide (CO₂) electrolysis has the potential to facilitate this transition by (1) substituting carbon-intensive petrochemical and fuel production and (2) using CO₂ otherwise emitted from industrial processes or CO₂ from the atmosphere; however, because of existing technical and economic challenges, the industrial deployment of this technology is not yet imminent. Here, we present an overview of CO₂ electrolysis technologies to identify key hurdles in view of the industrial deployment of this technology in net-zero emissions energy systems. From the technology standpoint, catalysts should be developed with enhanced activity, selectivity, and stability/durability as well as membranes and reactors that prevent carbonate formation or crossover, achieve higher reaction rates, e.g., >1 A/cm², and demonstrate long-term stability, e.g., >5 years. Conversely, from the system integration standpoint, impurity-tolerant CO₂ electrolysis systems need to be developed and tested under relevant conditions, e.g., CO₂ streams with traces of impurities (NO_x, SO_x, O₂, N₂, H₂S, etc.). Additionally, the quantification of pros and cons of different integration pathways for CO₂ capture and CO₂ electrolysis requires further research. Moreover, the integration with variable renewable power sources—e.g., wind and solar photovoltaic power—and electricity markets requires a better understanding. For instance, the value of CO₂ electrolysis flexibility in view of variable renewable power supply or dynamic electricity prices is not well understood.