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

Abstract

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 (NOx, SOx, 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. 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 (NOx, SOx, 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.