Toward a circular carbon economy: Production of green C1 compounds through high-temperature CO₂ electrolysis

The electrochemical reduction of CO₂ to value-added carbon-containing chemicals using solid oxide electrolysis cells presents a significant opportunity for mitigating carbon emissions and enabling a circular carbon economy. Within this context, single-carbon compounds are of particular interest due to their extensive applications as both chemical precursors and fuels. This review summarizes recent advancements in the conversion of CO₂ to green methane and methanol through high-temperature electrolysis pathways. To enhance the efficiency and economic viability of this process, comprehensive system-level analysis has been conducted, focusing on system architecture, operational strategy refinement, and techno-economic assessment. The findings indicate that the integration of fluctuating renewable energy inputs can be effectively managed through strategic capacity allocation and energy management protocols. Additionally, modulating operational temperatures and the H₂/CO ratio emerges as a promising, albeit challenging, approach to enhance product yields, given the complex kinetics of CO₂ reduction. Furthermore, reducing the costs associated with electrolyzer fabrication and electricity consumption is identified as a pivotal factor for the commercial viability of this technology. There is a recognized need for further investigation into hydrogen-proton-conducting solid oxide electrolysis cells systems, particularly regarding the design of component assemblies and a more detailed techno-economic evaluation. Ultimately, this paper proposes a circular economy framework as an innovative solution to the resource challenges inherent in developing a sustainable, green infrastructure for the chemicals and energy sectors.