CO₂ conversion via coupled plasma-electrolysis process

Surplus renewable electricity used to convert CO₂ into CO, the building block of liquid fuels, advances the energy transition by enabling large-scale, long-term energy storage and the synthesis of fuel for long-haul transportation. Among the various technologies developed, renewable electricity driven conversion of CO₂ by high-temperature electrolysis and by plasmolysis offer a tantalising potential. High-temperature electrolysis is characterized by high-yield and energy-efficiency and the direct separation of the CO₂ dissociation products CO and O₂. However, the difficulty to break the carbon-oxygen double bond poses challenging requirements on electrode materials. CO₂ plasmolysis on the other hand, offers a similar energy efficiency, does not employ scarce materials, is easy to upscale, but requires efficient gas separation and recuperation because the produced CO remains mixed with O₂ and residual CO₂. Here, we demonstrate that the coupling of the two processes leads to a renewable-electricity-driven route for producing CO from CO₂, overcoming the main bottleneck of CO₂ plasmolysis. A simulated CO₂ plasmolysis gas mixture is supplied to a high-temperature electrolyser to separate the product gases electrochemically. Our results show that the product stream of the coupled-process contains 91% less oxygen and 138% more CO compared with the bare plasmolysis process. Apart from upgrading the produced gas mixture, this coupled approach benefits from material stability. Durability tests (~100 h) show better stability in coupled operation when compared with conventional CO₂ electrolysis. Synergy between plasmolysis and electrolysis opens up a novel route to efficient CO₂ conversion into valuable CO feedstock for the synthesis of long-chain hydrocarbons.