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Abstract |
We investigate plasma-based CO2 conversion into CO, a valuable feedstock for producing hydrocarbons via Fischer-Tropsch synthesis. However, CO-rich outputs for industrial use are currently limited by recombination reactions and the presence of O2 in the product stream. To address this, we place a carbon bed after the plasma to convert O2 into additional CO, while exploiting the reverse Boudouard reaction to further enhance CO2 conversion and CO enrichment. Previous studies have shown promising results, but reactor designs still need optimization, and the interaction between plasma and carbon bed remains unclear. In this study, we improve the coupling between the plasma and carbon bed, achieving outstanding performance, with CO2 conversion exceeding 40 % and energy cost below 2.8 eV/molecule (or 278 kJ/mol, corresponding to ca. 5 GJ per tonne CO or 1.4 kWh per kilogramme CO). This represents over a fourfold increase in conversion and nearly a fourfold reduction in energy cost compared to plasma experiments without carbon bed. Our detailed kinetic modeling reveals that the performance improvement is primarily due to the efficient removal of O2, which is converted into CO2, followed by the reverse Boudouard reaction, which enriches the CO output due to the high temperatures from close plasma contact. Thus, coupling a CO2 plasma with a carbon bed boosts the industrial viability of CO2 valorization, offering an attractive alternative to existing plasma-based CO2 splitting technologies, which typically require an order of magnitude more energy for similar conversion levels. |
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