Tandem Plasma-Thermocatalytic Reactors for C2H6-Assisted Sequestration of CO2 as Carbon Nanomaterials

Converting CO2 into value-added carbon nanomaterials offers a compelling strategy for long-term carbon sequestration by generating commercially valuable products. Here, we demonstrate tandem plasma–thermocatalytic reactors for the coconversion of CO2 and C2H6 into carbon nanotubes (CNTs) and carbon nanofibers (CNFs). A dielectric barrier discharge plasma reactor activates a C2H6/CO2 feed mixture, generating reactive intermediates that serve as precursors for downstream thermocatalytic production of CNT over Co/Al2O3 at 750 °C and CNF over Co12K5/CeO2 at 450 °C. Systematic variation of plasma power and thermocatalytic reactor zone length reveals that these parameters strongly influence reactant conversion, product distribution, and carbon weight gain, enabling independent optimization of the plasma activation and thermocatalytic carbon growth. The tandem configuration enables CNT and CNF synthesis at lower temperatures than conventional chemical vapor deposition processes. An energy and CO2 footprint analysis demonstrates that, when powered by renewable electricity, the plasma–thermocatalytic system offers a modular, electrified pathway for carbon-negative sequestration. These results establish tandem plasma–thermocatalytic reactors as a flexible platform for reacting CO2 with light alkanes to produce carbon nanomaterials.