Enhancing carbon nanotube production from carbon dioxide and ethane using bimetallic catalysts

Converting CO₂ into carbon nanotubes (CNTs) offers a promising method of CO₂ utilization and sequestration, potentially mitigating environmental impacts from anthropogenic emissions. This study reports that bimetallic CoFe catalysts can increase CNT production from the reaction of CO₂ and C₂H₆ by an order of magnitude compared to their monometallic counterparts. The active sites and CNT morphologies are composition dependent: Co-rich catalysts (Co/Fe ratio ≥ 5) form stable face-centered cubic (fcc) CoFe alloys, producing cylindrical CNTs, and Fe-containing catalysts (Co/Fe ≤ 2) favor body-centered cubic (bcc) CoFe alloys upon reduction, which transforms into carbides, resulting in bamboo-like CNTs. Experimental evidence and density functional theory (DFT) calculations reveal that adjacent Fe and Co atoms modulate CO and C_xH_y adsorption, regulating CNT production pathways through the CO Boudouard reaction and C₂H₆ decomposition. These results highlight the dual benefits of bimetallic catalysts in enhancing CNT yield and controlling CNT morphology through adjustment of catalyst compositions.