Activity Boost for Cobalt–Selectivity Shift and Activation During CO ₂ Methanation by Carbon Nitride‐Modified Al ₂ O ₃ Support

Abstract This research demonstrates an approach to enhance performance during CO 2 hydrogenation by using carbon nitride (CN)‐coated Al 2 O 3 composites as a support for cobalt‐based catalysts. Unlike conventional fine powdered CN with a typically low surface area, the CN coating on Al 2 O 3 enables tuneable porosity and minimizes pressure drop in fixed‐bed reactors. Modification of the Al 2 O 3 support with CN induced a significantly improved distribution of separately prepared Co 3 O 4 nanoparticles. The CN layer interacted strongly with the nanoparticles, preventing aggregation. An enhanced stabilization of nanoparticles was also identified when comparing the Co/CN@Al 2 O 3 catalyst with the Co/Al 2 O 3 catalyst post reaction. Catalytic tests for CO 2 methanation revealed that Co/CN@Al 2 O 3 yields significantly higher CO 2 conversions of up to 63% and a methane selectivity of 94%. In contrast, the Co/Al 2 O 3 catalyst exhibits a lower CO 2 conversion of maximum 20% and a methane selectivity of up to 66%. These results illustrate the superior stability and activity of the Co/CN@Al 2 O 3 catalyst, which may be linked to a restructuring of the CN into a N‐doped carbon (N─C) layer and potential cobalt carbide formation during activation or CO 2 hydrogenation.