This study examined the catalytic activity and stability of transition metal@C (carbon) catalysts in methane pyrolysis for

hydrogen and solid carbon production. The carbon support for the catalysts was sustainably synthesized using CO 2 as the

carbon source. X-ray diff raction analysis was used to confi rm the presence of metallic phases in the as-calcined catalysts

without requiring an additional H 2 reduction step. The apparent activation energies of the catalysts were determined using

Arrhenius plots, with Ni@C having the lowest value (71 kJ∙mol −1 ), followed by Co@C (89 kJ∙mol −1 ), Fe@C (100 kJ∙mol −1 ),

and Cu@C (122 kJ∙mol −1 ). The carbon support exhibited an apparent activation energy of 150 kJ∙mol −1 , indicating its superior

catalytic performance compared with traditional carbon-based catalysts. The reaction order demonstrated fi rst-order

reactions, indicating that the rate-determining step is associated with the fi rst C–H bond cleavage in methane. The Ni@C and

Co@C catalysts demonstrated promising catalytic activity and stability for methane pyrolysis, with the formation of crystalline

carbon and metal particle fragmentation playing crucial roles in enhancing their performance. However, the formation

of carbide species contributed to the deactivation of Fe@C.

Methane pyrolysis · Methane decomposition · Hydrogen · Carbon nano-onion · CO 2 utilization

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