Catalytic Activity of CO₂-Derived Transition Metal–Carbon Catalysts in Methane Pyrolysis

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 CO₂ as the carbon source. X-ray diffraction analysis was used to confirm the presence of metallic phases in the as-calcined catalysts without requiring an additional H₂ 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 first-order reactions, indicating that the rate-determining step is associated with the first 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.