A theoretical study on the CO₂ methanation over Ni₅/AC catalysts by means of density functional theory. Part II: Reaction pathways

The methanation of carbon dioxide over Ni5 supported on activated carbon (Ni5/AC) was studied by using density functional theory and climbing image – nudged elastic band methods. A reaction diagram for the formation of methane via CO or HCOO species, which consists of 14 reaction steps was proposed. The reaction energy and activation energy for the overall steps involved in the reaction process were calculated and analyzed. Following the proposed mechanism possible carbon byproducts of the CO2 methanation reaction are CO and HCHO. Formation of these products can occur at high temperatures, but it is more thermodynamically difficult than formation of CH4. The formation of CH4 is more preferably occur via the CO pathway than the HCOO pathway.