Theoretical research the mechanism on the Ir/Ni (111) catalyst surface for CO2 methanation reaction

Iridium (Ir) demonstrates exceptional properties in CO2 hydrogenation reactions, yet the reaction mechanism remains unclear. Utilizing Density Functional Theory (DFT) calculations, the reaction mechanism on the Ir/Ni (111) surface has been investigated. Mulliken charge analysis indicates that CO2 is securely adsorbed and activated on the Ir/Ni (111) surface, forming CO2*, which is crucial for the subsequent hydrogenation process. By evaluating both the reaction energy barrier and the heat of reaction, the optimal methanation pathway CO2*→ COOH*→ CO*→ HCO*→ HCOH*→ CH*→ CH2*→ CH3*→ CH4* has been identified. The step of hydrogenation leading to HCO* is recognized as the rate-determining step in methanation, displaying the highest reaction activation energy. Furthermore, a greater energy barrier for C* formation proves advantageous in enhancing anti-carbon deposition properties and prolonging catalyst lifespan. Concurrently, the capability for C* hydrogenation sees dynamic and thermodynamic improvements, potentially augmenting the catalyst's methanation performance.