A Density Functional Study for the Reaction Mechanism of CO Oxidation on the Copper Cluster

摘要

We have studied the reaction mechanism of CO oxidation on the Cu13 cluster via density functional theory.There are two main reaction pathways to be considered:Eley-Rideal (ER) and Langmuir-Hinshelwood(LH) mechanisms,respectively.According to these two main reaction mechanisms,we have obtained five reaction pathways for the first CO oxidation (denoted as RER1,RER2,RLH1,RLH2 and RLH3,respectively):RER1 is CO(gas)+ O2 (ads) → O(ads) + CO2(gas);RER2 is CO(gas)+ O2(ads) → CO3(ads) → O(ads) + CO2(gas);RLH1 refers to CO(ads)+ O2(ads) → O(ads) + CO2(gas);RLH2 refers to CO(ads) + O2(ads) → OOCO(ads) → O(ads) + CO2(gas) and RLH3 refers to O2 (ads) + CO(ads) → O(ads) + O(ads) + CO(ads) → O(ads) + CO2(gas).These pathways have low energy barriers and are strongly exothermic,suggesting the CU13 cluster is very favorable catalyst for the first CO oxidation.However,there are higher energy barriers of 99.8 and 45.4 kJ/mol in the process of producing and decomposing intermediates along the RLH2 and RER2,indicating that RER1,RLH1 and RLH3 are superior pathways with lower energy barriers,especially the RER1 channel.Thereafter,the second CO is more prone to react with the remaining oxygen atom on Cu13 along the ER channel in comparison with the LH pathway,in which the moderate barrier is 70.0 kJ/mol and it is exothermic by 59.6 kJ/mol.Furthermore,the interaction between the absorbate and cluster is analyzed by electronic analysis to gain insights into high activity of the copper cluster.