Catalysis of Cu Cluster for NO Reduction by CO: Theoretical Insight into the Reaction Mechanism
Catalysis of Cu Cluster for NO Reduction by CO: Theoretical Insight into the Reaction Mechanism
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DOI：
10.1021/acsomega.8b02890
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发表时间：
2019-02
期刊：
影响因子：
4.1
通讯作者：
Nozomi Takagi;K. Ishimura;H. Miura;T. Shishido;R. Fukuda;M. Ehara;S. Sakaki
中科院分区：
文献类型：
--
作者：
Nozomi Takagi;K. Ishimura;H. Miura;T. Shishido;R. Fukuda;M. Ehara;S. Sakaki
密度泛函理论计算结果表明，Cu 38催化CO还原NO不是通过NO解离吸附，而是通过NO二聚。NO以桥连方式吸附在两个Cu原子上。NO的吸附能远大于CO的吸附能，NO分子的N-O键断裂需要很大的活化能（ΔG° C）。另一方面，两个NO分子在Cu 38表面上发生二聚，具有小的ΔG° ε和非常负的Gibbs反应能（ΔG°），以形成吸附到Cu 38上的ONNO物种。然后，CO分子被吸附在ONNO物种的邻近位置，并与ONNO反应，诱导N-O键断裂，ΔG°很小，ΔG°很负，导致N2 O和CO2分子在气相中吸附在Cu 38上。N_2O从Cu_（38）上解离下来，然后以最稳定的吸附结构重新吸附到Cu_（38）上。N2 O的N-O键容易发生断裂，ΔG °很小，ΔG°为负值，形成N2分子和吸附在Cu 38上的O原子。O原子与CO分子反应以提供CO2并再生Cu 38，这是速率决定的。在Cu/γ-Al_2O_3催化CO还原NO的反应中，实验观察到了N_2O物种的存在，这与该反应机理相一致。这种机制不同于Rh催化剂，其通过NO分子的N-O键裂解而发生。从Cu_（38）与NO的电荷转移相互作用和Cu_（38）的前线轨道能出发，讨论了NO二聚和CO氧化过程中的电子过程.
Density functional theory calculations here elucidated that Cu38-catalyzed NO reduction by CO occurred not through NO dissociative adsorption but through NO dimerization. NO is adsorbed to two Cu atoms in a bridging manner. NO adsorption energy is much larger than that of CO. N–O bond cleavage of the adsorbed NO molecule needs a very large activation energy (ΔG°‡). On the other hand, dimerization of two NO molecules occurs on the Cu38 surface with small ΔG°‡ and very negative Gibbs reaction energy (ΔG°) to form ONNO species adsorbed to Cu38. Then, a CO molecule is adsorbed at the neighboring position to the ONNO species and reacts with the ONNO to induce N–O bond cleavage with small ΔG°‡ and very negative ΔG°, leading to the formation of N2O adsorbed on Cu38 and CO2 molecule in the gas phase. N2O dissociates from Cu38, and then it is readsorbed to Cu38 in the most stable adsorption structure. N–O bond cleavage of N2O easily occurs with small ΔG°‡ and significantly negative ΔG° to form the N2 molecule and the O atom adsorbed on Cu38. The O atom reacts with the CO molecule to afford CO2 and regenerate Cu38, which is rate-determining. N2O species was experimentally observed in Cu/γ-Al2O3-catalyzed NO reduction by CO, which is consistent with this reaction mechanism. This mechanism differs from that proposed for the Rh catalyst, which occurs via N–O bond cleavage of the NO molecule. Electronic processes in the NO dimerization and the CO oxidation with the O atom adsorbed to Cu38 are discussed in terms of the charge-transfer interaction with Cu38 and Frontier orbital energy of Cu38.