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摘要
The catalytic decomposition of N2O using Au19Pd and Au19Pt clusters as catalysts with optimized geometries was studied using density functional theory (DFT). The optimized geometries of the Au19Pd and Au19Pt clusters were obtained as a function of structural and thermodynamic analyses, in which the heteroatoms are on the surfaces of the clusters. We selected the Au19Pd cluster as a model cluster to investigate the reaction mechanism of N2O decomposition. There are two reaction pathways to be considered: Eley-Rideal (ER) and Langmuir-Hinshelwood (LH). We found that the first N2O decomposition needs to surmount an energy barrier of 1.118 eV, and is exothermic by -0.371 eV. The elimination of the residual oxygen atom on the surface has an energy barrier of 1.920 eV along the ER pathway after N-2 desorption, which is higher than that along the LH channel (1.669 eV). The adsorption energy of the oxygen atom on the surface is 3.203 eV, and the oxygen atom diffusion on the surface needs to surmount an energy barrier of 0.113 eV along the LH pathway. This indicates that the oxygen atom is prone to transfer on the cluster to promote the generation of the O-2 molecule, and therefore the LH is the optimized reaction pathway. We investigated the catalytic activity of Au19Pt for N2O decomposition along the LH pathway in comparison with the Au19Pd cluster. Both platinum and palladium have catalytic activities for N2O decomposition, especially the palladium in this study. Comparison between this work and the theoretical study on periodic systems shows that these two clusters can be used as better catalysts for N2O decomposition, especially the Au19Pd cluster. Furthermore, the O-2 desorption is no longer the main barrier to the reaction, which further enhances the catalytic activities of these two clusters for N2O decomposition.
