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Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells.

Zhang N, Chen FY, Wu XQ - Sci Rep (2015)

Bottom Line: It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR).The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster.This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian 710072, China.

ABSTRACT
The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

No MeSH data available.


Related in: MedlinePlus

(a) DFT-level energy difference between the truncated octahedron and the polyicosahedral structures for Ag38, Cu38 and Ag32Cu6 clusters. (b) Caloric curves at the atomistic potential level for the truncated octahedron and the polyicosahedralAg32Cu6 core-shell clusters.
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f3: (a) DFT-level energy difference between the truncated octahedron and the polyicosahedral structures for Ag38, Cu38 and Ag32Cu6 clusters. (b) Caloric curves at the atomistic potential level for the truncated octahedron and the polyicosahedralAg32Cu6 core-shell clusters.

Mentions: A further comparison between atomistic and DFT results is significant for checking the reliability of the atomistic potential in producing the pIh and TO core-shell clusters. Figure 3(a) shows the total energy difference between the TO and the pIh structures for Ag38, Cu38 and Ag32Cu6 clusters obtained from the DFT optimization. It is shown that there are different levels of structural stability among the isomers of 38-atom clusters. In Ag38 nanocluster, the total energy of the TO structure is 0.565 eV less than the pIh structure, and similarly in the Cu38 nanoclusters, the total energy of the TO structure is 0.425 eV less than that of the pIh structure. The total energy of the TO structure is 0.425 eV less than that of the pIh structure. The energy difference between the TO and pIh structures in pure Cu38 is smaller than the corresponding energy difference in pure Ag38. These results indicate that the order of stability is TO > pIh. The findings are consistent with a previous report17. However, the Ag32Cu6 core-shell clusters where all the Ag atoms are on the surface and all Cu atoms are inside show that the total energy of the pIh structure is 0.564 eV less than that of the TO structure. The TO Ag32Cu6 core-shell cluster has both (100) and (111) facets in the surface layer, and the pIh Ag32Cu6 core-shell structure has only (111) facets in the surface layer. During the DFT optimization, as shown in Fig. 2(d), the TO Ag32Cu6 core-shell cluster shows instability and the surface layers can no longer be identified as (100) and (111) facets, so only the pIh Ag32Cu6 core-shell structure is further investigated for its catalytic characteristics. It is a newfound structural stability for 38-atom Ag-Cu bimetallic geometry. Previous work shows that the energy of TO Ag-Cu core-shell cluster is lower than TO Ag-Cu alloyed cluster18. We evaluate the catalytic performance of the pIh Ag32Cu6 core-shell structure because of its great academic importance.


Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells.

Zhang N, Chen FY, Wu XQ - Sci Rep (2015)

(a) DFT-level energy difference between the truncated octahedron and the polyicosahedral structures for Ag38, Cu38 and Ag32Cu6 clusters. (b) Caloric curves at the atomistic potential level for the truncated octahedron and the polyicosahedralAg32Cu6 core-shell clusters.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493688&req=5

f3: (a) DFT-level energy difference between the truncated octahedron and the polyicosahedral structures for Ag38, Cu38 and Ag32Cu6 clusters. (b) Caloric curves at the atomistic potential level for the truncated octahedron and the polyicosahedralAg32Cu6 core-shell clusters.
Mentions: A further comparison between atomistic and DFT results is significant for checking the reliability of the atomistic potential in producing the pIh and TO core-shell clusters. Figure 3(a) shows the total energy difference between the TO and the pIh structures for Ag38, Cu38 and Ag32Cu6 clusters obtained from the DFT optimization. It is shown that there are different levels of structural stability among the isomers of 38-atom clusters. In Ag38 nanocluster, the total energy of the TO structure is 0.565 eV less than the pIh structure, and similarly in the Cu38 nanoclusters, the total energy of the TO structure is 0.425 eV less than that of the pIh structure. The total energy of the TO structure is 0.425 eV less than that of the pIh structure. The energy difference between the TO and pIh structures in pure Cu38 is smaller than the corresponding energy difference in pure Ag38. These results indicate that the order of stability is TO > pIh. The findings are consistent with a previous report17. However, the Ag32Cu6 core-shell clusters where all the Ag atoms are on the surface and all Cu atoms are inside show that the total energy of the pIh structure is 0.564 eV less than that of the TO structure. The TO Ag32Cu6 core-shell cluster has both (100) and (111) facets in the surface layer, and the pIh Ag32Cu6 core-shell structure has only (111) facets in the surface layer. During the DFT optimization, as shown in Fig. 2(d), the TO Ag32Cu6 core-shell cluster shows instability and the surface layers can no longer be identified as (100) and (111) facets, so only the pIh Ag32Cu6 core-shell structure is further investigated for its catalytic characteristics. It is a newfound structural stability for 38-atom Ag-Cu bimetallic geometry. Previous work shows that the energy of TO Ag-Cu core-shell cluster is lower than TO Ag-Cu alloyed cluster18. We evaluate the catalytic performance of the pIh Ag32Cu6 core-shell structure because of its great academic importance.

Bottom Line: It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR).The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster.This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xian 710072, China.

ABSTRACT
The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

No MeSH data available.


Related in: MedlinePlus