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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) Profiles of potential-energy surfaces of four oxygen dissociation pathways on the pIh Ag32Cu6 core-shell cluster. (b) Center of d-band and density of states at the Fermi level (inset) of four O2-cluster adsorption configurations.
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f4: (a) Profiles of potential-energy surfaces of four oxygen dissociation pathways on the pIh Ag32Cu6 core-shell cluster. (b) Center of d-band and density of states at the Fermi level (inset) of four O2-cluster adsorption configurations.

Mentions: To investigate the oxygen dissociation reaction of ORR, four O2 dissociation energy paths for B1-4 sites have been calculated. Figure 4(a) shows the calculated dissociation potential-energy surfaces and the binding energy levels of the initial, transition and final states. Table 1 tabulates the oxygen dissociation reaction parameters. Among these four adsoption configurations, we notice that the adsorption energy on B4 site has a highest value of −0.149 eV, and also the highest value of 1.209 eV for the dissociation barrier, and an exothermicity of 0.259 eV, dissociating to H2 and H3 sites. The B1 site, which has similar adsorption energy to B4 site, −0.146 eV, dissociates to two H2 sites with barrier of 0.993 eV and exothermicity of 0.259 eV. The O2 on B2 and B3 sites with smaller adsorption energies is bond-cleavage from two bridge sites to two hollow sites with barriers of 0.715 and 1.134 eV, and exothermicities of 1.088 and 0.368 eV, respectively. It is clear that the most favorable pathway for the O2 dissociation is B2 site with an activation energy barrier of 0.715 eV.


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) Profiles of potential-energy surfaces of four oxygen dissociation pathways on the pIh Ag32Cu6 core-shell cluster. (b) Center of d-band and density of states at the Fermi level (inset) of four O2-cluster adsorption configurations.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: (a) Profiles of potential-energy surfaces of four oxygen dissociation pathways on the pIh Ag32Cu6 core-shell cluster. (b) Center of d-band and density of states at the Fermi level (inset) of four O2-cluster adsorption configurations.
Mentions: To investigate the oxygen dissociation reaction of ORR, four O2 dissociation energy paths for B1-4 sites have been calculated. Figure 4(a) shows the calculated dissociation potential-energy surfaces and the binding energy levels of the initial, transition and final states. Table 1 tabulates the oxygen dissociation reaction parameters. Among these four adsoption configurations, we notice that the adsorption energy on B4 site has a highest value of −0.149 eV, and also the highest value of 1.209 eV for the dissociation barrier, and an exothermicity of 0.259 eV, dissociating to H2 and H3 sites. The B1 site, which has similar adsorption energy to B4 site, −0.146 eV, dissociates to two H2 sites with barrier of 0.993 eV and exothermicity of 0.259 eV. The O2 on B2 and B3 sites with smaller adsorption energies is bond-cleavage from two bridge sites to two hollow sites with barriers of 0.715 and 1.134 eV, and exothermicities of 1.088 and 0.368 eV, respectively. It is clear that the most favorable pathway for the O2 dissociation is B2 site with an activation energy barrier of 0.715 eV.

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