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.
Highlights
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
Previous studies show that redox property of the silver catalyst is a controlling factor of the oxygen reduction reaction (ORR) activity which is affected by silver surface structure and chemical state
It should be noted that the population convergence does not always signify that the genetic algorithms (GA) has found the true global minimum
Summary
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. Alkaline fuel cells have advantages of using non-platinum metals as electrode catalysts, because alkaline solution is less corrosive than acidic media. The combination of reasonably high activity, good long-term stability, and relatively low price (~2% the price of Pt) make Ag attractive as an alkaline oxygen reduction reaction (ORR) electrode catalysts. The oxygen reduction reaction (ORR) in alkaline media is of great industrial importance. The ORR serves as the cathode reaction in alkaline fuel cells[3,4,5] and metal-air batteries[6,7,8]. The oxygen dissociation on the surface of catalyst is an initial step and is important for determining activity level of the ORR reaction[9]. 3d transition metals (Fe,Co,Ni,Cu) bind the OOH intermediate more strongly than pure Ag, thereby accelerate the rate-limiting step[13]
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