Electrooxidation of Ethanol and Formic Acid on Core-Shell Nanoparticles with Different Platinum Shell Thickness

Abstract

Core-shell nanoparticles with platinum as the shell and less expensive metal as a core allow for important reduction of the amount of expensive and rare platinum used while maintaining similar platinum active surface area. More efficient use of platinum is not the only benefit of core-shell nanoparticles. Platinum monolayer deposited on the core made from another metal exhibits modified catalytic and electronic properties. Partially responsible for this behavior are: i) charge transfer from the core metal and ii) changes induced by modified lattice parameter. The monolayer shell forms a so called “pseudomorphic monolayer” with lattice parameter equal to that of metal forming the core, resulting in altered conduction band width and center of d-band energy in relation to Fermi edge. In the case of platinum shell on a palladium core, contracted Pt lattice leads to broadening of the conduction band and shifting d-band center closer to the Fermi edge. Core-shell nanoparticles with platinum shell have been widely investigated as the catalyst in the process of oxygen reduction, but data available on their properties as the catalysts for oxidation of small organic molecules is scarce. Experimental investigation of such properties of core-shell nanoparticles with different platinum coverage and different platinum shell lattice parameter due to changes in shell thickness is an important step in determination of relation between electronic properties of the material used and reaction mechanism. Understanding this relation is crucial in constructing more effective direct ethanol fuel cell anode catalysts.