Enhanced Electrocatalytic Activity toward the Oxygen Reduction Reaction through Alloy Formation: Platinum–Silver Alloy Nanocages
2016
Bordley, Justin A. | El-Sayed, Mostafa A.
Platinum–silver nanocage catalysts with a precisely defined shape and composition were synthesized using the galvanic replacement reaction (GRR) and utilized as electrocatalysts for the oxygen reduction reaction (ORR). The electrocatalytic activity of these platinum–silver nanocages was determined as a function of platinum content. The specific current density of all platinum–silver nanocages was found to be 2–3 times greater than the specific current densities previously reported for solid platinum catalysts under similar conditions. The highest specific current densities were observed for the platinum–silver nanocages with the lowest platinum content. After a thorough structural and electronic investigation by TEM, XRD, and XPS, it was determined that all platinum–silver nanocage catalysts exibit an expanded lattice compared to pure platinum materials. This resulted in a negative shift in the onset potential of the oxygen reduction reaction. However, despite this negative shift, the catalyst with a low platinum content exhibited an enhanced catalytic activity due to an increased Pt 4f binding energy. This is an indication of a downshifted d-band position and advantageous shift in the adsorption energy of oxygen-containing intermediates on the surface of the catalyst.
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