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Controlling oxygen reduction reaction activities of Ag@Pt core-shell nanoparticles via tuning of Ag in the surface layer

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Savaci, Umut
Turan, Servet

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Herein, the effect of Pt shell thickness and Ag content in the surface layer on the oxygen reduction reaction activities of Ag@Pt core@shell nanoparticles (NPs) is discussed. Ag@Pt NPs are synthesized via the seeded-growth method, where colloidal Ag NPs are first synthesized and used as seeds for the growth of Pt. Electrochemical activity measurements in alkaline media show a remarkable dependency between the Ag content in the shell and the oxygen reduction reaction (ORR) activity, where the overpotentials required for -1.0 mA cm(-2) drop gradually, that is, 0.72, 0.77, and 0.80 V-RHE for Ag@Pt-25, Ag@Pt-35, and Ag@Pt-45, respectively. Tafel analysis also confirms this dependency with 73.5 mV dec(-1) for Ag@Pt-25, 71.3 mV dec(-1) for Ag@Pt-35, and 68.8 mV dec(-1) for Ag@Pt-45. A combination of the high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, and X-Ray diffraction analysis shows an increase of the Pt shell thickness. It is shown that the absence of Pt-H adsorption/desorption peaks in cyclic voltammetry of Ag@Pt NPs is correlated with Ag in the surface layer, which plays an important role in the ORR activity due to the blockage of Pt(111) terrace sites. Rate-limiting first-electron transfer to oxygen is facilitated by decreasing Ag amount at the surface.

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Wiley-V C H Verlag Gmbh

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Energy and fuels

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Energy Technology

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10.1002/ente.202201167

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