An XPS study on oxidation states of Pt and its alloys with Co and Cr and its relevance to electroreduction of oxygen

Arico, AS and Shukla, AK and Kim, H and Antonucci, V and Min, M and Park, S (2001) An XPS study on oxidation states of Pt and its alloys with Co and Cr and its relevance to electroreduction of oxygen. In: Applied Surface Science, 172 (1-2). pp. 33-40.

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Abstract

Cathodic reduction of oxygen in fuel cells is known to be enhanced on platinum alloys in relation to the platinum metal. The higher performance of the platinum alloys is as a result of the improved oxygen-reduction kinetics on the alloys but there is hardly any increase in the electrode platinum-surface-areas for the platinum alloys as compared to the platinum metal, and thus the higher performance is solely due to the enhanced electrocatalytic activity of the alloys as compared to the platinum metal. The present X-ray photoelectron spectroscopic (XPS) study on carbon-supported Pt, Pt–Co and Pt–Co–Cr electrocatalysts suggests the presence of a relatively lower Pt-oxide content on the alloys. The X-ray powder diffraction patterns for these electrocatalysts show that while the carbon-supported platinum electrocatalyst has a face-centered cubic (fcc) phase, carbon-supported Pt–Co and Pt–Co–Cr electrocatalysts exhibit a face-centered tetragonal (fct) phase. But, Pt electrocatalyst has a lower particle-size and, hence, a higher dispersion. Previous studies have shown higher activities on the Pt-alloys than on Pt, and have attributed it to changes in the electronic and structural characteristics of Pt. These changes can be correlated with the lower oxidation-state of Pt sites, as found in this study.

Item Type:	Journal Article
Publication:	Applied Surface Science
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	X-ray photoelectron spectroscopy;Polymer-electrolyte fuel cell;Solid-polymer-electrolyte direct methanol fuel cell; Oxygenreduction;Electrocatalysts;Platinum-metal alloys.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	02 Aug 2011 09:13
Last Modified:	02 Aug 2011 09:13
URI:	http://eprints.iisc.ac.in/id/eprint/39463

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