Alloys of platinum and early transition metals as oxygen reduction electrocatalysts

Abstract

The widespread use of low-temperature polymer electrolyte membrane fuel cells for mobile applications will require significant reductions in the amount of expensive Pt contained within their cathodes, which drive the oxygen reduction reaction (ORR). Although progress has been made in this respect, further reductions through the development of more active and stable electrocatalysts are still necessary. Here we describe a new set of ORR electrocatalysts consisting of Pd or Pt alloyed with early transition metals such as Sc or Y. They were identified using density functional theory calculations as being the most stable Pt- and Pd-based binary alloys with ORR activity likely to be better than Pt. Electrochemical measurements show that the activity of polycrystalline Pt(3)Sc and Pt(3)Y electrodes is enhanced relative to pure Pt by a factor of 1.5-1.8 and 6-10, respectively, in the range 0.9-0.87 V.

In situ X-ray probing reveals fingerprints of surface platinum oxide

“…Based on DFT calculations, oxygen has been predicted to be ca. 0.6 eV more strongly bound on Pt(111) than on Pt/Rh(111) 2 . This is in good agreement with our observations on Pt/Rh(111) that indicate only low coverages of chemisorbed oxygen-containing species at potentials up to 1.0 V and an oxide formation onset potential of ∼ 1 V.…”

“…Theoretical calculations show that the binding energy of chemisorbed atomic oxygen can be used as a descriptor for ORR activity on transition metal surfaces including bimetallic systems, and a volcano-type behavior was shown 1,2 . This computational approach was successful in predicting new catalyst materials such as Pt-Y alloy, which shows a ten-fold increase in activity compared to Pt 2 .…”

Exploring the phase space of time of flight mass selected PtxY nanoparticles

“…[39][40][41] In our laboratory we have taken a different approach, namely to study alloys of Pt and rare earths such as Y, Gd, Ce and La. 33,[42][43][44][45][46][47][48] These alloys have a particularly negative heat of formation, which should provide them with long term-kinetic stability against dealloying at the cathode of a fuel cell. Extended surfaces of Pt 3 Y and Pt 5 Gd show particularly high activity for oxygen reduction.…”

CatApp: A Web Application for Surface Chemistry and Heterogeneous Catalysis

“…The accuracy is not such that detailed predictions of absolute rates of elementary reaction steps can be made, but for classes of interesting catalysts (transition metals) it is possible to create systematic data with sufficient accuracy to predict trends in reactivity. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] In the present paper, we introduce such a set of calculated reaction energies and activation energies for a large number of elementary surface reactions on a series of metal single crystal surfaces including surfaces with defects such as steps. We will also introduce a simple web application (CatApp) that can be downloaded to access these data.…”