Improving Electrocatalysts for O2 Reduction by Fine-Tuning the Pt-Support Interaction: Pt Monolayer on the Surfaces of a Pd3Fe(111) Single-Crystal Alloy

Journal Article · Wed Sep 09 04:00:00 EDT 2009 · Journal of American Chemical Society

DOI:https://doi.org/10.1021/ja9039746· OSTI ID:1040229

Zhou, W P; Yang, X; Vukmirovic, M B; Koel, B E; Jiao, J; Peng, G; Mavrikakis, M; Adzic, R R

We improved the effectiveness of Pt monolayer electrocatalysts for the oxygen-reduction reaction (ORR) using a novel approach to fine-tuning the Pt monolayer interaction with its support, exemplified by an annealed Pd{sub 3}Fe(111) single-crystal alloy support having a segregated Pd layer. Low-energy ion scattering and low-energy electron diffraction studies revealed that a segregated Pd layer, with the same structure as Pd (111), is formed on the surface of high-temperature-annealed Pd{sub 3}Fe(111). This Pd layer is considerably more active than Pd(111); its ORR kinetics is comparable to that of a Pt(111) surface. The enhanced catalytic activity of the segregated Pd layer compared to that of bulk Pd apparently reflects the modification of Pd surface's electronic properties by underlying Fe. The Pd{sub 3}Fe(111) suffers a large loss in ORR activity when the subsurface Fe is depleted by potential cycling (i.e., repeated excursions to high potentials in acid solutions). The Pd{sub 3}Fe(111) surface is an excellent substrate for a Pt monolayer ORR catalyst, as verified by its enhanced ORR kinetics on PT{sub ML}/Pd/Pd{sub 3}Fe(111). Our density functional theory studies suggest that the observed enhancement of ORR activity originates mainly from the destabilization of OH binding and the decreased Pt-OH coverage on the Pt/Pd/Pd{sub 3}Fe(111) surface. The activity of Pt{sub ML}/Pd(111) and Pt(111) is limited by OH removal, whereas the activity of Pt{sub ML}/Pd/Pd{sub 3}Fe(111) is limited by the O-O bond scission, which places these two surfaces on the two sides of the volcano plot.

• Research Organization: Brookhaven National Laboratory (BNL) Center for Functional Nanomaterials
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1040229
• Report Number(s): BNL--90669-2009-JA; KC0302040
• Journal Information: Journal of American Chemical Society, Journal Name: Journal of American Chemical Society Journal Issue: 35 Vol. 131; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
ALLOYS
ELECTROCATALYSTS
ELECTRON DIFFRACTION
FUNCTIONALS
KINETICS
MODIFICATIONS
REMOVAL
SCATTERING
SUBSTRATES
fuel cells
functional nanomaterials
oxygen reduction
platinum alloys
platinum monolayer