skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters

Abstract

We demonstrated that platinum (Pt) oxygen-reduction fuel-cell electrocatalysts can be stabilized against dissolution under potential cycling regimes (a continuing problem in vehicle applications) by modifying Pt nanoparticles with gold (Au) clusters. This behavior was observed under the oxidizing conditions of the O{sub 2} reduction reaction and potential cycling between 0.6 and 1.1 volts in over 30,000 cycles. There were insignificant changes in the activity and surface area of Au-modified Pt over the course of cycling, in contrast to sizable losses observed with the pure Pt catalyst under the same conditions. In situ x-ray absorption near-edge spectroscopy and voltammetry data suggest that the Au clusters confer stability by raising the Pt oxidation potential.

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930625
Report Number(s):
BNL-80964-2008-JA
Journal ID: ISSN 0193-4511; SCEHDK; TRN: US200901%%1
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Science; Journal Volume: 315; Journal Issue: 5809
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; FUEL CELLS; ELECTROCATALYSTS; GOLD; PLATINUM; ADDITIVES; STABILIZATION; OXIDATION; national synchrotron light source

Citation Formats

Zhang,J., Sasaki, K., Sutter, E., and Adzic, R.. Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters. United States: N. p., 2007. Web. doi:10.1126/science.1134569.
Zhang,J., Sasaki, K., Sutter, E., & Adzic, R.. Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters. United States. doi:10.1126/science.1134569.
Zhang,J., Sasaki, K., Sutter, E., and Adzic, R.. Mon . "Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters". United States. doi:10.1126/science.1134569.
@article{osti_930625,
title = {Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters},
author = {Zhang,J. and Sasaki, K. and Sutter, E. and Adzic, R.},
abstractNote = {We demonstrated that platinum (Pt) oxygen-reduction fuel-cell electrocatalysts can be stabilized against dissolution under potential cycling regimes (a continuing problem in vehicle applications) by modifying Pt nanoparticles with gold (Au) clusters. This behavior was observed under the oxidizing conditions of the O{sub 2} reduction reaction and potential cycling between 0.6 and 1.1 volts in over 30,000 cycles. There were insignificant changes in the activity and surface area of Au-modified Pt over the course of cycling, in contrast to sizable losses observed with the pure Pt catalyst under the same conditions. In situ x-ray absorption near-edge spectroscopy and voltammetry data suggest that the Au clusters confer stability by raising the Pt oxidation potential.},
doi = {10.1126/science.1134569},
journal = {Science},
number = 5809,
volume = 315,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A long-chain polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), has been employed to stabilize platinum nanoparticles for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. Pt nanoparticles were synthesized by reducing H2PtCl6 with NaBH4 in the presence of PDDA and then deposited on carbon support (PDDA-Pt/C). Transmission electron microscope images showed that Pt nanoparticles of PDDA-Pt/C are uniformly dispersed on carbon support with a mean size of about 2.2 nm (2.1 nm for commercial Etek-Pt/C). PDDA-Pt/C exhibited a higher activity towards oxygen reduction reaction (ORR) than Etek-Pt/C. The durability of PDDA-Pt/C was improved by a factor of 2 as compared with Etek-Pt/C.more » X-ray photoelectron spectroscopy characterization of PDDA-Pt/C revealed the interaction between Pt nanoparticles and PDDA, which increased Pt oxidation potential. PDDA-Nafion ionic crosslinking "entraps" Pt nanoparticles and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support. This provides a promising strategy to improve both the durability and activity of electrocatalysts for fuel cells.« less
  • The objective of this work was to investigate the microstructural dependence of the oxygen reduction activity of carbon-supported thin-film Pt-Rh catalysts in comparison with that of thin-film Pt. Thin-film rotating-disk-electrode (RDE) techniques were applied to arrive at diffusion-corrected, i.e., true activity measurements at over potentials typical of current generation. Thin-films of Pt and Pt-Rh [80:20 atomic percent (a/o)] were prepared by sputter deposition onto graphite, characterized using transmission electron microscopy (TEM), and tested in 1M H{sub 2}SO{sub 4} at 25 C. The surface of Pt-Rh alloys becomes Pt rich when cycled repeatedly to potentials above ca. 1 V vs. reversiblemore » hydrogen electrode (RHE). The lattice parameter of thin-film Pt has been shown to decrease with decreasing grain size while that of thin-film Pt-Rh increases. The latter effect has been attributed to the presence of oxygen in the Pt-Rh lattice. The specific activity at 750 mV{sub RHE} of thin-film Pt increases with decreasing particle size while that of thin-film Pt-Rh also shows a slight increase and is much lower than Pt. Correspondingly, the mass activity of thin-film Pt-Rh is also less than for thin-film Pt. The lower specific activity of thin-film Pt-Rh is due to its lattice expansion and to the presence, at potentials of interest, of oxide on the surface. The activity of large-grained or heat-treated thin-film Pt-Rh is-more like the bulk material which previously has been shown to be less than Pt.« less
  • A Fe-Pt bimetallic catalyst was prepared by impregnating iron nitrate solution into a carbon-supported platinum catalyst. The catalyst was heat-treated in flowing Ar (nontreated) at 450 C (denoted as PF450), 750 C (PF750), and 900 C (PF900), or this process was followed by an acid-treatment in 1M H[sub 2]SO[sub 4] solution to leach out surface-enriched iron (acid-treated). The surface and catalytic properties of these catalysts were studied using H[sub 2]-O[sub 2] titration, XRD and TEM measurements, and oxygen reduction tests in PAFC. With increased heat-treatment temperature, the Pt surface area measured by hydrogen chemisorption (SA) decreases rapidly owing to particlemore » sintering, alloying effect, and enrichment of iron on the surface. The mass activity (mA/g Pt) of the alloyed catalyst is about the same as that of pure Pt catalyst due to the particle sintering in the alloyed catalyst. However, the specific activity (mA/m[sup 2] Pt, based on SA) of the alloyed catalyst is estimated at twice that of pure Pt catalyst. The acid-treatment leads to dissolution of surface-enriched iron and results in an increase of the Pt surface area due to surface roughening. Except for PF450, the specific activities of both nontreated and acid-treated catalysts are the same, indicating that SA is a good measure of active site for the reaction. After acid treatment of the partially alloyed PF750, a twofold increase in the Pt surface area was observed when compared with the nontreated Pt-Fe alloy catalyst.« less
  • The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We have synthesized a new class of electrocatalysts for the oxygen reduction reaction, consisting of a monolayer of Pt or mixed monolayer of Pt and another late transition metal (Au, Pd, Ir, Ru, Rh, Re or Os) deposited on a Pd(1 1 1) single crystal or on carbon-supported Pd nanoparticles. Several of these electrocatalysts exhibited very high activity, amounting tomore » 20-fold increase in a Pt mass activity, compared with conventional all-Pt electrocatalysts. Their superior activity reflects a low OH coverage on Pt, caused by the lateral repulsion between the OH adsorbed on Pt and the OH or O adsorbed on neighboring, other than Pt, late transition metal atoms. The origin of this effect was identified through a combination of experimental and theoretical methods, employing electrochemical techniques, X-ray absorption spectroscopy, and periodic, self-consistent density functional theory calculations. This new class of electrocatalysts promises to alleviate some major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.« less