Metal- and Metal Oxide-Supported Platinum Monolayer Electrocatalysts for Oxygen Reduction
 

Radoslav Adzic, Group Leader

Sub-group: Electrocatalysis and Surface Electrochemistry

Staff: Kotaro Sasaki, Miomir Vukmirovic, Jia Wang, Junliang Zhang

Students: Minhua Shao

Our research is directed towards the synthesis and characterization of Pt monolayer electrocatalysts supported by metal, metal alloy, non-noble metal - noble metal core - shell and oxide nanoparticles, or single crystal extended surfaces. This new approach has the potential to yield electrocatalysts with the lowest Pt content and improved catalytic activity, which can reduce the cost of fuel cells. In a parallel effort we are developing new improved Pd alloy electrocatalysts that can replace Pt in fuel cell cathodes. The structural, electronic and catalytic properties of electrocatalysts for O₂ reduction, methanol, ethanol and CO oxidation reactions are studied by in situ and ex situ synchrotron radiation, surface science, infrared and electrochemical techniques. The synthesis of Pt monolayer electrocatalysts is based on the unique method that involves a Pt monolayer deposition by displacement of an adsorbed Cu monolayer. Understanding the phenomena which determine the catalytic properties, structure-activity correlations, catalysts’ stability, segregation, structure and ordering of atomic and molecular monolayers at electrochemical interfaces is sought by combining the above techniques and kinetic analyses of the O₂ reduction reaction with intensive density functional theory calculations.

Research Activities:

 Electrocatalysis

1. Pt monolayer Electrocatalysts for O₂ reduction: atomic-level synthesis, Electronic properties of Pt monolayers on single crystals and nanoparticles, Pt-support interactions; Structure-activity correlations; Pd alloy electrocatalysts; In situ spectroscopic studies of the O₂ reduction intermediates; Kinetic analyses of the O₂ reduction reaction.

Pt monolayer cathode electrocatalyst
	structure	activity	stability
			fuel cell test

2. Pt submonolayer on Ru (PtRu₂₀) Electrocatalysts: H₂, CO and reformate H₂ oxidation; Pt content is 1/10 of that in commercial catalysts, high CO tolerance; Oxidation of Methanol and Ethanol; Adsorbate-Surface Interactions. Pt submonolayer anode electrocatalyst

The first Pt monolayer-level electrocatalyst
No change in performance during ca. 900
hours as anode under fuel cell operating conditions

Research Activities: Surface Electrochemistry

To obtain a true microscopic description of electrochemical interfaces, structural and electronic properties of atomic and molecular monolayers on single-crystal and nanoparticle substrates are investigated using in situ scanning
tunneling microscopy, surface x-ray scattering and x-ray
absorption spectroscopy.

RECENT PUBLICATIONS

J. Zhang, Y. Mo, M.B. Vukmirovic, R. Klie, K. Sasaki, R. R. Adzic, Platinum Monolayer Electrocatalysts for O₂ Reduction: Pt Monolayer on Pd(111) and on Carbon-supported Pd Nanoparticles, J. Phys. Chem. B, 108 (2004) 10955-1063.

J. Zhang, M. B. Vukmirovic, Y. Xu, M. Mavrikakis, R. R. Adzic, Controlling the Catalytic Activity of Platinum Monolayer Electrocatalysts for Oxygen Reduction with Different Substrates, Angew. Chem.. Int. Ed. 117 (2005) 2170.

J. Zhang, M. B Vukmirovic, K. Sasaki, F. Uribea, R. R. Adzic, Platinum monolayer electrocatalysts for oxygen reduction: effect of substrates, and long-term stability, J. Serb.Chem. Soc., 70 (2005) 513-525 (75th Anniversary issue).

Sasaki, J. Zhang, J. Wang, F. Uribe, R. Adzic, Platinum submonolayer-monolayer electrocatalysts, an electrochemical and x-ray absorption spectroscopy study, Res. Chem. Intermed, (special issue) 32 (2006) 543.

J. X. Wang,; N. M. Markovic,; R. R. Adzic, Simulation of O₂ reduction on Pt(111) in Acid Solutions: Intrinsic Kinetic Parameters and anion adsorption effects. J. Phys. Chem. B, 108 (2004) 4127.

Junliang Zhang, Miomir B. Vukmirovic, Kotaro Sasaki, Anand Udaykumar Nilekar, Manos Mavrikakis, and Radoslav R. Adzic, Mixed-Metal Pt Monolayer Electrocatalysts for Enhanced Oxygen Reduction Kinetics, J. Am. Chem. Soc., 127 (2005) 12480.

M.H. Shao, P. Liu, R.R. Adzic, Superoxide is the intermediate in the oxygen reduction reaction on platinum electrode. J. Am. Chem. Soc., 128 (2006) 7408.

J. Zhang, F.H.B. Lima, M. H. Shao, K. Sasaki, J.X. Wang, J. Hanson, R. R. Adzic, Platinum monolayer on non-noble metal - noble metal core-shell nanoparticles electrocatalysts for O₂ reduction, J. Phys. Chem. B, 109 (2005) 22701-22704.

M.H. Shao, K. Sasaki, R.R. Adzic, Pd-Fe nanoparticles as electrocatalysts for oxygen reduction. J. Am. Chem. Soc., 128 (2006) 3526.

Separate portions of this program are supported by the  the Division of Chemical Sciences, Geosciences, and Biosciences and by the Division of Materials Sciences and Engineering of the Office of Basic Energy Sciences of the Office of Science under contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

Last Modified: January 31, 2008

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