Dissolution of oxygen reduction electrocatalysts in acidic environment

Platinum (Pt) alloy nanoparticles are used as catalysts in electrochemical cells to reduce oxygen to water and to oxidize hydrogen; the overall reaction converts chemical energy into electrical energy. These nanocatalysts are deposited on a carbon substrate and their catalytic function takes place i...

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Main Author: Gu, Zhihui
Other Authors: Balbuena, Perla B
Format: Others
Language:en_US
Published: 2010
Subjects:
Online Access:http://hdl.handle.net/1969.1/ETD-TAMU-2458
http://hdl.handle.net/1969.1/ETD-TAMU-2458
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spelling ndltd-tamu.edu-oai-repository.tamu.edu-1969.1-ETD-TAMU-24582013-01-08T10:39:36ZDissolution of oxygen reduction electrocatalysts in acidic environmentGu, ZhihuiCathodePt catalystDissolutionPlatinum (Pt) alloy nanoparticles are used as catalysts in electrochemical cells to reduce oxygen to water and to oxidize hydrogen; the overall reaction converts chemical energy into electrical energy. These nanocatalysts are deposited on a carbon substrate and their catalytic function takes place in acid medium. This harsh environment causes an undesired reaction, which is the dissolution of the metal atoms into the acid medium; thus affecting the catalyst life. This dissertation aims to investigate the dissolution mechanism of fuel cell cathode catalysts at the atomic level starting from the oxygen reaction intermediates on the cathode catalyst surface and propose guidelines to improve cathode catalysts durability based on our proposed mechanism. Density functional theory is employed to study various possible scenarios with the goals of understanding the mechanism of the metal atom dissolution process and establishing some guidelines that permit a rational design of catalysts with better stability against dissolution. A thermodynamic analysis of potential metal dissolution reactions in acid medium is presented first, using density functional theory calculations to explore the relative stabilities of transition metals in relation to that of Pt. The study is performed by comparing the change in reaction Gibbs free energies for different metals in a given dissolution reaction. Then, a series of density functional theory studies, tending to investigate the adsorbed atomic oxygen absorption process from cathode catalyst surface into its subsurface, includes: 1) the oxygen adsorption on various catalyst surfaces and oxygen absorption in subsurface sites to figure out the minimum energy pathway and energy barrier of on-surface oxygen migration and absorption into subsurface; 2) the oxygen coverage, the other oxygen reduction reaction intermediates, and water effects on the oxygen absorption process according to reaction pathways, energy barriers, and thermodynamic analysis; 3) the oxygen absorption process on several Pt-based alloys with various compositions and components to find out the best alloy to inhibit atomic oxygen absorption including both kinetic and thermodynamic analyses, and the effects of such alloyed species on the inhibition process.Balbuena, Perla B2010-01-15T00:08:24Z2010-01-16T00:34:24Z2010-01-15T00:08:24Z2010-01-16T00:34:24Z2007-122009-05-15BookThesisElectronic Dissertationtextelectronicapplication/pdfborn digitalhttp://hdl.handle.net/1969.1/ETD-TAMU-2458http://hdl.handle.net/1969.1/ETD-TAMU-2458en_US
collection NDLTD
language en_US
format Others
sources NDLTD
topic Cathode
Pt catalyst
Dissolution
spellingShingle Cathode
Pt catalyst
Dissolution
Gu, Zhihui
Dissolution of oxygen reduction electrocatalysts in acidic environment
description Platinum (Pt) alloy nanoparticles are used as catalysts in electrochemical cells to reduce oxygen to water and to oxidize hydrogen; the overall reaction converts chemical energy into electrical energy. These nanocatalysts are deposited on a carbon substrate and their catalytic function takes place in acid medium. This harsh environment causes an undesired reaction, which is the dissolution of the metal atoms into the acid medium; thus affecting the catalyst life. This dissertation aims to investigate the dissolution mechanism of fuel cell cathode catalysts at the atomic level starting from the oxygen reaction intermediates on the cathode catalyst surface and propose guidelines to improve cathode catalysts durability based on our proposed mechanism. Density functional theory is employed to study various possible scenarios with the goals of understanding the mechanism of the metal atom dissolution process and establishing some guidelines that permit a rational design of catalysts with better stability against dissolution. A thermodynamic analysis of potential metal dissolution reactions in acid medium is presented first, using density functional theory calculations to explore the relative stabilities of transition metals in relation to that of Pt. The study is performed by comparing the change in reaction Gibbs free energies for different metals in a given dissolution reaction. Then, a series of density functional theory studies, tending to investigate the adsorbed atomic oxygen absorption process from cathode catalyst surface into its subsurface, includes: 1) the oxygen adsorption on various catalyst surfaces and oxygen absorption in subsurface sites to figure out the minimum energy pathway and energy barrier of on-surface oxygen migration and absorption into subsurface; 2) the oxygen coverage, the other oxygen reduction reaction intermediates, and water effects on the oxygen absorption process according to reaction pathways, energy barriers, and thermodynamic analysis; 3) the oxygen absorption process on several Pt-based alloys with various compositions and components to find out the best alloy to inhibit atomic oxygen absorption including both kinetic and thermodynamic analyses, and the effects of such alloyed species on the inhibition process.
author2 Balbuena, Perla B
author_facet Balbuena, Perla B
Gu, Zhihui
author Gu, Zhihui
author_sort Gu, Zhihui
title Dissolution of oxygen reduction electrocatalysts in acidic environment
title_short Dissolution of oxygen reduction electrocatalysts in acidic environment
title_full Dissolution of oxygen reduction electrocatalysts in acidic environment
title_fullStr Dissolution of oxygen reduction electrocatalysts in acidic environment
title_full_unstemmed Dissolution of oxygen reduction electrocatalysts in acidic environment
title_sort dissolution of oxygen reduction electrocatalysts in acidic environment
publishDate 2010
url http://hdl.handle.net/1969.1/ETD-TAMU-2458
http://hdl.handle.net/1969.1/ETD-TAMU-2458
work_keys_str_mv AT guzhihui dissolutionofoxygenreductionelectrocatalystsinacidicenvironment
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