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Analyzing the Influence of H3PO4as Catalyst Poison in High Temperature PEM Fuel Cells Usingin-operandoX-ray Absorption Spectroscopy

Kaserer, Sebastian ; Caldwell, Keegan M. ; Ramaker, David E. ; Roth, Christina (2013):
Analyzing the Influence of H3PO4as Catalyst Poison in High Temperature PEM Fuel Cells Usingin-operandoX-ray Absorption Spectroscopy.
In: The Journal of Physical Chemistry C, 117 (12), pp. 6210-6217. ACS Publications, ISSN 1932-7447,
[Article]

Abstract

The effect of H3PO4 as a poison in high temperature polymer electrolyte fuel cells using polybenzimidazole (PBI) membranes was studied as a function of phosphoric acid loading, potential, and temperature. In this work, for the first time, extensive in-operando X-ray absorption spectroscopy investigations were carried out on Pt/C fuel cell cathode catalysts at different temperatures and H3PO4 concentrations at varying fuel cell voltages. Under in-operando conditions, significant H3PO4 anion coverage of the Pt nanoparticles is observed. The Δμ-XANES analysis shows that the O(H)/H adsorption onset potential increases/decreases with temperature and that this is a result of phosphate anions being driven off the surface at high temperatures (170 °C). With initial coadsorption of H and O(H), the phosphate anions move into registry with the Pt, whereas random adsorption is observed when only phosphate anions are present on the Pt surface. By varying the temperature and the fuel cell potential, the adsorption geometry of the phosphoric acid anion changes with coverage, but in all cases, the anions block Pt sites and reduce the oxygen reduction reaction (ORR) rate.

Item Type: Article
Erschienen: 2013
Creators: Kaserer, Sebastian ; Caldwell, Keegan M. ; Ramaker, David E. ; Roth, Christina
Title: Analyzing the Influence of H3PO4as Catalyst Poison in High Temperature PEM Fuel Cells Usingin-operandoX-ray Absorption Spectroscopy
Language: English
Abstract:

The effect of H3PO4 as a poison in high temperature polymer electrolyte fuel cells using polybenzimidazole (PBI) membranes was studied as a function of phosphoric acid loading, potential, and temperature. In this work, for the first time, extensive in-operando X-ray absorption spectroscopy investigations were carried out on Pt/C fuel cell cathode catalysts at different temperatures and H3PO4 concentrations at varying fuel cell voltages. Under in-operando conditions, significant H3PO4 anion coverage of the Pt nanoparticles is observed. The Δμ-XANES analysis shows that the O(H)/H adsorption onset potential increases/decreases with temperature and that this is a result of phosphate anions being driven off the surface at high temperatures (170 °C). With initial coadsorption of H and O(H), the phosphate anions move into registry with the Pt, whereas random adsorption is observed when only phosphate anions are present on the Pt surface. By varying the temperature and the fuel cell potential, the adsorption geometry of the phosphoric acid anion changes with coverage, but in all cases, the anions block Pt sites and reduce the oxygen reduction reaction (ORR) rate.

Journal or Publication Title: The Journal of Physical Chemistry C
Journal volume: 117
Number: 12
Publisher: ACS Publications
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Erneuerbare Energien
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 07 Feb 2014 09:21
Official URL: http://dx.doi.org/10.1021/jp311924q
Identification Number: doi:10.1021/jp311924q
Funders: Financial support for this effort was provided by the EU project DEMMEA, Seventh Framework Programme.
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