Title: Quantifying and elucidating the effect of CO ₂ on the thermodynamics, kinetics and charge transport of AEMFCs

Abstract

It has been long-recognized that carbonation of anion exchange membrane fuel cells (AEMFCs) would be an important practical barrier for their implementation in applications that use ambient air containing atmospheric CO₂. Most literature discussion around AEMFC carbonation has hypothesized: (1) that the effect of carbonation is limited to an increase in the Ohmic resistance because carbonate has lower mobility than hydroxide; and/or (2) that the so-called “self-purging” mechanism could effectively decarbonate the cell and eliminate CO₂-related voltage losses during operation at a reasonable operating current density (>1 A cm^-2). However, this study definitively shows that neither of these assertions are correct. This work, the first experimental examination of its kind, studies the dynamics of cell carbonation and its effect on AEMFC performance over a wide range of operating currents (0.2–2.0 A cm^-2), operating temperatures (60–80 °C) and CO₂ concentrations in the reactant gases (5–3200 ppm). The resulting data provide for new fundamental relationships to be developed and for the root causes of increased polarization in the presence of CO₂ to be quantitatively probed and deconvoluted into Ohmic, Nernstian and charge transfer components, with the Nernstian and charge transfer components controlling the cell behavior under conditions of practical interest.

Authors:

Zheng, Yiwei ^[1]; Omasta, Travis J.  ^[1];

• Search DOE PAGES for author "Omasta, Travis J."
• Search DOE PAGES for ORCID "0000-0002-8002-6520"

Peng, Xiong ^[1]; Wang, Lianqin  ^[2];

• Search DOE PAGES for author "Wang, Lianqin"
• Search DOE PAGES for ORCID "0000-0002-2130-2935"

Varcoe, John R.  ^[2];

• Search DOE PAGES for author "Varcoe, John R."
• Search DOE PAGES for ORCID "0000-0001-9898-0235"

Pivovar, Bryan S. ^[3]; Mustain, William E.  ^[1]

• Search DOE PAGES for author "Mustain, William E."
• Search DOE PAGES for ORCID "0000-0001-7804-6410"

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+ Show Author Affiliations

1. Department of Chemical Engineering, University of South Carolina, Columbia, USA
2. National Renewable Energy Laboratory, Golden, USA
3. Department of Chemistry, University of Surrey, Guildford, UK

Publication Date:

Thu Sep 12 00:00:00 EDT 2019

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Hydrogen Fuel Cell Technologies Office

OSTI Identifier:

1543357

Alternate Identifier(s):

OSTI ID: 1569451

Report Number(s):

NREL/JA-5900-75049
Journal ID: ISSN 1754-5692; EESNBY

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Published Article

Journal Name:

Energy & Environmental Science

Additional Journal Information:

Journal Name: Energy & Environmental Science Journal Volume: 12 Journal Issue: 9; Journal ID: ISSN 1754-5692

Publisher:

Royal Society of Chemistry (RSC)

Country of Publication:

United Kingdom

Language:

English

Subject:

30 DIRECT ENERGY CONVERSION; alkaline fuel cells; carbonation; charge transfer; ion exchange membranes; ohmic contacts; thermodynamics