Carbonate Dynamics and Opportunities With Low Temperature, Anion Exchange Membrane-Based Electrochemical Carbon Dioxide Separators

[+] Author and Article Information
William A. Rigdon, Travis J. Omasta, Connor Lewis

Department of Chemical and
Biomolecular Engineering,
University of Connecticut,
Storrs, CT 06269;
Center for Clean Energy Engineering,
University of Connecticut,
Storrs, CT 06269

Michael A. Hickner

Department of Materials
Science and Engineering,
Pennsylvania State University,
State College, PA 16802

John R. Varcoe

Department of Chemistry,
University of Surrey,
Guildford GU2 7XH, UK

Julie N. Renner

Proton OnSite,
Wallingford, CT 60492

Kathy E. Ayers

Proton OnSite,
Wallingford, CT 06492

William E. Mustain

Department of Chemical and
Biomolecular Engineering,
University of Connecticut,
Storrs, CT 06269;
Center for Clean Energy Engineering,
University of Connecticut,
Storrs, CT 06269
e-mail: mustain@engr.uconn.edu

1Corresponding author.

Manuscript received February 10, 2016; final manuscript received March 28, 2016; published online May 2, 2017. Assoc. Editor: Dirk Henkensmeier.

J. Electrochem. En. Conv. Stor. 14(2), 020901 (May 02, 2017) (8 pages) Paper No: JEECS-16-1019; doi: 10.1115/1.4033411 History: Received February 10, 2016; Revised March 28, 2016

Fossil fuel power plants are responsible for a significant portion of anthropogenic atmospheric carbon dioxide (CO2) and due to concerns over global climate change, finding solutions that significantly reduce emissions at their source has become a vital concern. When oxygen (O2) is reduced along with CO2 at the cathode of an anion exchange membrane (AEM) electrochemical cell, carbonate and bicarbonate are formed which are transported through electrolyte by migration from the cathode to the anode where they are oxidized back to CO2 and O2. This behavior makes AEM-based devices scientifically interesting CO2 separation devices or “electrochemical CO2 pumps.” Electrochemical CO2 separation is a promising alternative to the state-of-the-art solvent-based methods because the cells operate at low temperatures and scale with surface area, not volume, suggesting that the industrial electrochemical systems could be more compact than amine sorption technologies. In this work, we investigate the impact of the CO2 separator cell potential on the CO2 flux, carbonate transport mechanism, and process costs. The applied electrical current and CO2 flux showed a strong correlation that was both stable and reversible. The dominant anion transport pathway, carbonate versus bicarbonate, undergoes a shift from carbonate to mixed carbonate/bicarbonate with increased potential. A preliminary techno-economic analysis shows that despite the limitations of present cells, there is a clear pathway to meet the U.S. Department of Energy (DOE) 2025 and 2035 targets for power plant retrofit CO2 capture systems through materials and systems-level advances.

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Grahic Jump Location
Fig. 1

Operating principles of an AEM electrolyte electrochemical CO2 separator

Grahic Jump Location
Fig. 2

Comparison of applied current and CO2 evolution at the anode with 0%vol and 50%vol CO2 in the O2-based cathode feed. The N2 flowrate was set at 200 mL/min to purposefully reduce the CO2 concentration to < 1000 ppm.

Grahic Jump Location
Fig. 3

(a) Correlation of the applied cell current (black) and measured CO2 evolution rate at the anode (red). (b) Current and CO2 evolution rate versus cell potential (forward and backward polarizations are shown).

Grahic Jump Location
Fig. 4

The number of electrons (blue) required to separate each CO2 molecule coupled with the separation energy and electrical costs (green) as a function of the cell potential

Grahic Jump Location
Fig. 5

(a) Existing operating requirements for amine and electrochemical separation showing how AEM-based electrochemical cell improvements can yield energy requirements below the thermodynamic limit for chemical sorption; (b) Influence of cell and stack improvements on the cost of electrochemical CO2 separation, showing that AEM-based electrochemical cell improvements can lead to very low costs (ca. ⅓ of chemical amine sorption)




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