The Effect of CO2 on Anion Exchange Membrane Fuel Cells

Noga Ziv, Nancy & Stephan Grand Technion Energy Program (GTEP), Technion IIT, Haifa, Israel
Christine Weinzierl, Institute Of Energy And Process Systems Engineering, Tu Braunschweig, Braunschweig, Germany
Ulrike Krewer, Institute Of Energy And Process Systems Engineering, Tu Braunschweig, Braunschweig, Germany
Dario R. Dekel, The Wolfson Department Of Chemical Engineering And Nancy & Stephan Grand Technion Energy Program (gtep), Technion Iit, Haifa, Israel


Anion exchange membrane fuel cells (AEMFCs) are highly efficient, environmentally friendly electrochemical devices that can produce green power by converting the chemical energy stored in clean fuel molecules into electricity. Anion exchange membranes (AEMs) used in this fuel cell technology, consist of polymer chains containing fixed positively charged groups, which serve to conduct anions (mainly hydroxide, OH-) from the cathode to the anode side of the fuel cell.
AEMs offer several advantages over the main stream proton exchange membranes as they provide a non-acidic environment that enables the use of platinum-free metals as catalysts and better reaction kinetics.
One of the main challenges of AEMFCs is the undesired reaction of OH- anions with atmospheric CO2, which converts OH- to a bulkier, less mobile CO32-/HCO3- anion (carbonation). This reaction takes place very quickly when the membrane is in contact with atmospheric air (which contains ~400ppm CO2). It has been shown that all OH- anions in the membrane are replaced by CO32-/HCO3- within 0.5-6 hours of exposure to air. This process causes a decrease in the membrane's conductivity and therefore decrease in the fuel cell's performance.
In order to mitigate the negative effect of CO2 on the AEM a better understanding of the dynamics of the carbonation reaction is needed. In addition, the effect of fuel cell's operation conditions on the carbonation must be studied and optimized for future use of AEMFCs in devices based on air as a reactant (such as fuel cell powered electric vehicles).