TY - JOUR
T1 - Quantification of carbon dioxide poisoning in air breathing alkaline fuel cells
AU - Tewari, A.
AU - Sambhy, V.
AU - Urquidi MacDonald, M.
AU - Sen, A.
N1 - Funding Information:
This work was supported by NSF grant serial number 415 3767CN. The author greatly acknowledges Dr. Pat Grimes for his insightful discussions, helpful suggestions and valuable comments, and Dr. Paul Werbos and Dr. Jim Mamoh for their economical support thoughout our NSF grant.
PY - 2006/1/23
Y1 - 2006/1/23
N2 - Carbon dioxide intolerance has impeded the development of alkaline fuel cells as an alternate source of power supply. The CO2, in a fuel cell system, could come from the anode side (if "dirty" H2 is used as fuel), from the cathode side (if air instead of pure O2 is used as an oxidant) or from inside the electrolyte (if methanol is used as a fuel). In this work, an novel analytical approach is proposed to study and quantify the carbon dioxide poisoning problem. Accelerated tests were carried out in an alkaline fuel cell using methanol as a fuel with different electrical loads and varying the concentration of carbon dioxide in a mixture CO 2/O2 used as oxidant. Two characteristic quantities, tmax and Rmax, were specified which were shown to comprehensively define the nature and extent of carbon dioxide poisoning in alkaline fuel cells. The poisoning phenomenon was successfully quantified by determining the dependence of these characteristic quantities on the operating parameters, viz. atmospheric carbon dioxide concentration and applied electrical load. Such quantification enabled the prediction of the output of a fuel cell operating in a carbon dioxide enriched atmosphere. In addition, static and dynamic analyses of electrolytes were carried out to determine the dependence of cell current on the electrolyte composition in a fuel cell undergoing poisoning. It was observed that there is a critical concentration of KOH in the electrolyte only below which the effect of carbon dioxide poisoning is reflected on the cell performance. Potentiostatic polarization tests confirmed that the underlying reason for the decreased cell performance because of carbon dioxide poisoning is the sluggish kinetics of methanol oxidation in the presence of potassium carbonate in the electrolyte. Moreover, the decreased conductivity of the electrolyte resulting from hydroxide to carbonate conversion was also shown to increase the ohmic loses in an alkaline fuel cell leading to lower efficiencies.
AB - Carbon dioxide intolerance has impeded the development of alkaline fuel cells as an alternate source of power supply. The CO2, in a fuel cell system, could come from the anode side (if "dirty" H2 is used as fuel), from the cathode side (if air instead of pure O2 is used as an oxidant) or from inside the electrolyte (if methanol is used as a fuel). In this work, an novel analytical approach is proposed to study and quantify the carbon dioxide poisoning problem. Accelerated tests were carried out in an alkaline fuel cell using methanol as a fuel with different electrical loads and varying the concentration of carbon dioxide in a mixture CO 2/O2 used as oxidant. Two characteristic quantities, tmax and Rmax, were specified which were shown to comprehensively define the nature and extent of carbon dioxide poisoning in alkaline fuel cells. The poisoning phenomenon was successfully quantified by determining the dependence of these characteristic quantities on the operating parameters, viz. atmospheric carbon dioxide concentration and applied electrical load. Such quantification enabled the prediction of the output of a fuel cell operating in a carbon dioxide enriched atmosphere. In addition, static and dynamic analyses of electrolytes were carried out to determine the dependence of cell current on the electrolyte composition in a fuel cell undergoing poisoning. It was observed that there is a critical concentration of KOH in the electrolyte only below which the effect of carbon dioxide poisoning is reflected on the cell performance. Potentiostatic polarization tests confirmed that the underlying reason for the decreased cell performance because of carbon dioxide poisoning is the sluggish kinetics of methanol oxidation in the presence of potassium carbonate in the electrolyte. Moreover, the decreased conductivity of the electrolyte resulting from hydroxide to carbonate conversion was also shown to increase the ohmic loses in an alkaline fuel cell leading to lower efficiencies.
UR - http://www.scopus.com/inward/record.url?scp=30144444094&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=30144444094&partnerID=8YFLogxK
U2 - 10.1016/j.jpowsour.2005.03.192
DO - 10.1016/j.jpowsour.2005.03.192
M3 - Article
AN - SCOPUS:30144444094
SN - 0378-7753
VL - 153
SP - 1
EP - 10
JO - Journal of Power Sources
JF - Journal of Power Sources
IS - 1
ER -