OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING
The dissolution of NiO cathodes during cell operation is a limiting factor to the successful commercialization of molten carbonate fuel cells (MCFCs). Microencapsulation of the NiO cathode has been adopted as a surface modification technique to increase the stability of NiO cathodes in the carbonate melt. The material used for surface modification should possess thermodynamic stability in the molten carbonate and also should be electro catalytically active for MCFC reactions. A simple first principles model was developed to understand the influence of exchange current density and conductivity of the electrode material on the polarization of MCFC cathodes. The model predictions suggest that cobalt can be used to improve the corrosion resistance of NiO cathode without affecting its performance. Cobalt was deposited on NiO cathode by electroless deposition. The morphology and thermal oxidation behavior of Co coated NiO was studied using scanning electron microscopy and thermal gravimetric analysis respectively. The electrochemical performance of cobalt encapsulated NiO cathodes were investigated with open circuit potential measurement and current-potential polarization studies. These results were compared to that of bare NiO. The electrochemical oxidation behavior of cobalt-coated electrodes is similar to that of the bare NiO cathode. Dissolution of nickel into the molten carbonate melt was less in case of cobalt encapsulated nickel cathodes. Co coated on the surface prevents the dissolution of Ni in the melt and thereby stabilizes the cathode. Finally, cobalt coated nickel shows similar polarization characteristics as nickel oxide. A similar surface modification technique has been used to improve the performance of the SS 304 current collectors used in MCFC cells. SS 304 was encapsulated with nanostructured layers of NiCo and NiMo by electroless deposition. The corrosion behavior of bare and surface modified SS 304 in molten carbonate under cathode gas atmosphere was investigated with cyclic voltammetry, open circuit potential studies, Tafel polarization, impedance analysis and atomic absorption spectroscopy. This study confirms that the presence of surface modification leads to the formation of complex scales with better barrier properties and electronic conductivity.
- Research Organization:
- University of South Carolina (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- AC26-99FT40714
- OSTI ID:
- 808969
- Resource Relation:
- Other Information: PBD: 30 Sep 2000
- Country of Publication:
- United States
- Language:
- English
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OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING
OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING