STRUCTURAL MODIFICATIONS OF A SPENT MOLTEN CARBONATE FUEL-CELL

Several performance and endurance tests have been carried out on molten carbonate fuel cells (MCFC) operating at different temperatures (873, 893 and 923 K). Electrochemical performance parameters, morphological characteristics and chemical analyses on samples of spent electrodes and tiles were evaluated. An output power decrease of 10% from the original value was taken to be the largest acceptable decay. Cell operation was stopped upon reaching this point. Electrolyte losses ranging from 18.6 to 24.5 of the original content were the determining factor in the MCFC performance decrease. Scanning electron microscopy showed that post-test anodes retained a satisfactory microstructure, while the tiles appeared to be very sensitive to the effect of operating temperature. The cathode structure, after an initial in situ oxidation, appeared to consist of agglomerates of 0.9 μm NiO crystallites. Long-term operation produces some modification of the pore size distributions of the used components, resulting in a final electrolyte distribution that was far from optimal. Due to the opposite effect of temperature on cell lifetime and power output, the highest power output and shortest cell lifetime were obtained for the 923 K test. © 1990 Chapman and Hall Ltd.