Cell Components in the MCFC

In the early days of the MCFC, the electrode materials used were, in many cases, precious metals, but the technology soon evolved during the 1960s and the 1970s saw the use of nickel-based alloys at the anode and oxides at the cathode. Since the mid-1970s, the materials for the state-of-the-art electrodes and electrolyte structure (molten 

Cathode Ag20 or Uthiated NiO Lithiated NiO Lithiated NiO 7-15 ixm pore size 70-80% initial porosity 60-65% after lithiation and oxidation 0.5-1-mm thickness 0.5 m /g 

Electrolyte Support MgO 10-20 mVg Mixture of a-P-y-UMO2 0.1-12mVg a -Li AIO2 P -Li AIO2 0.5-1-mm thickness 

The ohmic resistance of the MCFC electrolyte, and especially the ceramic matrix, has an important and large effect on the operating voltage, compared with most other fuel cells. Under typical MCFC operating conditions Yuh et al. (1992) found that the electrolyte accounted for 70% of the ohmic losses. Furthermore, the losses were dependent on the thickness of the electrolyte according to the formula 

The anode of the MCFC needs to provide more than just electro-catalytic activity. Because the anode reaction is relatively fast at MCFC temperatures, a high surface area is not required, compared with the cathode. Partial flooding of anode with molten carbonate is therefore acceptable, and this is used to good effect to act as a reservoir for carbonate, much in the same way that the porous carbon substrate does in the PAFC. The partial flooding of the anode also provides a means for replenishing carbonate in a stack during prolonged use. 

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