Page 32 - Introduction to Transfer Phenomena in PEM Fuel Cells

1.2.1.4.2. Advantages and disadvantages
Compared with polymer membrane cells, PAFCs have the following
advantages [BLU 07, BOU 07, SPI 07]: Introduction to Hydrogen Technology 21
– a better tolerance to carbon monoxide (tolerates ~1%) is the advantage
of phosphoric acid batteries;
– not sensitive to CO 2;

– possibility of cogeneration (electricity-heat).

However, these batteries have a number of disadvantages:
– the electrolyte solidifies around 40°C, so the battery must be kept at a
higher temperature to avoid damaging the electrodes;
– the strong corrosivity of the acid causes deterioration of the electrodes;

– sulfur sensitivity;
– relatively high start-up time;
– high cost of the catalyst (platinum).

1.2.1.4.3. Aging

Given the operating temperature of the PAFC cell, certain components
are subject to modifications, such as the electrolyte, for example, which
tends to degrade or evaporate; the catalyst also loses its catalytic activity
during aging.
1.2.1.5. Molten carbonate fuel cell (MCFC)

In this type of cell, the reactions involved are more complex than in
proton-exchange membrane, alkaline or phosphoric acid fuel cells. The ionic
2–
conduction is ensured by the migration of carbonate ions (CO 3 ) from the
anode to the cathode through the electrolyte constituted by molten
carbonates. One of the special features of MCFC batteries (such as the SOFC
battery) is that the operating temperature allows the use of carbon monoxide
(CO) as a fuel. We must remember that carbon monoxide is considered a
poison for low and medium temperature batteries. This can come from the
process of reforming a hydrocarbon. There can therefore be two kinds of
electrochemical reactions at the anode. The first is the main reaction of