Page 35 - Introduction to Transfer Phenomena in PEM Fuel Cells

24 Introduction to Transfer Phenomena in PEM Fuel Cells
– high efficiency;
– nickel catalyst;
– possibility of cogeneration.
However, one of the difficulties encountered with this type of battery
relates to the corrosion of nickel oxide by the electrolyte; other
disadvantages include:

– controlling the CO 2 taken from the anode and reinjected at the cathode
complicates the operation;

– the relatively long start-up time;
– sensitivity to sulfur;
– the dissolution of the cathode (nickel);

– low current density.

1.2.1.5.3. Aging
In a MCFC, adverse reactions can occur. This is due to the high operating
temperatures as well as the corrosive nature of the electrolyte.
2+
Indeed, the dissolution of Ni ions in the electrolyte at the cathode and
their diffusion towards the anode (with the possibility of short circuit if they
are reduced in the form of nickel).

In addition, the mechanical stability of the electrodes is also affected at
these temperatures, resulting in deformations detrimental to high efficiency.
The structure of the liAlO 2 electrolyte matrix can also be modified (increase
in particle size and porosity).

1.2.1.6. Solid oxide fuel cell (SOFC)
Solid oxide fuel cells (SOFCs) appear to be used in large, high power
plants such as power plants in industry.

A solid oxide system is generally made of a hard ceramic material,
comprising zirconium solid oxide and a small amount of yttria to replace the
liquid electrolyte. The operating temperature of these solid oxide batteries
can reach 1,000°C. Their efficiency can reach 60 to 85% with cogeneration,