Alkaline Fuel Cell (AFC) using an electrolyte solution (KOH) or alkaline solution.
Operating temperature between 150 °C - 200 °C using hydrogen fuel and
pure oxygen and free of CO2. Because impurities can cause side reactions and CO2 reacts
with the electrolyte to form a precipitate carbonate will seal the surface of
the catalyst and inhibit the reaction at the surface of the anode and cathode.
Alkaline fuel cell (AFC) has been used as a source of power for spacecraft
since 1960.
Alkaline systems operate well at room
temperature, yield the highest voltage (at comparable current densities) of all
fuel cell systems, and cell and electrodes can be built from low-cost carbon and
plastics. Because of a good compatibility with many construction materials AFCs
can achieve a long operating life
Complete reaction can be
seen as below:
Anode reaction:
2H2 + 4OH- à 4H2O + 4e-
Cathode reaction:
O2 + 2H2O
+ 4e- à 4OH-
The overall reaction:
2H2 + O2 à 2H2O
Started working mechanism
of the reaction of water and oxygen at the cathode generates hydroxyl ions (OH-).
Hydroxyl ions through the electrolyte transferred to the anode side. On
the anode side hydrogen reacts with hydroxyl ions produce water and liberate
electrons. Electrons generated at the anode side out of the system and used as
electric power and then back to the cathode. On the cathode side the electrons
react with oxygen. To more clearly below show the mechanism of action (AFC):
Figure 1.
AFC structure
The
AFCs for remote applications (space, undersea, military) are not strongly constrained
by cost. On the other hand, the consumer and industrial markets require the development
of low-cost components to successfully compete with alternative technologies. Much
of the recent interest in AFCs for mobile and stationary terrestrial applications
has addressed the development of low-cost cell components.
