Environmental Engineering Reference
In-Depth Information
FIGURE 9.1 Schematic drawing of a hydrogen/oxygen fuel cell and its reactions based on the proton
exchange membrane fuel cell. Source : Reproduced with permission from Carrette et al. [4]. (See color
insert.)
electrode assembly (MEA) in which hydrogen gas (H 2 ) is oxidized on the
anode and oxygen gas (O 2 ) is reduced on the MEA cathode, all compressed
by bipolar plates that introduce gaseous reactants and coolants to the MEA
and harvest the electric current. The electrochemical reactions occur at the
MEA electrodes, each attached to a solid polymer ion exchange membrane
that conducts protons but not electrons. Both the cathode oxygen reduction
reaction (ORR) and anode hydrogen oxidation reaction occur on the surfaces
of Pt-based catalysts. Pure water and heat are the only by-products. Porous
gas diffusion layers transport reactants and product water between the flow
fields and catalyst surfaces while exchanging electrons between them. The
major reactions are given below.
Anode H
:
2
H
+
+
2
e
(9.3)
2
Cathode H
: 4
+
+
4
e
+ →
O
2
H O
(9.4)
2
2
Overall H
:
2
+ →
O
2
H O
.
(9.5)
2
2
2
9.1.3 Operation of Fuel Cells
The operation of fuel cells is virtually electrochemical reactions, and the
overall properties can be characterized by Nernst equation. For the oxidation
Search WWH ::




Custom Search