
128 Fuel Cells
For this reaction, the mole fractions and the partial pressures are given as
Hydrogen:
x
H
2
1=
and
P
H
MPa
2
01= .
Oxygen:
Y
n
nn
O
O
ON
2
2
22
05
05 05 376
021=
+
=
+
=
.
.(.)(. )
.
and
P
O
MP
Pa
2
021010021=× =.. .
Water:
Y
n
nn
HO
HO
HO N
2
2
22
1
105376
0 347=
+
=
+×
=
..
.
and
P
HO
MP
Pa
2
0 347 01 0 0347=× =.. .
The reversible voltage for this fuel cell is given as
EE
RT
F
P
PP
=−
0
12
2
2
2
2
ln
HO
H
O
/
E =−
×
1 2289
8 314 298
296 485
0 0347
01 002
.
.
()(, )
ln
.
(.)( .
11)
E = 1.2289 V – 0.03601129
E = 1.1929 V.
4.4.3.1 Effect of Hydrogen Partial Pressure
In order to show the effect of variation of hydrogen partial pressure in a
hydrogen–oxygen fuel cell, let us rearrange Equation 4.5