1 Introduction
5
At a certain temperature, the theoretical output voltage of this reaction under
reversible conditions is expressed as follows.
E = E
0
+
RT
nF
ln
(
p H 2
p
∗
H 2
)
2
(
p O 2
p
∗
O 2
)
(1.2)
In the formula, p H 2 , p O 2 , etc. are the partial pressures of hydrogen and oxygen, E
0
is the reversible electrode potential, n represents the number of transferred electrons in
the reaction, and for the reaction formula (1.1), the number of transferred electrons
is 2, and F is Faraday constant. At room temperature and normal pressure, the
theoretical voltage of hydrogen–oxygen fuel cell is 1.229 V. However, in actual use,
the actual voltage is much lower than 1.229 V due to the influence of impedance and
membrane mass transfer (see the following section for specific analysis).
1.2.2 Dynamic Process of Proton Exchange Membrane Fuel
Cell
Formula (1.3) is the contribution of different kinetic processes to the potential loss
of PEMFC.
E cell = E−η HOR −i ∗ R
e f f ective
H + , anode − i ∗ R − i ∗ R
e f f ective
H + , cathode − η ORR −η mt (1.3)
In the above formula, E cell is the actual open-circuit potential of a proton exchange
membrane fuel cell when the current density is i, E is the theoretical potential under
nonequilibrium conditions, η HOR is the overpotential of hydrogen oxidation reaction,
i*R
e f f ective
H + , anode and i*R
e f f ective
H + , cathode are the voltage drop caused by proton conduction in
anode and cathode catalyst layers, I * R is the voltage drop caused by electron
conduction and proton transmission on the membrane, η ORR is the overpotential
of oxygen reduction reaction, and η mt is the voltage drop caused by mass transfer
impedance. Next, by explaining each part of this formula, we will further analyze
the causes of voltage drop in PEMFC.
Among the above potential losses, the voltage drop caused by proton and electron
conduction resistance may be best understood. The electron conduction resistance
and proton conduction resistance R on the membrane can be expressed by the
following formula,
R = R e + R mem
(1.4)
R e is the electronic conduction resistance of proton exchange membrane fuel cell,
including the resistance of the cell itself and the contact resistance. R mem is the
resistance of proton conduction in the membrane. R e can be obtained by directly
5
At a certain temperature, the theoretical output voltage of this reaction under
reversible conditions is expressed as follows.
E = E
0
+
RT
nF
ln
(
p H 2
p
∗
H 2
)
2
(
p O 2
p
∗
O 2
)
(1.2)
In the formula, p H 2 , p O 2 , etc. are the partial pressures of hydrogen and oxygen, E
0
is the reversible electrode potential, n represents the number of transferred electrons in
the reaction, and for the reaction formula (1.1), the number of transferred electrons
is 2, and F is Faraday constant. At room temperature and normal pressure, the
theoretical voltage of hydrogen–oxygen fuel cell is 1.229 V. However, in actual use,
the actual voltage is much lower than 1.229 V due to the influence of impedance and
membrane mass transfer (see the following section for specific analysis).
1.2.2 Dynamic Process of Proton Exchange Membrane Fuel
Cell
Formula (1.3) is the contribution of different kinetic processes to the potential loss
of PEMFC.
E cell = E−η HOR −i ∗ R
e f f ective
H + , anode − i ∗ R − i ∗ R
e f f ective
H + , cathode − η ORR −η mt (1.3)
In the above formula, E cell is the actual open-circuit potential of a proton exchange
membrane fuel cell when the current density is i, E is the theoretical potential under
nonequilibrium conditions, η HOR is the overpotential of hydrogen oxidation reaction,
i*R
e f f ective
H + , anode and i*R
e f f ective
H + , cathode are the voltage drop caused by proton conduction in
anode and cathode catalyst layers, I * R is the voltage drop caused by electron
conduction and proton transmission on the membrane, η ORR is the overpotential
of oxygen reduction reaction, and η mt is the voltage drop caused by mass transfer
impedance. Next, by explaining each part of this formula, we will further analyze
the causes of voltage drop in PEMFC.
Among the above potential losses, the voltage drop caused by proton and electron
conduction resistance may be best understood. The electron conduction resistance
and proton conduction resistance R on the membrane can be expressed by the
following formula,
R = R e + R mem
(1.4)
R e is the electronic conduction resistance of proton exchange membrane fuel cell,
including the resistance of the cell itself and the contact resistance. R mem is the
resistance of proton conduction in the membrane. R e can be obtained by directly