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5 – Applications
The polymer electrolyte Nafion is a proton conductor with the formula
— [(CF 2 — CF 2 ) n — (CF 2 — CF)] x —
|
OCF 2 — CF — CF 3
|
OCF 2 — CF 2 — SO 3 H
The hydrogen must be free of carbon monoxide, which poisons the platinum.
This fuel cell operates from 60 to 90 °C.
2 Another example is the direct methanol fuel cell (DMFC). It uses the
same membrane as electrolyte as the PEMFCs and operates at temperatures ranging from 60 to 80 °C. At the anode, methanol CH 3 OH is oxidized at a catalyst layer according to the reaction
CH 3 OH + H 2 O $ CO 2 + 6H
+ + 6e
and oxygen is reduced at the cathode:
O 2 + 4H
+ + 4e $ 2H 2 O
We observe that water is consumed at the anode and produced at the
cathode. The overall operating reaction is
2CH 3 OH + 3O 2 $ 2CO 2 + 4H 2 O
with proton transfer to the membrane. The DMFC does not require a priori
catalytic reforming of the fuel. However, the diffusion of liquid methanol
across the membrane and the need for a water reservoir at the anode are
drawbacks, notably in terms of the specific energy of the cell.
3. Molecular hydrogen H 2 does not exist in the free state and must thus be
fabricated.
2 Fabrication of H 2 by reforming methane CH 4 with water vapor
CH 4 + H 2 O m CO + 3H 2
in the presence of iron as catalyst, followed by the reaction
CO + H 2 O m CO 2 + H 2
catalyzed by Fe 2 CO 3 , Cr 2 (CO 3 ) 3 , …
The balanced reaction equation is
CH 4 + 2H 2 O m CO 2 + 4H 2
2 Fabrication of H 2 by partial oxidation of methane CH 4
5 – Applications
The polymer electrolyte Nafion is a proton conductor with the formula
— [(CF 2 — CF 2 ) n — (CF 2 — CF)] x —
|
OCF 2 — CF — CF 3
|
OCF 2 — CF 2 — SO 3 H
The hydrogen must be free of carbon monoxide, which poisons the platinum.
This fuel cell operates from 60 to 90 °C.
2 Another example is the direct methanol fuel cell (DMFC). It uses the
same membrane as electrolyte as the PEMFCs and operates at temperatures ranging from 60 to 80 °C. At the anode, methanol CH 3 OH is oxidized at a catalyst layer according to the reaction
CH 3 OH + H 2 O $ CO 2 + 6H
+ + 6e
and oxygen is reduced at the cathode:
O 2 + 4H
+ + 4e $ 2H 2 O
We observe that water is consumed at the anode and produced at the
cathode. The overall operating reaction is
2CH 3 OH + 3O 2 $ 2CO 2 + 4H 2 O
with proton transfer to the membrane. The DMFC does not require a priori
catalytic reforming of the fuel. However, the diffusion of liquid methanol
across the membrane and the need for a water reservoir at the anode are
drawbacks, notably in terms of the specific energy of the cell.
3. Molecular hydrogen H 2 does not exist in the free state and must thus be
fabricated.
2 Fabrication of H 2 by reforming methane CH 4 with water vapor
CH 4 + H 2 O m CO + 3H 2
in the presence of iron as catalyst, followed by the reaction
CO + H 2 O m CO 2 + H 2
catalyzed by Fe 2 CO 3 , Cr 2 (CO 3 ) 3 , …
The balanced reaction equation is
CH 4 + 2H 2 O m CO 2 + 4H 2
2 Fabrication of H 2 by partial oxidation of methane CH 4