Deduce the half-equations and the overall equation for the reactions taking place in a direct methanol fuel cell (DMFC) under acidic conditions.

Outline one advantage and one disadvantage of the methanol cell (DMFC) compared with a hydrogen-oxygen fuel cell.

Negative electrode (anode):

CH₃OH (aq) + H₂O (l) → CO₂ (g) + 6H⁺ (aq) + 6e^–

Positive electrode (cathode):
O₂ (g) + 4H⁺ (aq) + 4e^– → 2H₂O (l)

Overall equation:

2CH₃OH (aq) + 3O₂ (g) → 2CO₂ (g) + 4H₂O (l)

Accept any whole or fractional coefficients in balanced equations.

Award [1 max] for correct half-equations at wrong electrodes for M1 and M2.

Advantage:

Any one of:

liquid methanol is easier to transport/store than gaseous hydrogen

OR

hydrogen is explosive

longer membrane life «as it operates in aqueous environment»

methanol has greater energy density than hydrogen

Disadvantage:

Any one of:

lower voltage

lower power per unit mass «of the cell»

lower efficiency

toxic/can be mistaken for ethanol

lower specific energy

Ignore any cost references throughout.

Accept “CO₂/greenhouse gas produced” OR “requires a more highly efficient catalyst”.

Do not award marks for converse statements for the advantage and disadvantage.