A fuel cell is drawn as a container of concentrated aqueous sodium hydroxide with two porous carbon electrodes containing finely divided platinum or palladium. Hydrogen gas is bubbled in through one electrode and oxygen through the other, and water leaves the cell. Which reaction takes place at the electrode fed with oxygen?
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In the H2–O2 fuel cell with an NaOH electrolyte, oxygen is reduced at the cathode: O2 + 2H2O + 4e⁻ → 4OH⁻. Hydrogen is oxidised at the anode, and the overall reaction is 2H2 + O2 → 2H2O.
- A.
This is the oxidation of hydrogen at the anode, not the oxygen electrode.
- B.
The electrolyte is alkaline NaOH, so the reduction of oxygen produces OH⁻ ions rather than consuming H⁺ ions.
- C.
Oxygen is reduced at the cathode; this equation shows OH⁻ being oxidised to oxygen.
NCERT: Class 12 Chemistry, Chapter 2