Question

Identify the reaction taking place at cathode in fuel cell.

• A. $O_2+2H_{2}O+4e^{-}\to 4{OH}^{-}$
• B. $2H_2+4{OH}^{-}\to 4H_{2}O+4e^{-}$
• C. $O_2+2H_{2}O+4e^{-}\to 4{OH}^{-}+H^{+}$
• D. $4H_{2}O+4e^{-}\to 2H^2+4{OH}^{-}$

Answer 1

The correct option is A $O_2+2H_{2}O+4e^{-}\to 4{OH}^{-}$

In a fuel cell the hydrogen enters the fuel cell at the anode. A chemical reaction strips the hydrogen molecules of their electrons and the atoms become ionized to form $H^{+}$. The electrons travel through wires to provide a current to do work. The oxygen enters at the cathode, usually from the air. The oxygen picks up the electrons that have completed their circuit. The oxygen then combines with the ionized hydrogen atoms $\left(H^{+}\right)$, and water $\left(H_{2}O\right)$ is formed as the waste product which exits the fuel cell.
Cathode side (a reduction reaction): $O_2+4H^{+}+4e^{-}\to 2H_{2}O$
or $O_2+2H_{2}O+4e^{-}\to 4{OH}^{-}$