Question

In $H_2-O_2$ fuel cell a reaction occuring at cathode is:

• A. $2H_{2}O+O_2+4e^{-}\to 4O{H}^{-}$
• B. $2H_2+O_2\to 2H_{2}O\left(l\right)$
• C. $H^{+}+O{H}^{-}\to H_{2}O$
• D. $H^{+}+e^{-}\to \frac{1}{2}{H}_2.$

Answer 1

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

Fuel cells:

A hydrogen-oxygen fuel cell consists of an electrolyte solution, such as KOH solution and two inert carbon electrodes. Hydorgen and oxygen gases are bubbled through the anode and cathode compartments, where the following reactions takes place.

At anode: $2H_2\left(g\right)+4O{H}^{-}\to 4H_{2}O\left(l\right)+4e^{-}$

At cathode: $O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{-}$

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Net cell reaction: $2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right)$

The standard emf of the cell is $1.23$V, which indicates that the cell reaction is spontaneous under standard conditions. The porous carbon electrodes serve as electrical conductors and also provide the necessary surfaces for the initial decomposition of the molecules into atomic species, prior to electron transfer. A hydrogen-oxygen fuel cell assembly is shown in Figure.