What substance is reduced in a lead storage battery?

In lead acid battery, chemical reactions are induced to do work on charge and produce a voltage difference between the two output terminals.

In a lead storage battery, the negative terminal is composed of lead electrode (Pb2+) while in the positive terminal it is composed of lead dioxide electrode (PbO2).

The chemical half reactions in each electrode are:

Negative Terminal: Pb2 + + SO4 (2-) - - - > PbSO4 + 2e

Lead electrode is oxidized to supply electrons.

Positive Terminal: PbO2 + H2SO4 + e - - - > PbSO4

Lead dioxide electrode is reduced by the addition of electrons.

Answer: Lead dioxide is reduced.