Preparation of the PbO2 cathode for use in a lead acid bench-scale cell for experimental studies. The strip of lead metal is placed in commercial 10% bleach solution for 24-48 hours at 20 deg C. The oxidized lead electrode is removed, washed with distilled water and ready for use. For bench-scale demonstrations or experimental work, this is probably a good method vs. painting PbO2 ("red lead") ,with binder, on a lead surface.
The Pb(IV) oxide electrode is the cathode in a lead-acid battery. During discharge, the cathode is where electrons are reduced, and Pb(IV) oxide is reduced to PbSO4. The half-cell reaction at the cathode is:
PbO2 + 3H+ + HSO4- + 2e- → PbSO4 + 2H2O
The other electrode in a lead-acid battery is the lead anode, where electrons are oxidized during discharge. The half-cell reaction at the anode is:
Pb + HSO4- → PbSO4 + H+ + 2e-
Overall, the chemical reaction for the discharge of a lead-acid battery is:
Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O
When the battery is charging, the reactions at the electrodes are reversed. The PbSO4 at the cathode is oxidized to PbO2, and the PbSO4 at the anode is reduced to Pb.