PbO₂(s) + Pb(s) → PbSO₄(s) (pH = 1, sulfuric acid)

oxidation/reduction under an acidic environment

PbO₂(s) + H₂SO₄(aq) + 2 H⁺(aq) + 2 e^– → PbSO₄(s) + 2 H₂O(l)

Pb(s) + H₂SO₄(aq) → PbSO₄(s) + 2 H⁺(aq) + 2 e^–

PbO₂(s) + Pb(s) + 2 H₂SO₄(aq) → 2 PbSO₄(s) + 2 H₂O(l)

This is known as a comproportionation reaction (two reactants lead to the same product).

This reaction is the one that drives the lead/acid battery in your automobile.