Cu2O undergoes disproportionation to form Cu2+ and Cu.
2Cu2+(aq) > Cu2+(aq) + Cu(s)
Thus, Cu2O acts both as an oxidant as well as a reductant.
(i) When heated in air, Cu2O is oxidized to CuO;
and Cu2O acts as a reductant and reduces O2 to O2-
(ii) When heated with Cu2S it oxidizes S2- to SO2 and hence Cu2O acts as an oxidants