The occurrence of various sequences of complex bursting and mixed-mode oscillations is described during the hydrogen peroxide reduction on a rotating platinum disk from sulphuric acid solution. It is shown that the current and electrode potential oscillations that occur under fixed applied potential-conditions are caused by a cathodic passivation process related to a hydride-layer formation, in conjunction with the solution and external ohmic resistance. Impedance measurements reveal that the potential oscillations that can be observed under galvanostatic conditions do not find an explanation in terms of negative impedance characteristics, and hence their origin remains unclear.