Potential oscillation generated by formaldehyde oxidation in the presence of dissolved oxygen

The influence of dissolved oxygen on the potential oscillation patterns is investigated during the oxidation of 0.1 M formaldehyde on polycrystalline platinum in an acidic solution at 315 K under galvanostatic conditions. We have found that, with increasing dissolved oxygen concentration from 0 to 1 mM, chaotic oscillations persist to appear as well as periodic ones, both oscillations show fluctuations in their amplitude and the period length doubles. Voltammograms show that a current peak appears at ca. 0.6 V and becomes large, which is found to be due to the oxidation of the adsorbed CO with oxygen but not due to the slowing down of the formation velocity of the adsorbed CO. The results are discussed regarding the conditions for the appearance of chaos.