Oscillations during formaldehyde oxidation

During the oxidation of formic acid and formaldehyde on platinum electrodes, an oscillatory behavior is frequently observed. " The surface poisoning species play a central role in the triggering of the oscillatory phenomena. Recent studies on formic acid and formaldehyde oxidation confirm this view. Inzelt and Kert sz reported that by the use of electrochemical quartz crystal microbalance technique (EQCM), the periodical accumulation and consumption of strongly bound species can be observed in the course of potential oscillation produced by the galvanostatic oxidation of formic acid. 

Mishina F, Karantonis A, Yu Q-K, Nakabayashi S. 2002. Optical second harmoitic generation during the electrocatalytic oxidation of formaldehyde on Pt(lll) Potentiostatic regime versus galvanostatic potential oscillations. J Phys Chem B 106 10199-10204. 

The phenomenon of oscillating reactions is widely recognized in chemistry. In those cases in which a surface-boxmd species or the surface itself is involved in the complex sequence of steps, the EQCM offers the prospect of additional information. An example of this is the role of an oxide layer in the oxidation of formaldehyde at Pt and Rh [174], Similarly, in the oxidation of 2-propanol at Pt electrodes, it was found that the oscillations (in potential and mass, at constant ourent) increased in amphtude until the positive extreme of the potential excursion reached a value consistent with PtOH and/or PtO formation [175]. Oscillations in mass at open-circuit potential were also observed during the dissolution of Cu in sulfate media when the solution concentration of Cu " " was sufficiently high (c > 0.045 mol dm ) [176], although in this case the potential excursions were such that oxide formation/dissolution was ruled out. 

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