Mechanistic signatures in the oxidation of butan-1-ol at a rotating Pd disk in alkaline media from combining cyclic voltammetry with instabilities

Palladium, in contrast to platinum, is a poor electrochemical catalyst for primary alcohols in acid solution. Cyclic voltammetry has been applied to the oxidation of butan-1-ol at a rotating Pd-disk electrode in alkaline solution. The activity of butan-1-ol at Pd is compared with that at Pt. Substantially higher current densities are achieved at Pd. At low concentrations, a peak exists in the current-potential curve for both electrodes that originates from the oxidation of an aldehyde intermediate to the carboxylate ion. For Pd, increasing the concentration of butan-1-ol causes the peak to disappear. At large concentrations, increasing the upper limit of the potential cycle from a low value induces a transition from the typical period-one cyclic voltammetric response to a period-two response. The current-potential curve for the period-two response has the same form as those for processes where formation and removal of surface-bonded carbon monoxide dominate the electrode kinetics. Many other high-order periodic states are observed. For Pt, increasing the concentration does not cause the peak corresponding to carboxylate production to disappear. No high-order periodic states are observed in the oxidation of butan-1-ol at Pt. It is concluded that, in alkaline solution, Pd is more effective than Pt in cleaving the bond between the first two carbon atoms.