The oxidation of formic acid at noble metal electrodes Part III. Intermediates and mechanism on platinum electrodes

The charge required to oxidize the strongly bound intermediate on Pt electrodes in 1 M H 2 SO 4 is determined ( a ) from sweep measurements extrapolated to infinite speed, ( b ) from the oxidation of the intermediate in the absence of bulk reaction using a dipping technique. Both methods give a value of about 1.3 electrons per site. It is suggested that is the predominant species. The rate of formation of this species is strongly dependent on the amount of hydrogen adsorbed on the electrode and mechanisms are proposed to account for this. The oxidation of the intermediate follows the simple model proposed by Gileadi and Srinivasan under sweep conditions. Evidence for Langmuir adsorption is also obtained from steady-state experiments. The first anodic peak on Pt electrodes follows the same mechanism as the single peak on Pd. Here formic acid is oxidized to CO 2 via the weakly bound . The formation of the peak cannot be explained in terms of a simple two-step reaction or by oxide inhibition, but can be explained if an intermediate such as is formed.