The role of the surface structure in the oxidation mechanism of methanol

Pulsed voltammetry has been used to study methanol oxidation in acid media on platinum stepped surfaces to determine the kinetics of the reaction and the role of the surface structure in the reactivity. From the current transients at different potentials, the intrinsic activity of the electrode through the active intermediate reaction path (jdir,ini), as well as the rate constant for the CO formation (kads) and CO oxidation (kox) have been calculated. The kinetics for methanol oxidation through the active intermediate reaction path is strongly dependent on the surface structure of the electrode, with the highest activity found for the Pt(1 0 0) surface. The presence of (1 1 1) and (1 0 0) steps, both on (1 0 0) and (1 1 1) terraces, respectively, does not increase the activity of these surfaces, while (1 1 0) steps do improve the catalytic activity. These results are compared to those obtained with formic acid and ethanol to better understand methanol oxidation reaction. Thus, it is obtained that first step in the mechanism is a dehydrogenation step, which is the slowest step in the process. Also, the effect of the anions in the oxidation process is studied.

► Methanol oxidation mechanism is very dependent on the surface geometry.
► The presence of (1 0 0) steps on (1 1 1) terraces increases the activity.
► The first step in the reaction is the dehydrogenation step.