Effect of electrogenerated random defects on Pt(111) surface over methanol electrooxidation: Electrochemical and spectroscopic studies

In the present paper, the influence of electrogenerated (110) defects in the methanol oxidation reaction (MOR) on a Pt(111) electrode has been studied. It is shown that methanol oxidation is favored at the defected surfaces as evidenced by the displacement of the onset potential to lower values and the increase of the peak current density. The currents obtained by transient curves at short times (0.015 - 0.50 s) at 0.50 V vs RHE demonstrate the faster formation of strongly adsorbed species on disordered surfaces when compared to Pt(111). On the other hand, for long-term transient currents (600 s), the surface with a higher surface density of (110) defects presented the best activity among all ones studied. Galvanostatic results showed that potential oscillations emerged only on disordered surfaces. The large induction time up to the beginning of the oscillations as well as the lower frequency registered on these surfaces demonstrates the enhancement of CO formation on defects. This point is confirmed by in situ FTIR experiments. From the results obtained by using electrochemical techniques, it was possible to infer that the dehydration rate constant (kdh) and the rate constant for CO oxidation (kCO) are affected by the number of (110) defects, which give rise to kCO and kdh values higher than those obtained for Pt(111).