Effect of non-specifically adsorbed ions on the surface oxidation of Pt(111).

The oxidation processes of a Pt(111) electrode in alkaline electrolytes depend on non-specifically adsorbed ions according to in situ X-ray diffraction and infrared spectroscopic measurements. In an aqueous solution of LiOH, an OHad adlayer is formed in the first oxidation step of the Pt(111) electrode as a result of the strong interaction between Li(+) and OHad , whereas Pt oxidation proceeds without OHad formation in CsOH solution. Structural analysis by X-ray diffraction indicates that Li(+) is strongly protective against surface roughening caused by subsurface oxidation. Although Cs(+) is situated near the Pt surface, the weak protective effect of Cs(+) results in irreversible surface roughening due to subsurface oxidation.