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Abstract

The structural changes of a reconstructed Pt(100) surface after electrochemical treatments are characterized by LEED/RHEED under UHV conditions. It is found that the reconstructed Pt(100) structure is stable in the range of −0.2↔+0.4 V (vs. Ag/AgCl) in 0.01 M H₂SO₄ solution, though slightly disordered by hydrogen adsorption. It transforms to a (1×1) structure through an intermediate phase if the electrode potential is scanned to the oxide formation region (>0.9 V). At intermediate potentials, regular arrays of steps running along the [011] direction perpendicular to the fivefold periodicity are formed with a mean spacing of 2.8 nm that is only detected by RHEED. The structural transitions conform to the concurrent changes of the voltammetric features. The cyclic voltammogram of the reconstructed surface is intrinsically different from that of an unreconstructed surface, the latter being almost identical to that of a Pt(100)-(1×1) surface prepared by Ar⁺-sputtering at room temperature without any annealing above 300 K.