In-situ observation of an ordered sulfate adlayer on Au(100) electrodes

An ordered adlayer of sulfate or bisulfate has been found on the unreconstructed Au(100) surface in 0.1 M H₂SO₄ by in-situ STM. The ordered adlayer is formed concomitantly with lifting of the (hex)-reconstruction. The new structure consists of sulfate/bisulfate rows that run parallel to the edges of the islands that were created during the (hex)→(1×1) transition. The distance between the adions within the rows is 4.0±0.3 Å, and that between rows 10.4±0.7 Å, corresponding to a superstructure with a surface coverage of about 0.2.