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

An ordered adlayer of sulfate or bisulfate has been found on the unreconstr ucted 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 str ucture consists of sulfate/bisulfate rows that run parallel to the edges of the islands that were created during the (hex)-->(1 x 1) transition. The d istance between the adions within the rows is 4.0+/-0.3 Angstrom, and that between rows 10.4+/-0.7 Angstrom, corresponding to a ((1.4+/-0.1)(0) (0)(3. 6+/-0.2))superstructure with a surface coverage of about 0.2. (C) 1999 Else vier Science B.V. All rights reserved.