Potential Dependent Chromate Adsorption on Gold

The adsorption and reduction of chromate on Au(111) were studied using cyclic voltammetry (CV), surface enhanced Raman spectroscopy (SERS), in situ atomic force microscopy (AFM), and scanning tunneling microscopy in slightly acidic media. CV results show the evolution of the species present with each subsequent scan revealing intermediate processes in the deposition of chromate on the surface. SERS indicates that the deposition involves oxidation and reduction cycles between chromate and α - Cr 2 O 3 . The intermediate step involves a chromate species chemically bound to the surface. The final film is a mixed Cr(III)/Cr(VI) layer. In situ AFM demonstrates that the Cr 2 O 3 adlayer exhibits a ( √ 3 × √ 3 ) R 30 ° adlattice relative to the underlying Au(111).