Two dimensional metal–oxianion surface complexes formation during the upd process on a Au(1 1 1) electrode studied by in situ surface X-ray diffraction and infrared reflection absorption spectroscopy

Throughout the whole potential ranges where underpotential deposition (upd) proceeds, the stretching absorption bands of both sulfate and phosphate anions (vSO and vPO) do not change at all with regard to band-center position. Sulfate and phosphate anions are combined with copper or zinc ions to form surface metal complexes on a Au(1 1 1) electrode surface, respectively: transition metal–oxianion (sulfate and phosphate) pseudo-complexes are formed in the course of upd processes. The surface structure of the Au(1 1 1) electrode in the topmost layer is the same as the bulk structure (1×1), and lifting of surface reconstruction takes place in the case of Cu-upd where Cu(I)2SO4 and Cu(I)3SO4 pseudo-complexes extend on the surface, while surface reconstruction of a Au(1 1 1) electrode continues to occur in the case of Zn-upd where the Zn(I)2PO4 or Zn(I)3PO4 pseudo-complex locates.