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O: Oberflächenphysik
O 13: Solid-liquid interfaces
O 13.7: Talk
Monday, March 27, 2006, 16:30–16:45, WIL C207
Electrochemistry of Two Dimensional Copper Sulphide Films on Au(111) Studied by in situ STM and Cyclic Voltammetry — •Daniel Friebel, Christian Schlaup, and Klaus Wandelt — Institut für Physikalische und Theoretische Chemie, Wegelerstr. 12, D-53115 Bonn, Germany
For the electrochemical preparation of ultrathin copper sulphide films on Au(111), Cu underpotential deposition from 1 mM CuSO 4 + 0.1 M H 2 SO 4 is followed by two consecutive electrolyte exchanges for (i) acid blank solution (0.1 M H 2 SO 4 ) and (ii) reactive solution (0.5 mM Na 2 S + 0.1 M NaOH). We can stabilize the first upd layer (θ Cu = 2/3) with its well-known (√3 × √3)R30∘ structure in the acid blank solution for over 2 hours. In the reactive solution, we observe islands of two ordered Cu x S phases: a rectangular and, at higher potentials, an incommensurate hexagonal phase. Cu-free, S-covered Au(111) regions are identified by their characteristic (√3 × √3)R30∘ structure. At strongly anodic potentials, Cu x S is irreversibly dissolved. The latter process cannot be directly observed with STM because HS − (aq) is oxidized to S 8 (ads) multilayers. Therefore, we have extended our investigations by a third electrolyte exchange, subsequent to Cu x S formation, for alkaline blank solution (0.1 M NaOH), to get further insights into the Cu x S electrooxidation. Obviously, anodic Cu dissolution in alkaline solutions is enhanced by complexation of Cu(II) with bi- or polysulphides.