A self-terminating rapid electrodeposition process for controlled growth of platinum (Pt) monolayer films from a K(2)PtCl(4)-NaCl electrolyte has been developed that is tantamount to wet atomic layer deposition. Despite the deposition overpotential being in excess of 1 volt, Pt deposition was quenched at potentials just negative of proton reduction by an alteration of the double-layer structure induced by a saturated surface coverage of underpotential deposited H (H(upd)). The surface was reactivated for further Pt deposition by stepping the potential to more positive values, where H(upd) is oxidized and fresh sites for the adsorption of PtCl(4)(2-) become available. Periodic pulsing of the potential enables sequential deposition of two-dimensional Pt layers to fabricate films of desired thickness, relevant to a range of advanced technologies.

The work exploring the stoichiometry of Pt deposition via surface-limited redox replacement of the underpotentially deposited ͑UPD͒ Cu monolayer on Au͑111͒ is presented. The Cu UPD monolayer is formed from 10 −3 M Cu 2+ + 0.1 M HClO 4 solution, whereas the Pt deposition via surface-limited redox replacement reaction is carried out in 10 −3 M ͕PtCl 6 ͖ 2− + 0.1 M HClO 4 solution at open-circuit potential. Our results indicate that the Pt submonolayers have two-dimensional morphology and linear dependence of their coverage on the amount ͑coverage͒ of the replaced Cu UPD monolayers. Our analysis shows that the oxidation state of Cu during redox replacement reaction is 1+, suggesting that four Cu UPD adatoms are replaced by each deposited Pt adatom. This work stresses the general importance of the anions, determining the stoichiometry of metal deposition reaction via surface-limited redox replacement of the UPD monolayers.

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