The early stages of Ag electrodeposition on columnar structured Pt electrodes was investigated in acid solutions covering the underpotential deposition (upd) and overpotential deposition (opd) ranges. Results show a remarkable dependence of the Ag growth mode on the electrode roughness and potential sweep rate. At high potential sweep rates and large substrate roughness factors a 3-D to 2-D rearrangement can be detected. This process appears to be also accompanied by a Pt-Ag formation. For this type of electrode, both processes hinder the nucleation and growth of the 3-D Ag phase. Under certain conditions the complete Ag plating of the entire porous structure can be produced and the voltammetric behaviour of the system then approaches that observed for the Ag/Ag+ electrode reaction at an electrochemical thin layer cell.

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