Electrodeposition of Ag-Au Alloys and Design of Nanoporous Gold with Controlled Porosity
Authors: Vasiljevic Natasa , Cruz San Martin Vinicius , Szczepanska Alicja 
Published: December 2024

Due to its unique physicochemical, mechanical, and optical properties, Nanoporous gold (NPG) is of interest for various applications.[1-3] Its monolithic structure with the nanoscale size of ligaments and rich surface electrochemistry make the NPG materials unique for use in electrocatalysts, energy storage, sensors and plasmonics. The length scale of NPG porosity (ligaments & open pores) and its effect on the properties is essential for such a broad range of applications. The porosity size can be controlled by parent alloy composition, dealloying (chemical, electrochemical) method, and the temperature of dealloying and annealing. Using the electrochemical surface processes to change and fine-tune the size, uniformity and hierarchy of the ligament network has been attracting attention as a possible tool for manipulating and designing new and improved NPG functionalities. [4, 5]
We will present an all-electrochemical approach to creating NPG thin films with different sizes of porosity from AgxAu1-x alloys. The alloys of various compositions were electrodeposited at the constant potential from a thiosulfate-based solution by controlling the potential and concentration of Ag+ and Au+ ions.[6] The electrodeposited alloys' structural (SEM, AFM) and composition (XPS) characterisation was followed by the selective dissolution of Ag under electrochemical control. Pb monolayer underpotential deposition (UPD) was used to measure the surface area of as-created NPG structures. [7] The surface stress-driven surface alloying [8] taking place during this UPD process was exploited as an electrochemical tool to modify the NPG structure. Combining electrochemical and structural characterisation, we followed the evolution of porosity by controlling the range of the UPD potentials, scan rate and the number of cycles applied.

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