A comparative study of the electrochemical deposition kinetics of iron-palladium alloys on a flat electrode and in a porous alumina template

• Hindered diffusion of Fe3+ and Pd2+ complexes in an AAO template.
• Same kinetics of Fe and Pd ions and constant DFe/DPd ratio irrespective of the WE.
• Alloy composition is independent of working electrode's geometry.

Fe-Pd alloys have many potential applications because of their unique chemical and magnetic properties, which can be tailored by changing their composition. In this study we have investigated the kinetic parameters for depositing Fe and Pd and their influence on the Fe-Pd alloy's composition, while performing the deposition on a flat Au electrode and into an Au-sputtered porous alumina template. The electrodeposition of Fe and Pd was found to be irreversible and diffusion-controlled. Diffusion coefficients and charge-transfer coefficients were determined by cyclic voltammetry. The exchange current densities for both metallic ions in the porous alumina template and on the flat electrode were determined via a Butler-Volmer analysis. The diffusion coefficient was found to be lower for both metallic ions, by 2-3 times, when the template was used as a working electrode. Due to the hydrogen evolution overlapping with the reduction of the Fe2+, the kinetics of the Fe and of the Pd deposition was calculated using the Butler-Volmer model. We found that the exchange current densities, i.e., the rate of the deposition reaction, are comparable for Fe2+ and Pd2+ on both working electrodes. This indicates that the kinetics of the electrodeposition process is not influenced by the electrode geometry. Because of similar diffusion-coefficient ratios and similar kinetics on both the investigated working electrodes, using the same deposition conditions (i.e., solution and applied potential) results in Fe-Pd-based thin films and nanowires having similar compositions.