Anodization of Pd in H2SO4 Solutions: Influence of Potential, Polarization Time, and Electrolyte Concentration

The anodization of Pd in H2SO4 solutions has been investigated by electrochemical measurements, considering the effect of the applied potential, polarization time, and electrolyte concentration. The anodization and subsequent reduction result in the formation of Pd nanostructures on the electrode surface. Compared to the bulk Pd, the anodization of Pd in H2SO4 solutions leads to different cyclic voltammetry (CV) behaviors including well-separated adsorption/desorption peaks in the hydrogen region and relatively larger reduction peak areas. The improvement of electrochemically active surface areas (EASAs) of the anodized Pd samples is strongly dependent upon the electrolyte concentration, and the optimum H2SO4 concentration is 1.0 M. Both the applied potential and polarization time have a significant influence on the anodization process of Pd. For the given electrolyte concentration, there exist desirable applied potential and polarization time to achieve greater EASAs. The EASAs of the anodized Pd obtained under the optimum polarization conditions can reach as large as 890 times compared to its geometric area. In addition, the formation mechanism of Pd nanostructures on the electrode surface has been discussed on the basis of microstructural analysis. The present findings provide a promising route to fabricate nanostructured Pd electrocatalysts with ultrahigh EASAs.