Effects of Palladium(II) Chlorocomplex Speciation on the Controlled Interaction with a Polyaniline Film in Acid

In this study, we determined the Pd(II) chlorocomplex species that has the most favorable interaction with an electropolymerized and protonated polyaniline (PANI) film. This study was completed with the intent to use this species to electrochemically build atomic palladium clusters in the PANI matrix. Varying amounts of NaCl were added to a K₂PdCl₄/HClO₄ solution to result in three species studied: PdCl₂(H₂O)₂, PdCl₃(H₂O)^-, and PdCl₄^2-. UV-vis spectroscopy was used to confirm the speciation, and Raman spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammograms were used to probe the interaction between the Pd species and PANI. It was determined that PdCl₃(H₂O)^- most effectively interacts with PANI as a result of the charge balance between the anion and the protonated nitrogen-containing groups in the polymer. It has been also found that some fraction of inserted Pd(II) cannot be reduced to Pd(0).