Graphite electrode-assisted electroless deposition of palladium in the absence and presence of poly(3,4-ethylenedioxythiophene) coatings

Abstract

Electroless deposition of Pd in the absence of solute reducing species is studied on pre-reduced non-coated and poly(3,4-ethylenedioxythiophene)(PEDOT)-coated graphite electrodes. PEDOT coatings doped with either dodecyl sulfate (SDS) or polysterene sulfonate (PSS) ions are used in the studies. Electrochemical reductive pre-treatment occurs at negative enough potential to initiate hydrogen reduction at the modified electrodes. Large amounts of deposited Pd significantly exceeding the quantity that is expected to be reduced at the expense of PEDOT re-oxidation alone are found to deposit irrespective of the polymer coating’s thickness. Pd particles are observed to deposit also at bare pre-reduced graphite electrode. It is suggested that molecular hydrogen entrapped during the reductive treatment plays the role of additional reductant for the electroless Pd deposition. SEM, UV–vis and Raman investigations are used to study possible structural changes of PEDOT provoked by the strong reductive treatment. The data give evidence for irreversible structural change in the PEDOT/SDS case resulting in a dense morphology that inhibits ionic transport and supports Pd electroless deposition.