Electroless deposition of palladium nanoparticles on poly(3,4-ethylene-dioxythiophene)-role of the electrode substrate

Electroless deposition of Pd is studied comparatively on glassy carbon (GCE) and spectral graphite (SGE) electrodes modified with electrodeposited poly(3,4-ethylene-dioxythiophene) (PEDOT) layers. Computed microtomography is used to explore the bulk structure of both types of carbon electrodes. It is found that SGE has high (27%) open porosity in contrast to GCE, the latter characterized by a dense and homogeneous structure with no porosity. Despite the structural difference of the electrodes, the intrinsic electrochemical activity of PEDOT is found to remain unaffected by the type of the underlying carbon substrate used for PEDOT electrochemical deposition. Electroless deposition of Pd is carried out on pre-reduced PEDOT-coated electrodes, in the absence of additional reductants in the electrolyte solution and expected to occur at the expense of PEDOT oxidation. It is found that at constant polymerization charge of PEDOT, the amount of metal deposited on PEDOT/SGE is several times higher in comparison to PEDOT/GCE. The high effectiveness for electroless metal deposition on PEDOT/SGE is explained by the involvement of pre-reduced hydrogen embedded in the highly porous structure of SGE that acts further as additional (apart from PEDOT) reductant contributing markedly to the amount of reduced Pd ions.