Electrochimica Acta 50 (2005) 1885–1893 Reticulated vitreous carbon–polyaniline–palladium composite electrodes Anna Frydrychewicz a,∗ , Sergey Yu. Vassiliev b , Galina A. Tsirlina b,1 , Krystyna Jackowska a,1 a Laboratory of Electrochemistry, ChemicalFaculty, Warsaw University, 02-093 Warsaw, Pasteur 1,Poland b Department of Electrochemistry, Faculty of Chemistry, Moscow State University, Leninskie Gory 1 – str. 3, 119992, Moscow, Russia Received 8 March 2004; received in revised form 16 June 2004; accepted 28 August 2004 Available online 5 October 2004 Abstract Multicomponent electrodes composed of reticulated vitreous carbon (RVC), polyaniline (PANI) and palladium (Pd) were prepared by a two-step method and then investigated. In the sample synthesis cyclic voltammetry and chronoamperometry modes were subsequently applied. A strict procedure of sample synthesis and a model to estimate the partial loading values were established. The latter, allowed for precise coulometric determination of sample composition i.e. the amount of PANI (4–86 nmol/cm 2 ) and Pd (0.2–2.1 mol/cm 2 ) in RVC/PANI/Pd electrode. Low PANI/Pd ratio (mainly ≪ 1) assured the predominating contribution of electrodeposition process as compared to possible chemical deposition. The presence of polymer affected the rate of Pd electrodeposition. The morphology and electrochemical properties of RVC/PANI/Pd and RVC/Pd systems were studied. SEM and STM images have shown that the amount of PANI in the sample influences the size and the distribution of palladium aggregates. The size of Pd crystals forming the aggregates was ca. 5 nm. Pd coalescent crystals tend to locate in the vicinity of polymer chains. Cyclic voltammograms of RVC/PANI/Pd were found to combine RVC/PANI and RVC/Pd electrochemical characteristic, with very slight mutual effect of components. RVC/PANI/Pd electrodes were studied with respect to hydrogen sorption abilities. RVC/PANI/Pd electrodes absorb smaller amounts of hydrogen in the -phase than their RVC/Pd counterparts. The latter is caused by partial isolation of Pd in the course of absorption period, by reduced non-conducting PANI film. © 2004 Elsevier Ltd. All rights reserved. Keywords: Multicomponents electrodes; RVC; PANI; Pd; Morphology; Hydrogen sorption 1. Introduction Multicomponent electrochemical systems have received appreciable attention in the last years because some of the most desirable properties of certain substances are enhanced once they become integral parts of more complex systems. In particular, the preparation and application of various elec- troactive polymers with incorporated metal particles is widely studied. The approaches to the preparation of complex poly- mer/metal systems include different templates, which may affect the distribution, size and activity of the dispersed metal clusters. Three types of such approaches can be marked out: (i) electroless reduction of metal salts by electroactive poly- ∗ Corresponding author. Tel.: +48 22 822 02 11 369; fax: +48 22 822 59 96. 1 ISE member. mer films, powders or solutions [1–6], (ii) the incorporation of metal particles in the course of polymer electrosynthesis [7,8] (so-called one-step method), (iii) the electrodeposition of metal particles on electroactive polymer electrodes [9–13] (two-step method). The systems investigated in this work are composed of reticulated vitreous carbon (RVC), conductive polymer— polyaniline (PANI) and palladium (Pd). The latter is con- sidered as the key component, regarding its catalytic prop- erties and hydrogen sorption ability, while other constituents make the modification of Pd properties possible. Usual tech- niques of Pd electrodeposition on metallic supports result in pronounced coalescence of nanocrystals and corresponding decrease of the surface available for electrode reactions. De- position potential can affect bulk defectiveness sometimes related to the sorption capacity [14,15]. In order to increase the specific surface area, one should prevent coalescence by 0013-4686/$ – see front matter © 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2004.08.041