Structure and properties of C60–Pd films formed by electroreduction of C60 and palladium(ii) acetate trimer: evidence for the presence of palladium nanoparticles

Abstract

The composition, surface morphology, structure, and electrochemical properties of thin solid films of the polymer, C 60 -Pd, were studied by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and energy dispersive X-ray fluorescence (EDXRF) as well as being examined by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) with selective area diffraction (SAD) and by cyclic voltammetry (CV), respectively. The C 60 -Pd films were deposited onto Au or Pt electrodes by electroreductive co-polymerization of C 60 and the palladium(II) acetate trimer, [Pd(ac) 2 ] 3 , in a mixed acetonitrile-toluene (4 : 1, v/v) solution of 0.1 M tetra(n-butyl)ammonium perchlorate under multicyclic voltammetry or potentiostatic conditions. The structure and composition of the C 60 -Pd films were dependent on the relative concentration of the polymer precursors, i.e., C 60 and [Pd(ac) 2 ] 3 , in the solution for electropolymerization. That is, in films grown in solutions with a high [Pd(ac) 2 ] 3 : C 60 ratio, (-C 60 -Pd-) n polymeric chains were separated by the Pd nanoclusters. These films were relatively smooth and uniform. In contrast, films electropolymerized in solutions with a low [Pd(ac) 2 ] 3 : C 60 ratio were rough, porous and much less uniform. The presence of the Pd nanoclusters in the C 60 -Pd film influenced the electrode processes of probing redox species dissolved in solution. That is, electro-oxidation of an N,N,N',N'-tetramethyl-1,4phenylenediamine (TMPDA) electrochemical redox probe was partially inhibited at the electrode coated by the C 60 -Pd film with a relatively low Pd nanocluster content. In contrast, electro-oxidation of TMPDA was effectively mediated by the C 60 -Pd film containing appreciable amounts of dispersed Pd nanoclusters.

Electrochemically formed two-component films comprised of fullerene and transition-metal components

“…11, the effect of different ratios of the concentration of the precursors, [Pd(acetate) 2 ] 3 and C 60 , on the morphology of C 60 /Pd films formed under cyclic voltammetry conditions is shown [48]. With a high ratio, a relatively smooth film of uniform thickness is grown.…”

“…Fig. 10 shows a high-resolution transmission electron microscope image and selected area diffraction pattern for the C 60 /Pd film formed in a solution containing a high concentration of palladium(II) acetate [48]. A cubic crystalline phase of palladium metal is present in the film.…”

“…palladium(II) acetate or Pd(benzonitrile) 2 Cl 2 ) or platinum(II) complexes (e.g. cis-Pt(py) 2 Cl 2 or {Pt(μ-Cl)Cl(C 2 H 4 )} 2 ) have been studied the most intensively [41,42,[45][46][47][48][49]. In both systems, the fullerene moieties are believed to be bonded to the metal atoms in η 2 fashion to form extended chains.…”

“…The rate of charge transfer through the layer depends on the size of counter ions transport during the film reduction. The conductivity properties of these C 60 /M (M = Pd and Pt) films affect the electron transfer processes of redox-active species dissolved in solution [48,49]. Fig.…”

Comparison of electrochemical properties of two-component C60-Pd polymers formed under electrochemical conditions and by chemical synthesis

“…Recently, we developed an electrochemical procedure for the formation of two-component fullerene films based on the electroreduction carried out in a solution containing fullerene [45][46][47][48][49][50] or fullerene derivatives [51][52][53][54] and various transition metal complexes. In these polymers, fullerene moieties are covalently bonded to transition metal atoms or their complexes to form a polymeric network.…”