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Electrochemical formation and properties of two-component films of transition metal complexes and C60 or C70

Research paper by Emilia Grodzka, Joanna Grabowska, Monika Wysocka-Żołopa, Krzysztof Winkler

Indexed on: 08 Jan '08Published on: 08 Jan '08Published in: Journal of Solid State Electrochemistry



Abstract

The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes, C60 or C70, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes, yields of formation of films containing C70 are higher than yields of electrodeposition of their C60 analogs. C70/M films also exhibit higher porosity in comparison to C60/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical responses of these films in acetonitrile containing supporting electrolyte only. C70/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C60/Pd and C70/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte. The C70/Pd film exhibits much better capacitance performance comparison to C60/Pd polymer.