Thick (10 μm) C60 films are prepared by sublimation at 575 °C for 5 min on a pyrolytic carbon film electrode. Scanning electron microscopy shows that the fullerene film consists of crystallites of random size and orientation. Raman spectroscopy shows peaks characteristic of C60 films at 273, 495, 773, 1464, and 1571 cm-1. The electrochemistry of these thick films is consistent with a reduction mechanism that is dominated by ion transport. In the proposed mechanism, swelling of the film and direct intercalation of cations compete as modes of ion transport. During swelling, ferrocene (Fc) diffuses into the C60 film and can be trapped after film reoxidation. When Fc is present, a greater percentage of the film is reduced. The stability of the film with respect to successive redox cycles is also increased.

The stability of pyrolytic carbon film electrodes based on Macor substrates was evaluated. Electrode activity, estimated via cyclic voltammetry of ferricyanide, was virtually unchanged after 120 min in solution (kO = 0.018 cm/s). The response decayed by less than 40% after 20 h in solution. Electrodes were deactivated by air exposure but could be restored to good levels of performance via electrode anodization (to kO = 0.005 cm/s). Other reactivation methods were evaluated. Heat treatment in an Ar atmosphere and an acetone wash were nearly as effective as anodization but were less reliable. Polishing was relatively ineffective.

Pyrolytk carbon fllm electrode8 were fabrkatd by low-temperature (850 "C) pyrolyds of methane onto a machinable

Pyrolytic carbon films were produced at temperatures between 728 and 1100 °C on macor substrates. Scanning electron microscopy Indicated that film morphology varied with temperature and that the most adherent films were obtained at 926 °C. Increases In pyrolysis time resulted In thicker, less adherent films. Rate of charge transfer were determined via cyclic voltammetry for the ferrl/ferrocyanlde redox couple. Films generated at 728 °C exhibited sluggish charge-transfer kinetics. Films fabricated at other temperatures displayed rate constants between 3.8 and 15.4 X 10"* cm/s. Electrode capacitance decreased with Increased pyrolysis temperature. Film formation did not occur on quartz substrates unless pyrolysis temperatures were In excess of 783 °C. Two distinct types of film were formed on quartz, depending on pyrolysis temperature. Rates of charge transfer for both types of film were similar to those obtained for macor-based films, but electrode capacitance was significantly higher for one of the film types. Films obtained on quartz at any temperature were much less adherent than those formed on macor.

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