Evidence for Nucleation-Growth, Redistribution, and Dissolution Mechanisms during the Course of Redox Cycling Experiments on the C₆₀/NBu₄C₆₀ Solid-State Redox System:  Voltammetric, SEM, and in Situ AFM Studies

Abstract

The electrochemical reduction of solid C 60 abrasively attached in the form of microcrystals to graphite and glassy carbon electrode surfaces and then immersed in acetonitrile containing 0.1 M NBu 4 PF 6 or NBu 4 ClO 4 as the electrolyte has been studied. Voltammetric responses observed after the initial stages of redox cycling experiments, when redistribution processes occur, are consistent with those observed previously for so-called "film" deposits. The characteristic "steady-state" shape of the solid-state voltammetric response with a large potential gap between reduction and reoxidation responses is shown by chronoamperometric experiments to be associated with the presence of a nucleation and growth-type mechanism. The initial three reduction processes of C 60 attached to the electrode surface, which lead to the chemically reversible formation of only slightly soluble C 60 -and C 60 2-and finally to the loss of the soluble C 60 3-have been followed by ex situ SEM and in situ AFM experiments. The extent of the electrochemical conversion is shown to depend strongly on the crystal size, with larger crystals being affected only at the solid-liquid interfacial region. Evidence for stochastic processes further supports the proposed nucleation and growth-type mechanism. Crystal redistribution processes also are identified by the AFM measurements.

Discrete Fulleride Anions and Fullerenium Cations

“…In another development, solid-to-solid electrochemistry of C 60 to produce a Bu 4 N + fulleride has been shown to give a microcrystalline phase as opposed to a film. 191 …”

Electroanalytical chemistry for the analysis of solids: Characterization and classification (IUPAC Technical Report)

“…Additionally, SSEAC methods provide information on the reactivity of solid compounds, both from a thermodynamic as well as from a kinetic point of view. Available examples include nucleation, growth, redistribution, and dissolution processes in fullerenes [165] and metal-organic frameworks [159,160], electrochemical lattice reconstruction in hexacyanometallates [166], electron self-exchange in the solid state [167], and formation of solid inclusion complexes [168].…”

The role of dissolution in the voltammetry of microdroplets and microparticles adhered to electrode surfaces in contact with aqueous electrolytes or ionic liquids

“…5(a)). When the voltammetric studies are undertaken with a TCNQ-modified electrode in contact with aqueous (0.1 M KPF 6 ) electrolyte, the characteristics of the voltammograms obtained under these conditions have been attributed to nucleation-growth mechanisms [3,4]. The reaction scheme relevant to this process is shown in the following equation: …”

“…For example, under conditions of cyclic voltammetry, a large separation between the oxidation and reduction peaks [2] may be explained by a nucleation and crystal growth mechanism [3,4], whereas thin film type behaviour tends to produce broader peaks, with smaller peak separations [1]. However, in principle, the voltammetry of adhered films or solid microparticles may be accompanied by dissolution processes.…”