Exploring the origins of the apparent "electrocatalysis" observed at C60 film-modified electrodes

We have recently revised the oft-cited model of cation insertion into electroreduced C-60 film-modified electrodes in aqueous, basic electrolytes [L. Xiao, G.G. Wildgoose, A. Crossley, R.G. Compton, The electroreduction of "C-60" films in aqueous electrolyte does not lead to alkali metal ion insertion-evidence for the involvement of adventitious poly-epoxidated C-60 (C60On), submitted for publication]. Instead we have proposed that the observed reduction corresponds to adventitious polyepoxidated C60On within the starting material [L. Xiao, G.C. Wildgoose, A. Crossley, R.G. Compton, The electroreduction of "C-60" films in aqueous electrolyte does not lead to alkali metal ion insertion-evidence for the involvement of adventitious poly-epoxidated C-60 (C60On), submitted for publication]. In this paper, we further show, using scanning electron microscopy and cyclic voltammetry of ascorbic acid, how our alternative model can be used to explain both the voltammetry behaviour observed during the reduction of "C60" films in aqueous electrolytes, and how the structure of these films can give rise to misleading claims of apparent "electrocatalytic" behaviour. The latter arises due to restructuring of the deposited C-60 film giving rise to a porous, partially blocked electrode, coupled with possible thin-layer effects. We find no evidence that C-60 itself is reduced within the potential window offered by aqueous electrolytes. nor that it is involved in any form of electron mediation or electrocatalysis. (C) 2009 Elsevier B.V. All rights reserved.