Uncovering the Electroactivity of Novel sp2 Carbon Materials through Quantitative High Resolution Visualisation

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Electrochemistry is a key enabling science of the 21st century, underpinning important topics and technologies such as energy (conversion and storage), catalysis/electrocatalysis, and sensing (chemical and biochemical). All of these applications demand new electrode materials which can outperform existing technologies and offer environmental benefits. In this context, carbon is very attractive: while (precious) metals have to be mined and processed (with high energy costs), carbon materials can be grown from carbon-containing gases quickly, cheaply and efficiently. The recent emergence of new forms of carbon, in particular, graphene (a one-atom-thick planar sheet of sp2 carbon atoms in a honeycomb arrangement) and single-walled carbon nanotubes (SWNTs), which may be viewed as graphene rolled into tubes with a diameter on the nanometer (one-billionth of a meter) scale, presents an exciting opportunity for electrochemistry. SWNTs have displayed astonishing properties for electrochemical (current-sensing) detection, and it is anticipated that graphene will offer even better prospects for electroanalysis and electrocatalysis. Both materials constitute particularly interesting platforms for the assembly of catalysts (metal, semiconductor, enzymes, cells, etc.) and could find application as transparent electrodes in solar cells. These applications, and many others, require that the fundamental aspects of charge transfer (current flow) between carbon electrodes and molecules in solution is understood. This poses a major experimental challenge. While having long-range order, sp2 carbon materials (graphene, graphite and SWNTs) possess surface features (defects and/or steps); the extent to which these, rather than the basal surface, contribute to the overall activity is a major open question and a matter of considerable debate and importance.This proposal will take on the challenge of elucidating, for the first time, the true activity of sp2 carbon materials through the development and application of the highest spatial-resolution electrochemical imaging techniques ever. These techniques will be able to measure electrochemical activity across a surface on a scale which has not been possible hitherto. The techniques are based on the 'scanned probe' concept in which a nanoscale-probe is moved across a surface; in this case, it will measure the electrochemical activity in minute detail and relate it to the underlying surface properties (structural and electrical), via the use of complementary microscopy methods. We expect to obtain definitive proof of the origin of the activity of related sp2 carbon materials and to determine whether charge transfer is driven only at defects. Answering this question for a wide range of important electrochemical processes is vital for the advancement of the field and will reveal the best strategies for the future development of sp2 carbon-based electrochemical technologies.The uncertainty surrounding the active sites on solid electrodes is widespread and of a general nature, and we fully expect the techniques proposed to be applied extensively in electrochemistry and materials science, where one seeks to understand surface reactivity. Downstream applications of the techniques could include understanding corrosion and supported fuel cell catalysts. Ultimately, the techniques could find considerable use in the life sciences, including probing living systems and organelles, where one would be able to measure chemical fluxes on a minute scale. This proposal is therefore of fundamental importance to the basic understanding of new materials, as well as more broadly to electrochemistry and surface reactivity. It will lead to new methods of sensing and electrochemical transformations, and will provide scientists with novel high resolution techniques with far-reaching multidisciplinary impact.