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

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.

This project, which involves major technique development, the fabrication and characterisation of novel carbon electrode materials, and fundamental studies of electron transfer has the potential to deliver major impact on several fronts: (i) novel instruments for nanoscale (electro)chemical imaging will be created which could be used in many areas of research beyond that in the project; (ii) new formats for (electrochemical) sensors, based on the improved understanding of carbon materials, resulting from the programme, are expected. Beneficiaries of (i) include a wide range of industrial sectors. Since its inception in 1992, the Warwick Electrochemistry and Interfaces Group, led by the applicants, has had a strong ethos in ensuring that fundamental discoveries (funded by EPSRC and other agencies) are taken up in industrial programmes. The applicants currently have 7 funded contracts with 6 companies on a wide range of projects, including sensor development, understanding new surface-active formulations, high resolution imaging, fuel cell catalysts, crystal growth and dental processes, with two additional companies as project partners in a sensor development project. In total, the applicants have worked with 12 companies on > 25 funded projects in the past 12 years alone. These projects have utilised science, techniques and know-how developed in EPSRC programmes. We have found colleagues in industry to be receptive to our fundamental technique developments and fully expect the techniques that we will develop in this project to have major applications in other areas. Potential applications include understanding corrosion, electrocatalysts, surface processes - such as dissolution/crystallisation - and life sciences problems (probing cells and organelles). As the project develops we will ensure that commercial end users are aware of our developments, via our network of existing and past collaborators, and new external contacts that we are making through the EPSRC Warwick Centre for Analytical Science, which serves as a hub for analytical instrumentation development. Furthermore, our involvement in the Advantage West Midlands Science City project gives us access to a dedicated business development manager. We typically have approximately 12 - 15 industrial visitors per year to our laboratories and a small number of industrial secondments. These will serve as additional mechanisms to ensure that end-users are aware of, and can make use of, our research. During the course of the project we will also consider ways to license our instrumentation developments. At the end of the project, for example, we would have a unique instrument capable of SECM, SICM and SNCM imaging, which could be attractive to industrial and academic users. Industrialists will be able to take part in the workshop we will run. The fundamental understanding gained of the various carbon materials will be beneficial in designing formats for new electrochemical sensors that would greatly enhance the detection limits compared to conventional electrodes. In this area, we would seek to protect IP and know-how, consider licensing or the formation of a spin-out company and enter into discussions with sensor companies in the water quality and diagnostics markets about adopting new carbon materials for sensor applications. Again, we have a track record of ensuring that we deliver impact in this regard: our recent work on carbon (SWNTs and diamond) electrodes has resulted in 5 patent applications and the commisioning of a business development report to identify how to take this forward. Imaging, nanoscience and new forms of carbon are highly visual and potentially exciting topics to convey to school children. Warwick Chemistry has an active outreach progarmme (engaging with 3,500 children in the past year alone) and we plan to devise activities based on the project for use in outreach/engagement activities.