The synthesis and characterisation of single-walled carbon nanotubes and graphene for electrochemical applications

In recent years sp2 carbon materials, including single-walled carbon nanotubes (SWNT) and graphene have attracted significant attention, especially in the field of electrochemistry. However there is a marked disparity of opinion concerning the fundamental inherent electron transfer (ET) properties of these materials, largely due to complications regarding their synthesis, characterisation and the methods utilised to measure their electrochemical characteristics. As shown in this thesis, catalysed chemical vapour deposition (cCVD) allows the growth of very high quality SWNT directly onto insulating substrates and so it is considered by many to be the ideal method to produce SWNT for fundamental studies and applications. However, graphene must be transferred post cCVD growth to insulating substrates, as it grows on metal foil catalysts and this process is currently associated with issues with contamination and mechanical damage. In this thesis SWNTs with both 2D and 3D geometries are investigated using micro- or nano- scale capillary electrochemical methods. By using outer sphere redox mediators and by isolating the SWNT sidewalls and end-caps it is shown that ET at SWNTs is both fast and occurs on both pristine sidewalls and closed ends. This opposes the commonly held view that ET only happens at open ends and defects. Then, it is shown that functionality can be introduced into pristine SWNTs either by platinum nanoparticle (NP) electrodeposition or anodic pre-treatment. These activated SWNTs are shown to display improved ET to a range of complex and inner sphere redox reactions, including becoming electrocatalytic for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR). Also in this thesis a method of performing generation/collection (G/C) electrochemical measurements within the meniscus of a microcapillary is demonstrated. This system is shown to be effective at both investigating processes on complex electrode surfaces and at investigating the mechanistic aspects of the ORR.