The active site behaviour and spontaneous decoration of electrodeposited gold and platinum nanomaterials
Creators: name: PLOWMAN, Blake
Publisher: name: RMIT University
Year: 2024

description: The formation of nanostructured materials is an important field of research in materials science. While attention has been placed on the synthesis of inorganic or carbon-based materials, including carbon nanotubes, graphene and other nanostructures, the fabrication of metallic nanostructures is another key area of study. This research is largely driven by the different properties shown by the metals in their nanostructured form, where altered optical, electronic, catalytic and electrocatalytic behaviour is displayed compared with the bulk metal structure. Since the pioneering work of Haruta and co-workers on the catalytic activity of gold nanoparticles towards carbon monoxide oxidation, the synthesis and behaviour of a range of metallic and metal oxide nanostructures have been intensively studied. This has involved a host of fabrication methods, including chemical, electrochemical and biological methods, as well as physical methods such as evaporation and vapour deposition. Amongst these methods the electrochemical synthesis route provides a facile means to fabricate surface-bound metallic nanostructures with control over the morphology, shape and crystallographic orientation of the deposited material. This method can also avoid the contamination of the surface with capping agents which may alter the behaviour of the nanostructures. <br><br>While much work has been performed on the synthesis, electrochemical behaviour and applications of electrodeposited metallic nanostructures, more research in this field is required to understand the complex nature of these nanomaterials. This includes the effects of the size, shape, crystallographic orientation, composition and porosity of the materials, and so the design of novel nanomaterials with properties tailored towards important applications requires a more complete understanding of these surface properties. Another important property of metal surfaces is the ability to oxidise at potentials lower than that expected for the bulk surface. This activity, known as premonolayer oxidation, has been reported to occur in the double layer region of a number of metal surfaces such as gold, silver, platinum, palladium, copper and ruthenium, and has been postulated to be caused by the oxidation of low lattice coordinated atoms or clusters of atoms on the metal surface known as active sites. The premonolayer oxidation of these active sites is closely related to the electrocatalytic activity towards a range of important electrocatalytic reactions, however due to their often low coverage and complex nature further study is required to better understand and synthesise more effective materials for these applications.<br><br>The aims of this current research are to study the active site behaviour of gold and platinum nanomaterials, as these represent two important electrocatalytically active materials which are known to undergo premonolayer oxidation. As active sites are thought to be located at defects in the bulk surface structure and may be promoted at the disrupted surfaces present on nanostructures, the formation of novel gold and platinum nanostructures was performed as a means to increase the presence of active sites. Electrodeposition was chosen as a means of fabricating these nanostructured materials, especially as uncapped metallic nanostructures may be formed and allow a direct study of the active sites present on the surfaces.