Investigation into radiolytic preparation of graphene-noble metal nanocomposites with electrocatalytic properties

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Metal nanoparticles (NPs) are highly attractive materials for a wide range of applications. Promising fields for NPs commercialisation include fuel cell technology, catalysis, information storage, sensing, photonics and optoelectronics, among many others. However, currently adopted synthetic protocols for production of NPs generally don't allow for the rational control over critical steps of the nucleation and growth of metal nanoparticles. The tendency of NPs to aggregate constitutes another challenge for stable performance of devices based on metal nanoparticles.A sensible strategy to mitigate the aggregation of NPs is to use supporting materials to stabilise metal nanoparticles in a dispersed state. Graphene and its derivative, reduced graphene oxide (rGO), are appealing candidates for such templates. By combining the advantageous properties of graphene with those of metal NPs a powerful synergistic effect in catalytic performance of such nanocomposites is achieved, i.e. the nanocomposite performance appears to be far superior with respect to the individual components. Furthermore, the usage of a carbon support reduces noble metal content of the catalyst while enhancing overall catalytic activity due to the increased active surface area.In order to achieve fully controlled, rational design of metal-decorated nanostructures, advanced synthesis techniques need to be developed. An "ideal" preparation protocol is expected to yield high quality nanomaterials in uniform size, while possessing excellent reproducibility and scalability. Preparation procedure of supported metal nanoparticles shall also avoid the use of harsh chemicals or high temperatures and pressures. The radiation chemical technique proposed in this project meets these essential requirements. The method relies on the use of active reducing species formed in the radiolysis of solvents for prompt and simultaneous reduction of precursor metal ions and GO into zero-valent metal nanoparticles and rGO, respectively. The main advantages of the proposed radiolytic approach are the following: (1) it is a solution-based, one-step, scalable synthesis conducted at ambient conditions; (2) reduction of metal ions can be done in a variety of solvents; wide selection of reducing radicals formed upon radiolysis is available; (3) reducing radicals are produced uniformly in solution, and the rate of their formation can be easily manipulated.In this work, we are going to develop of a new platform for a controlled synthesis of carbon-supported metal nanoparticles, for electrocatalysis applications. More specifically, we will radiolytically synthesise a series of gold and palladium nanoparticles on two different graphene-based supports and in four different solvents. This work will endeavor to close the gap in understanding of the effect of complexation between precursor metal ions and graphene-based templates on the relevant properties of synthesised nanocomposites. We will also explore whether the radiation chemistry of a solvent, deployed for the reduction reaction, can be used to effectively manipulate the shape and size-dependent properties of the metal-decorated nanomaterials. The catalytic efficiency of the synthesised nanocomposites will be screened by performing the electrooxidation of glucose into gluconic acid in alkaline conditions. Subsequently, prepared nanocatalysts will be fully characterised in terms of their size, structure and composition. Such elaborate analysis will allow us to gain a better understanding of observed "structure-property" relationships, thus creating the scientific basis for a controlled design of nanomaterials using radiation chemical approach.