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

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.

The outcomes from this project are expected to produce a significant societal and economic impact. Societal benefits will be to radiation technology professionals, industrial technologists and general public. Economic benefits will be realised by manufacturers of advanced materials, customers buying innovative products and the overall UK economy.

Potential routes to impact:

Currently, there is a strong interest in using radiation technology for manufacturing of various useful nanomaterials globally. Many industrially developed countries, including the USA, South Korea, Japan, China and France, have supported major research programmes in the field of radiation-driven processes in nanotechnology. It is of critical importance for the UK to keep up with its peers in this promising area. This project will contribute towards filling a currently existing gap in the expertise of the UK Radiation Science &Technology community.

Potential industrial beneficiaries of the proposed project are existing or emerging companies involved in manufacturing of advanced materials, in particular, of supported metal nanoparticles with useful functional properties. The proposed project will help to develop an industrial process that offers improved control over the properties of produced nanocomposites. In other words, the outcome of this research will benefit those manufacturers who are seeking innovative, more efficient ways to produce supported nanomaterials. Within a 5-10 year timescale this research has a potential to benefit numerous industrial users of nanocomposites, which deploy these products to manufacture catalysts, healthcare and household items, electronic devices, sensors, barrier coatings, etc. Analysis of the current landscape of industrial nanotechnology in the UK indicates that the proposed project is timely and meaningful; it has a strong potential to produce an economic impact by engaging numerous UK companies specialising in production of nanomaterials, e.g. Intrisiq Materials Ltd; Nanoco Technologies; Promethean particles; 2D Tech.

By manufacturing nanoscale materials in a controllable manner with an emphasis on scalability, improved particle size distribution and environmental safety this project is expected to benefit the UK industry directly through creation of new products with higher added value and robust global competitiveness. On a 10-15 year timescale the outcomes of this project have a potential to elevate the profitability of the UK manufacturing by improving efficiency of industrial processes, providing cost-savings and generating higher added value products. Radiation technology approach promoted in this proposal will help to create new jobs for highly skilled and innovative engineering staff. General public will benefit from reduced cost and improved quality of consumer items, production of which will be enabled by this technology.

In order to promote the benefits of radiation chemical synthesis of carbon-supported metal nanoparticles and to maximise the impact of the described innovative approach, results of this work need to be effectively communicated to a broad scientific community including radiation technologists, graphene research specialists and catalysis experts. Then, by engaging interested businesses and general public, the impact of proposed study will be maximised. Direct dissemination of research findings in this broad community will facilitate the uptake of proposed method by nanotechnology specialists and, thus, accelerate realisation of long-term impacts of the project discussed above.