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

金属纳米颗粒（NPs）是一种具有广泛应用前景的材料。NPs商业化的有前景的领域包括燃料电池技术、催化、信息存储、传感、光子学和光电子学等。然而，目前采用的生产纳米粒子的合成方案通常不允许对金属纳米粒子成核和生长的关键步骤进行合理控制。纳米粒子聚集的趋势构成了基于金属纳米粒子的器件稳定性能的另一个挑战。减轻纳米粒子聚集的一个明智的策略是使用支撑材料将金属纳米粒子稳定在分散状态。石墨烯及其衍生物，还原氧化石墨烯（rGO），是这种模板的有吸引力的候选者。通过将石墨烯的优势特性与金属纳米粒子的优势特性相结合，在这种纳米复合材料的催化性能中实现了强大的协同效应，即纳米复合材料的性能相对于单个组分而言似乎要优越得多。此外，碳载体的使用减少了催化剂的贵金属含量，同时由于活性表面积的增加而提高了整体催化活性。为了实现金属修饰纳米结构的完全可控、合理设计，需要发展先进的合成技术。一种“理想”的制备方案有望产生均匀尺寸的高质量纳米材料，同时具有良好的可重复性和可扩展性。支撑金属纳米颗粒的制备过程也应避免使用刺激性化学品或高温高压。本课题提出的辐射化学技术满足了这些基本要求。该方法依赖于使用在溶剂辐射分解中形成的活性还原物质，将前体金属离子和氧化石墨烯分别迅速和同时还原为零价金属纳米颗粒和还原氧化石墨烯。所提出的辐射分解方法的主要优点如下：(1)它是在环境条件下进行的基于溶液的一步可扩展合成；(2)金属离子的还原可在多种溶剂中进行；广泛选择在辐射溶解形成的还原自由基；(3)还原自由基在溶液中均匀产生，其形成速度易于操纵。在这项工作中，我们将开发一个新的平台，用于控制碳负载金属纳米颗粒的合成，用于电催化应用。更具体地说，我们将在两种不同的石墨烯基载体和四种不同的溶剂中放射性地合成一系列金和钯纳米颗粒。这项工作将努力弥补在理解前体金属离子与石墨烯基模板之间的络合作用对合成纳米复合材料相关性能的影响方面的差距。我们还将探索用于还原反应的溶剂的辐射化学是否可以用于有效地操纵金属修饰纳米材料的形状和尺寸依赖性质。合成的纳米复合材料的催化效率将通过在碱性条件下将葡萄糖电氧化成葡萄糖酸来筛选。随后，制备的纳米催化剂将在其大小，结构和组成方面进行全面表征。这种精细的分析将使我们能够更好地理解所观察到的“结构-性质”关系，从而为使用辐射化学方法控制纳米材料的设计创造科学基础。

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.