Insights on metal nanoclusters (MNCs) (de)hydrogenation for on-board hydrogen storage application using electron microscopy and spectroscopy technique

开发体积效率高的固态氢（H2）储存材料对于运输部门的脱碳至关重要。氢化镁纳米颗粒作为最有前途的储氢材料之一，其优点包括其高的储氢容量（7.6wt.%）成本低（3美元/kg）。然而，缓慢的动力学和高的工作温度（约。250 ℃）限制了其用于机载H2存储的商业应用。为了改善其性能（更高的动力学，更低的温度），该项目将利用金属纳米团簇（MNCs），与更广泛使用的金属纳米颗粒（直径>2 nm）相比，这是根本不同的，其中大多数金属原子仍然“隐藏”在晶格中，并被排除在有用的化学参与之外。相比之下，大多数的原子在MNCs是完全可访问的物理化学过程，而新的功能特性，在散装金属或纳米粒子中无法访问，可以出现作为限制在MNCs的结果。理论计算预测，当使用Mg/MgH 2的NC时，纳米调节可以降低氢化（脱氢化）反应能量，因此降低工作温度[JACS，2005，127，16675-80]。这将大大降低车载氢气储存成本，使其能够用于燃料电池车辆的零排放运输。这是诺丁汉大学和钻石光源的合作项目。具体步骤将涉及（i）合成石墨碳氮化物（g-C3 N4），由于其氮“空腔”，其是用于稳定MNC的理想载体。（诺丁汉），（ii）沉积一系列具有不同大小和组成的跨国公司（即Mg和Pd，以及它们的纳米合金）在g-C3 N4上的反应及其表征：AC-STEM包括化学填图和深度剖面，以及XPS / NAP-XPS在金刚石中的应用。（iii）研究了不同温度下H2环境下MNCs的电子变化（金刚石中的AC-STEM和NAP-XPS），（iv）H2存储性能的评价，包括容量、动力学、热力学和循环测试（在诺丁汉）。

The development of volumetric efficient solid-state hydrogen (H2) storage materials is crucial for decarbonisation in the transport sector. As one of the most promising H2 storage materials, the advantages of magnesium hydride nanoparticles includes their high H2 storage capacity (7.6 wt.%) and low cost ($3/kg). However, slow kinetics and a high working temperature (ca. 250 C) limit its commercial application for on-board H2 storage. In order to improve its properties (higher kinetics, lower temperature), this project will utilise metal nanoclusters (MNCs), which are fundamentally different compared to more widely used metal nanoparticles (diameters >2 nm), where the majority of metal atoms remain 'hidden' within the lattice and are excluded from participation in useful chemistry. In contrast, the majority of the atoms in MNCs are fully accessible for physicochemical processes, while new functional properties, inaccessible in bulk metals or in nanoparticles, can emerge as a result of confinement in MNCs. Theoretical calculations predict that nano-tuning could reduce the (de)hydrogenation reaction energy when NCs of Mg/MgH2 are used, therefore reducing the working temperature [JACS, 2005, 127, 16675-80]. This would substantially reduce the on-board H2 storage cost enabling their use in fuel cell vehicles for zero-emission transport. This is a collaboration project between University of Nottingham and Diamond Light Source. The specific steps will involve (i) synthesis of graphitic carbon nitride (g-C3N4), which is an ideal support for stabilisation of MNCs due to its nitrogen "cavity" (Nottingham), (ii) depositing a series of MNCs with different sizes and composition (i.e. Mg and Pd, and their nano-alloys) on g-C3N4 and their characterisation: AC-STEM including chemical mapping and depth profile, and XPS / NAP-XPS in Diamond, (iii) Investigating the electronic changes on MNCs under H2 environment at different temperatures (AC-STEM and NAP-XPS in Diamond), (iv) evaluation of H2 storage properties including capacity, kinetics, thermodynamics and cycling test (in Nottingham).