Probing 2D materials for sustainable electrocatalysis using X-ray spectroscopies

2维(2D)材料从根本上来说很耐人寻味，因为它们的物理特性不仅会因其组成而变化很大，而且其维度(即层的数量)也会有很大的变化。这种可调性使它们成为晶体管、气体传感器和燃料电池等一系列先进技术和设备的潜在候选者。2D材料的一个潜在的变革性应用是电催化，用于可再生能源可持续合成化学品。铂是最常用的析氢多相电催化剂，但其稀缺性和成本引起了人们对替代材料的浓厚兴趣。二硫化钼(MoS_2)是一种过渡金属二卤化物(TMD)，在理论上表现出与铂相似的吸氢能量，在实验上表现出相同数量级的翻转频率。了解如何调整成本较低的催化剂，如MoS2，以获得与铂族金属相似的性能，将对使电化学合成更具商业可行性产生重大影响。对于简单的金属催化剂，基于d电子的模型在描述催化行为与电子结构密切相关方面非常有效。本项目的目的是通过实验和理论相结合的方法，将这一认识进一步扩展到TMD电催化剂。这将涉及利用化学气相沉积在各种衬底上生产TMD的生长配方的开发。然后，这些材料将通过光电子能谱(UPS/XPS)和X射线吸收光谱(NEXAFS)进行表征，从而允许对价带和导带电子结构进行实验探索。基于从2D材料创建电子透明窗口的高级操作员能力，然后将被用于探测在电化学反应环境中电子结构的变化。D电子模型的适用性将在这些系统上使用量子力学模拟(密度泛函理论)进行测试，以确定不同支撑衬底和TMD表面引入吸附原子时能带结构的变化。这些模拟结果将与能带结构和催化性能的实验测量结果进行比较，然后用于负载型2D材料催化剂的设计。该项目属于EPSRC储能和物理科学研究领域，涉及受控2D材料沉积过程的开发，使用新的操纵面表征方法，以及应用最先进的模拟方法。这将包括使用钻石光源公司现有的X射线技术以及其他国际设施。这些方法将有助于揭示2D材料所获得的催化性能的来源，并为2D材料电催化剂的设计和调整提供理论基础。

2-dimensional (2D) materials are fundamentally intriguing as their physical properties can vary considerably by not just their composition, but also their dimensionality i.e. the number of layers. This tunability makes them promising candidates for a range of advanced technologies and devices such as transistors, gas sensors and fuel cells. A potentially transformative application for 2D materials is in electrocatalysis, for the sustainable synthesis of chemicals from renewable energy sources. Platinum is the most commonly employed heterogeneous electrocatalyst for hydrogen evolution, however its scarcity and cost has triggered intense interest in alternative materials. Molybdenum disulphide (MoS2) is a transition metal dichalcogenide (TMD), which theoretically displays a similar energy for H adsorption as Pt, and experimentally the same order of magnitude turnover frequency. Understanding how lower-cost catalysts such as MoS2 can be tuned to achieve performance similar to platinum group metals would have a significant impact in making electrochemical synthesis more commercially viable.For simple metal catalysts, models based on d-electrons exist have been extremely powerful in describing how catalytic behaviour is intimately linked with electron structure. The aim of this project is to extend this understanding further to TMD electrocatalysts by combining experimental and theoretical approaches. This will involve the development of growth recipes to produce TMDs on a variety of substrates using chemical vapour deposition. These materials will then be characterised by photoemission spectroscopy (UPS/XPS) and X-ray absorption spectroscopy (NEXAFS), allowing both the valence and conduction band electronic structures to be experimentally probed. Advanced operando capabilities based on creating electron transparent windows from 2D materials, will then be used to probe changes to the electronic structure when in the electrochemical reaction environment. The applicability of the d-electron model will be tested on these systems using quantum mechanical simulations (density functional theory), to determine how the band structure changes with different support substrates and with the introduction of adatoms to the TMD surface. These results of these simulations will be compared with experimental measurements of band structure and catalytic performance, and then used to inform the design of supported 2D material catalysts.This project falls within the EPSRC research areas of Energy Storage and Physical Sciences, involving the development of controlled 2D material deposition processes, the use novel operando characterisation methods, and the application of with state-of-the-art simulation methods. This will include the use of X-ray techniques available at Diamond light source, as well as other international facilities. Together these approaches will help reveal the origins of the catalytic performance achieved with 2D materials, and provide a rationale for designing and tuning 2D material electrocatalysts.