Expanding the Environmental Frontiers of Operando Metrology for Advanced Device Materials Development

开尔文勋爵有一句名言：“当你无法衡量它，当你无法用数字来表达它时，你的知识就是一种贫乏和令人不满意的知识”。对于今天的纳米技术来说，这一点最正确。新兴材料，如2D过渡金属二卤化物(TMD)化合物，提供了从新型(光电)电子器件到能量存储和催化能量转换的令人兴奋的广泛机会。对于后者，像MoS2这样的TMDS材料已经显示出高催化活性，并作为富含地球的电催化剂提供了巨大的潜力，例如将废弃的二氧化碳转化为与工业相关的化学品/燃料和可持续地生产氢气，这些过程对于可持续、清洁的未来经济具有极其重要的战略意义。然而，TMD催化剂在反应过程中会发生显著的化学和结构变化，其高催化活性的机理在很大程度上仍不清楚。我们目前在材料合成方面的知识同样贫乏。人们对TMD实际上是如何生长的，以及这些材料的结构和性能如何进行可伸缩控制知之甚少。这些挑战和缺乏理解是许多新兴材料的共同之处。这其中的一个关键原因是，它们通常只能在“死后”阶段得到解决和充分表征，而我们只能猜测在与工业相关的“真实世界”条件下，究竟是什么机制控制着生长或材料的功能。这项提议旨在对TMD等新型材料在高温下与工业相关的反应气氛中进行真实的操作表征，通过对其设计和功能的基本了解，对其未来的使用产生革命性的影响。我们的重点将放在电子显微镜和光谱学上，特别是扫描电子显微镜和X射线光电子能谱，它们是现代科学中最广泛和最通用的表征技术之一，在学术界和工业界的所有学科中都被使用。它们具有很高的(近)表面敏感性，使它们成为分析表面和界面的结构和化学成分的强大工具。然而，低能电子也会被气体分子强烈散射，因此所有这些技术都是在高真空或有限的环境条件下进行的。我们提出了新的环境单元方法，可以灵活地实施许多基于电子的技术来克服这些限制，并能够在温度高达1000摄氏度和在活性气体或液体环境中以高空间和/或化学分辨率在前所未有的工业相关工艺条件下进行直接表征。该提议建立在曼彻斯特、剑桥和钻石光源/哈威尔最近的战略设备投资的基础上，与市场领先的工业合作伙伴一起，我们的愿景是开创多功能方法，开辟适用于有机半导体、电池/能源研究、催化和生命科学等广泛领域的新的相关、多模式操作探测能力。这也将与模拟和理论联系起来，以达到新的理解水平和预测能力。将这种能力应用于TMD材料，将使我们能够直接询问TMD在工业相关反应堆条件下的成核和生长，以开发新的制造工艺，包括迄今基本上未探索的金属化合物。这将进一步使我们首次系统地研究反应条件下的模型TMD催化剂。特别是，我们建议探索像NbS_2这样的金属TMD，因为与半导体MoS_2不同，它们的催化活性可以延伸到整个基面，为设计低过电位和高电流密度的新型电催化剂开辟了新的方向。

Lord Kelvin famously stated "when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind". This holds none more true than for nanotechnology today. Emergent materials such as 2D transition metal dichalcogenide (TMD) compounds offer exciting, wide opportunities from novel (opto-) electronic devices to energy storage and catalytic energy conversion. For the latter, TMDs materials like MoS2 have shown high catalytic activity and offer large potential as earth abundant electro-catalysts to for instance convert waste CO2 into industrially relevant chemicals/fuels and to generate hydrogen sustainably, i.e. processes of utmost significance as strategies for a sustainable, clean future economy. However, TMD catalysts can undergo significant chemical and structural changes during reactions, and the mechanisms that give the high catalytic activity remain largely unknown. Our knowledge is currently equally meagre in terms of materials synthesis. There is very little understanding how TMDs actually grow and hence how the structure and properties of these materials can be scalably controlled. These challenges and lack of understanding are common to numerous emerging materials. One key reason for this is that they typically can only be resolved and adequately characterised at a "post-mortem" stage, and we are left to speculate what mechanisms actually govern growth or material functionality at industrially relevant "real-world" conditions.This proposal aims at true operando characterisation of novel materials like TMDs under industrially relevant reactive atmospheres at elevated temperatures, to have a transformative impact on their future use by developing a fundamental understanding of their design and functionality. Our focus will be on electron microscopy and spectroscopy, in particular scanning electron microscopy and X-ray photoelectron spectroscopy, which are among the most wide-spread and versatile characterisation techniques in modern science, used across all disciplines in academia and industry. They are endowed with high (near-)surface sensitivity, making them powerful tools for analysing the structure and chemistry of surfaces and interfaces. However, low-energy electrons are also strongly scattered by gas molecules, and therefore all these techniques are conventionally performed under high vacuum or restricted environmental conditions. We propose new environmental cell approaches that can be flexibly implemented for the many electron-based techniques to overcome these restrictions, and enable direct characterisation at high spatial and/or chemical resolution across an unprecedented range of industrially relevant process conditions for temperatures as high as 1000C and in reactive gaseous or liquid environments. The proposal builds on recent strategic equipment investment at Manchester, Cambridge and the Diamond Light Source/Harwell, and together with market-leading industrial partners our vision is to pioneer versatile approaches that open up new correlative, multi-modal operando probing capability applicable to a wide range of fields including organic semiconductors, battery/energy research, catalysis and life sciences. This will also link to simulation and theory to achieve new levels of understanding and predictive power. Applied to TMD materials, this capability will allow us to directly interrogate TMD nucleation and growth at industrially relevant reactor conditions, to develop new manufacturing processes including for so far largely unexplored metallic compounds. This will further allow us for the first time to systematically study model TMD catalysts under reaction conditions. In particular, we propose to explore metallic TMDs like NbS2, as unlike to semiconducting MoS2, their catalytic activity could extend over the entire basal plane, opening new directions to design novel electro-catalysts with low overpotential and high current densities.