Development of a bespoke sample environment for operando neutron diffraction studies of chemical looping materials and processes.

纽卡斯尔大学的MatCoRE团队在推进化学循环（CL）工艺方面拥有丰富的专业知识，可用于多种应用，包括水煤气变换（WGS）反应制氢。化学发光的核心概念是将目标反应分解为两个或多个独立的反应，这些反应由中间材料促进。这确保了反应物永远不会直接混合，因此产品不需要分离，从而提高了整个过程的效率。任何CL过程的成功都高度依赖于所使用的中间材料的性质。对于WGS反应和其他氧化过程，如化学链燃烧（CLC），所使用的材料被称为氧载体材料（OCM），它允许氧在反应物之间间接转移，从而形成产物。具有钙钛矿（ABO 3-o）结构的非化学计量氧化物是目前大多数开发工作的重点，因为它们能够在保持结构完整性的同时经历连续的氧化还原循环。为了评估这些材料的CL工艺，了解材料在还原和氧化过程中晶体结构如何变化并将这些变化与氧含量和非化学计量程度（0）联系起来至关重要。梅特卡夫小组最近使用同步辐射X射线衍射（XRD）实现了这一点。然而，中子衍射可以提供显着的优势，相对于XRD的这些结构的说明，主要是由于较高的灵敏度氧原子。该项目旨在设计，建造和调试一个样品环境，将允许一个工作的CL反应堆进行监测operando中子衍射。目前，在ISIS和其他地方有实验能力在高温下和还原性和氧化性气体环境下进行原位中子衍射，因此可以模拟CL条件。然而，目前还没有现有的样品环境，将允许一个工作的CL反应堆进行实时探测中子衍射。特别地，将反应堆床的离散部分定位到中子束中并在操作期间获得结构轮廓的能力目前是不可能的。该项目旨在弥合这一方法上的差距，并推进我们对使用中子衍射的OCM的理解，从而能够开发用于CL的上级材料。据设想，样品环境将有利于未来研究流动系统和催化在ISIS的团体，因此将在设计时考虑到操作的灵活性。

The MatCoRE group at Newcastle University has significant expertise in the advancement of chemical looping (CL) processes for a number of applications, including hydrogen production from the water-gas-shift (WGS) reaction. The central concept of CL is to split a target reaction into two or more separate reactions which are facilitated by an intermediate material. This ensures that reactants are never directly mixed and so products do not require separation, therefore improving the efficiency of the overall process.The success of any CL process is highly dependent on the nature of the intermediate material used. For the WGS reaction, and other oxidation processes such as chemical looping combustion (CLC), the material used is termed an oxygen carrier material (OCM) and it allows oxygen to be indirectly transferred between the reactants leading to formation of the products. Non-stoichiometric oxides with the perovskite (ABO3-o) structure are the current focus of most development work due to their ability to undergo successive redox cycles while maintaining structural integrity.In order to evaluate these materials for CL processes it is paramount to understand how the crystal structure changes during reduction and oxidation of the material and relate these changes to oxygen content and degree of non-stoichiometry (0). The Metcalfe group have recently achieved this using operando synchrotron X-ray diffraction (XRD). However, neutron diffraction can offer significant advantages versus XRD for the elucidation of these structures, primarily due to a higher sensitivity to oxygen atoms. This project aims to design, construct and commission a sample environment that will allow a working CL reactor to be monitored operando by neutron diffraction. At present, there is experimental capability at ISIS and elsewhere to perform in situ neutron diffraction at high temperatures and under reducing and oxidising gas environments, therefore allowing CL conditions to be mimicked. However, there is currently no existing sample environment that would allow a working CL reactor to be probed in real-time by neutron diffraction. In particular, the ability to position discrete sections of the reactor bed into the neutron beam and obtain a structural profile during operation is not currently possible. This project aims to bridge this gap in methodology and advance our understanding of OCMs using neutron diffraction, enabling the development of superior materials for CL. It is envisaged that the sample environment will be beneficial to future groups studying flow systems and catalysis at ISIS and will therefore be designed with operational flexibility in mind.