Structure / reactivity relationships in N-containing Liquid Organic Hydrogen Carrier (LOHC) systems

在旨在将氢储存在富氢固体或液体中的化学能量储存技术中，液态有机氢载体（LOHC）特别有吸引力，因为它们允许在当今燃料的基础设施中进行氢处理。LOHC系统是储氢介质，其由成对的贫氢的、典型地芳香族或杂芳香族液体（H 0-LOHC）和富氢的、典型地脂环族或杂脂环族液体（Hx-LOHC）组成。H 0-LOHC通过放热催化氢化反应储存氢，而Hx-LOHC通过吸热催化脱氢反应释放氢。到目前为止，考虑用作LOHC系统的分子的选择在很大程度上是由实际和工程考虑驱动的。像“它能大量供应吗？"，“它是否足够健壮？"，“够便宜吗？"，“生态毒性呢？”在很大程度上主导了选拔过程。因此，到目前为止，已经对相对少量的不同分子进行了更详细的研究。显然非常相关的追求“理想的LOHC对”在纯粹的基础科学的理由还没有发生。特别地，现代计算化学与最先进的分析学、表面科学和“真实的”催化研究相结合的潜力迄今为止还没有被应用于发现用于可逆氢化/脱氢循环中的储氢的更好的LOHC分子。在这个项目中，我们的目标是开发和评估含氮LOHC系统的基础上的非均相脱氢反应中使用模型表面和模型基板的结构/反应性关系的基本理解。新分子将根据其特定功能和最有利的热力学和动力学计算进行预筛选。这些特性将与化学稳定性相结合，以允许重复充电和释放循环。目标Hx-LOHC分子将实现例如极低的脱氢温度、氢化/脱氢循环中的高耐久性以及极低的熔点。这将通过适当选择所选分子的官能度和几何形状来实现。因此，以知识为基础的开发具有增强性能的储氢化合物为目标。

Among the chemical energy storage technologies aiming for storing hydrogen in hydrogen-rich solids or liquids, Liquid Organic Hydrogen Carriers (LOHC) are particular appealing as they allow for hydrogen handling in the infrastructure of today’s fuels. LOHC systems are hydrogen storage media, that consist of pairs of hydrogen-lean, typically aromatic or heteroaromatic liquids (H0-LOHC) and hydrogen-rich, typically alicyclic or heteroalicyclic liquids (Hx-LOHC). H0-LOHC stores hydrogen by an exothermic catalytic hydrogenation reaction while Hx-LOHC releases hydrogen by an endothermic catalytic dehydrogenation reaction. So far, the selection of molecules considered for the use as LOHC systems was very much driven by practical and engineering considerations. Questions like “is it available in large quantities?”, “is it robust enough?”, “is it cheap enough?”, “what about ecotoxicity?” have largely dominated the selection process. Consequently, a relatively small number of different molecules have been investigated so far in greater detail. The obviously very relevant quest for “the ideal LOHC pair” on purely fundamental scientific grounds has not been taken place so far. In particular, the potential of modern, computational chemistry in combination with state of the art analytics, surface science and “real” catalytic studies has so far not been applied to find better LOHC molecules for hydrogen storage in reversible hydrogenation/dehydrogenation cycles. In this project, we aim to develop and evaluate nitrogen-containing LOHC systems based on the fundamental understanding of the structure / reactivity relationship in the heterogeneous dehydrogenation reaction using model surfaces and model substrates. The new molecules will be selected based on a pre-screening by computations for their specific functionality and the most favorable thermodynamics and kinetics. These properties will be combined with chemical robustness to allow for repeated charging and release cycles. Target Hx-LOHC molecules will enable, for example, extremely low dehydrogenation temperatures, high durability in hydrogenation / dehydrogenation cycles combined with very low melting points. This will be realized by a proper choice of functionality and geometry of the selected molecules. Thus, a knowledge-based development of hydrogen storage compounds with enhanced performance is targeted.