Electrochemical Oxidation of Low Molecular Weight Alkanes to Liquid Fuels at Molecular Interfaces

低分子量烷烃（LMWA）在低温和低压下部分氧化生成相应的醇被认为是催化和能源领域的重大挑战之一。甲烷的大规模开采涉及能源密集型加工，如蒸汽和二氧化碳重整，以及从开采现场运输的液化。考虑到包括英国在内的世界各地分布着大量的天然气，以及当地由原料产生的甲烷，开发低成本/能源的甲烷催化转化为易于运输的液体燃料（而不是液化）是一个令人信服的案例。在这种情况下，电化学方法为甲烷的部分氧化提供了一种极具吸引力的方法，不仅在可扩展性方面，而且由于这种技术固有的低碳足迹。原则上，界面过程所需的过电位可以通过(i)催化剂的直接光激发或（ii）电化学反应器与光伏器件的耦合来产生。然而，迄今为止，还没有设计出可行的电化学方法来氧化烷烃。本项目与传统的催化方法不同，结合了多相催化、光催化和纳米级电催化的元素。甲烷的复杂氧化是这个项目的关键，它将在水和不混溶的有机溶液的界面上被激活，在这个界面上，伽伐尼电位差可以从外部调节。这种方法的基本原理是最大化高效纳米结构电催化剂、有机相中积累的LMWA和作为OH自由基来源的水之间的反应横截面。界面电位差不仅在改变氧化的驱动力方面起着重要的作用，而且在氧化物和碳基纳米结构支撑的高活性催化中心的组装中也起着重要的作用。二氧化钛等胶体氧化物载体在此过程中可以发挥多种作用，包括：促进表面OH基团与活性中心的相互作用，在紫外线照射下产生高活性OH自由基，避免金属活性中心的不可逆聚集/凝固。在碳纳米管和石墨烯的情况下，这些支撑也将增强电催化活性纳米中心的稳定性，并提取在甲烷氧化过程中积累在纳米结构上的电子。在液/液界面的恒电位控制下，电化学和光电化学技术将监测界面过程的动力学。此外，产品和中间体的生成将通过各种原位和非原位技术（如拉曼光谱和色谱方法）进行研究。由于甲烷的天然丰度，它是一个关键的目标，但由于其低反应性，被认为是一个特别的挑战。因此，该方法也将被扩展到其他低分子量wa的电氧化，如乙烷、丙烷和丁烷。该项目将侧重于两个关键目标：1。建立了甲烷和其他低分子量水分子在极化液/液界面上电化学/光电氧化生成相应醇的物理原理。分子界面上与能量相关的多电子转移反应的新方法和催化剂。

The partial oxidation of low molecular weight alkanes (LMWA), to their corresponding alcohols, at low temperature and pressure is considered to be one of the grand challenges in the area of catalysis and energy. Large scale exploitation of methane involves energy intensive processing, such as steam and carbon dioxide reforming, as well as liquefaction for transport from the extraction field. Considering the vast amount of natural gas distributed around the world, including the UK, in addition to local methane produced by feedstock, there is a compelling case to develop low cost/energy catalytic conversion of methane to easily transportable liquid fuels (rather than liquefaction). In this context, electrochemical methods provide an extremely attractive approach to the partial oxidation of methane, not only in terms of scalability, but also due to the inherent low carbon footprint of such technology. In principle, the required overpotential for the interfacial process can be generated by (i) direct photoexcitation of the catalyst or by (ii) coupling electrochemical reactors to photovoltaic devices. However, to date, no viable electrochemical method has been designed for alkane oxidation. This project departs from all conventional catalytic approaches, in order to combine elements of heterogeneous catalysis, photocatalysis and nanoscale electrocatalysis. The complex oxidation of methane, the key LMWA in this project, will be activated at the interface between an aqueous and an immiscible organic solution, at which the Galvani potential difference can be tuned externally. The rationale behind this approach is to maximise the reaction cross-section between high performing nanostructured electrocatalysts, LMWA accumulated in the organic phase and water as a source of OH radicals. The interfacial potential difference can play an important role, not only in changing the driving force for the oxidation, but also in the assembly of highly reactive catalytic centres supported on oxides and carbon based-nanostructures. Colloidal oxide supports such as TiO2 can play multiple roles in the process, including: promoting the interaction between surface OH groups and the active centres, generating highly active OH radicals upon UV-illumination and avoiding irreversible aggregation/coagulation of the metallic active centres. In the case of carbon nanotubes and graphene, these supports will also enhance the stability of the electrocatalytically active nanocentres, as well as extracting electrons accumulated at the nanostructures during methane oxidation. The dynamics of the interfacial processes will be monitored by electrochemical and photoelectrochemical techniques, under potentiostatic control of the liquid/liquid interface. Furthermore, the generation of products and intermediates will be investigated by a variety of in-situ and ex-situ techniques such as Raman spectroscopy and chromatographic methods. Methane is a key target due to its natural abundance, but is recognised to be a particular challenge due to its low reactivity. Consequently the approach will also be broadened to span the electro-oxidation of other LMWA such as ethane, propane and butane. The project will focus on two key goals:i. Establishing the physical principles underlying the electrochemical / photoelectrochemical oxidation of methane and other LMWA to the corresponding alcohols at polarisable liquid/liquid junctionsii. Novel approaches and catalysts for multi-electron transfer reactions of relevance to the energy sector at molecular interfaces.