Operando EPR study of automotive catalysts for NOx removal

选择性催化还原(SCR)是每一辆柴油车都在使用的一种减少有害NOx气体排放的反应。欧盟6排放标准要求使用高效和选择性的SCR催化剂，将NOx排放降至0.080毫克/公里以下。尽管商用车用SCR催化剂已经使用了十年，但实际的活性中心和反应机理仍不清楚，也存在争议。操作光谱学是一种将反应材料的光谱表征与催化活性和选择性的测量相结合的方法，可以探测活性中心的行为，并帮助理解活性中心的行为。本研究旨在应用OPANDO电子顺磁共振(EPR)技术来研究和了解Cu2+在SCR中的活性中心。在这项研究计划中将开发的Operando EPR设施将是世界上为数不多的，在英国也是独一无二的。它可以直接探测活性中心，定量测量氧化态和配位环境的状态/变化，同时记录反应动力学。通过这种方法，将建立催化剂的结构-活性关系。这样的设施不仅对催化很重要，而且对英国的材料发现也至关重要。该项目的成功与OPANDO X射线吸收光谱分析(XAS)和红外光谱(IR)相结合，将提供对反应的基本了解，并有助于开发更具选择性的SCR催化剂。希望通过与其他光谱技术的结合，深入了解许多工业上重要反应的催化机理，从而优化未来催化剂的设计和开发。

Selective catalytic reduction (SCR) is a reaction that used in every diesel vehicle to reduce the emission of harmful NOx gas. The EU 6 emission standard calls for efficient and selective SCR catalysts that reduce the NOx emission to less than 0.080 mg/km. Though commercial catalysts for vehicle SCR have been used for a decade, the actual active site and the reaction mechanism are still not understood and under debate. Operando spectroscopy, a methodology wherein the spectroscopic characterization of materials undergoing reaction is coupled simultaneously with measurement of catalytic activity and selectivity, can probe the active site behaviours and help understand the active site behaviours. This research program aims to apply operando Electron Paramagnetic Resonance (EPR) technique in order to study and understand the Cu2+ active site for SCR. The operando EPR facility that will be developed in this research program will be one of few around world and unique in the UK. It directly probes the active sites and can quantitatively measure the status/changes of the oxidation state and coordination environment, while recording the reaction kinetics simultaneously. In this way, a structure-activity relationship of the catalysts will be established. Such facility will not only be important for catalysis, but also crucial for materials discovery in the UK. Together with operando X-ray absorption spectroscopy (XAS) and IR, the success of this program will provide fundamental understanding of the reaction and help develop more selective SCR catalysts. It is expected that operando EPR, together with other operando spectroscopies, will provide deep understanding of catalysis mechanisms in many industrially important reactions, and thus optimize the design and development of future catalysts.