Operando EPR study of automotive catalysts for NOx removal

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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.