Hu Wenshuo, Selleri Tommaso, Gramigni Federica, Fenes Endre, Rout Kumar R, Liu Shaojun, Nova Isabella, Chen De, Gao Xiang, Tronconi Enrico
State Key Laboratory of Clean Energy Utilization, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, China.
Laboratory of Catalysis and Catalytic Processes, Dipartimento di Energia, Politecnico di Milano, Via La Masa 34, 20156, Milano, Italy.
Angew Chem Int Ed Engl. 2021 Mar 22;60(13):7197-7204. doi: 10.1002/anie.202014926. Epub 2021 Feb 18.
Cu-CHA is the state-of-the-art catalyst for the Selective Catalytic Reduction (SCR) of NOx in vehicle applications. Although extensively studied, diverse mechanistic proposals still stand in terms of the nature of active Cu-ions and reaction pathways in SCR working conditions. Herein we address the redox mechanism underlying Low-Temperature (LT) SCR on Cu-CHA by an integration of chemical-trapping techniques, transient-response methods, operando UV/Vis-NIR spectroscopy with modelling tools based on transient kinetic analysis and density functional theory calculations. We show that the rates of the Reduction Half-Cycle (RHC) of LT-SCR display a quadratic dependence on Cu , thus questioning mechanisms based on isolated Cu -ions. We propose, instead, a Cu -pair mediated LT-RHC pathway, in which NO oxidative activation to mobile nitrite-precursor intermediates accounts for Cu reduction. These results highlight the role of dinuclear Cu complexes not only in the oxidation part of LT-SCR, but also in the RHC reaction cascade.
Cu-CHA是车辆应用中用于氮氧化物选择性催化还原（SCR）的最先进催化剂。尽管已进行了广泛研究，但就SCR工作条件下活性铜离子的性质和反应途径而言，仍存在多种机理假设。在此，我们通过整合化学捕获技术、瞬态响应方法、原位紫外/可见-近红外光谱以及基于瞬态动力学分析和密度泛函理论计算的建模工具，来探讨Cu-CHA上低温（LT）SCR的氧化还原机理。我们表明，LT-SCR还原半周期（RHC）的速率对Cu呈二次依赖性，从而对基于孤立Cu离子的机理提出质疑。相反，我们提出了一种由Cu对介导的LT-RHC途径，其中NO氧化活化为可移动的亚硝酸盐前体中间体导致Cu还原。这些结果突出了双核铜配合物不仅在LT-SCR的氧化部分，而且在RHC反应级联中的作用。
