The hydrothermal stability of Cu/SSZ-13 SCR catalysts has been extensively studied, yet atomic-level understanding of changes to the zeolite support and the Cu active sites during hydrothermal aging are still lacking. In this work, via the utilization of spectroscopic methods including solid-state ²⁷Al and ²⁹Si NMR, EPR, DRIFTS, and XPS, together with imaging and elemental mapping using STEM, detailed kinetic analyses, and theoretical calculations with DFT, various Cu species, including two types of isolated active sites and CuO_x clusters, were precisely quantified for samples hydrothermally aged under varying conditions. This quantification convincingly confirms the exceptional hydrothermal stability of isolated Cu²⁺-2Z sites and the gradual conversion of [Cu(OH)]⁺-Z to CuO_x clusters with increasing aging severity. This stability difference is rationalized from the hydrolysis activation barrier difference between the two isolated sites via DFT. Discussions are provided on the nature of the CuO_x clusters and their possible detrimental roles on catalyst stability. Finally, a few rational design principles for Cu/SSZ-13 are derived rigorously from the atomic-level understanding of this catalyst obtained here.

中文翻译：

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Cu / SSZ-13选择性催化还原催化剂的合理设计：对水热稳定性的原子水平理解

已经对Cu / SSZ-13 SCR催化剂的水热稳定性进行了广泛的研究，但是仍然缺乏原子级对水热老化过程中沸石载体和Cu活性位点变化的理解。在这项工作中，通过利用包括固态²⁷ Al和²⁹ Si NMR，EPR，DRIFTS和XPS在内的光谱方法，以及使用STEM进行成像和元素映射，详细的动力学分析以及DFT和各种Cu种类的理论计算包括两种类型的分离的活性位点和CuO _x团簇，可以在不同条件下经过水热老化的样品中精确定量。该定量令人信服地证实了分离出的Cu ²⁺具有出色的水热稳定性。-2Z位点和[Cu（OH）] ⁺ -Z逐渐转化为CuO _x团簇，其时效程度越来越高。从两个分离的位点之间通过DFT产生的水解活化势垒差异可以合理化这种稳定性差异。讨论了CuO _x团簇的性质及其对催化剂稳定性的可能有害作用。最后，从此处获得的这种催化剂的原子级理解上，严格得出了Cu / SSZ-13的一些合理设计原理。