Unraveling the Hydrolysis of Z2Cu2+ to ZCu2+(OH)- and Its Consequences for the Low-Temperature Selective Catalytic Reduction of NO on Cu-CHA Catalysts
Unraveling the Hydrolysis of Z2Cu2+ to ZCu2+(OH)- and Its Consequences for the Low-Temperature Selective Catalytic Reduction of NO on Cu-CHA Catalysts
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DOI：
10.1021/acscatal.1c02761
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发表时间：
2021-09-03
期刊：
影响因子：
12.9
通讯作者：
Tronconi, Enrico
中科院分区：
文献类型：
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作者：
Hu, Wenshuo;Iacobone, Umberto;Tronconi, Enrico
作为最先进的选择性催化还原（SCR）NOx 催化剂，Cu-CHA 在实用和基础方面都得到了广泛的研究。其中，SCR活性位点Z(2)Cu(2+)如何参与低温（LT）SCR反应仍存在争议。在这里，我们提出了一种涉及Z(2)Cu(2+)水解为ZCu(2+)(OH)(-)的方案，这是一种在LT-SCR条件下热力学和动力学上有利的过程，基于来自探针反应（瞬时CO氧化）、瞬时Cu2+还原动力学运行、原位FTIR光谱和第一原理计算的多项证据。这样的综合研究明确地表明，在NH3存在下，Z(2)Cu(2+)水解成ZCu(2+)(OH)(-)很容易发生，因此可以调和Z(2)Cu(2+)/ZCu(2+)(OH)(-)还原的相同二次动力学与Z(2)Cu(2+)在Cu2+对形成中的不活性。因此，我们强调 NH3 辅助水解在 LT-SCR 中起着至关重要的作用，特别是在讨论 Z(2)Cu(2+) 上的 SCR 反应细节时应予以考虑。
As the state-of-the-art catalyst for the selective catalytic reduction (SCR) of NOx, Cu-CHA has been extensively investigated in both its practical and fundamental aspects. Among the latter, how Z(2)Cu(2+), an active site for SCR, participates in low-temperature (LT) SCR reactions remains debated. Here, we propose a scheme involving the hydrolysis of Z(2)Cu(2+) to ZCu(2+)(OH)(-), a thermodynamically and kinetically favorable process under LT-SCR conditions, based on multiple pieces of evidence from a probe reaction (transient CO oxidation), transient Cu2+ reduction kinetic runs, in situ FTIR spectroscopy, and first-principles calculations. Such an integrated investigation reveals unambiguously that the hydrolysis of Z(2)Cu(2+) to ZCu(2+)(OH)(-) occurs facilely in the presence of NH3, which may thus reconcile the identical quadratic kinetics of Z(2)Cu(2+)/ZCu(2+)(OH)(-) reduction with the inactivity of Z(2)Cu(2+) in the formation of Cu2+ pairs. Accordingly, we highlight that NH3-assisted hydrolysis plays a critical role in LT-SCR and should be taken into account especially when discussing SCR reaction details over Z(2)Cu(2+).