Rigorous comparisons between single site- and nanoparticle (NP)-dispersed catalysts featuring the same composition, in terms of activity, selectivity, and reaction mechanism, are limited. This limitation is partly due to the tendency of single metal atoms to sinter into aggregated NPs at high loadings and elevated temperatures, driven by a decrease in metal surface free energy. Here, we have developed a unique two-step method for the synthesis of single Cu sites on ZSM-5 (termed Cu S /ZSM-5) with high thermal stability. The atomic-level dispersion of single Cu sites was confirmed through scanning transmission electron microscopy, X-ray absorption fine structure (XAFS), and electron paramagnetic resonance spectroscopy. The Cu S /ZSM-5 catalyst was compared to a CuO NP-based catalyst (termed Cu N /ZSM-5) in the oxidation of NH 3 to N 2 , with the former exhibiting superior activity and selectivity. Furthermore, operando XAFS and diffuse reflectance infrared Fourier transform spectroscopy studies were conducted to simultaneously assess the fate of the Cu and the surface adsorbates, providing a comprehensive understanding of the mechanism of the two catalysts. The study shows that the facile redox behavior exhibited by single Cu sites correlates with the enhanced activity observed for the Cu S /ZSM-5 catalyst.

中文翻译：

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ZSM-5 上热稳定的高负载单 Cu 位点用于​​ NH 3 的选择性催化氧化


具有相同组成的单中心分散催化剂和纳米粒子（NP）分散催化剂在活性、选择性和反应机理方面的严格比较是有限的。这种限制部分是由于金属表面自由能的降低导致单金属原子在高负载和高温下倾向于烧结成聚集的纳米粒子。在这里，我们开发了一种独特的两步法，用于在 ZSM-5 上合成具有高热稳定性的单 Cu 位点（称为 Cu S /ZSM-5）。通过扫描透射电子显微镜、X射线吸收精细结构（XAFS）和电子顺磁共振光谱证实了单个Cu位点的原子级分散。在NH 3 氧化为N 2 过程中，将Cu S /ZSM-5 催化剂与CuO NP 基催化剂（称为Cu N /ZSM-5）进行比较，前者表现出优异的活性和选择性。此外，还进行了原位 XAFS 和漫反射红外傅里叶变换光谱研究，以同时评估 Cu 和表面吸附物的命运，从而全面了解两种催化剂的机理。研究表明，单个 Cu 位点表现出的轻松氧化还原行为与 Cu S /ZSM-5 催化剂观察到的增强活性相关。