Ce/BEA has great potential as a passive NO absorber (PNA) to reduce the NO emissions during the cold start phase especially in diesel engine for its high resistance to CO and suitable NO desorption temperature range. However, as a novel material, its physical and chemical properties still remain unknown. In this work, Ce/BEA was synthesized by ion-exchange method to identify the active species in NO adsorption, compared with aggregated Ce species in Ce/SiAlO prepared by impregnation method. X-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM) and aberration-corrected-scanning transmission electron microscopy (AC-STEM) were performed to confirm the isolated single atom formation of Ce species in Ce/BEA. UV-vis diffraction reflection spectra (DRS) and X-ray photoelectron spectroscopy (XPS) were conducted to find the difference of chemical environment between the isolated Ce species and aggregated ones. PNA performance evaluation and temperature programmed reduction of hydrogen (H-TPR) results show the high NO storage capacity and active oxygen species quantity in Ce/BEA. It is also found that the main NO adsorption species are Ce–O∗ rather than Ce. NO-diffuse reflectance infrared Fourier transform spectroscopy (NO-DRIFTS) confirms that the bidentate nitrite species are the critical NO adsorption intermediates and the conception of NO adsorption and desorption processes is proposed.

中文翻译：

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Ce/BEA作为被动NOx吸附剂的研究：1.铈的出现和吸附行为


Ce/BEA 作为被动 NO 吸收剂（PNA）具有巨大的潜力，可减少冷启动阶段的 NO 排放，特别是在柴油发动机中，因为其对 CO 的高抵抗力和合适的 NO 解吸温度范围。然而，作为一种新型材料，其物理和化学性质仍然未知。在这项工作中，通过离子交换法合成了Ce/BEA，以鉴定NO吸附中的活性物种，并与浸渍法制备的Ce/SiAlO中聚集的Ce物种进行比较。采用 X 射线衍射 (XRD)、高分辨率透射电子显微镜 (HR-TEM) 和像差校正扫描透射电子显微镜 (AC-STEM) 来证实 Ce/BEA 中 Ce 物种的孤立单原子形成。通过紫外可见衍射反射光谱（DRS）和X射线光电子能谱（XPS）来发现孤立的Ce物种和聚集的Ce物种之间的化学环境差异。 PNA 性能评估和程序升温还原氢 (H-TPR) 结果表明 Ce/BEA 具有高 NO 存储容量和活性氧物质数量。还发现主要的 NO 吸附物种是 Ce–O* 而不是 Ce。 NO-漫反射红外傅里叶变换光谱（NO-DRIFTS）证实了二齿亚硝酸盐是NO吸附的关键中间体，并提出了NO吸附和解吸过程的概念。