A novel ceria hollow nanosphere catalyst for low temperature NOx storage

In this work, a highly active CeO2 catalyst with hollow nanosphere morphology for low temperature NOx storage was prepared by a surfactant-assisted solvothermal reaction. The physicochemical properties of ceria samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 adsorption-desorption, H-2-temperature programmed reduction (H-2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The as-prepared CeO2 nanosphere possesses excellent NO oxidation capacity, smaller mesopores, better reducibility and more surface Ce3+ content. Compared with CeO2 with nanorod and nanoparticle morphologies, CeO2 nanosphere shows better intrinsic low temperature NOx trapping performance, with a wide operating temperature window (150-300 degrees C), high NOx adsorption capacity (NAC, 640-745 mu mol/g) and high NOx storage capacity (NSC, 250-350 mu mol/g). Two reaction pathways are speculated for NOx adsorption on CeO2 nanosphere, including nitrate route and nitrite route. The thermally unstable surface nitrites formed on the CeO2 nanosphere allow ceria to release more NOx during the desorption process. The present work provides a new ceria morphology for NOx traps, which may become a potential excellent NOx storage material. (C) 2021 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

A highly active CeO2 catalyst with a hollow nanosphere morphology for low temperature NOx storage was prepared, showing excellent NO oxidation capacity, smaller mesopores, better reducibility, and higher NOx storage capacity compared to CeO2 with nanorod and nanoparticle morphologies. This new ceria morphology may become a potential excellent NOx storage material.