Unusual properties of nanostructured Ce1−xCoxO2−y, Ce1−xNixO2−y and Ce1−(x+y)CoxNiyO2−z: structural studies and catalytic activity

Abstract

In this paper, a series of nanostructured CeO₂ spheres with two different dopants, Co²⁺ and Ni²⁺, were synthesized by a one-step hydrothermal synthesis free from the template-assisted calcination, and were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS) and nitrogen adsorption–desorption measurements. The formation process of the produced spheres involved Ostwald ripening, secondary nucleation and oriented attachment. Both the presence of Co²⁺, Ni²⁺ and the interaction of Ce⁴⁺/Ce³⁺ with dopants promoted the production of oxygen vacancies, which explained the result that the catalytic performance in CO oxidation of CeO₂ with both dopants was better than that with single dopant, and that with single dopant held much advantage towards pure CeO₂.