Heterosturcture NiO/Ce1−xNixO2: synthesis and synergistic effect of simultaneous surface modification and internal doping for superior catalytic performance

Abstract

In this work, a two-step method that involves a hydrothermal reaction and a subsequent calcination was initiated to prepare a novel heterostructure (1 − x)CeO2·xNiO. All samples were systematically characterized by X-ray diffraction, Raman spectra, Transmission electron microscopy, In situ DRIFT spectra, Brunauer–Emmett–Teller technique, H2-temperature-programmed-reduction, and O2-temperature-programmed-desorption. Distinct from the conventional sol–gel or co-precipitation methods, the present methodology allows Ni2+ to be simultaneously doped in the CeO2 lattice and dispersed onto the surfaces of CeO2 nanoparticles by simply varying the calcination temperature from 400 to 700 °C. When calcined at an optimized temperature of 500 °C, the heterostructure at x = 0.1 showed a mean grain size of 18 nm, specific surface area of 69.3 m2 g−1, the smallest lattice parameter, and the largest amount of surface adsorbed and desorped oxygen species, which has led to an excellent catalytic performance towards CO and CH4 oxidation. Such a superior performance benefits from the unique synergistic effects of the finely dispersed NiO and Ni–O–Ce solid solution species detected in the heterostructure.