Rapid synthesis of mesoporous ceria–zirconia solid solutions via a novel salt-assisted combustion process

Mesoporous ceria–zirconia solid solutions were prepared by a novel salt-assisted combustion process using ethylene glycol as a fuel and nitrate as an oxidant. The effects of various operating conditions such as the fuel-to-oxidant ratio and the nature and amount of added salt on the characteristics of the products were investigated by X-ray diffraction (XRD) and nitrogen adsorption analysis. Results from transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) showed that the introduction of leachable inert inorganic salt as a hard agglomeration inhibitor into the redox mixture precursor led to the breakup of fractal nanocrystallite agglomerates and the mesoporous structure formed by the loose agglomeration of monodispersed nanoparticles, which was also confirmed by small-angle XRD and nitrogen adsorption analysis. The presence of salt was found to result in a more than 10-fold increase in the specific surface area of the products from 17.34 to 208.17 m2/g at a given molar ratio of ethylene glycol–nitrate. A mechanism scheme was proposed to illustrate the possible formation processes and discuss the role of the salt additives.