Synthesis of porous Cr2O3 hollow microspheres via a facile template-free approach

•Porous Cr2O3 hollow microspheres were prepared via a template-free method.•Shells of the Cr2O3 hollow microspheres are assembled by Cr2O3 nanoparticles.•An inside-out formation mechanism process is proposed to reveal the formation mechanism of the Cr2O3 precursor hollow microspheres.

Porous Cr2O3 hollow microspheres assembled by nanoparticles have been successfully synthesized by thermal decomposition of a precursor which was prepared via a mild template-free hydrothermal approach. The average dimensions of these Cr2O3 hollow microspheres were about 2.2 µm in diameter and 130 nm in thickness of spherical shell. The structures and morphologies of the synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Moreover, the formation mechanism of the Cr2O3 precursor hollow structure was suggested to be an inside-out formation mechanism process through tracking the morphology evolution with different reaction times.