Topotactic synthesis of Co3O4 nanoboxes from Co(OH)2 nanoflakes

Hollow nanocubes of spinel Co3O4 with the dimension of 20 nm were successfully prepared via a facile and reproducible solvothermal route. The structure and morphology of Co3O4 nanoboxes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) techniques. And a possible growth mechanism of Co3O4 nanoboxes were suggested that solid Co3O4 nanocubes nucleate in-situ and grow epitaxially from hexagonal β-Co(OH)2 precursors with the structural matching relationship of [0 0 1] β-Co(OH)2//[1 1 1] Co3O4, and then solid Co3O4 nanocubes gradually hollow and convert to single-crystal nanoboxes owing to Ostwald ripening.