Droplet-oriented construction of porous metal oxide hollow microspheres and their assembly into superstructures

Hollow porous materials with internal spaces or voids and highly porous structures have revealed nice effectiveness in numerous areas. However, the traditional template methods are constrained to sophisticated operations, cost of templates and industry manufacture. Herein, with the aim to establish an efficient route for scale-up and low-cost production of hollow materials under mild conditions, we report a facile and versatile template-free strategy to prepare hollow porous metal oxide spheres with high specific surface areas, large pore volumes and abundant pores. The as-prepared NiO microspheres demonstrated a noteworthy surface area of 351m2/g and a large pore volume of 0.55 mL/g. The features of the preparation were based on spray technology and wet chemical method. Moreover, we demonstrate the construction pathway and the possible formation mechanism of these hollow superstructures. The regulation of the shell thickness of the hollow microspheres was explored. Moreover, a series of hierarchical architectures and multicomponent hollow materials (e.g., MgO/Al2O3) were also designed and investigated.