A Generalized Synthesis of Metal Oxide Hollow Spheres Using a Hydrothermal Approach

TLDR

The study reports the synthesis of Fe₂O₃, NiO, Co₃O₄, CeO₂, MgO, and CuO hollow spheres composed of nanoparticles. A one‑pot hydrothermal method dissolving metal salts with carbohydrates, heating to 180 °C to form carbon spheres incorporating metal ions, then calcining to remove carbon and produce hollow metal‑oxide spheres. The process yields carbon spheres with metal ions in their shell, enabling production of diverse metal‑oxide hollow spheres not achievable by sol‑gel chemistry, with tunable surface area and shell thickness via carbohydrate:metal salt ratio.

Abstract

Hollow spheres of crystalline metal oxides were synthesized in a simple one-pot synthesis via a hydrothermal approach. Various metal salts were dissolved together with carbohydrates in water, and the mixtures were heated to 180 °C in an autoclave. During the hydrothermal treatment, carbon spheres are formed with metal ions incorporated into their hydrophilic shell. The removal of carbon via calcination yields hollow metal oxide spheres. Using this process, we can produce a wide range of metal oxide hollow spheres that are not accessible via sol−gel chemistry. In this paper, we report the synthesis of Fe2O3, NiO, Co3O4, CeO2, MgO, and CuO hollow spheres that are composed of nanoparticles. The surface area and thickness of the shell can be varied or controlled by the carbohydrate:metal salt concentration.