Ni2+ ions assisted hydrothermal synthesis of flowerlike Co11(HPO3)8(OH)6 superstructures and shape control

Abstract

In this paper, flowerlike Co₁₁(HPO₃)₈(OH)₆ superstructures were selectively synthesized via a facile hydrothermal route on a large scale in the presence of a certain amount of Ni²⁺ ions, employing CoCl₂·6H₂O and NaH₂PO₂·H₂O as the reactants, NaHCO₃ as the pH adjustor. HPO₃⁻ ions were provided based on the dismutation of H₂PO₂⁻ ions in a weak basic solution. The reaction was carried out at 170 °C for 10 h. The as-obtained products were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). Research showed that the Ni²⁺ ions in the system played a crucial role in the formation of flowerlike Co₁₁(HPO₃)₈(OH)₆ superstructures. Some factors influencing the morphology of Co₁₁(HPO₃)₈(OH)₆, including the reaction time, temperature, and the kinds of metal ions were investigated. A possible growth mechanism was proposed.