Direct Hydrothermal Synthesis of Size-Controlled Co₃O₄ Nanocubes under Highly Condensed Conditions

Abstract

Cobalt oxide (Co₃O₄) nanocubes with high crystallinity and a narrow size distribution have been synthesized in one pot process under highly condensed hydrothermal reactions using cobalt(II) nitrate (Co(NO₃)₂) and sodium hydroxide or tetramethylammonium hydroxide. The particle morphology was controlled to a cubic shape by change in the initial pH. The particle mean diameter was also gradually controlled by the change in the initial pH in the range from 18 nm to 66 nm. Co(OH)₂ hexagonal thin platelet particles were obtained as the predominant product when CoSO₄, CoCl₂, and Co(CH₃COO)₂ were used as the Co-source. The result indicated that oxidation ability of nitrate anions played an important role to obtain the Co₃O₄ nanocubes in the one pot process.

Fig. 10 TEM patterns of solid particles obtained by changing the aging times of the hydrothermal treatment: (a) 0 h; (b) 1 h; (c) 6 h. The scale bar shown in (a) is the same for all images.