An investigation of the thermal hydrolysis of nickel and copper acetate mixtures at 90°C to yield acetate-intercalated layered double hydroxides has led to discovery of an unusual dependence of the products on the ratio of the metal ions. The bimetallic layered double hydroxides (LDHs) produced, NixCu1-x(OAc)x(OH)2-x●nH2O, are markedly enriched in copper in comparison to the ratio of nickel and copper ions in the initial solutions. The acetate content also varies: it is approximately 0.5 molar equivalents per total metal ions in all cases except for very high copper ratios where it drops to 0.25 equivalents. The bimetallic nickel-copper LDHs are excellent precursors for stochiometric bimetallic nickel-copper oxides such as NiCu4O and NiCu2O. The LDHs were characterized by FTIR spectroscopy, elemental analysis, thermogravimetric analysis (TGA) and X-ray powder diffraction. SEM images revealed that the LDH’s are composed of thin square plates with thicknesses ranging from nanometers to micrometers and lengths and widths in the order of micrometers. The hydrothermal reactions were investigated by dynamic light scattering (DLS) experiments. A two-step mechanism is proposed for the growth of the bimetallic LDHs based on the DLS investigation – (i) initial incubation period while nucleation occurs, followed by (ii) rapid growth of the nucleated particles to the final products, NixCu1-x(OAc)x(OH)2-x●nH2O. Additionally, these hydrothermal reactions deposited the bimetallic nickel-coper LDHs as films. These films can be converted to corresponding bimetallic oxide films by pyrolysis. The present study will open the door for investigating hydrothermal reactions of mixtures of other transition metal acetates.

Synthesis of acetate-intercalated nickel-copper layered double hydroxides

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