Effect of Synthesis Method on Properties of Layered Double Hydroxides Containing Ni(III)

Unstable oxidation state +3 of nickel can be stabilized in the structure of layered double hydroxides, the resulting crystallinity and properties being dependent on the synthesis method. Three different wet chemical methods (co-precipitation at variable pH, co-precipitation followed by hydrothermal treatment, co-precipitation with microwave treatment) were used to synthesize Mg/Ni-Al layered double hydroxides containing triply charged nickel cations. Lattice parameters of the samples synthesized by various methods were found to differ from each other by about 1.5%. The most crystallized sample was obtained by hydrothermal synthesis. The oxidation state of nickel in the LDH samples was confirmed by XPS. TEM mapping gave evidence of the uniform distribution of nickel in all the samples. The LDHs' reduction with hydrogen and thermal transformations of the phase composition and morphology of LDHs were studied in detail. The properties of the samples synthesized by the different methods were shown to be quite similar.

Automated summary

The unstable oxidation state of nickel at +3 can be stabilized in layered double hydroxides, with the resulting crystallinity and properties depending on the synthesis method. Three wet chemical methods were used to synthesize Mg/Ni-Al LDHs, with lattice parameters of the samples differing by about 1.5% among the different methods. XPS confirmed the oxidation state of nickel in the LDH samples, with TEM mapping showing uniform distribution of nickel. Reduction with hydrogen and thermal transformations were studied, revealing similar properties among samples synthesized by different methods.