Synthesis of Copper(II)-Containing Nickel(II) Hydroxide Particles as Precursors of Copper(II)-Substituted Nickel(II) Oxides

Copper(II)-containing nickel(II) hydroxide particles, i.e., α-Ni 1 - x Cu x (OH) 2 (0 < x ≤ 0.4), have been prepared by aging 0.5 mol dm - 3 urea, Ni(NO 3 ) 2, and Cu(NO 3 ) 2 solutions at 363 K. After 3 h, coprecipitation is almost complete. The formed solids, characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersion X-ray spectroscopy, and Fourier transform infrared spectroscopy, preserve the typical characteristics of α-Ni(OH) 2 . Still, their chemical composition, i.e., the copper-to-nickel ratio, is nearly that of the initial solutions. The analysis of the processes that take place during the formation of α-Ni 1 - x Cu x (OH) 2 indicates that, although Cu(II) and Ni(II) precipitation are separate events, the simultaneity of am -Cu(OH) 2 (amorphous copper(II) hydroxide) redissolution and α-Ni(OH) 2 growth provides the appropriate conditions for the intercalation of aqueous Cu(II) species within the interlayer space of the growing α-Ni(OH) 2 particles. Upon mild thermal treatment, i.e., T ≥ 523 K, α-Ni 1 - x Cu x (OH) 2 powders are readily converted in Ni 1 - x Cu x O (bunsenite), provided x ≤ 0.33; when x is larger than 0.33, the thermodynamically expected segregation of tenorite is realized. The ease of Ni 1 - x Cu x O (bunsenite) formation is rationalized in terms of the topotatic relationship between the layered structure of the precursors and the rock salt structure of the mixed oxide.