Reduction of Ni2+ by hydrazine in solution for the preparation of nickel nano-particles

• Published in: Journal of materials science 2006-06, Vol.41 (11), p.3473-3480
• Main Authors: Li, Zhiyu, Han, Chenghui, Shen, Jianyi
• Format: Article
• Language: English
• Subjects: Applied sciences; Catalysis; Catalysts; Catalysts: preparations and properties; Chemical synthesis methods; Chemistry; Cross-disciplinary physics: materials science; rheology; Decomposition reactions; Disproportionation; Exact sciences and technology; General and physical chemistry; hydrazine; Hydrazines; Materials science; Metals. Metallurgy; Methods of nanofabrication; nanoparticles; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Nickel; Physics; Reduction; surface area; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-005-5874-z

The reduction of Ni²⁺ by hydrazine in solution for the preparation of nickel nano-particles has been studied. It was found that the reactions occur in two stages. The first stage is the reduction of Ni²⁺ by N₂H₄ according to 2Ni²⁺ + N₂H₄ + 4OH⁻ = 2Ni↓ + N₂↑+ 4H₂O, while the second stage consists of two side reactions, the decomposition of hydrazine (N₂H₄ = N₂↑ + 2H₂↑) and the disproportionation of hydrazine (3N₂H₄ = N₂↑ + 4NH₃↑) catalyzed by the formed nickel nano-particles. The reaction for the formation of nickel is also catalyzed by nickel as an autocatalytic reaction. Accordingly, a small amount of inducing agent, NaBH₄ can be added to initiate the reaction that can then proceed continuously at 288 K. Kinetic study reveals that the reaction orders with respect to Ni²⁺, N₂H₄ and Ni are 1, 0 and 1, respectively. Thus, the increase of the initial concentration of Ni²⁺ and the amount of inducing agent used accelerate the reaction rate and decrease the consumption of N₂H₄ significantly. Pure nickel nano-particles with high surface areas are produced and the surface area can increase from 18 to 79 m²/g with the increase of concentration of Ni²⁺ used. The fully understanding of the reaction between Ni²⁺ and hydrazine in solution may provide a new optimized technique to prepare the nickel catalysts with high surface areas, in addition to the currently available techniques for the preparation of Raney nickel and supported nickel catalysts.