Influence of ultrasound on the instantaneous synthesis of tridimensional α-Ni(OH)₂ nanostructures and derived NiO nanoparticles

Abstract

Nickel hydroxides present an extraordinary importance in the development of electrochemical devices. In contrast to the use of ammonia as a direct precipitating agent, we present herein the instantaneous precipitation of α-NiIJOH) 2 nanopowders by the addition of a nickel salt to an ammonia solution. The synthesis is based on the oversaturation of the solution in the absence of any additive or other metallic cations, where ammonia plays a role as a complexing agent for intermediate nickel compounds. The influence of ultrasound on both the microstructure and the crystalline structure is discussed and the differences are referred to a new parameter (S parameter) which quantifies the amount of power in watts per cm 2 that a mol of ijNiIJNH 3 ) 6 ] 2+ experiences. The description of the nucleation and growth processes of the different powders studied led to the understanding of the effect of ultrasound on the crystallography of α-NiIJOH) 2 . The porosity of the samples is also evaluated and its percentage and type are also correlated to the synthesis conditions. The transformation of α-NiIJOH) 2 to NiO is also considered and their optical properties are evaluated as an initial indicator of their promising use as electrochemical devices. CrystEngCommThis journal is

Electrochemical performance of pseudo-capacitor electrodes fabricated by Electrophoretic Deposition inducing Ni(OH)2 nanoplatelets agglomeration by Layer-by-Layer

“…For LbL core-shell suspensions (NH-1LbL, NH-3LbL and NH-5LbL), the properties were adjusted not only to slow down the massive arrival of core-shells to the substrate (Table 2 and Figure 3b), but for reduce as much as possible the conductivity of the suspension and avoid collateral phenomena derived from the electrophoretic movement of contra and co-ions, and the presence of excessively charged nanostructures. On the other hand, low suspension conductivity relatively impedes the nanoplatelets flocculation in the suspension [29], and is enough to maintain a stable current density during EPD providing reliability to the mesostructures formation.…”

“…a LbL system of PEI and PAA polyelectrolytes onto the surface of β-Ni(OH)2 nanoparticles with platelet morphologywas demonstrated[22].Figure 1ashows schematically the β-Ni(OH)2 nanoplatelets stacking when precipitates during their synthesis with the aid of ultrasound. This particular kind of synthesis modifies the morphology and crystallography of the nanostructure at several levels[27,29]. The unit cell of nickel hydroxide stacks in a layer by layer structure of OH − and Ni along the c-axis.…”

Semiconductor-metal core-shell nanostructures by colloidal heterocoagulation in aqueous medium

“…Considering the oxidation-reduction potentials of these species, NPs can't be synthetized under pH 9.5 according to the Nerst equation [12]. Noting that our synthesis took place in presence of ultrasound, and as a consequence of the sonocrystallization the formation of numerous nuclei, homogeneously dispersed in the aqueous solvent, was expected [13]. It is known that ultrasonic treatment can lead to the formation of clusters of nanoparticles.…”

“…Taking account these aspects, the influence of variables as ion nickel concentration, ultrasound time and the ultrasound power was evaluated in terms of the called "S parameter" [W/(mol/L)•s] which is equivalent to the number of watts per second that a mol/L of Ni 2+ experiences in each synthesis. This parameter was defined to quantify the efficiency of each factor on the resulting size of the NPs [13,14]. .…”

Framework of ruthenium-containing nickel hydrotalcite-type material: preparation, characterisation, and its catalytic application

“…Currently, there are many studies on the facile fabrication of bimetallic nickel systems that present potential alternatives for noble metal catalysts, which are expensive, in terms of the catalytic activity and stability. 23,[33][34][35][36][37][38][39][40][41][42] Thus, it will be interesting to introduce a small amount of trivalent ruthenium ions, which possess excellent activity in various organic transformations such as hydrogenation, C-C coupling, and metathesis, to the monometallic nickel HT-type materials. In this work, we intend to prepare HT-type a-Ni(OH) 2 containing ruthenium ions by using a simple coprecipitation method and used as a potential catalyst for the hydrogenation of nitro compounds to corresponding anilines.…”