Ni(OH)₂-Type Nanoparticles Derived from Ni Salen Polymers: Structural Design toward Functional Materials for Improved Electrocatalytic Performance

Abstract

Herein, we report the potential-driven electrochemical transformation carried out in basic media of two Ni2+ salen polymers, (poly­(NiSalen)­s), abbreviated as poly­(meso-NiSaldMe) and poly­(NiSaltMe). These two polymers, with different configurations of methyl substituents on the imine bridge, were used as precursors for the preparation of electrocatalytically active nickel hydroxide [Ni­(OH)2]-type nanoparticles (NPs) anchored in the polymeric matrix as poly­[SalenNi­(OH)2]. The use of potentiodynamic and potentiostatic electropolymerization conditions for the deposition of polymeric precursors allowed us to control the molecular architecture of poly­(NiSalen)­s and NPs derived from them. Thus, we obtained different arrangements of NPs embedded in morphologically different poly­(Salen) matrixes, indicating their electrocatalytic activity toward ethanol to different extents. Moreover, we found a direct relationship between the electrochemical stability of the poly­(NiSalen) precursors operating in the organic solvent-based electrolyte solutions and the easiness of their transformation into Ni­(OH)2 NPs operating in the aqueous alkaline media. Poly­(NiSalen)­s and Ni­(OH)2-type NPs were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy.

Rational Design of NiZnx@CuO Nanoarray Architectures for Electrocatalytic Oxidation of Methanol

“…Figure b illustrates the Nyquist plots of the five samples, which all present a semicircle shape. The obtained data were fitted to suitable equivalent circuit models shown in the inset of Figure b, wherein R s , R ct , and CPE represent the solution resistance, charge transfer resistance, and constant phase element, respectively . The R ct values obtained from these semicircles have been calculated, as shown in Table S1.…”

“…The obtained data were fitted to suitable equivalent circuit models shown in the inset of Figure 6b, wherein R s , R ct , and CPE represent the solution resistance, charge transfer resistance, and constant phase element, respectively. 47 The R ct values obtained from these semicircles have been calculated, as shown in Table S1. The semicircle diameter stands for the charge transfer resistance (R ct ), demonstrating that the MOR on the NiZn x @CuO nanoarray surface is dominated by the kinetics of the reaction rather than the diffusion of methanol.…”

Enhancement of Supercapacitor Performance of Electrochemically Grown Nickel Oxide by Graphene Oxide

“…It was stated that the three transits correspond to the formation of the following phases: α-Ni(OH) 2 , β-Ni(OH) 2 , and NiOOH hydroxide/oxide, respectively [17,18]. The kinetics and mechanisms of the formation of α-Ni(OH) 2 and NiOOH have already been extensively studied using different electrochemical methods, such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, and the nature of surface films using ex-situ ultra-high vacuum (UHV) analyses [16][17][18][19][20][21] has also been studied.…”