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

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.