New quaternized poly(4-vinylpyridine-co-divinylbenzene) material containing nickel(II) Schiff base complex: synthesis, thermogravimetry, and application for heterogeneous electrooxidation of ethanol

摘要

Poly(4-vinylpyridine) crosslinked by 2% divinylbenzene was partially quaternized (20% monomer equivalents) by a bidentate Schiff base nickel complex containing C-Br function in its molecular structure using dioxane as solvent. The resulting poly(4-vinylpyridine-co-divinylbenzene)-Ni(II) Schiff base complex (PVP-co-DVB-Ni(II)-L-2) was characterized using various techniques such as elemental analysis and Fourier-transform infrared (FT-IR) spectroscopy. Thermogravimetric (TG)/differential thermogravimetry (DTG) analysis of the nonmodified copolymer, free complex, and the copolymer modified with the nickel complex was carried out to elucidate the thermal behavior. The synthesized copolymer covalently grafted with the nickel(II) complex was mixed with carbon black paste to prepare a new modified electrode material. This electrode was characterized by wide-angle X-ray diffraction analysis, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and cyclic voltammetry. The electrochemical properties of the resulting modified electrode, recorded in alkaline solution, were investigated by cyclic voltammetry, revealing a well-defined redox process corresponding to the Ni-III/Ni-II redox couple. The effects of parameters such as the scan rate and ethanol concentration were explored for electrooxidation of ethanol using this modified electrode. A mechanism for the electrooxidation of ethanol is suggested based on the cyclic voltammetry results.