A Breakthrough in the Processability of NiSalen Polymers: Chemical Polymerization of NiSalens

Polymeric salen-type nickel complexes, polyNiSalen, are an emerging family of functional materials for a wide range of applications, such as energy storage, battery protection, electrocatalysis, electroanalysis, and sensing. The main drawback of these materials, impeding their practical implementation, is their poor processability since they are accessible only by an electrochemical deposition on the conductive electrodes. Herein, we report the first scalable method for the preparation of polyNiSalen by chemical polymerization in solution, which affords an easily processable powder material. The key feature of the proposed method is the polymerization in concentrated LiClO4 solution using ceric ammonium nitrate as an oxidant, which provides sufficient anionic doping of the prepared material, which results in the formation of conductive and electroactive polymers. We have performed a systematic optimization of the polymerization conditions, which allows us to obtain the material nearly similar to those prepared electrochemically in terms of the electrochemical behavior. Moreover, the capacity of the obtained material was found to be ca. 3 times higher compared with the results previously reported for the electrochemically obtained samples, reaching 70 mAh g–1. The resulting material was examined by means of scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy techniques; electrochemical characteristics were studied using CV and GCD methods.