Electrochemical transformations of polymers formed from nickel (II) complexes with salen-type ligands in aqueous alkaline electrolytes

The polymeric nickel complexes with salen-type ligands can serve as useful materials for a range of applications, including catalytic systems and energy storage devices. Despite the fact that electrochemical properties of such complexes were investigated in detail in non-aqueous solutions, there has still remained scarce information about their behavior in aqueous systems. This work is devoted to studying such properties of poly[Ni(salen)] films in aqueous alkaline electrolytes. By combination of electrochemical methods with X-ray photoelectron and Raman spectroscopy it was shown that the redox transformations observed result in ligand exchange and formation of nickel hydroxide thin films deposited on the working electrodes. The obtained material consists of uniformly distributed nanoparticles with the characteristic size of about 10 nm. Catalytic activity of the produced modified electrodes in reactions of ethanol and methanol oxidation, as well as their ability to be charged and discharged reversibly for more than 1000 cycles, makes them promising materials for applications in catalytic and energy storage devices.