Pseudocapacitive Energy Storage in Schiff Base Polymer with Salphen-Type Ligands

Salphen-type nickel Schiff bases Ni(salphen), Ni(CH3-salphen), and Ni(CH3O-salphen) are synthesized and electropolymerized on stable ITO electrode, respectively. The morphologies of the three polymer electrodes were evaluated by field emission scanning electron microscopy (FESEM). X-ray photoelectron spectroscopy (XPS) measurements were carried out to shed light on the polymerization mode and energy storage mechanism. Meanwhile, kinetic analysis of the redox reactions was used to verify the pseudocapacitive mechanisms of charge storage. The result signals that the polymerization mode and the mechanism of energy storage are related to the reversible conversion of the azomethine nitrogen group (−N═CH−) in the six-membered ring of Schiff base instead of the Ni2+/Ni3+ process. Meanwhile, the azomethine nitrogen group was found to be directly affected by the addition of the electron-donating group methyl and methoxy so that additional peaks of the CV curve are generated, making polyNi(CH3-salphen) and polyNi(C...