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

Abstract

Salphen-type nickel Schiff bases Ni(salphen), Ni(CH 3 -salphen), and Ni(CH 3 O-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 Ni 2+ /Ni 3+ 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(CH 3 -salphen) and polyNi(CH 3 O-salphen) have higher doping level, charge transfer ability, and better pseudocapacitive energy storage property than the pristine polyNi(salphen) polymer. At the current density of 0.05 mA cm −2 , the specific capacity of the polyNi(CH 3 Osalphen) electrode was about 216 F g −1 , higher than the specific capacity of 85 F g −1 for polyNi(salphen) and 133 F g −1 for polyNi(CH 3 -salphen). In the meantime, the conductivity of polyNi(CH 3 O-salphen) is 108.7 S cm −1 higher than that of the other two polymers. Therefore, the addition of the stronger methoxy group for electron-donating substituents makes polyNi(CH 3 Osalphen) have more excellent electrochemical kinetics and pseudocapacitive characteristics.

Synthesis of Bimetallic Conductive 2D Metal–Organic Framework (CoxNiy‐CAT) and Its Mass Production: Enhanced Electrochemical Oxygen Reduction Activity

“…The energy‐dispersive X‐ray spectroscopy (EDX) spectra of the products revealed the incorporation of both cobalt and nickel ions within the products as metal nodes, as evidenced by the detection of both cobalt and nickel, in addition to carbon and oxygen originating from the organic building blocks (Figure c and Figure S2, Supporting Information). The high‐resolution X‐ray photoelectron spectroscopy (XPS) data of Co x Ni y ‐CATs (Figure e,f) for Co 2p and Ni 2p confirmed the presence of divalent Co 2+ and Ni 2+ , as evidenced by a Co 2p3/2 peak at 780.7 eV and a Ni 2p3/2 peak at 855.5 eV, respectively. Moreover, the ratios between Co 2+ and Ni 2+ within the five samples of Co x Ni y ‐CATs were determined to be ≈49:51, 41:59, 32:68, 27:73, and 15:85, as measured from the EDX spectra (Figure S2, Supporting Information).…”

CoS2 as a Sulfur Redox-Active Cathode Material for High-Capacity Nonaqueous Zn Batteries

“…To look into the relative contributions of Faradic and capacitive processes to the total capacity, we used cyclic voltammetry following a method that has been previously reported for studies of pyrites in Li/Na-ion battery chemistries (details shown in the Supporting Information). − From this analysis, the ratio between capacities coming from capacitive and Faradic processes was determined to be 0.23:1. The total capacity is therefore found to be 203 mAh/g, of which 165 mAh/g is Faradic in nature and 38 mAh/g is capacitive.…”

The Fast and the Capacious: A [Ni(Salen)]‐TEMPO Redox‐Conducting Polymer for Organic Batteries

“…Polymeric bis(salicilydenimine) complexes of transition metals (MSalens) represent a class of conductive polymers with distinct properties. Specifically, polymeric Salen complexes based on nickel have a large reversible electroactivity window, perfectly matching the TEMPO/TEMPO + redox potential (anodic limit of electroactivity reaches 4.3 V vs Li/Li + ), [15] and a conductivity up to 100 S cm −1 , [16] while their specific redox capacitance and energy density (ca. 330 J g −1 ) [17] exceed those of most conductive polymers.…”