Porous Conducting Polymer/Heteropolyoxometalate Hybrid Material for Electrochemical Supercapacitor Applications

Abstract

A porous conducting polymer/heteropolyoxometalate hybrid material that displays high specific capacitance and low ionic resistance has been prepared for electrochemical supercapacitor applications. Polypyrrole/phosphomolybdate composite films were chemically synthesized in tetrahydrofuran in the presence of sodium sulfate, which acts as a porogen. While the phosphomolydic acid could be removed from the film upon rinsing with pure tetrahydrofuran or acetone, rinsing with water or methanol resulted in retention of the heteropolyoxometalate at a level high enough to easily observe its electrochemistry. The retained phosphomolybdate exhibits fast and reversible redox behavior, adding a significant amount of pseudocapacitance to the polymer. Porous films were obtained by leaching out the sodium sulfate porogen from the films using water. The morphology obtained using this method is altered by varying the monomer-to-porogen ratio. Increasing the porosity increases the rate at which the hybrid material can be charged/discharged (i.e., oxidized/reduced) by increasing the ionic conductivity and in turn lowering the resistor-capacitor time constant of the material. The ability to tune the porosity of the material allows the optimization of performance characteristics for use in supercapacitor applications. Impedance measurements indicate that the ionic conductivity of these porous structures can be increased more than an order of magnitude over that observed for standard conducting polymer films and that the hybrid material displays peak specific capacitance of around 700 F/g as well as excellent reversibility and cyclability.

Electrochemical Characteristics of Polyoxometalate/Polypyrrole/Carbon Cloth Electrode Synthesized by Electrochemical Deposition Method

“…At low current density of 1 mA/cm 2 , the POM-Ppy/CC had a maximum areal capacitance of 561 mF/cm 2 . This result are much better than previously reported values from the Ppy-based electrode materials [24]. As the current density was increased to 30 mA/cm 2 , the areal capacitance of the POM-Ppy/CC decreased slightly; 561 mF/cm 2 ), respectively.…”

“…This study showed high specific capacitances of 120 F/g for POM-doped polyaniline [23]. Freund et al reported a higher specific capacitance (210 F/g) for pseudocapacitors based on porous structure of POM-doped polypyrrole electrodes [24]. The porous structure enabled efficient and rapid ion transfer, and thus improved electrochemical performances.…”

Synthesis of porous NiO nanocrystals with controllable surface area and their application as supercapacitor electrodes

“…Porous nanostructures have received great attention because of their wide-ranging applications, such as in lithium-ion batteries [1][2][3], ion exchange membranes [4], catalysis supports [5][6][7][8], solar cells [9], and supercapacitor electrodes [10][11][12][13][14] due to their high surface area and enhanced interaction with the environment [15]. In the case of charge storage applications, transition metal oxide nanostructures are attractive candidates by virtue of their excellent pseudocapacitive behavior and high electrical conductivity [16][17][18][19][20][21].…”

Graphene Sheet/Porous NiO Hybrid Film for Supercapacitor Applications

“…[14][15][16][17][18][19] Recently, extensive research has been launched into the development of graphene-based composites for supercapacitor applications, especially for composites that consist of graphene and transition-metal oxides because they can combine the advantages of both components and may offer special properties through the reinforcement or modification of each other. [20,21] Several graphene/transition-metal oxide composites, such as graphene/MnO 2 , graphene/Mn 3 O 4 , graphene/ Bi 2 O 3 , graphene/Co 3 O 4 , and graphene/ZnO, [22][23][24] have been exploited and improved pseudocapacitor performances have been found in these composite systems. Nevertheless, all these investigations focused on composite powder materials, and there are few reports dedicated to graphene/transitionmetal oxide hybrid films.…”