Construction of an electrochemical stable conductive network to improve the pseudocapacitance of polyaniline

Preparation of Symmetrical Capacitors from Lignin-Derived Phenol and PANI Composites with Good Electrical Conductivity

As a natural polymer, lignin is only less abundant in nature than cellulose. It has the form of an aromatic macromolecule, with benzene propane monomers connected by molecular bonds such as C-C and C-O-C. One method to accomplish high-value lignin conversion is degradation. The use of deep eutectic solvents (DESs) to degrade lignin is a simple, efficient and environmentally friendly degradation method. After degradation, the lignin is broken due to β-O-4 to produce phenolic aromatic monomers. In this work, lignin degradation products were evaluated as additives for the preparation of polyaniline conductive polymers, which not only avoids solvent waste but also achieves a high-value use of lignin. The morphological and structural characteristics of the LDP/PANI composites were investigated using ¹H NMR, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and elemental analysis. The LDP/PANI nanocomposite provides a specific capacitance of 416.6 F/g at 1 A/g and can be used as a lignin-based supercapacitor with good conductivity. Assembled as a symmetrical supercapacitor device, it provides an energy density of 57.86 Wh/kg, an excellent power density of 952.43 W/kg and, better still, a sustained cycling stability. Thus, the combination of polyaniline and lignin degradate, which is environmentally friendly, amplifies the capacitive function on the basis of polyaniline.

Metal-Free Homocoupling of Pyrene inside the Pores of Mesoporous Carbons via Electrochemical Oxidation: Application for Electrochemical Capacitors

A pyrene dimer (PYD) is synthesized by electrochemical oxidation via homocoupling of pyrene (PY) inside the pores of MgO-templated mesoporous carbons without any metal catalysts or organic solvents. The resulting MgO-C/PYD hybrids can be used as high-performance aqueous electrochemical capacitor electrodes due to the reversible redox property of PYD and large contact area between the hybridized PYD and conductive carbon surfaces, which enable rapid charge transfer at the large contact interface. In our previous study, PY was considered to polymerize through electrochemical oxidation, and activated carbon with the pore sizes of ∼4 nm was used as a porous carbon substrate. In this study, the MgO-templated carbons have the average pore sizes of 5, 10, and 30 nm, and their large mesopore volumes can accommodate a large amount of PYD for enhancing the capacitance. To develop high-performance electrochemical capacitors, the dependence of the capacitance enhancement and the capacitance retention on the amount of PY and the pore sizes of MgO-templated carbons are studied. It is found that mesopores are necessary for fast charging/discharging, but the capacitance retention and capacitance enhancement decrease with increasing the mesopore sizes and the amount of PY due to the decreased utilization ratio of PY.

In-situelectrochemical polymerization of aniline on flexible conductive substrates for supercapacitors and non-enzymatic ascorbic acid sensors

Polyaniline, as a kind of conductive polymer with commercial application prospects, is still under researches in its synthesis and applications. In this work, polyaniline was fabricated on flexible substrates including carbon cloths and polyethylene naphthalate byin situelectropolymerization method. The synthesized flexible electrodes were characterized by scanning electron microscopy, High resolution transmission electron microscope, atomic force microscope, Fourier transform infrared, x-ray diffraction, and x-ray photoelectron spectroscopy. Owing to the conductivity and the reversible redox property, the polyaniline/carbon cloth electrodes show excellent properties such as decent supercapacitor performance and good detection capability toward ascorbic acid. As supercapacitors, the electrodes exhibit a specific capacitance as high as 776 F g^-1at a current density of 1 A g^-1and a long cycle life of 20 000 times in the three-electrode system. As ascorbic acid sensors, the flexible electrodes demonstrate stable response to ascorbic acid in the range of 1-3000μM with an outstanding sensitivity (4228μA mM^-1cm^-2), low detection limit (1μM), and a fast response time. This work holds promise for high-performance and low-cost flexible electrodes for both supercapacitors and non-enzymatic ascorbic acid sensors, and may inspire inventions of self-powered electrochemical sensor.