One-Step Electrodeposition of Polyaniline Nanorods on Carbon Cloth for High-Performance Flexible Supercapacitors

The electrochemical performance of the carbon cloth (CC)-based electrodes is determined by the kind, content, morphology, and size of the modified pseudocapacitive materials, as well as the interaction with CC. Also, such structural parameters were mainly dependent on the deposition condition. More uniform polyaniline (PANI) could be obtained by electrochemical polymerization in comparison to chemical oxidation polymerization. However, two steps of electrodeposition were usually needed for nucleation and growth. Here, based on the comprehensive optimization of the electrodeposition condition, well-defined PANI nanorods anchored on the functionalized carbon cloth (FCC) as flexible electrodes (FCC@PANI) were synthesized by a facile one-step electrochemical polymerization. Compared with the FCC electrode, the resultant FCC@PANI-4 sample possessed good cycling stability (98.3% capacitance retention after 10,000 cycles), higher specific capacitances of 2312 mF cm-2 (1.0 mA cm-2) and 107 F g-1 (1.0 A g-1) with the boosting ratio in the areal specific capacitance (CA), and mass specific capacitances (Cm) of 169 and 181%, respectively. The improvement in both specific capacitance and cycling stability was obtained by the strong interaction between the FCC and the modified PANI nanorods with enhanced utilization efficiency of electroactive materials. Furthermore, the symmetric solid-state device assembled using the FCC@PANI-4 electrode delivered a maximum energy density of 0.079 mWh cm-2 at a power density of 0.363 mW cm-2.

High-Efficiency Recovery of Acetic Acid from Water Using Electroactive Gas-Stripping Membranes

Recovery of carbon-based resources from waste is a critical need for achieving carbon neutrality and reducing fossil carbon extraction. We demonstrate a new approach for extracting volatile fatty acids (VFAs) using a multifunctional direct heated and pH swing membrane contactor. The membrane is a multilayer laminate composed of a carbon fiber (CF) bound to a hydrophobic membrane and sealed with a layer of polydimethylsiloxane (PDMS); this CF is used as a resistive heater to provide a thermal driving force for PDMS that, while a highly hydrophobic material, is known for its ability to rapidly pass gases, including water vapor. The transport mechanism for gas transport involves the diffusion of molecules through the free volume of the polymer matrix. CF coated with polyaniline (PANI) is used as an anode to induce an acidic pH swing at the interface between the membrane and water, which can protonate the VFA molecule. The innovative multilayer membrane used in this study has successfully demonstrated a highly efficient recovery of VFAs by simultaneously combining pH swing and joule heating. This novel technique has revealed a new concept in the field of VFA recovery, offering promising prospects for further advancements in this area. The energy consumption was 3.37 kWh/kg for acetic acid (AA), and an excellent separation factor of AA/water of 51.55 ± 2.11 was obtained with high AA fluxes of 51.00 ± 0.82 g.m^-2hr^-1. The interfacial electrochemical reactions enable the extraction of VFAs without the need for bulk temperature and pH modification.

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.

A review of π-conjugated polymer-based nanocomposites for metal-ion batteries and supercapacitors

Owing to their extraordinary properties of π-conjugated polymers (π-CPs), such as light weight, structural versatility, ease of synthesis and environmentally friendly nature, they have attracted considerable attention as electrode material for metal-ion batteries (MIBs) and supercapacitors (SCPs). Recently, researchers have focused on developing nanostructured π-CPs and their composites with metal oxides and carbon-based materials to enhance the energy density and capacitive performance of MIBs and SCPs. Also, the researchers recently demonstrated various novel strategies to combine high electrical conductivity and high redox activity of different π-CPs. To reflect this fact, the present review investigates the current advancements in the synthesis of nanostructured π-CPs and their composites. Further, this review explores the recent development in different methods for the fabrication and design of π-CPs electrodes for MIBs and SCPs. In review, finally, the future prospects and challenges of π-CPs as an electrode materials for strategies for MIBs and SCPs are also presented.

Preparation of hybrid paper electrode based on hexagonal boron nitride integrated graphene nanocomposite for free-standing flexible supercapacitors

Flexible energy storage devices have received great interest due to the increasing demand for wearable and flexible electronic devices with high-power energy sources. Herein, a novel hybrid flexible hexagonal boron nitride integrated graphene paper (BN/GrP) is fabricated from 2D hexagonal boron nitride (h-BN) nanosheets integrated with graphene sheets dispersion via a simple vacuum filtration method. FE-SEM indicated that layered graphene nanosheets tightly confined with h-BN nanosheets. Further, the Raman spectroscopy confirmed successful integration of BN with graphene. As-prepared BN/GrP free-standing flexible conductive paper showed high electrical conductivity of 5.36 × 104 S m-1 with the sheet resistance of 8.87 Ω sq-1. However, after 1000 continuous bending cycles, the BN/GrP sheet resistance increased just about 8.7% which indicated good flexibility of the paper. Furthermore, as-prepared BN/GrP showed excellent specific capacitance of 321.95 F g-1 at current density of 0.5 A g-1. In addition, the power and energy densities were obtained as 3588.3 W kg-1, and 44.7 W h kg-1, respectively. The stability of the prepared flexible electrode was tested in galvanostatic charge/discharge cycles, where the results showed the 96.3% retention even after 6000 cycles. These results exhibited that the proposed BN/GrP may be useful to prepare flexible energy-storage systems.

Current Research of Graphene-Based Nanocomposites and Their Application for Supercapacitors

This review acmes the latest developments of composites of metal oxides/sulfide comprising of graphene and its analogues as electrode materials in the construction of the next generation of supercapacitors (SCs). SCs have become an indispensable device of energy-storage modes. A prompt increase in the number of scientific accomplishments in this field, including publications, patents, and device fabrication, has evidenced the immense attention they have attracted from scientific communities. These efforts have resulted in rapid advancements in the field of SCs, focusing on the development of electrode materials with features of high performance, economic viability, and robustness. It has been demonstrated that carbon-based electrode materials mixed with metal oxides and sulfoxides can perform extremely well in terms of energy density, durability, and exceptional cyclic stability. Herein, the state-of-the-art technologies relevant to the fabrication, characterization, and property assessment of graphene-based SCs are discussed in detail, especially for the composite forms when mixing with metal sulfide, metal oxides, metal foams, and nanohybrids. Effective synthetic methodologies for the nanocomposite fabrications via intercalation, coating, wrapping, and covalent interactions will be reviewed. We will first introduce some fundamental aspects of SCs, and briefly highlight the impact of graphene-based nanostructures on the basic principle of SCs, and then the recent progress in graphene-based electrodes, electrolytes, and all-solid-state SCs will be covered. The important surface properties of the metal oxides/sulfides electrode materials (nickel oxide, nickel sulfide, molybdenum oxide, ruthenium oxides, stannous oxide, nickel-cobalt sulfide manganese oxides, multiferroic materials like BaMnF, core-shell materials, etc.) will be described in each section as per requirement. Finally, we will show that composites of graphene-based electrodes are promising for the construction of the next generation of high performance, robust SCs that hold the prospects for practical applications.

Enhanced Adsorptive Properties and Pseudocapacitance of Flexible Polyaniline-Activated Carbon Cloth Composites Synthesized Electrochemically in a Filter-Press Cell

Electrochemical polymerization is known to be a suitable route to obtain conducting polymer-carbon composites uniformly covering the carbon support. In this work, we report the application of a filter-press electrochemical cell to polymerize polyaniline (PAni) on the surface of large-sized activated carbon cloth (ACC) by simple galvanostatic electropolymerization of an aniline-containing H₂SO₄ electrolyte. Flexible composites with different PAni loadings were synthesized by controlling the treatment time and characterized by means of Scanning Electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), physical adsorption of gases, thermogravimetric analysis (TGA), cyclic voltammetry and direct current (DC) conductivity measurements. PAni grows first as a thin film mostly deposited inside ACC micro- and mesoporosity. At prolonged electropolymerization time, the amount of deposited PAni rises sharply to form a brittle and porous, thick coating of nanofibrous or nanowire-shaped structures. Composites with low-loading PAni thin films show enhanced specific capacitance, lower sheet resistance and faster adsorption kinetics of Acid Red 27. Instead, thick nanofibrous coatings have a deleterious effect, which is attributed to a dramatic decrease in the specific surface area caused by strong pore blockage and to the occurrence of contact electrical resistance. Our results demonstrate that mass-production restrictions often claimed for electropolymerization can be easily overcome.

Highly Uniform Atomic Layer-Deposited MoS2@3D-Ni-Foam: A Novel Approach To Prepare an Electrode for Supercapacitors

This article takes an effort to establish the potential of atomic layer deposition (ALD) technique toward the field of supercapacitors by preparing molybdenum disulfide (MoS₂) as its electrode. While molybdenum hexacarbonyl [Mo(CO)₆] serves as a novel precursor toward the low-temperature synthesis of ALD-grown MoS₂, H₂S plasma helps to deposit its polycrystalline phase at 200 °C. Several ex situ characterizations such as X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and so forth are performed in detail to study the as-grown MoS₂ film on a Si/SiO₂ substrate. While stoichiometric MoS₂ with very negligible amount of C and O impurities was evident from XPS, the XRD and high-resolution transmission electron microscopy analyses confirmed the (002)-oriented polycrystalline h-MoS₂ phase of the as-grown film. A comparative study of ALD-grown MoS₂ as a supercapacitor electrode on 2-dimensional stainless steel and on 3-dimensional (3D) Ni-foam substrates clearly reflects the advantage and the potential of ALD for growing a uniform and conformal electrode material on a 3D-scaffold layer. Cyclic voltammetry measurements showed both double-layer capacitance and capacitance contributed by the faradic reaction at the MoS₂ electrode surface. The optimum number of ALD cycles was also found out for achieving maximum capacitance for such a MoS₂@3D-Ni-foam electrode. A record high areal capacitance of 3400 mF/cm² was achieved for MoS₂@3D-Ni-foam grown by 400 ALD cycles at a current density of 3 mA/cm². Moreover, the ALD-grown MoS₂@3D-Ni-foam composite also retains high areal capacitance, even up to a high current density of 50 mA/cm². Finally, this directly grown MoS₂ electrode on 3D-Ni-foam by ALD shows high cyclic stability (>80%) over 4500 charge-discharge cycles which must invoke the research community to further explore the potential of ALD for such applications.