Electrochemical Capacitive Properties Research Articles

Versatile Activated Carbon Fibers Derived from the Cotton Fibers Used as CO2 Solid-State Adsorbents and Electrode Materials.

Activated carbon has an excellent porous structure and is considered a promising adsorbent and electrode material. In this study, activated carbon fibers (ACFs) with abundant microporous structures, derived from natural cotton fibers, were successfully synthesized at a certain temperature in an Ar atmosphere and then activated with KOH. The obtained ACFs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental analysis, nitrogen and carbon dioxide adsorption-desorption analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption measurement. The obtained ACFs showed high porous qualities and had a surface area from 673 to 1597 m2/g and a pore volume from 0.33 to 0.79 cm3/g. The CO2 capture capacities of prepared ACFs were measured and the maximum capture capacity for CO2 up to 6.9 mmol/g or 4.6 mmol/g could be achieved at 0 °C or 25 °C and 1 standard atmospheric pressure (1 atm). Furthermore, the electrochemical capacitive properties of as-prepared ACFs in KOH aqueous electrolyte were also studied. It is important to note that the pore volume of the pores below 0.90 nm plays key roles to determine both the CO2 capture ability and the electrochemical capacitance. This study provides guidance for designing porous carbon materials with high CO2 capture capacity or excellent capacitance performance.

NxCyMz metal hydroxide with Br− intercalation for high-performance structural supercapacitors

The rational design of advanced structural electrodes with superior electrochemical capacitive properties is one of the crucial hindrances be overcome for high energy density all-solid-state structural supercapacitors (ASSC). Herein, a simple synthesis of flower-like NxCyMz-layered metal hydroxides with high performance on nickel foam (NF) was proposed. Br− was inlaid to NxCyMz as a modified anion for the first time (denoted as B-N3C1M0.5-6U-1Br−). Compared with N3C1M0.5, the electrochemical performance of B-N3C1M0.5-6U-1Br− has been significantly enhanced. It reaches a maximum areal capacitance of 16.2 F/cm2 at 10 mA/cm2 and maintains a high capacitance retention of 11.6 F/cm2 even at a current density of 50 mA/cm2. Furthermore, the assembled asymmetric ASSC with B-N3C1M0.5-6U-1Br− as the positive electrode achieves a high areal energy density of 135.47 μWh/cm2 at a power density of 2250 μW/cm2. More importantly, six fully charged ASSCs with a total volume of 3 cm3 connected in series can power a temperature and humidity indicator successfully for approximately 18 min. These results demonstrate the good application potential of our B-N3C1M0.5-6U-1Br− electrode in buildings.

Effect of Substrate Temperature on the Electrochemical and Supercapacitance Properties of Pulsed Laser-Deposited Titanium Oxynitride Thin Films

Abstract Electrocatalytically active titanium oxynitride (TiNO) thin films were fabricated on commercially available titanium metal plates using a pulsed laser deposition (PLD) method for energy storage applications. The elemental composition and nature of bonding were analyzed using x-ray photoelectron spectroscopy (XPS) to reveal the reacting species and active sites responsible for the enhanced electrochemical performance of the TiNO electrodes. Symmetric supercapacitor devices were fabricated using two TiNO working electrodes separated by an ion-transporting layer to analyze their real-time performance. The galvanostatic charge-discharge studies on the symmetric cell have indicated that TiNO films deposited on the polycrystalline titanium plates at lower temperatures are superior to TiNO films deposited at higher temperatures in terms of storage characteristics. For example, TiNO films deposited at 300°C exhibited the highest specific capacity of 69 mF/cm2 at 0.125 mA/cm2 with an energy density of 7.5 Wh/cm2. The performance of this supercapacitor (300°C TiNO) device is also found to be ∼ 22 % better compared to that of a 500°C TiNO supercapacitor with a capacitance retention ability of 90% after 1000 cycles. The difference in the electrochemical storage and capacitance properties is attributed to the reduced leaching away of oxygen from the TiNO films by the Ti plate at lower deposition temperatures, leading to higher oxygen content in the TiNO films and, consequently, a high redox activity at the electrode/electrolyte interface.

Electrochemical Investigation of Lithium Perchlorate-Doped Polypyrrole Growing on Titanium Substrate

Lithium perchlorate-doped polypyrrole growing on titanium substrate (LiClO4-PPy/Ti) has been fabricated to act as electroactive electrode material for feasible electrochemical energy storage. A theoretical and experimental investigation is adopted to disclose the conductivity, electroactivity properties and interfacial interaction-dependent capacitance of LiClO4-PPy/Ti electrode. The experimental measurement results disclose that LiClO4-PPy/Ti reveals lower ohmic resistance (0.2226 Ω cm−2) and charge transfer resistance (2116 Ω cm−2) to exhibit higher electrochemical conductivity, a more reactive surface, and feasible ion diffusion to present higher double-layer capacitance (0.1930 mF cm−2) rather than LiClO4/Ti (0.3660 Ω cm−2, 65,250 Ω cm−2, 0.0334 mF cm−2). LiClO4-PPy/Ti reveals higher Faradaic capacitance caused by the reversible doping and dedoping process of perchlorate ion on PPy than the electrical double-layer capacitance of LiClO4/Ti caused by the reversible adsorption and desorption process of the LiClO4 electrolyte on Ti. Theoretical simulation calculation results prove that a more intensive electrostatic interaction of pyrrole N···Ti (2.450 Å) in LiClO4-PPy/Ti rather than perchlorate O···Ti (3.537 Å) in LiClO4/Ti. LiClO4-PPy/Ti exhibits higher density of states (57.321 electrons/eV) at Fermi energy and lower HOMO-LUMO molecule orbital energy gap (0.032 eV) than LiClO4/Ti (9.652 electrons/eV, 0.340 eV) to present the enhanced electronic conductivity. LiClO4-PPy/Ti also exhibits a more declined interface energy (−1.461 × 104) than LiClO4/Ti (−5.202 × 103 eV) to present the intensified interfacial interaction. LiClO4-PPy/Ti accordingly exhibits much higher specific capacitances of 0.123~0.0122 mF cm−2 at current densities of 0.01~0.10 mA cm−2 rather than LiClO4/Ti (0.010~0.0095 mF cm−2, presenting superior electroactivity and electrochemical capacitance properties. LiClO4-PPy/Ti could well act as the electroactive supercapacitor electrode for feasible energy storage.

Scalable electrochemical grafting of anthraquinone for fabrication of multifunctional carbon fibers

Carbon fiber electrodes were prepared by grafting anthraquinone molecules via a scalable electrochemical approach which simultaneously increased interfacial and electrochemical capacitance properties. In this work, anthraquinone diazonium salts were synthesized and grafted onto carbon fiber tows at various concentrations. These modified fibers were subsequently evaluated mechanically and electrochemically to analyze their suitability in structural supercapacitors. Compared to control fibers, the grafted anthraquinone groups resulted in a 30% increase in interfacial shear strength (IFSS) and 6.6× increase in specific capacitance. Industry application was also a focus thus carbon fibers were also modified with in-situ generated diazonium salts to determine the applicability to an in-line industrial process. Specifically, potentiostatic functionalization of fibers with in-situ generated diazonium salts AQ-1 and AQ-2, showed 3× and 4.3× increase in specific capacitance, respectively, relative to unmodified carbon fiber (CF). We expect that implementing a scalable method to introduce a conductive and electrochemically active covalently bound surface chemistry layer onto carbon fiber exhibits a higher specific capacitance than carbon fiber grafted with most other small molecules reported in literature. This will open new avenues for manufacturing multifunctional and high-performance fibers with tailored properties for specific/targeted applications.

Electrochemical capacitance and hydrogen adsorption behavior of activated carbon derived from cattail fiber

AbstractIn this paper, we have reported the synthesis of activated carbon (AC) from biomass cattail fiber through hydrothermal carbonization, followed by chemical activation, and its electrochemical capacitance and hydrogen storage properties. The AC exhibits a Brunauer‐Emmett‐Teller (BET) surface area (SBET) of 1597.5 m2g−1, determined from the low‐pressure N2 adsorption isotherm at 77 K using a BET‐multipoint plot. The AC sample shows a reversible hydrogen adsorption capacity of 0.25 wt.% H2 (1.25 mmol H2 g−1) at 293 K and 74 atm. The capacitance performance of AC was investigated with various conductive additives such as carbon nanotubes (CNTs), carbon black (CB), and reduced graphene‐oxide (rGO). From galvanostatic charge discharge (GCD) and cyclic voltammetry (CV) measurements, the as‐derived AC with polymer binder exhibits a specific capacitance (Cs) of 245.2 F g−1 at 0.2 A g−1 and 158.1 F g−1 at 5 mV s−1. Among the investigated conductive additives, AC with CNTs in KOH electrolyte exhibit highest Cs of 326 F g−1 at 0.2 A g−1 and 173 F g−1 at 5 mV s−1. Furthermore, the symmetrical two‐electrode device fabricated using AC with CNTs (as a conductive additive) in 1 M aq. Na2SO4 electrolyte shows a Cs of 97.2 F g−1 at 0.1 A g−1. The energy and power densities of the two‐electrode device were observed to be 28 kW kg−1 and 2.64 Wh kg−1, respectively.

NiCoZn-LDH grown with NiMoO4 nanoneedles as a high-performance electrode for supercapacitors

One of the key obstacles in preparing high-performance supercapacitors is designing advanced structures with excellent electrochemical capacitance properties. This paper proposes a simple and fast hydrothermal synthesis method for synthesizing high-performance flower-shaped NiCoZn layered hydroxides (NiCoZn-LDH) on a foam nickel substrate with a heterostructure of NiMoO4 (NMO) nanoneedles, and further forming a heterostructure with NiCoZn-LDH nanoflowers. The electrode material synthesized by this method has significantly improved electrochemical performance. Its specific capacitance reached 3030 mF/cm2 (863C/g) at 4 mA/cm2 and 2317 mF/cm2 (662C/g) at 10 mA/cm2. In addition, an asymmetric supercapacitor (ASC) constructs with NiCoZn-LDH@NMO@NF as the positive electrode material and activated carbon as the negative electrode material achieves an energy density of 0.222 mWh/cm2 at a power density of 0.08 W/cm2. Experimental studies shown that the heterostructure of NiCoZn-LDH@NMO plays a crucial role in improving the electrochemical performance of asymmetric supercapacitors. This provides new insights for the design of next-generation ASC active materials and is beneficial for the development of new energy storage devices.

A mixed dual-ion electrolyte for high-rate performance and remarkable cycling stability of NaMnO2 in hybrid supercapacitors

Recently, pre-sodiated manganese oxides are gaining more attention due to their higher specific capacitance and better cycling stability compared to pristine manganese oxides. However, previous reports on their electrochemical performances are limited to the aqueous electrolytes of Na+ and K+ ions. In this study, the electrochemical capacitance properties of hydrothermally synthesized NaMnO2 are investigated in aqueous electrolytes of 0.5 M NaNO3, 0.5 M Mg(NO3)2, and the mixed dual-ion electrolyte of 0.5 M NaNO3 and 0.25 M Mg(NO3)2. Although 0.5 M Mg(NO3)2 enables a higher specific capacitance of 427 F g−1 compared to that of 267 F g−1 in NaNO3 electrolyte, both electrolytes provide limited rate capability. On the other hand, the mixed dual-ion electrolyte of 0.5 M NaNO3+0.25 M Mg(NO3)2 enables highly improved rate capability along with a high specific capacitance of 325 F g−1, signifying the importance of the mixed dual-ion electrolyte for optimizing the specific capacitance and the high-rate capability of NaMnO2. An aqueous hybrid supercapacitor of activated carbon||NaMnO2 demonstrates excellent cycling stability of 98.9 % capacitance retention in the mixed electrolyte as compared to 96.9 % in NaNO3 electrolyte after 6000 cycles.

Sandwich structured pedot-TiO2/GO/PEDOT-TiO2 electrodes for supercapacitor

In this study, we fabricated a divergent strategy to enhance the electrochemical capacitive properties of electrodes via the cost-effective multistep green and facile electrodeposition and brush coating technique of PEDOT-TiO2/GO/PEDOT-TiO2 composite. The synthesised composite showed both EDLCs and pseudocapacitive behaviour with a good specific capacitance of 501 Fg−1 for sandwiched structure at 1 Ag−1. From the results, synthesized composite has a better ion transportation mechanism which leads to a fast charge–discharge cycle as well as a very high value of power density (500 kW/ kg) suitable for supercapacitor applications. The substance demonstrated excellent electrochemical stability, retaining 94 % of capacitance after 2000 cycles. The obtained nanocomposites were examined by FTIR, XRD, Raman, SEM-EDX and electrochemical analyses such as CV, GCD and EIS analyses. We consider that the highly stable PEDOT-TiO2/GO/PEDOT-TiO2 nanocomposite with super-capacitive behaviours is a very promising material for high-performance electrochemical storage.

Structural, morphological, and electrochemical capacitive properties of sputtered ZrN thin films for supercapacitor

Structural, morphological, and electrochemical capacitive properties of sputtered ZrN thin films for supercapacitor

MnO2 nanoflowers-decorated MXene nanosheets with enhanced supercapacitor performance

As typical energy storage devices, the extensive application of the supercapacitors is largely restricted by their relatively low energy storage efficiency, which motivates the development of various advanced electrode materials with sophisticated architectural design. Herein, we put forward a robust and controllable approach to construct a series of hybrid nanoarchitectures consisting of nanoflower-shaped MnO2 nanocrystals grown on super-thin Ti3C2Tx MXene nanosheets (MNF/Ti3C2Tx) via a convenient co-precipitation process. Such a delicate configuration enables the nanoarchitectures to provide prominent structural merits, such as 2D thin-sheet structure with large surface area, porous MnO2 nanoflower frameworks, activated electronic structure, and high electron conductivity. As a consequence, the optimized MNF/Ti3C2Tx electrode manifests superior electrochemical capacitive properties with a maximum specific capacitance of 348.5 F g−1 at 0.5 A g−1, excellent rate property, and reliable cycling stability with 91.9% retention of initial capacitance after 5000 cycles, all of which are more competitive than those of conventional MnO2 and Ti3C2Tx electrodes.

Modulating the Combinatorial Target Power of MgSnN2 via RF Magnetron Sputtering for Enhanced Optoelectronic Performance: Mechanistic Insights from DFT Studies.

The unique structural features of many ternary nitride materials with strong chemical bonding and band gaps above 2.0 eV are limited and are experimentally unexplored. It is important to identify candidate materials for optoelectronic devices, particularly for light-emitting diodes (LEDs) and absorbers in tandem photovoltaics. Here, we fabricated MgSnN2 thin films, as promising II-IV-N2 semiconductors, on stainless-steel, glass, and silicon substrates via combinatorial radio-frequency magnetron sputtering. The structural defects of the MgSnN2 films were studied as a function of the Sn power density, while the Mg and Sn atomic ratios remained constant. Polycrystalline orthorhombic MgSnN2 was grown on the (120) orientation within a wide optical band gap range of ∼2.20-2.17 eV. The carrier densities of 2.18× 1020 to 1.02 × 1021 cm-3, mobilities between 3.75 and 2.24 cm2/Vs, and a decrease in resistivity from 7.64 to 2.73 × 10-3 Ω cm were confirmed by Hall-effect measurements. These high carrier concentrations suggested that the optical band gap measurements were affected by a Burstein-Moss shift. Furthermore, the electrochemical capacitance properties of the optimal MgSnN2 film exhibited an areal capacitance of 152.5 mF/cm2 at 10 mV/s with high retention stability. The experimental and theoretical results showed that MgSnN2 films were effective semiconductor nitrides toward the progression of solar absorbers and LEDs.

Nanoporous Hollow Carbon Spheres Derived from Fullerene Assembly as Electrode Materials for High-Performance Supercapacitors

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m2 g-1) and large pore volumes (0.925 to 1.346 cm3 g-1) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g-1 at a 1 A g-1 current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g-1 at 1 A g-1 with sustained 50% capacitance at 10 A g-1 accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications.

Mg-doped NiCoP microflower grown on Ni foam for high-capacity supercapacitor electrode

In this work, a binder-free electrode Mg-doped NiCoP/Ni foam (MNCP-x/NF) was prepared via hydrothermal and phosphorization process, in which echinoid microflower-like MNCP-xwas densely loaded on the NF skeleton. By regulating the Mg2+doping amount, remarkable enhancements in the morphology, mass-loading of MNCP, electrode conductivity and overall electrochemical capacitive properties of MNCP-x/NF have been achieved. Particularly, moderate doped MNCP-0.5/NF exhibits the best energy storage performances with a superior specific capacity (4461 mC cm−2@ 2 mA cm−2), acceptable rate capability (retaining 50.1% @ 50 mA cm−2), and striking cyclability (retaining 83% over 5000 cycles). Moreover, a solid-state asymmetric supercapacitor constructed with MNCP-0.5/NF as cathode, graphene hydrogel/NF (GH/NF) as anode, PVA/KOH gel as electrolyte, outputs the notable energy density of 39.8 Wh kg−1(1.8 mWh cm−3) and power density of 16674 W kg−1(750 mW cm−3), companied by a superior cyclability (retaining 87% over 5000 cycles).

Electrochemical capacitance properties of pre-sodiated manganese oxide for aqueous Na-ion supercapacitors.

Mn-based oxides are widely investigated as electrode materials for electrochemical supercapacitors, because of their high specific capacitance in addition to the high abundance, low cost, and environmental friendliness of Mn. The pre-insertion of alkali metal ions is found to improve the capacitance properties of MnO2. While the capacitance properties of MnO2, Mn2O3, P2-Na0.5MnO2, and O3-NaMnO2etc. are reported, there is no report yet on the capacitive performance of P2-Na2/3MnO2, which has already been studied as a potential positive electrode material for Na-ion batteries. In this work, we have synthesized sodiated manganese oxide, P2-Na2/3MnO2 by a hydrothermal method followed by annealing at a high temperature of about 900 °C for 12 h. For comparison, manganese oxide Mn2O3 (without pre-sodiation) is synthesized by following the same method, but annealing at 400 °C. While P2-Na2/3MnO2 exhibits a high specific capacitance of 234 F g-1, Mn2O3 can deliver only 115 F g-1 when cycled at 0.4 A g-1 in an aqueous electrolyte of 1.0 M Na2SO4 in a three-electrode cell. An asymmetric supercapacitor Na2/3MnO2‖AC is assembled, which can exhibit a SC of 37.7 F g-1 at 0.1 A g-1 with an energy density of 20.9 W h kg-1, based on the total weight of Na2/3MnO2 and AC with an operational voltage of 2.0 V and possesses excellent cycling stability. This asymmetric Na2/3MnO2‖AC supercapacitor can be cost-effective considering the high abundance, low-cost and environmental friendliness of Mn-based oxides and aqueous Na2SO4 electrolyte.

Layered graphite foil/poly(3,4-ethylenedioxythiophene) electrode-enabled flexible electrochemical capacitors with observably boosted performances

• A simple mechanically exfoliated method is proposed to prepare LGF current collector. • LGF shows a unique layered microstructure with observably enlarged surface area. • The electrochemical properties of PEDOT are significantly affected by polymerized parameters. • LGF-constructed electrodes show observably enhanced electrochemical properties. • LGF/PEDOT flexible EC features high electrochemical properties and mechanical flexibility. Seeking a cheap flexible current collector and further enhancing charge storage capacity are still two crucial challenges to promote the practical applications of flexible electrochemical capacitors. In this work, we first fabricate layered graphite foil (LGF) current collector from low-cost GF by a facile and scalable mechanically exfoliated method. And meanwhile, the electropolymerization parameter-dependent supercapacitive performance of the poly(3,4-ethylenedioxythiophene) (PEDOT) as the electroactive material is investigated in detail. Electrochemical measurements verify that the electrochemical performances of PEDOT are notably improved via optimizing the electropolymerization parameters. More importantly, the capacitive behaviors of PEDOT electrodes are further observably boosted through using LGF current collector compared to GF, attributed to the 3D interface established between the PEDOT films and LGF. The LGF/PEDOT electrodes yield an areal-specific capacitance of 122.3 mF cm −2 and achieve high rate capability. Furthermore, a symmetrical electrochemical capacitor assembled by the LGF/PEDOT electrodes show superior electrochemical capacitive properties and highly mechanical flexibility. Even more impressively, it retains 92.1% and 94.3% of initial capacitance after 10,000 charge–discharge cycles and harsh mechanical deformation for 500 times, respectively. The LGF we develop not only ensures its high flexibility but distinctly enhances its electrochemical properties.

Low-temperature synthesized Mo2C and novel Mo2C–MnO2 heterostructure for highly efficient hydrogen evolution reaction and high-performance capacitors

Here, a facile and cost-effective way is proposed to synthesize Mo2C nanoparticles and Mo2C/MnO2 heterostructures by utilizing laboratory waste. The Mo2C nanoparticles are well encapsulated by graphitic carbon layers, which provide high cyclic and structural stability to Mo2C. The electrochemical hydrogen evolution reaction (HER) activity and capacitive properties of these samples are studied in detail. Mo2C synthesized at 500 °C exhibits higher HER activity with a Tafel slope of 79 mV dec−1. To further improve the HER activity of Mo2C nanoparticles, the heterostructure of Mo2C and MnO2 is developed. The optimized Mo2C/MnO2 (2:1) heterostructure delivers a current density of 10 mA cm−2 at a low overpotential of 58.3 mV and shows a very low Tafel slope of 36 mV dec−1. It exhibited long-term cyclic stability up to 5000 cyclic voltammetry (CV) cycles. This paper describes a novel and effective method for fabricating noble metal-free HER electrocatalysts utilizing laboratory waste as a carbon precursor.

Stable TiVCTx/poly-o-phenylenediamine composites with three-dimensional tremella-like architecture for supercapacitor and Li-ion battery applications

Two-dimensional double transition metal carbides and nitrides (MXenes) with unique out-of-plane ordering of the two metal atoms, have distinct and advantageous electrical properties owing to their chemical versatility and structural intricacy signify. However, MXenes are inclined to easily oxidized unstable surface, and lamellar structure agglomeration or stack, which impede their practicable application prospect in energy utilization and storage. Here, we propose a new strategy of spontaneous transforming few-layered TiVCTx MXene nanosheets directly into three-dimensional (3D) stable tremella-like architecture TiVCTx/poly-o-PD composites (N-TiVCTx) by utilizing o-phenylenediamine (oPD) as the monomer of oxidant-free polymerization. Meanwhile, the electrochemical performance of the supercapacitor using TiVCTx and N-TiVCTx in acidic and neutral electrolyte was examined for the first time. Notedly, N-TiVCTx composites show outstanding electrochemical capacitance property with a high specific capacitance of 282F g−1 at 10 mV s−1. Compared to TiVCTx, the capacitance was increased by 50 %. Besides, the 3D N-TiVCTx electrodes exhibit well stable pseudocapacitive charge storage with capacity up to 415.6 mAh g−1 at 0.1A g−1 and retain outstanding performance of 224 mAh g−1 at 2 A g−1 for lithium ion storage. The N-TiVCTx MXene greatly increased the stability consist of thermal stability, preferably chemical and electrochemical stability. Our work broadens the application of TiVCTx as electrode materials in energy storage domain and provides tactics to improve the other few-layered MXenes energy storage capacity as well as chemical stability.

Electrochemical Capacitive Properties of Ny/PP/GO Electro-spun Composite Coating on Stainless Steel in Acid Media

Composite materials were manufactured to obtain singular properties to be used as in electrochemical driven energy systems. An electrochemical evaluation was performed on electro-spun nylon 6,6 fibers (Ny), with different concentrations of tetra-para-amino-phenyl porphyrin (PP) and graphene oxide (GO) composite coating over stainless steel (SS), immersed in 1M H2SO4 aggressive sulfuric acid solution. Different film coatings behavior was obtained and compared using electrochemical impedance spectroscopy (EIS). Also, cyclic voltametry (CV) were performed on nylon/PP/GO composite coating system at different scan rates, and over film covered carbon cloth. For the electro-spun composite coating on stainless steel EIS, lower electro-spinning times present higher impedance, hence some corrosion protection. For greater electro-spinning times, larger capacitance values were observed. These were possibly due to thicker coating or mass transport adsorption-diffusion process through the composite film, respectively. For the composite coating, porphyrins, and graphene oxide interaction present ionic conductivity, reducing the impedance and promoting proton formation, property which could be used in charge storage systems.

Flexible, all-solid-state supercapacitors derived from waste polyurethane foams

Recently, flexible energy storage devices have attracted increasing interests for their promise in wearable electronic devices. In this study, the waste polyurethane foam (WPUF), a common polymeric waste having caused considerable environmental pollutions, is employed for the first time in the fabrication of flexible electrodes through wrapping carbon nanotubes (CNTs) and cellulose nanofibers (CNFs), pressing into thin foams with molds and in-situ growth of polyaniline (PANI). Within the hybrid foam, the CNT/CNF layer provides good electrical conductivity and hydrophilicity, while the highly porous structure still retained after appropriate hot pressing offers numerous pathways for efficient electrolyte ions transportation, and the loaded polyaniline is mainly responsible for the improved electrochemical capacitive properties. A symmetrical all-solid-state SC is assembled using the as-prepared WPUF-derived electrode, which displays superb physical and electrochemical performances, namely, excellent flexibility, high specific capacitance, and great stability at different bending angles. Interestingly, a flexible neat polyurethane membrane can also be easily prepared from WPUF via hot pressing, which is then applied to encapsulate SC to form a novel all-WPUF-based energy wristband to power an electronic watch. This study demonstrates a facile and scalable strategy for the fabrication of high-performance electrodes for wearable electronic devices, using the abundant polymeric wastes as the raw materials.