Symmetric Electrodes Research Articles

Spatial Auditory Masking Affects the Interhemispheric Asymmetry of Evoked Responses

Interhemispheric asymmetry of electrical brain activity was investigated in the conditions of spatial auditory masking. Moving test signals were presented either in silence or against the background of stationary maskers of various spatial positions. The spatial properties of the stimuli were defined by interaural level differences (ILD). Onset-energy responses (ON-responses), motion-onset responses (MOR) and OFF-responses were analyzed. To compute the topograms and to analyze asymmetry, the amplitudes of each component were averaged over the symmetric electrode clusters in the left and right hemispheres. The ON-responses showed a contralateral dominance of the N1 component in silence, and the degree of contralateral bias increased in masking conditions. Interhemispheric asymmetry of the P2 component was absent in silence. However, the P2 amplitude was higher in the right hemisphere in all combinations of masker and signal. The asymmetry of both deflections was maximal when the masker and the initial portion of the signal were separated by 180 degrees. On the contrary, the interhemispheric asymmetry of the motion-onset response was found only in silence: the cN1 deflection was biased to the side contralateral to the signal. The topography of the OFF-response was symmetrical under all experimental conditions.

High well‐matched energy gravimetric–volumetric symmetric super‐capacitor derived from hollow paper stack‐like biomass‐based functional carbon

AbstractBACKGROUNDTwo‐ and three‐dimensional porous activated carbon (C)‐based symmetrical supercapacitors show great potential for extraordinary gravimetric performance as sustainable energy storage. However, the applications of portable and microdimensional supercapacitors are limited by their low volumetric performance stemming from reduced density resulting from increased porosity and high fabrication costs. This study aimed to demonstrate the high gravimetric–volumetric performance of symmetrical supercapacitors from biomass‐based porous carbon‐sources materials through an environmentally benign development method. Unique porous C sourced from TENERA‐type palm oil stick waste was prepared using potassium hydroxide (KOH) as an activating agent. The electrode set resembled a solid plate with an encapsulation density of ≈1.40 g cm−3.RESULTThe study used superior gravimetric–volumetric electrode materials, including an adjusted specific surface area of 934 m2 g−1, single‐doped optimization, and a hollow paper‐stack‐like morphological structure with a high C content of 91%. The results showed that the best electrode in the 1 mol L−1 H2SO4 electrolytes exhibited a high gravimetric capacitance of 233 F g−1 and an extraordinary volumetric capacitance of 326 F cm−3 at 1 A g−1. Furthermore, their coulombic efficiency was ≈99.1% at 10 A g−1. The symmetrical electrode device performed a high gravimetric–volumetric energy density of 19.03 Wh kg−1 and 26.6 Wh L−1 at a maximum output power density of 1.7 kW kg−1 and 1.9 kW L−1, respectively.CONCLUSIONThese results indicate that the applied method development and the C‐biomass‐based electrode material design could achieve a high, well‐matched gravimetric–volumetric performance balance in symmetric supercapacitor devices. © 2023 Society of Chemical Industry.

Interlayer Injection of Low‐Valence Zn Atoms to Activate MXene‐Based Micro‐Redox Capacitors With Battery‐Type Voltage Plateaus

AbstractInsufficient and unstable energy output is the bottleneck issue radically restricting the application of micro‐supercapacitors (MSCs). Herein, an interlayer atom injection strategy that can anchor low‐valence Zn atoms (Znδ+, 0 < δ <2) on O‐terminals of Ti3C2Tx (MXene) flakes within the MXene/silver‐nanowires hybrid cathode of symmetric MSCs is first presented. Combining the polyacrylamide/ZnCl2 hydrogel electrolyte rich in Cl− and Zn2+ ions, the matched Znδ+/Zn2+ (−0.76 V vs SHE) and Ag/AgCl (0.23 V vs SHE), redox couples between the symmetrical electrodes are activated to offer faradaic charge storage beside ions‐intercalation involved pseudocapacitance. Thus, a battery‐type voltage plateau (≈0.9 V) appears in the discharge curve of a fabricated pseudo‐symmetric micro‐redox capacitor, simultaneously achieving energy density enhancement (117 µWh cm−2 at 0.5 mA cm−2) and substantially improved power output stability (46% of the energy from the plateau region) relative to that before activation (98 µWh cm−2 without voltage platform). The work provides a fire‐new strategy to overcome the performance bottlenecks confronting conventional MSCs.

Preparation and Characterization of Physically Activated Carbon and Its Energetic Application for All-Solid-State Supercapacitors: A Case Study.

Biomass-derived activated carbons have gained significant attention as electrode materials for supercapacitors (SCs) due to their renewability, low-cost, and ready availability. In this work, we have derived physically activated carbon from date seed biomass as symmetric electrodes and PVA/KOH has been used as a gel polymer electrolyte for all-solid-state SCs. Initially, the date seed biomass was carbonized at 600 °C (C-600) and then it was used to obtain physically activated carbon through CO2 activation at 850 °C (C-850). The SEM and TEM images of C-850 displayed its porous, flaky, and multilayer type morphologies. The fabricated electrodes from C-850 with PVA/KOH electrolytes showed the best electrochemical performances in SCs (Lu et al. Energy Environ. Sci., 2014, 7, 2160) application. Cyclic voltammetry was performed from 5 to 100 mV s-1, illustrating an electric double layer behavior. The C-850 electrode delivered a specific capacitance of 138.12 F g-1 at 5 mV s-1, whereas it retained 16 F g-1 capacitance at 100 mV s-1. Our assembled all-solid-state SCs exhibit an energy density of 9.6 Wh kg-1 with a power density of 87.86 W kg-1. The internal and charge transfer resistances of the assembled SCs were 0.54 and 17.86 Ω, respectively. These innovative findings provide a universal and KOH-free activation process for the synthesis of physically activated carbon for all solid-state SCs applications.

Second-harmonic currents in rf-biased, inductively coupled discharges

Capacitively-coupled plasmas generate strong current or voltage signals at harmonics of their driving frequencies. Inductively coupled plasma (icp) systems generally do not, unless they are equipped with capacitively-coupled rf bias, which generates strong signals at harmonics of its driving frequency. Recently, however, at an asymmetric, rf-biased electrode, a current component was detected at the second harmonic of the inductive source frequency, not the rf-bias frequency. The origin of this current is here investigated (in argon discharges at 1.3 Pa) by comparison with measurements made at a symmetric electrode and predictions made by two numerical models. The first simulates the sheath at the rf-biased electrode; the second models the plasma. Because capacitive coupling from the inductive source was minimized by a Faraday shield, the nonlinearity of the sheath contributes negligible second-harmonic current. Modulation of the photon flux in the plasma, however, produces a second-harmonic current photoemitted from the rf-biased electrode. The external circuitry and nonlinear inductive coupling produce a second-harmonic sheath voltage, which in turn generates second-harmonic current both directly and through a transit-time effect. The second model simulates how electrons emitted from the electrode—and then reflected at the quartz dielectric window of the inductive source—are deflected by the electric and magnetic fields in the plasma. It also gives predictions for the transit-time effect. Magnetic deflections and the transit-time effect usually dominate the electric deflection. Together these three mechanisms produce a second-harmonic current that has a Fourier amplitude approximately half the current that is elastically reflected at the icp window. These results suggest it may be possible to use the second-harmonic current to determine the elastic reflection coefficient at the window.

Fabrication of tricarboxylate-neodymium metal organic frameworks and its nanocomposite with graphene oxide by hydrothermal synthesis for a symmetric supercapacitor electrode material

Efficient energy storage and delivery of electrical energy is necessary for the use of advanced electrode materials in super-capacitors, rendering their development pivotal. We employed simple and economical hydrothermal technique to synthesize Nd-metal organic frameworks (MOFs) and Nd-MOFs/GO composite and evaluated their suitability as electrode materials through comprehensive investigation. Characterizations of the synthesized materials were done by various techniques, including XRD, FTIR (using ATR method) and SEM. Based on the results obtained, it was found that the Nd-MOFs/GO composite-based electrode had a specific capacitance of 633.5 Fg−1 when tested at a current density of 0.3 Ag−1, which is significantly higher than that of Nd-MOFs electrode (11.3 Fg−1). Additionally, electrochemical impedance spectroscopy (EIS) analysis demonstrated the lowest equivalent series resistance (ESR) of 0.8 Ω for the Nd-MOFs/GO electrode. The Nd-MOFs/GO composite electrode exhibited a cyclic stability of 88.76 % after 4000 cycles and coulombic efficiency of 95.1%, when subjected to a current density of 3 Ag−1. Moreover XRD showed that the synthesized hybrid exhibited an improved crystallinity of the hexagonal phase. The FTIR analysis using ATR method confirmed the presence of organic ligands and functional groups in the synthesized materials. The results of our study indicate that the Nd-MOFs/GO hybrid nanocomposite-based electrode material holds potential as a highly efficient candidate for super-capacitor applications. The reported method of synthesizing MOFs provides an effective approach to fabricate new electrode materials with excellent electrochemical characteristics.

High-Performance Planar Self-Driven Visible and Near-Infrared Photodetector Based on Pb-Sn Perovskite Single Crystals.

MAPbI3 single crystals (SCs) are promising candidates for self-driven photodetectors due to their spontaneous polarization properties. However, their absorption cutoff wavelength, which is limited to 850 nm, severely hinders their further application in near-infrared photodetectors. In this work, a series of high-quality (MAPbI3)x(FASnI3)1-x (x = 0.8, 0.5 and 0.2) SCs with low defect density and wide absorption range were obtained by employing 1,4-pentanolactone as the solvent at low temperature. Typically, (MAPbI3)0.2(FASnI3)0.8 SCs grown at 32 °C realize absorption in the UV-vis-NIR range from 200 to 1120 nm, which is superior among the absorption wavelengths reported for Pb-Sn perovskite SCs. Resultantly, by merit of the spontaneously polarized built-in electric field, for (MAPbI3)0.2(FASnI3)0.8 SCs based self-driven photodetectors with planar symmetric electrodes exhibiting significant responsivities at 405-1064 nm, the device achieved a maximum responsiveness and detection of 0.247 A/W and 1.17 × 1012 Jones, respectively.

The Performance of Chitosan-based Activated Carbon for Supercapacitor Applications towards Sustainable Energy Technologies

In sustainable technologies, the application of supercapacitors (SC) for energy conversion and storage systems is rapidly increasing. Supercapacitors are widely employed in applications that require fast charge and discharge phases, such as in the automobile industry, where they are utilized in energy storage. Chitosan (CS) is a natural polymer material utilized in supercapacitor fabrication. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period, and longer lifetime. In this research, the fabrication of symmetric supercapacitors with activated carbon (AC) electrodes has been investigated in order to analyze their performance characteristics. AC is derived from CS biomass, which has remarkable biodegradability. It has been chemically activated using ZnCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as the activating agent. CS has been activated inside a furnace at 500, 600, and 700°C in an inert N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> atmosphere. A 1M aqueous potassium hydroxide (KOH) solution is used as the electrolyte. The test using electrolytes (KOH) revealed that the electrode's specific capacitance was 74.7 Fg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , the highest value discovered. However, using organic electrolytes would have produced better results that can be used as a guide for future advancements. The influence of activation temperature on the porous characteristics of prepared AC was investigated utilizing surface area and pore size analyses. The morphological characteristics of synthesized AC were analyzed through scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). Symmetric SC electrodes fabricated is analyzed in a two-electrode system applying standard electrochemical characterization methods using the potentiostat. Symmetric SC electrodes fabricated are analyzed in a two-electrode system applying standard electrochemical characterization methods using the potentiostat.

Electrowetting lattice Boltzmann method for micro- and nano-droplet manipulations.

Electrowetting has become a widely used tool for manipulating tiny amounts of liquids on surfaces. This paper proposes an electrowetting lattice Boltzmann method for manipulating micro-nano droplets. The hydrodynamics with the nonideal effect is modeled by the chemical-potential multiphase model, in which the phase transition and equilibrium are directly driven by chemical potential. For electrostatics, droplets in the micro-nano scale cannot be considered as equipotential as macroscopic droplets due to the Debye screening effect. Therefore, we linearly discretize the continuous Poisson-Boltzmann equationin a Cartesian coordinate system, and the electric potential distribution is stabilized by iterative computations. The electric potential distribution of droplets at different scales suggests that the electric field can still penetrate micro-nano droplets even with the screening effect. The accuracy of the numerical method is verified by simulating the static equilibrium of the droplet under the applied voltage, and the results show the apparent contact angles agree very well with the Lippmann-Young equation. The microscopic contact angles present some obvious deviations due to the sharp decrease of electric field strength near the three-phase contact point. These are consistent with previously reported experimental and theoretical analyses. Then, the droplet migrations on different electrode structures are simulated, and the results show that droplet speed can be stabilized more quickly due to the more uniform force on the droplet in the closed symmetric electrode structure. Finally, the electrowetting multiphase model is applied to study the lateral rebound of droplets impacting on the electrically heterogeneous surface. The electrostatic force prevents the droplets from contracting on the side which is applied voltage, resulting in the lateral rebound and transport toward the side.

Micro-Cup Architecture for Printing and Coating Asymmetric 2d-Material-Based Solid-State Supercapacitors.

High energy density micro-supercapacitors (MSCs) are in high demand for miniaturized electronics and microsystems. Research efforts today focus on materials development, applied in the planar interdigitated, symmetric electrode architecture. Anovel "cup & core" device architecture that allows for printing of asymmetric devices without the need of accurately positioning the second finger electrode here have been introduced. The bottom electrode is either produced by laser ablation of a blade-coated graphene layer or directly screen-printed with graphene inks to create grids with high aspect ratio walls forming an array of "micro-cups". A quasi-solid-state ionic liquid electrolyte is spray-deposited on the walls; the top electrode material -MXene inks- is then spray-coated to fill the cup structure. The architecture combines the advantages of interdigitated electrodes for facilitated ion-diffusion, which is critical for 2D-material-based energy storage systems by providing vertical interfaces with the layer-by-layer processing of the sandwich geometry. Compared to flat reference devices, volumetric capacitance of printed "micro-cups" MSC increased considerably, while the time constant decreased (by 58%). Importantly, the high energy density (3.99 µWh cm-2 ) of the "micro-cups" MSC is also superior to other reported MXene and graphene-based MSCs.

Development of titanium-doped SmBaMn2O5+δ layered perovskite as a robust electrode for symmetrical solid oxide fuel cells

It is a big challenge ahead of finding a symmetric electrode material that optimally works as both anode and cathode, with excellent structural and chemical stability and high catalytic activity. Herein, we propose a high-performance symmetric electrode material, SmBaMn1.9Ti0.1O5+δ (SBMTi), with a single A-site layered perovskite phase in both reducing and oxidizing atmospheres. Owing to the high binding energy, titanium doping can enhance the structural stability and improve the catalytic activity to the hydrogen oxidation and oxygen reduction processes. The simple Ti-doping strategy enables a dramatic reduction in stoichiometric oxygen change upon oxidizing and reducing atmosphere alternation, and a considerable decrease in thermal expansion coefficient. The symmetrical cell with SBMTi electrode can provide a maximum power density of 603 mW cm−2 at 900 °C, and shows a relatively stable thermal-cycle and atmosphere alternation performance. The developed SmBaMn1.9Ti0.1O5+δ shows great potential as symmetric electrode in symmetrical solid oxide fuel cells.

Fabrication of high energy density symmetric polyaniline/functionalized multiwalled carbon nanotubes supercapacitor device with swift charge transport in different electrolytic mediums

This work is conducted with aim of enhancing the energy density and cycling performance of PANI/fMWCNTs within a very low molar concentration of the mixed acidic/neutral electrolyte where not only the medium, but the structure too facilitates easy charge transfer because of increased ionic mobility. A promising optimized flower-like morphology of symmetric supercapacitor electrode of functionalized Multi-walled Carbon Nanotubes (f-MWCNTs) with Polyaniline (PANI) composites are prepared by in-situ chemical oxidative polymerization method with different doping concentrations of f-MWCNTs (5 wt% and 10 wt%). The synthesized PANI/f-MWCNTs (5 wt%) composite provides a large surface area (133.55 m2/g), high porosity (11.24 nm), low internal resistance (6.16 Ω) and charge transfer property (2.74 Ω) between the electrode within a mixed (0.1 M H2SO4 + 0.1 M Na2SO4) electrolyte interface. To overcome the cracking/swelling of PANI during electrochemical performance, the electrodes of PANI are incorporated with different doping concentration of f-MWCNT (5 wt% or 10 wt%). With a specific capacitance of 867 F g−1 at 10 mV/s, energy density ~77.0 Whkg−1 and power density ~801 Wkg−1, PFC1 nanocomposite indicates ~20 % more stability than pure PANI. Also, the nanocomposite electrode cell shows a columbic efficiency of 97 % and 98.5 % of its initial value of specific capacitance after 10,000 GCD cycles in a mixed acidic/neutral (0.1 M H2SO4 + 0.1 M Na2SO4) aqueous electrolytic solution.

Highly stable electrodeposited 2D Mn0.2Co0.8 LDH nanoplatelets based symmetric supercapacitor electrode

High performance Mn0.2Co0.8 layered double hydroxide (LDH)-based binder free supercapacitor symmetric electrode is fabricated via single step electrochemical deposition. The synthesized Mn0.2Co0.8 electrode shows specific capacitance of 370.58–141.17 F/g (315–120 C/g) at 2–40 A/g within potential range −0.45–0.4 V along with 172.72% capacitance retention for 9000 GCD cycles. Additionally, a symmetric supercapacitor is also made utilizing Mn0.2Co0.8 LDH both as cathode and anode. The high potential of synthesized electrode as a supercapacitor material is shown by achieving a specific capacitance of 106.91–34.57 F/g at 0.5–3 A/g within a cell voltage of 0 to 0.8 V, as well as outstanding cyclic stability over 5000 GCD cycles. Red LEDs are used to analyze the real world application of the fabricated symmetric supercapacitor for energy storage and it is assumed that the future portable electrical systems and gadgets might benefit from the device based on the reported material and synthesis technique.

Intrinsic Properties of GO/RGO Bilayer Electrodes Dictate Their Inter-/Intralayer Intractability to Modulate Their Capacitance Performance.

The demand for high-capacity energy storage along with high power output and faster charging has made supercapacitors a key area of energy research. The charge storage capacity of capacitors is largely dependent on the electrode materials utilized. To that end, graphene oxide (GO) and reduced GO (RGO) have been extensively employed for preparing supercapacitors. However, to date, no study has reported utilizing a GO/RGO bilayer electrode material for supercapacitor application. Herein, we report the synthesis of GO/RGO bilayer electrodes on fluorine-doped tin oxide (FTO) conducting substrates with four different combinations, namely, RGO-RGO, RGO-GO, GO-RGO, and GO-GO. Electrochemical capacitance analysis based on a symmetrical electrode configuration revealed that FTO-GO-RGO electrodes had the best areal capacitance performance. However, the highest specific areal capacitance (27.85 mF/cm2) for both symmetric/asymmetric configurations was achieved with FTO-GO-RGO as the anode and FTO-GO-GO as the cathode. The heterogeneous capacitance performance of the GO/RGO bilayer systems was analyzed based on structural characterization and computational simulation methods. Based on our analysis, we identified that inter-/intralayer molecular interaction of the GO/RGO bilayer sheets through the confinement pressure effect might have prompted their unique physicochemical properties. This work highlights the importance of probing multilayer GO/RGO electrode fabrication methods for preparation of high-capacity supercapacitors through fine-tuning their structural and molecular properties.

Ultraslim and highly flexible supercapacitor based on chemical vapor deposited nitrogen-doped bernal graphene for wearable electronics

Nitrogen-doped Bernal graphene has several advantages, including improved electrical conductivity, enhanced stability and better compatibility with electrolytes. This article presents the synthesis of few-layer pristine graphene and nitrogen-doped Bernal graphene (CVDNG) through the Low-pressure chemical vapor deposition approach and its application for flexible supercapacitors. A novel hot lamination-assisted approach is employed to transfer the graphene on the desired substrates, enabling the reusability of copper. Raman mapping is utilized to analyze the characteristic bands and statistical distribution of Bernal stacking in CVDNG. The doping in graphene is confirmed through the X-ray photoelectron spectroscopy suggesting the content of pyrrolic-N (73.38%), pyridinic-N (20.28%) and graphitic-N (6.38%) in the CVDNG. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy are performed by sandwiching the polyvinyl alcohol-sodium perchlorate based hydrogel membrane between two symmetrical supercapacitor electrodes. CVDNG symmetrical supercapacitor device delivers an enhanced areal capacitance of 26.75 mF cm−2 with a high energy density of 2.14 mWh cm−2 with a power density of 72 mW cm−2 at 0.05 mA cm−2. The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions and excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles.

High-Performance Ambipolar and n-Type Emissive Semiconductors Based on Perfluorophenyl-Substituted Perylene and Anthracene.

Emissive organic semiconductors are highly demanding for organic light-emitting transistors (OLETs) and electrically pumped organic lasers (EPOLs). However, it remains a great challenge to obtain organic semiconductors with high carrier mobility and high photoluminescence quantum yield simultaneously. Here, a new design strategy is reported for highly emissive ambipolar and even n-type semiconductors by introducing perfluorophenyl groups into polycyclic aromatic hydrocarbons such as perylene and anthracene. The results reveal that 3,9-diperfluorophenyl perylene (5FDPP) exhibits the ambipolar semiconducting property with hole and electron mobilities up to 0.12 and 1.89 cm2 V-1 s-1 , and a photoluminescence quantum yield of 55%. One of the crystal forms of 5FDPA exhibits blue emission with an emission quantum yield of 52% and simultaneously shows the n-type semiconducting property with an electron mobility up to 2.65 cm2 V-1 s-1 , which is the highest value among the reported organic emissive n-type semiconductors. Furthermore, crystals of 5FDPP are utilized to fabricate OLETs by using Ag as source-drain electrodes. The electroluminescence is detected in the transporting channels with an external quantum efficiency (EQE) of up to 2.2%, and the current density is up to 145 kA cm-2 , which are among the highest values for single-component OLETs with symmetric electrodes.

Diagnostics of supercapacitors using cyclic voltammetry: Modeling and experimental applications

In this article, we analyzed a method of cyclic voltammetry (CV) with respect to diagnostics of supercapacitors. The main goal deals with the study of the voltage sweep rate limits allowing to reach equilibrium conditions during recording of CV curves. A mathematical model of cycling based on the De Levie model has been developed. Using this model, the CV curves of a supercapacitor with two symmetric porous electrodes and a separator have been calculated numerically for different sweep rates. These curves are in a good agreement with experimental CV curves. For the first time, an exact analytical solution is obtained for linear voltage sweep for a symmetric supercapacitor during the charge process. The concept of equilibrium CV curves is proposed and the criterium for the equilibrium conditions depending on voltage sweep rate and other parameters of the system is established. When the potential sweep rate exceeds the equilibrium conditions, the CV curves deviate from a rectangular shape and take the form of a “modified ellipses with sharp edges”. A review of publications related with experimental measurements of CV curves has been provided using the developed concept of equilibrium conditions. Application of themathematical model to experimental CV curves makes it possible to reveal the presence of Faraday reactions.

Mixed-phase MoS2 nanosheets anchored carbon nanofibers for high energy symmetric supercapacitors

Mixed-phase MoS2 (MS) nanosheets anchored carbon nanofibers (CNFs) have been synthesized via a hydrothermal route. The concentration of CNFs has been varied in the MS/CNF-x composite (where, x = 1, 1.5, 2, and 3 represents the molar concentration of CNFs) to investigate the impact of CNFs on the electrochemical behavior of the material. The incorporation of CNFs offers a conductive path for the diffusion of ions and provides structural support which limits the restacking of the MoS2 layers during the charging/discharging. The MS/CNF-2 composite delivered superior electrochemical performance compared with the other composites owing to the positive synergy between MoS2 and CNFs. The specific capacitance manifested by MS/CNF-2 (626.08 F g−1 at 1 A g−1) is about four times that of pristine MS (159.35 F g−1). It is also observed that MS/CNF-2 exhibited higher electrochemical stability than pristine MS. Furthermore, the symmetric supercapacitor (SSC) device achieved a tremendous energy density of 42.6 Wh kg−1 at 2.4 kW kg−1. To test its practical applicability, LEDs of different color (red, green, and blue) have been illuminated using a series combination of three symmetric electrode cells. The red, green, and blue LEDs lighted up for 15 mins, 7 mins, and 3 mins. The results demonstrate the superiority of the MS/CNF composite for symmetric supercapacitors.

Porous polymer cement composites for quasi-solid graphene supercapacitors

We reported a strong and cheap polymer modified Portland cement (PC) composites with interconnected pores as solid electrolyte for graphene supercapacitors. The porous polymer cement composites solved the low ionic conductivity question of construction materials. Herein, the effects of PAA molecular weight, PAA content and curing age on electrical energy storage and mechanical property were investigated in detail. The PAA (Mw = 5000)/PC-5 % sample delivers the best multifunctionality. Moreover, the as-assembled solid supercapacitor exhibits an optimum energy density of 15.93 mW h cm−2, as well as a considerable compressive strength of 16.2 MPa at 28 days. In addition, introducing PAA can result in high porosity which is conductive to ion migration. The symmetric electrode is directly loaded with GO on Ni foam by electrophoretic, followed by high temperature thermal reduction. The integrated solid supercapacitors are effective, holistic and effortless to operate at room temperature, and they exert a crucial role in energy storage field of inorganic building materials application.

Funnel Devices Based on Asymmetrically Strained Transition Metal Dichalcogenides.

The strain applied to transition metal dichalcogenides (TMDs) reduces their energy bandgap, and local strains result in a funnel-like band structure in which funneled excitons move toward the most strained region. Herein, a funnel device based on asymmetrically strained WS2 and MoS2 is reported. Asymmetric strains are induced by transferring the TMD flakes onto a fork-shaped SU-8 microstructure. Raman and photoluminescence spectra peaks are shifted according to the morphology of the SU-8 microstructure, indicating the application of asymmetric strains to the TMDs. To investigate whether funneled excitons can be converted to electrical currents, various devices are constructed by depositing symmetric and asymmetric electrodes onto the strained TMDs. The scanning photocurrent mapping images follow a fork-shaped pattern, indicating probable conversion of the funneled excitons into electrical currents. In the case of the funnel devices with asymmetric Au and Al electrodes, short-circuit current (ISC ) of WS2 is enhanced by the strains, whereas ISC of MoS2 is suppressed because the Schottky barrier lowers with increasing strain for the MoS2 . These results demonstrate that the funnel devices can be implemented using asymmetrically strained TMDs and the effect of strains on the Schottky barrier is dependent on the TMD used.