Graphene Electrodes Research Articles

Stretchable supercapacitors made with plasticine/graphene/CeNdNiO2 composite electrodes

Mechanically strong, flexible and deformable supercapacitors (SCs) are of particular interest for the wearable electronics. Therefore, stretchable dual SCs composed of two single devices were fabricated and studied in this research. Soft SC electrodes were made of plasticine decorated with graphene microplates and had cylindrical shape. To enhance the capacitance of the devices, Ce0.8Nd0.1Ni0.1O2-δ (CNNO) particles were added as redox material in the SC electrodes. Electrochemical tests were performed for the single SCs made only with graphene electrodes and produced capacitances/energy-densities of 178–215 F g−1/24–30 W h kg−1. When the single graphene supercapacitors are connected in-series, a maximum specific capacitance/energy density of 370.9 F g−1/51.4 W h kg−1 is obtained. The single SCs made with CNNO particles had higher specific capacitances/energy-densities of 326–436 F g−1/45–61 W h kg−1. The SCs made with CNNO were connected in-series and in-parallel, producing specific capacitances/energy densities of 257.1 F g−1/35.7 W h kg−1 and 516 F g−1/71.7 W h kg−1, respectively. Thus, incorporating the CNNO particles to the SCs enhanced their capacitance by 51–144%. According to the CV curves, the current densities are increased from 6 to 15 A g−1 to 37 A g−1 when the single devices are connected in-parallel. If the single devices are connected in-series, the output voltages of the supercapacitors increased from 1 to 1.3 V. The devices were also subjected to stretching at 25% and the capacitance dropped by 90–96.5% because the electrodes were broken. However, the devices were unstretched and the capacitance was recovered by ≈ 40–60%. If those last devices are heated at 50 °C, the SC electrodes are totally repaired, and the capacitance is even 12–33% higher in comparison with the original capacitance for the non-stretched device. Additionally, absorbance, Raman and XPS analyses revealed the presence of oxygen vacancies, Ce3+/Ce4+, Nd0/Nd1+/Nd3+ and Ni0/Ni2+/Ni3+, which worked as redox centers for the charge storage. In summary, the results presented here demonstrate that our stretchable SC can operate in-series or in-parallel connection and their electrodes can be re-built after applying heat. The cost of those SCs is drastically reduced because they are made with plasticine and due to their flexibility and stretchability, they are good candidates for wearable applications, which require deformable devices.

Flexible self-supporting laser-induced graphene electrode devices for highly sensitive electrochemical analysis of Allura Red

Flexible self-supporting laser-induced graphene electrode devices for highly sensitive electrochemical analysis of Allura Red

MOFs-derived 3D porous ZnCo2O4 nanocubes intercalated 3D graphene electrode for Superior lifespan hybrid supercapacitors.

MOFs-derived 3D porous ZnCo2O4 nanocubes intercalated 3D graphene electrode for Superior lifespan hybrid supercapacitors.

Non-enzymatic glucose detection with screen-printed chemiresistive sensor using green synthesised silver nanoparticle and multi-walled carbon nanotubes-zinc oxide nanofibers

Non-enzymatic screen-printed chemiresistive interdigitated electrodes (SPCIE) were designed and fabricated using a low-cost screen-printing method for detection of the glucose. The interdigitated electrodes (IDE) pattern was printed using conductive graphene ink on the glossy surface of the photo paper. The proposed glossy photo paper-based SPCIE are functionalized with multi-walled carbon nanotubes-zinc oxide (MWCNTs-ZnO) nanofibers to create the chemiresistive matrix. Further, to bind these nanofibers with the graphene electrode surface, we have used the green synthesized silver nanoparticles (AgNPs) with banana flower stem fluid (BFSF) as a binder solution. AgNPs with BFSF form the conductive porous natural binder layer (CPNBL). It does not allow to increase the resistivity of the deposited material on graphene electrodes and also keeps the nanofibers intact with paper-based SPCIE. The synthesized material of MWCNT-ZnO nanofibers and green synthesized AgNPs with BFSF as a binder were characterized by Ultraviolet-visible spectroscopy (UV–vis), scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The amperometric measurements were performed on the proposed SPCIE sensor to detect the glucose sample directly. The innovative paper-based SPCIE glucose sensor exhibits a linear corelation between current measurements and glucose concentration in the range between 45.22 μm and 20 mm, with a regression coefficient (R 2) of 0.9902 and a lower limit of detection (LoD) of 45.22 μm (n = 5). The sensitivity of the developed SPCIE sensor was 2178.57 μAmM−1cm−2, and the sensor’s response time determined was approximately equal to 18 s. The proposed sensor was also tested for real blood serum sample, and relative standard deviation (RSD) was found equal to 2.95%.

In-situ Mg-Al LDH infused lignin-derived laser scribed graphene for facilitated ion transport in flexible supercapacitor application

BackgroundInnovations in the synthesis of hybrid materials have led to technology advancement of the microsupercapacitor. Delaminated layered double hydroxide (LDH) reduces self-agglomeration and increases energy density in graphene-based supercapacitors. The incorporation of delaminated LDH with oil palm lignin derived laser scribed graphene in neutral PAAS/K2SO4 gel electrolyte for flexible microsupercapacitor applications was investigated. MethodVarious concentrations of positively charged sucrose-delaminated Mg-Al LDH nanosheets produced through the coprecipitation method were hybridised with negatively charged oil palm lignin-derived laser scribed graphene (L-LSG) through electrostatic interaction. Significant FindingsHybrid laser scribed graphene developed from delaminated Mg-Al LDH at a concentration of 10 gL−1 (L-LSG/D-MgAl-10) had the largest surface area of 49.335 m2g−1. The incorporation of Mg-Al LDH nanosheets on l-LSG were further validated by FESEM, TEM, XRD, Zeta potential and other characterizations. It also had the highest areal capacitance and energy density, measuring 40 mFcm−2 and 0.00296 mWhcm−2, respectively, at a current density of 0.08 mAcm−2. The fabricated microsupercapacitor has exceptional bending capabilities and capacitance retention of 89.2% after 5000 cycles. In summary, by inducing additional pseudocapacitance, delaminated Mg-Al LDH improved the overall effectiveness of the oil palm lignin derived graphene electrode compared to pristine graphene.

Tailoring single-molecule conductance with structured graphene electrodes

Modulation of electric currents through single-molecule junctions is usually achieved by synthesis of molecules with desired functionalities, in conjunction with suitable molecule–electrode contacts through specific anchoring groups. An alternative to this approach, barely explored so far, is to use structured electrodes, where conductivity could eventually be controlled by changing the specific anchoring site within the very same electrode. Here, we theoretically investigate how to exploit the pronounced anisotropy of corrugated graphene deposited on Ru(0001) (Gr/Ru) to tailor single-molecule conductivity in 4-aminophenyl and 4-aminobenzonitrile. We show that currents induced in the upper and lower anchoring positions in the Gr/Ru moiré are substantially different, irrespective of the chosen molecule. The magnitude of these currents can differ by as much as an order of magnitude at specific bias voltages. We also show that both molecules display rectifying properties, which can differ by up to a factor of five in different anchoring sites. Interestingly, the observed modulations strongly depend on the chemical binding nature between the molecule and the electrode, (strong) covalent bond for 4-aminophenyl and (weak) physisorption for 4-aminobenzonitrile. All this suggests that Gr/Ru can be an ideal electrode to modulate single-molecule electric conductivity under experimental conditions that are available in many laboratories.

Enhancing energy storage performance in flexible all-solid-state laser-induced graphene-based microsupercapacitors through the addition of carbon black and Prussian blue

In this study, we present an efficient and scalable method for the stepwise modification of polyimide (PI)-based laser-induced graphene using environmentally friendly additives. The as-prepared composite materials were applied as flexible electrodes for high-performance all-solid-state microsupercapacitors (MSCs). The electrochemical deposition of carbon black (CB) microparticles and Prussian blue (PB) inorganic redox dye onto the laser-induced graphene electrode surface significantly enhanced the electrochemical performance of the devices. The areal capacitance of MSCs increased by 116 % after the addition of CB to the electrode composition, 201 % after the modification of the electrode surface with PB, and 325 % after incorporating both CB and PB (CB-PB). The exhibited capacitance values at an applied current density of 0.1 mA·cm−2 are equal to 27.6, 38.5 and 54.4 mF·cm−2 upon incorporating CB, PB and CB-PB, respectively. Furthermore, the use of a PVA/H2SO4 gel electrolyte led to a large stability electrochemical window of 3.0 V, resulting in an energy density as high as 68.1 μWh·cm−2 with a power density of 0.3 mW·cm−2 at 0.10 mA·cm−2. Additionally, the MSCs modified with CB-PB showed an excellent electrochemical stability, retaining over 95.8 % of their initial capacitance after 6000 galvanostatic charge-discharge cycles. Overall, this study presents a facile, convenient, and scalable approach for designing cost-effective and high-performance MSCs with a low-carbon footprint suitable for powering low-energy-consuming electronics.

Piezoelectric sensor design of graphite-aluminium with dynamic surface interaction method as an environmental technology

Today, graphite is a phenomenal material as an environmentally friendly technology in alternative piezoelectric. Graphite materials with electrical conductivity as electrodes have been widely applied in lithium batteries to support electricity with zero-emissions. Many previous studies used graphene electrodes to harvest electrical energy from raindrops colliding on the electrodes. The voltage generated by the impulse of raindrops on the electrodes is about 129 microvolts. Limitations may arise from rain power generation; namely, the space for system installation is proportional to the amount of power generated. Therefore, electrical power is able to generate using immersing the electrodes into seawater. This type of power generation overcomes the space problem as they can be stacked vertically producing a piezoelectric effect. This study aims to design a piezoelectric sensor of graphite and aluminium reacted to seawater after being subjected to pressure. The experimental results show that the increase in graphite composition greatly affects the voltage results and the composition of seawater will decrease the voltage. Voltage arranged in series from the piezoelectric sensor contributes an increase in voltage about twice the voltage of the unit voltage.

Gate-controlled suppression of light-driven proton transport through graphene electrodes

Recent experiments demonstrated that proton transport through graphene electrodes can be accelerated by over an order of magnitude with low intensity illumination. Here we show that this photo-effect can be suppressed for a tuneable fraction of the infra-red spectrum by applying a voltage bias. Using photocurrent measurements and Raman spectroscopy, we show that such fraction can be selected by tuning the Fermi energy of electrons in graphene with a bias, a phenomenon controlled by Pauli blocking of photo-excited electrons. These findings demonstrate a dependence between graphene’s electronic and proton transport properties and provide fundamental insights into molecularly thin electrode-electrolyte interfaces and their interaction with light.

Electrostatically-induced strain of graphene on GaN nanorods

Few-layer graphene deposited on semiconductor nanorods separated by undoped spacers has been studied in perspective for the fabrication of stable nanoresonators. We show that an applied bias between the graphene layer and the nanorod substrate affects the graphene electrode in two ways: 1) by a change of the carrier concentration in graphene and 2) by inducing strain, as demonstrated by the Raman spectroscopy. The capacitance of the investigated structures scales with the area of graphene in contact with the nanorods. Due to the reduced contact surface, the efficiency of graphene gating is one order of magnitude lower than for a comparable structure without nanorods. The shift of graphene Raman modes observed under bias clearly shows the presence of electrostatically-induced strain and only a weak modification of carrier concentration, both independent of number of graphene layers. A higher impact of bias on strain was observed for samples with a larger contact area between the graphene and the nanorods which shows perspective for the construction of sensors and nanoresonator devices.

A Promising Approach towards the Commercialization of Lithium Sulfur Batteries: Prelithiated Graphene

AbstractLithium‐sulfur (Li‐S) batteries are a promising candidate technology for high‐energy rechargeable batteries due to their advantages of abundant materials and inherently high energy. However, the practical applications of Li‐S batteries are challenged by several obstacles, including the low sulfur utilization and poor lifespan, which are partly attributed to the shuttle of lithium polysulfides and lithium dendrite growth during cycling.[1] The shuttling of polysulfide ions between the electrodes in a Li‐S battery is a major technical issue triggering the self‐discharge and limiting the cycle life.[2] A stable lithium anode is essential for maintaining the good cycle stability of Li‐S batteries in practical applications.[3] To address these lithium related issues, various carbon materials, including graphite and graphene, have been investigated as suitable lithium hosts to use as anode materials for Li‐S batteries.[4] In this study, prelithiated graphite and graphene‐based anode materials are obtained by galvanostatic charging method to improve the performance of Li‐S batteries and compare the electrochemical properties especially in terms of capacity retention and rate capability. According to the results, graphene showed better performance due to its high lithium storage capacity and fast lithium‐ion diffusion rate. Inductively Coupled Plasma Emission Spectrometer (ICP‐OES) results showed that the Li+ content of the graphite, graphite/graphene, and graphene electrodes measured as 26.5, 33.2, and 45.6 wt%, respectively after the lithiation process. 1 Ah pouch cell was assembled with prelithiated graphene anode showing an energy density of about 400 Wh kg−1 in the first cycle and protected its specific capacity of 60 % after 100 cycles in a liquid‐based Li‐S battery system.

Improved Transfer-Free Sustainable Graphene Electrode using Silver Nanowires for Organic Photovoltaics

Improved Transfer-Free Sustainable Graphene Electrode using Silver Nanowires for Organic Photovoltaics

Brain Mapping Using a Graphene Electrode Array.

Cortical maps represent the spatial organization of location-dependent neural responses to sensorimotor stimuli in the cerebral cortex, enabling the prediction of physiologically relevant behaviors. Various methods, such as penetrating electrodes, electroencephalography, positron emission tomography, magnetoencephalography, and functional magnetic resonance imaging, have been used to obtain cortical maps. However, these methods are limited by poor spatiotemporal resolution, low signal-to-noise ratio (SNR), high costs, and non-biocompatibility or cause physical damage to the brain. This study proposes a graphene array-based somatosensory mapping method as a feature of electrocorticography that offers superior biocompatibility, high spatiotemporal resolution, desirable SNR, and minimized tissue damage, overcoming the drawbacks of previous methods. This study demonstrated the feasibility of a graphene electrode array for somatosensory mapping in rats. The presented protocol can be applied not only to the somatosensory cortex but also to other cortices such as the auditory, visual, and motor cortex, providing advanced technology for clinical implementation.

Enhancing the charge transfer and redox characteristics in energy storage devices with a layered ZnNbS@graphene nanocomposite electrode material for biomedical application

Hybrid supercapacitors, a type of device that integrates the functionalities of both supercapacitors and batteries, exhibit significantly enhanced power and energy densities. Two-dimensional materials particularly graphene with remarkable characteristics such as conductivity, sensitivity, and storage capacity, have garnered significant attention in the realm of energy storage. Herein, a composite electrode of zinc niobium sulfide (ZnNbS) and graphene (Gr) is designed and measured the electrochemical and biomedical applications. The composite electrode ZnNbS@Gr (75/25 ratio) showed a high value of specific capacity of 1573.01 Cg−1, much better than pristine ZnNbS (854.32Cg−1) because of the improvement in charge transfer and redox characteristics. Further, a hybrid supercapacitor device (ZnNbS@graphene//AC) is designed and achieves a specific capacity (179.2 C/g) at 1.5 A/g. The energy density is establish 42.1 WhKg−1, whereas the power density is 2500 WKg−1. This device is measured up to 5000 charging and discharging cycles, obtained a high value of capacity recantation of 96 %. Besides, this device is used to accurately detect the glucose to a small amount of 0.01 mM. The conclusions of our investigation provide a remarkable beginning for the advancement of high-capacity energy storage systems and biomedical applications.

Enhanced performance of densified laser-induced graphene supercapacitor electrodes in dimpled polyimide

We fabricate a densified laser-induced graphene (d-LIG) electrode derived from a dimpled polyimide (PI) sheet. The fabrication process involves placing a PI sheet on a Si wafer and generating dimples on the PI surface via laser irradiation at the PI/Si interface. d-LIG is fabricated using the duplicated laser-induced carbonization, during which regular LIG is infiltrated with polyamic acid (PAA) and then irradiated with a CO2 laser. Compared to pristine PI, the LIG based on the dimpled PI facilitates deeper penetration of the PAA solution into the interior of the LIG, resulting in an increased amount of d-LIG and high nitrogen doping. When tested in a three-electrode configuration, the d-LIG derived from the dimpled PI (or d-LIG-D) exhibits a high specific capacitance of 67 mF/cm2 at 0.2 mA/cm2, which is almost twice that of the d-LIG derived from pristine PI (or d-LIG-P) (28.9 mF/cm2). When fabricated into a flexible solid-state supercapacitor with polyvinyl alcohol-H2SO4 gel-type electrolyte, d-LIG-D exhibits a higher specific capacitance (19.5 mF/cm2 at 0.05 mA/cm2) than d-LIG-P (8.4 mF/cm2). Furthermore, it possesses good capacitance retention, Coulombic efficiency, and mechanical flexibility. These properties make d-LIG-D a promising candidate for advanced supercapacitor applications, offering enhanced energy storage capabilities and robust performance.

Investigating the integration of physical-electrochemical-biological processes in the rehabilitation of dead soils contaminated with lead and phenanthrene

<p>This study was carried out with the aim of using three processes of soil washing, electrofenton and biological leaching method in order to rehabilitate the soil contaminated with lead and phenanthrene around the south Tehran oil refinery. The variables examined in this study are the amount of soil (500, 1000, 1500, 2000 mg), the ratio of surfactant to soil (7.50, 15, 22.50, 30, 37.50 L/Kg), time (6, 12, 18, 24, 30 hours), lead concentration (25, 50, 37.50, 62.50 mg/kg) and phenanthrene concentration (50, 100, 15, 200 mg/kg). In the washing process, the highest percentage of lead removal is 78.23% at the contact surface of 2000 mg, the surfactant-to-soil ratio is 30 ml/kg, the time is 24 hours, the concentration of lead and phenanthrene is 50 and 100 mg/kg and the highest removal percentage of phenanthrene (73.4%) in the soil amount of 1000 mg, the ratio of soil to surfactant equal to 30 liters/kg, in 12 hours, the amount of lead and phenanthrene were obtained equal to 25 and 100 mg/kg. Next, the soil was placed in a discontinuous reactor with graphene electrode as cathode and iron electrode as anode to conduct electrofenton. The investigated variables are solution pH (2, 4, 6, 8, 10), reaction time (12.5, 25, 37.5, 50, 62.5 minutes), hydrogen peroxide concentration (0.5, 1, 1.5, 2, 2.5 w/w) and direct electric current (0.75, 1.5, 2.25, 3, 3.75 A). The results indicated that in the electrofenton pH process, hydrogen peroxide concentration and then voltage had the greatest effect and time had the least effect on the removal of lead and phenanthrene. In this way, the highest percentage of lead removal was 85.4% at pH equal to 8, hydrogen peroxide concentration equal to 2 W/W, current equal to 1.5 A and 50 minutes and the highest percentage of phenanthrene removal (85.9%) at pH equal to 6, hydrogen peroxide concentration equal to 1.5W/W, current equal to 2.25 A and 37.5 minutes were obtained. In the biological leaching method, the purified strain (Pseudomonas aeruginosa) was isolated from the soils around the refinery. Environmental pH (3, 5, 7, 9, 11), pollutant to biomass ratio (7.50, 15, 22.50, 30, 37.5 mg/g) and retention time (1, 2, 3, 4, 5 hour) were considered as main variables. pH was the most important parameter influencing the removal of lead and phenanthrene from soil in biological method. The highest percentage of lead removal with 85.4% was obtained at pH equal to 8, hydrogen peroxide concentration equal to 2W/W, current 1.5 A and 50 minutes time. In the case of phenanthrene, the highest removal percentage of phenanthrene (85.9%) was measured at pH equal to 6, hydrogen peroxide concentration of 1.5 W/W, current of 2.25 A and in 37.5 minutes. Comparing the results of the third stage of soil cleaning with the control sample without preparation steps with the removal percentage of 0.67 and 0.42 for lead and phenanthrene, shows the effect of the soil preparation process in order to improve the ability of bacteria to function and shows that by combining three methods of washing, electrofenton and biologic, it is possible to rehabilitate contaminated soils resistant to biological decomposition.</p>

Enhanced sensitivity and detection range of a flexible pressure sensor utilizing a nano-cracked PVP hierarchical nanofiber membrane formed by BiI3 sublimation

The development of a highly sensitive and wide-range flexible pressure sensor is great significant to realize the practical applications in human–computer interaction, health monitoring, and motion detection. Here, a dielectric layer of nano-cracked polyvinyl pyrrolidone (PVP) hierarchical nanofiber membrane (HNM) was fabricated by sublimating BiI3 from an electrospun BiI3/PVP composite nanofiber membrane (NM) via one-step annealing process. The upper and lower electrodes of porous laser-induced graphene (LIG) were produced through the engraving process on polyimide (PI) substrates. Subsequently, a flexible capacitive pressure sensor was constructed by assembling the middle PVP HNM dielectric layer with upper and lower LIG electrodes, which demonstrates enhanced sensitivity and detection range for motion posture recognition. Experimental results indicate that compared with traditional PVP NM-based pressure sensor, the assembled sensor in this work exhibits 22 times higher sensitivity (at 2–100 kPa) and 4 times wider detection range (0–200 kPa). Additionally, the sensor boasts a fast response/recovery time of 29/41 ms, an exceptionally low detection limit of 2.7 Pa, and an outstanding stability of 3000 cycles. With the aid of a convolutional neural network (CNN) algorithm, a shooting posture recognition system was developed by multiple sensors to accurately identify (accuracy: 93.89 %) and guide the shooting postures of basketball players.

Ratiometric electrochemical lateral flow immunoassay for the detection of Streptococcus suis serotype 2

An electrochemical lateral flow immunoassay (eLFIA) strip with high reproducibility was developed to rapidly and accurately detect Streptococcus suis serotype 2. This proposed strip was fabricated by integrating ratiometric electrochemical detection and LFIA (R-eLFIA). The R-eLFIA exhibited excellent reproducibility, which was improved by 3.8 times compared to a single electrode. A dual-working screen-printed graphene electrode (SPGE) was designed by tuning the working electrode with electroactive species in the biosensing system. Ferrocene carboxylic acid (Fc) was used as a signal probe, and sunset yellow (SY) at one working electrode was used as an internal reference signal to provide a built-in correction for reducing the effects of inherent background current. S. suis serotype 2-specific antibodies were immobilized on a nitrocellulose membrane of LFIA, which is located on the position of Fc-SPGE. In the presence of the analyte, an immunocomplex formed on the region of Fc-SPGE, causing a decrease in Fc current while SY current remained constant. The current ratio's decrease was proportional to S. suis serotype 2's concentration. Under optimization, this biosensor showed good linearity in the range of 102–1010 CFU/mL with a limit of detection of 10 CFU/mL and achieved a rapid detection time (15 min). Moreover, the R-eLFIA biosensor exhibited excellent reproducibility and high selectivity and was applied in human serum samples. Thus, this study successfully matched the advantages of the ratiometric strategy and LFIA and has great potential to be used as an effective tool for rapidly detecting S. suis serotype 2 in clinical samples.

Gate Controlled Photocurrent Generation Mechanism in Air-Grown Organic Single Crystals for High-Speed Multiband Imaging.

Organic semiconductors herald new opportunities for fabricating high-performance flexible and wearable optoelectronic devices owing to their intrinsic mechanical flexibility, excellent optical absorption, and cool-free operation. The photocurrent generation mechanisms are of multiple physical origins, including photoconductive, photovoltaic, and photogating effects, and the influence of individual effects on the device figures-of-merit is still not well understood. Here we fabricated a high-performance pentacene single-crystal transistor employing graphene electrodes and demonstrated the modulation from the photogating mechanism to the photoconduction effect by controlling gate bias. Control experiments indicate that the calculation based on transfer curves tends to overestimate the responsivity due to nearby trap states. Using a high frequency-modulated light signal to suppress the trapping process, we successfully measured its intrinsic -3 dB bandwidth of 75 kHz. Finally, high-resolution and UV-NIR high-speed imaging capability was demonstrated. Our work provides new guidelines for understanding the photophysical process and intrinsic performances of organic devices and also confirms the potential of organic single crystals in high-speed imaging applications.

Analysis and Modeling of Bipolar Resistive Switching in 2-D Graphene Electrode- Based Memristor

Analysis and Modeling of Bipolar Resistive Switching in 2-D Graphene Electrode- Based Memristor