Graphite Paper Research Articles

One-step construction of δ-MnO2 cathodes with an interconnected nanosheet structure on graphite paper for high-performance aqueous asymmetric supercapacitors

Among various supercapacitor materials, transition metal oxides have attracted wide attention due to their high theoretical capacitance, and however a great challenge associated with the related materials is to fabricate nanostructured electrodes with high comprehensive performance including high capacitance, excellent cycle stability and good rate performance by a simple and green method. Herein, a high-performance self-supporting cathode consisting of interconnected δ-MnO2 nanosheets on graphite paper (GP) is developed by water bath only at 40°C. Benefiting from the synergetic effects from the interconnected and open nanosheet structure of δ-MnO2 and the GP substrate including effective contact with the electrolyte, a large specific surface area, efficient stress relief, improved ion diffusion and charge transfer, and small equivalent series resistance, a high specific capacitance of 446.6 F g–1 at 1 A g–1, 1.3 V potential window, and outstanding cycle stability with the capacitance retention of ~ 86.1% after 10000 cycles at 8 A g–1 and Columbic efficiency around 100% during cycling can be achieved for the cathodes. The aqueous asymmetric supercapacitors assembled using the δ-MnO2 cathode and active carbon anode and 1 M NaNO3 aqueous solution electrolyte can deliver a specific energy of 47.2 and 19.8 W h kg−1 at 1150 and 115000 W kg−1, respectively. Moreover, long cycle stability with 87.2% capacitance retention even after 30000 cycles at 4 A g−1 can be maintained by the ASCs. Thanks to the simple and green preparation and high performance of the electrodes, valuable exploration of developing high-performance ASCs can be provided by this work.

The in situ growth of Cu2O with a honeycomb structure on a roughed graphite paper for the efficient electroreduction of CO2 to C2H4

A Cu2O/NGP self-supporting electrocatalyst is used for the electrocatalytic reduction of CO2 to ethylene to solve environmental and energy problems.

Fluorinated Graphite Paper Used for Self-Powered Water Speed Sensors by Immersion-Type Tribovoltaic Effect-Dominated Triboelectric Nanogenerators

Fluorinated Graphite Paper Used for Self-Powered Water Speed Sensors by Immersion-Type Tribovoltaic Effect-Dominated Triboelectric Nanogenerators

In situ fabrication of mesoporous NiO@ Graphite paper electrode with multilayered nanosheet wall structures for high-performance supercapacitors

A mesoporous NiO@graphite paper with multilayered nanosheet wall structures (M- NiO@GP) was synthesized through a facile and low-cost hydrothermal reaction and thermal annealing process. The as-prepared M-NiO@GP electrode presents high specific capacitance (2.57 F cm−2), exhibits superior cyclic stability (92.3% capacitance retention after 10000 chargedischarge cycles) and brilliant rate capability (about 56.0% capacitance retention when the current density increased 20 times). Such high-performance capacitive behavior is attributed to the wall structure of NiO with the multilayer nanosheets, which could shorten the ion transfer distance. Meanwhile, the high specific surface area and mesoporous structure of the electrode could serve as an efficient path for OH− transfer and diffusion. The improved electrical conductivity of the electrode enabled stable and efficient electron transports and consequently improved the overall electrochemical performance of supercapacitors. Therefore, the demonstrated high conductive M-NiO@GP electrode is a promising candidate for practical supercapacitor applications.

A novel and disposable GP- based impedimetric biosensor using electropolymerization process with PGA for highly sensitive determination of leptin: Early diagnosis of childhood obesity

This study presents a novel, single-use electrochemical biosensor for the leptin biomarker, which may have potential use for early diagnosis of childhood obesity. The graphite paper working electrode was used for the first time in impedimetric biosensors. All immobilization procedure, investigation of the optimal parameters and characterization of biosensors were followed and evaluated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The Scanning Electron Microscope (SEM) was utilized to visualize the morphology of the electrode surface during the immobilization steps of the immunosensor. Moreover, the characterization of the interactions between anti-leptin and leptin was investigated by using Single Frequency Technique (SFI). The applicability of the designed biosensor for real serum samples was tested for clinical use. It was observed that the biosensor allows high sensitivity in the analyte detection (leptin) in real serum samples. Moreover, it was suggested that the developed biosensor presents advantages such as long shelf life (5% loss of activity after 8 weeks and 60% loss after 10 weeks), ability to determine analyte concentrations at picogram level (0.2 pg mL−1 -20 pg mL−1), low limit of detection (0.00813 pg mL− 1), reproducibility, reusability (12 times) and high sensitivity.

An impedimetric biosensor system based on disposable graphite paper electrodes: Detection of ST2 as a potential biomarker for cardiovascular disease in human serum

In present study, we developed a highly sensitive, electrochemical immunosensor based on fullerene C60-modified disposable graphite paper (GP) electrode for determination of Suppression of Tumorigenicity 2 (ST2) in human serum. The synthesis of the ST2 immunosensor was monitored with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques and single frequency impedance (SFI) technique which is utilized for the specific interaction between anti-ST2 and ST2 antigen. Moreover, the morphological alteration of each GP surface was examined by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). All parameters such as fullerene C60 concentration, antibody concentration and antibody incubation time were optimized. Analytical characteristics such as linear determination range, repeatability, reproducibility, regeneration and surface coverage were determined for the immunosensor. The ST2 electrochemical immunosensor had excellent repeatability, reproducibility and a wide detection range (from 0.1 fg mL−1 to 100 fg mL−1). The proposed immunosensor also had low limit of detection (LOD) and limit of quantification (LOQ) values of 0.124 fg mL−1 and 0.414 fg mL−1, respectively. The proposed immunosensor was applied to real samples to test applicability in clinical practice.

Non-enzymatic lactose molecularly imprinted sensor based on disposable graphite paper electrode

Lactose (LAC) is a disaccharide - major sugar, present in milk and dairy products. LAC content is an important indicator of milk quality and abnormalities in food industries, as well as in human and animal health. The present study reports the development of an innovative imprinted voltammetric sensor for sensitive detection of LAC. The sensor was constructed using electropolymerized pyrrole (Py) molecularly imprinted polymer (MIP) on graphite paper electrode (PE). The MIP film was constructed through the electrosynthesis of polypyrrole (PPy) in the presence of LAC (template molecule) on PE (PPy/PE). To optimize the detection conditions, several factors affecting the PPy/PE sensor performance were assessed by multivariate methods (Plackett–Burman design and central composite design). Under optimized conditions, the proposed analytical method was applied for LAC detection in whole and LAC-free milks, where it demonstrated high sensitivity and selectivity, with two dynamic linear ranges of concentration (1.0–10 nmol L−1 and 25–125 nmol L−1) and a detection limit of 0.88 nmol L−1. The MIP sensor showed selective molecular recognition for LAC in the presence of structurally related molecules. The proposed PPy/PE sensor exhibited good stability, as well as excellent reproducibility and repeatability. Based on the results obtained, the PPy/PE is found to be highly promising for sensitive detection of LAC.

Effect of N-S-Functionalization of Graphite Electrode on Electrochemical Performance of Vanadium Redox Flow Battery

The vanadium redox flow battery (VRFB) is under consideration as a promising energy storage system because of its flexible design, long lifetime, and safety against explosion. The electrode in a VRFB plays the essential role of providing reaction sites, which mainly affect the polarization of the system. Insufficient active sites on the surface of the electrode, specifically that made of carbon-based material such as graphite felt and carbon paper, leads to high polarization and poor electrochemical performance. Therefore, several groups have studied methods of electrode surface modification aimed at increasing the number of active sites, such as acid or thermal treatment and introducing of electrocatalyst (noble metal, metal oxide, or carbon-based material) on the electrode surface. In this study, we report a simple and easy method for nitrogen-sulfur dual functionalization on the graphite felt surface to enhance the energy efficiency of VRFB via self-polymerization and graft method. In addition, surface properties were investigated using various analytical techniques, and effect of dual functionalization was examined through comparison with the nitrogen functionalized graphite felt

High-k Boron Nitride Sheets/Polyimide Hybrid Dielectric Layers for the Fabrication of Flexible Organic Transistors on Commercial Graphite Paper

Organic transistors are crucial components in future flexible electronics due to their excellent properties and ease of circuit integration. Previously, we demonstrated that flexible organic (polyimide) thermal transistors could be prepared using commercial graphite paper as the substrate. These materials exhibited excellent temperature sensitivity, linearity and recoverability due to the intrinsically high thermal conductivity of graphite. In this study, boron nitride (BN) sheets/polyimide hybrid dielectric layers were synthesized for the fabrication of flexible organic transistors using a commercial graphite paper. Under test, the results showed that the introduction of BN sheets was beneficial in improving the mobility and transistor characteristics of the device, as well as enhancing the overall stability. The as-fabricated transistors virtually exhibited no hysteresis at all BN contents.

A Facile and Cost-Effective Approach to Fabricate In-Situ Synthesized Graphene Nanosheet Reinforced 316L Stainless Steel

A facile and cost-effective approach was used to fabricate in situ synthesized graphene nanosheet reinforced 316L stainless steel (GNS-316L), which involved in situ synthesis of graphene nanosheets (GNS) in 316L stainless steel (316L) powder by three-dimensional vibration milling of 316L powder with graphite paper as the carbon source, along with consolidation via spark plasma sintering. The microstructure was characterized by scanning electron microscope (SEM) and the mechanical properties were determined by tensile tests. As a result, a microhardness of 408 HV and an ultimate tensile strength of 508 MPa can be attained for the 0.05 wt.% GNS-316L, which are respectively enhanced by 35% and 23% as compared to 316L stainless steel. The merits of this method are its low cost, simple preparation, and absence of harmful chemical reagents used during the preparation process. This work can open up practical applications for preparing GNS reinforced metal matrix materials in large-scale production.

Investigation on the Effect of Different Mild Acidic Electrolyte on ZIBs Electrode/Electrolyte Interface and the Performance Improvements With the Optimized Cathode.

Zinc ion batteries (ZIBs), as promising alternatives of lithium ion batteries (LIBs), have aroused revived interest in the energy storage field recently. To obtain good performance, the choice of electrolyte plays a vital role. Therefore, in this work, three kinds of aqueous electrolyte have been assessed for interfacial effect and ZIB performance. Through the comparison, ZnSO4 electrolyte showed advantages on ionic conductivity over both Zn(NO3)2 and Zn(CH3COO)2 solution, Zn(CH3COO)2 exhibited considerable Zn stripping/plating kinetics with ZnSO4, and there was no characteristic peak pair of Zn dissolution/deposition found in Zn(NO3)2. Additionally, a lower charge transfer resistance was proved when the cell with 1 M ZnSO4 solution. Besides, to further study on cathodic graphite paper, activation and optimization has been conducted, and cells with optimized graphite paper showed an outstanding enhancement.

Self-supported nickel cobalt carbonate hydroxide nanowires encapsulated cathodically expanded graphite paper for supercapacitor electrodes

The self-standing electrode materials with large surface area and high electronic conductivity have attracted intensive attention in energy storage devices. Herein, the expanded graphite paper (EGP) is fabricated via a controlled cathodic expansion in acetonitrile with tetrabutylammonium bromide at 10 V. The as-prepared EGP exhibits a three-dimensional porous structure with large specific surface area and high electronic conductivity, which is a favorable support for in situ growing nickel cobalt carbonate hydroxide (NiCo-CH) nanowires via a simple hydrothermal method. The as-prepared NiCo-CH@EGP composite achieves high areal capacity of 2.55 C cm−2 at 0.5 mA cm−2, and still remains 1.38 C cm−2 even at 60 mA cm−2. The assembled NiCo-CH@EGP//activated carbon asymmetric supercapacitor exhibits the maximum energy density of 0.30 mWh cm−2 at a power density of 0.92 mW cm−2, and a suitable cyclic stability with the capacity retention of 78.1 % after 10,000 cycles at 20 mA cm−2. The results indicate that the self-standing NiCo-CH@EGP is a potential electrode material for energy storage devices.

Low-voltage driven flexible double-layer electrothermal actuator for smart human-machine interactions

Self-driven smart materials have a wide range of applications in smart textiles, artificial muscles, soft robots, human-machine interactions and so on. Flexible electrothermally driven smart materials are essentially required in self-driven smart devices due to their excellent flexibility and simple operation. However, there are still some issues should be solved such as the high driving voltage, how to achieve excellent driving performance at low voltage is highly desired. In this work, three kinds of flexible double-layer electrothermal actuators (ETAs) are made of “U”-shaped graphite paper and polyimide (PI) film. The thermal expansion coefficients of graphite and PI vary widely and graphite has excellent electrothermal performance, which enable flexible double-layer ETA has a good driving performance at low voltage in a short time. The bending angle of the actuator can reach 248.6° and the bending curvature can reach 1.23 cm −1 at 6 V such low driving voltage in ten seconds, meanwhile, exhibits excellent driving performance and high durability. Two ETAs were assembled into a flexible smart gripper and the gripper can achieve the desired driving performance while applying a low voltage. By combining the actuator with the robot design the smart robot that can execute commands for grasping objects smoothly while moving freely. It has great potential in various human-machine interactions fields and intelligent drive fields.

Sensitive detection of butylated hydroxyanisole based on free-standing paper decorated with gold and NiO nanoparticles

It’s significant to determine butylated hydroxyanisole (BHA) in food or other products to ensure human health since BHA has been found to cause a loss of nourishment and even produce toxic effects. The development of the high-quality electrode materials with low cost, high surface area, and good conductivity is of great interest in the field of electrochemical sensing. Herein, a free-standing exfoliated graphite paper (EGP) was employed as a substrate electrode material for the electrochemical determination of BHA. With the successive modification of gold nanoparticles (AuNPs) and NiO nanoparticles, the constructed electrochemical sensor showed wrinkled multi-layers structure with uniform distribution of the nanoparticles. The great specific surface area of EGP not only was suitable for the load of more nanoparticles but also offered abundant pathways for fast electron diffusion. Based on the advantages of high surface area of EGP, the good conductivity of both EGP and AuNPs, and the electrocatalytic activity of NiO nanoparticles, the prepared electrochemical sensor exhibited good detected ability to BHA. Under the optimal conditions, the sensor showed a wide linear range of 3.0 × 10−8 mol/L–5.0 × 10−5 mol/L with a low limit of detection of 2.0 × 10−8 mol/L (S/N = 3) for the determination of BHA. Moreover, this disposable sensor can be used for the sensitive determination of BHA in edible oil samples. It’s obvious that the versatile EGP with the merits of low cost, easy modification, great surface area, and good conductivity, is one of the best candidates of the substrate electrode materials for the construction of other electrochemical sensors.

Graphene-modified graphite paper cathode for the efficient bioelectrochemical removal of chromium

Metal-free electrocatalysts have been widely used as cathodes for the reduction of hexavalent chromium [Cr(VI)] in microbial fuel cells (MFCs). The electrocatalytic activity of such system needs to be increased due to the low anodic potential provided by bacteria. In this study, graphite paper (GP) was treated by liquid nitrogen to form three-dimensional graphite foam (3DGF), improving the Cr(VI) reduction by 17% and the total Cr removal by 81% at 30 h in MFCs. X-ray absorption spectroscopy confirmed the Cr(VI) reduction product as Cr(OH)3. Through the spectroscopy characterizations, electrochemical measurements, and density functional theory calculations, the porous structures, edges, and O-doped defects on the 3DGF surface resulted in a higher electro-conducting rate and a lower mass transfer rate, which provide more active sites for the Cr(VI) reduction. Additionally, the scrolled graphene-like carbon nanosheets and porous structures on the 3DGF surface might limit the OH− diffusion and result in a high local pH, which accelerated the Cr(OH)3 formation. The results of this study are expected to provide a simple method to manipulate the carbon materials and insights into mechanisms of Cr(VI) reduction in MFCs by the 3DGF with in situ exfoliated edges and O-functionalized graphene.

Imprinted polymer/Fe3O4 micro-particles decorated multi-layer graphite paper: Electrochemical and colorimetric dual-modal sensing interface for aloe-emodin assay

A novel dual-modal sensing interface was constructed for the electrochemical/colorimetric dual-modal sensing of aloe-emodin (AE). Fe3O4 micro-particles were directly synthesized on a multi-layer exfoliated graphite paper (EGP) by the in-situ hydrothermal approach, which was subsequently modified with a layer of molecularly imprinted polymer (MIP) using pyrrole and aloe emodin (AE) as monomer and template, respectively. Due to the specific recognition ability of MIP, the prepared sensing interface showed a good selectivity to AE. The advantages of the multi-layer EGP, such as the large surface area and the excellent conductivity, enabled the sensing interface to sensitively detect AE based on the electrochemical mode. Moreover, due to the peroxidase-like activity of the modified Fe3O4 micro-particles, 3,3′, 5,5′-tetramethyl-benzidine can be oxidized to deep blue by the prepared sensor in the presence of H2O2. However, the rebound AE molecules in imprinted cavities blocked the activity of Fe3O4 micro-particles and caused the light blue of color, which achieved the visual colorimetric assay of AE with the good sensitivity and selectivity. With the merits of easy preparation, good selectivity, and high sensitivity, the present electrochemical/colorimetric dual-modal strategy would greatly broaden the practical application of the molecular imprinting.

An Ultrahigh Energy Density Flexible Asymmetric Microsupercapacitor Based on Ti3C2Tx and PPy/MnO2 with Wide Voltage Window

AbstractTi3C2Tx MXene, as a new 2D material, with unique physical and chemical properties, is ideal for building high performance miniaturized electrochemical energy storage devices. However, the operating voltage window of Ti3C2Tx based microsupercapacitor (MSC) in symmetric structure is very narrow (≤0.6 V), which affects its practical application. Herein, a flexible asymmetric microsupercapacitor (AMSC) based on Ti3C2Tx//polypyrrole (PPy)/MnO2 is reported, where Ti3C2Tx is deposited on graphite paper (GP) by electrophoresis method as negative electrodes, MnO2 and PPy are electrochemically deposited on GP successively as positive electrodes, and polyvinyl alcohol/sulfuric acid (PVA/H2SO4) as the quasi‐solid electrolyte. This AMSC based on Ti3C2Tx//PPy/MnO2 operates at 1.2 V voltage window, which is two times wider than symmetric Ti3C2Tx based MSC. And its maximum areal capacitance and areal energy density can reach up to 61.5 mF cm−2 and 6.73 µWh cm−2 respectively. Moreover, three above AMSCs in series connection can turn on three lights after being charged. And the AMSC also shows high flexibility under mechanical bending level (bending angle with 0°–180°). The flexible AMSC based on Ti3C2Tx//PPy/MnO2 with ultrahigh energy density is a promising candidate for exploiting and fabricating next‐generation miniature integrated energy storage devices.

Effects of anode materials on the performance and anode microbial community of soil microbial fuel cell

Five soil microbial fuel cells (SMFCs) with graphite felt, aluminium sheet, activated carbon fibre felt, graphite paper and carbon cloth as anodes were constructed using the petroleum hydrocarbon polluted soils as substrates. After 115 days of operation, the SMFC with graphite felt anode performed the best in both bioelectricity output and removal of target pollutants, with the bioelectricity output parameters of 345 mV for stable voltage, 24.0 mW/m2 for power density and 774 Ω for internal resistance, and the removal rates of 59.14 % for total petroleum hydrocarbon, 61.65 % for anthracene, and 55.92 % for pyrene, respectively. The conductivity of the material was the key factor affecting the electron transfer rate of the anode, which determined the electric acclimation and screening intensity of SMFC to soil microbes, leading to the growth and succession of the electricigens-dominanted anode microbial community with various abundances of phyla and genera. The surface structure of the anode material played a critical role in the internal resistance of SMFC through affecting the mass transfer of substrate and metabolites, and it might also change the abundance of microbes especially those non-electricigens on the community through different adhesion.

Accordion-like bimetal-organic framework anchoring on the partially-exfoliated graphite paper for high-performance supercapacitors

Metal-organic frameworks (MOFs) are considered as a promising energy storage material owing to their inherent advantages of large surface area, regulatable pore size and functional groups. However, the relative poor electronic conductivity is an obstacle to their wide practical application. Herein, the partially-exfoliated graphite paper (EGP) composed of graphene nanosheets is prepared by a controlled cathodic exfoliation. EGP exhibits 3D hierarchical porous structure and good electronic conductivity, which acts as an ideal substrate for growing accordion-like structure NiCo-based bimetal-organic framework (NCMOF). The as-synthesized NCMOF/EGP shows high areal specific capacitance of 2.41 F cm−2 at 0.5 mA cm−2, and good rate performance of 72.6% at the current densities from 0.5 to 20 mA cm−2. Furthermore, the constructed NCMOF/EGP//active carbon delivers an energy density of 0.11 mW h cm−2 at a power density of 0.75 mW cm−2, and long cycle life. The outstanding electrochemical energy storage performance of NCMOF/EGP are assigned to 3D hierarchical porous structure and good electronic conductivity of EGP combined with layered structure of NCMOF.

4.2 V Stack of metaloxide‐polypyrrole‐based composite electrodes and their power management

Polypyrrole (PPy)-based composites containing nanostructured VO x, PbO x, and MnO x are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm2) formed as a result of the intercalation with their metals. Both intercalation and synthesis are performed in the synthesis solution containing metal(II)tetrafluoroborate salts, pyrrole monomer, HBF4, H2O, Triton-X 100 (TX100), and carboxymethyl cellulose (CMC). The mass loading of the composite at the electrode is maintained at 10 mg cm−2. Symmetric and asymmetric unit cells are prepared in polyvinyl alcohol (PVA)/H2SO4 (1:1) gel electrolyte using composites synthesized on the treated graphite paper electrode. The electrical properties of these cells are examined by electrochemical impedance spectroscopy and their capacitive properties by cyclic voltammetry and galvanostatic-charge discharge test. The asymmetrical cell, prepared with PPy/PbO x/CMC composite having energy density and cycle life better than others, exhibits 7.77 Wh kg−1 and 0.51 kW kg−1 at a working voltage of 1.4 V, considering the total mass of all sub-components. The three-cell asymmetric stack design, which is prepared using these composite-coated electrodes, achieves a coulombic efficiency of 76% at 4.2 V. Finally, an electronic control system (DC/DC buck-boost converter) is designed and implemented to manage the charge and discharge cycles of single-cell and bipolarly connected stack to operate the asymmetric supercapacitor arrays with high performance.