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• Carbon paper electrode shows poor mechanical stability, affecting the AORFB performance. • The mechanical robustness of carbon cloth electrode contributes to a reliable and durable AORFB performance. • Carbon cloth electrode showed high stability when used on quinone oxidation–reduction cycles. • Electrochemical active sites on the carbon cloth increase current densities and AORFB power density. • Carbon cloth electrode provides higher AORFB power density at high electrolyte flow rate. Aqueous organic redox flow batteries (AORFBs) are emerging as promising candidates for efficient energy storage in grid-scale applications. In this study, we present a comprehensive analysis comparing the performance of thermally treated carbon paper and chemically oxidized carbon cloth electrodes, which have been extensively examined for their potential suitability in AORFBs. Results indicate that carbon cloth electrodes exhibit a higher concentration of oxygenated functional groups, contributing to enhanced electrochemical kinetics and improved electrochemical stability. These attributes translate to an AORFB with 62 times higher power density when compared to paper-based electrodes used. Through repeated charge-discharge cycles utilizing the BQDS║AQS model as a representative AORFB prototype, superior performance in the carbon cloth electrodes is consistently observed. Our findings even suggest the potential for optimizing the flow rate of the electrolyte to further enhance performance. [ABSTRACT FROM AUTHOR]

Abstract With the legalization of recreational cannabis use, there is a need to develop a rapid and accurate roadside test that can be used to analyze human saliva samples for Δ9-tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis. Here we demonstrate a novel drug detection method where THC is infused into carbon paper electrodes followed by electrochemical detection in a pH 10 aqueous solution. This method produces a linear, sensitive (down to ∼ 1 pmol), dose-dependent change in the oxidation peak current that varies with THC surface densities. These results, as well as the peak charge per real carbon surface area and linear current/scan-rate dependence, support a model for the distribution of THC on the carbon surface in a thin-layer configuration, facilitating the oxidation of the deposited drug. We also demonstrate electro-oxidation of the two major metabolites of THC, the psychoactive 11-hydroxy-tetrahydrocannabinol (OH-THC), and the non-psychoactive 11-nor-9-carboxy-tetrahydrocannabinol (COOH-THC), that also produce linear, dose-dependent changes in peak charge. However, COOH-THC exhibits a much lower Faradaic efficiency than OH-THC and THC, suggesting that variations in the THC functional groups affect the electro-oxidation of the cannabinoids. Overall, this work illustrates a novel, reproducible, and sensitive method for the analysis of THC and oxidation properties of its common metabolites that could be adapted for use with human saliva samples in future work. [ABSTRACT FROM AUTHOR]

Abstract In this paper, carbon paper (CP) was modified by three-dimensional reduced graphene oxide (3DrGO/CP) and binders. Based on physical (field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy) and electrochemical tests (cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charging/discharging curves), the physical and chemical properties of 3GrGO/CP electrode were investigated. The physical characterization and electrochemical performance analysis indicated that the different binders significantly influenced the hydrophilicity and the wet surface area of electrode. Nitrogen doping three-dimensional reduced graphene oxide facilitates the electron transfer on electrode/electrolyte interface for both oxidation and reduction processes of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-HO-TEMPO), provides more reaction area and reduces concentration polarization. Therefore, the modified carbon paper electrode exhibits better electrochemical activity and reversibility compared with the pristine carbon paper electrode in a methyl viologen (MV)/4-HO-TEMPO redox flow battery (RFB). Graphical abstract Image 1 Highlights • N doping 3DrGO facilitates the electron transfer on electrode/electrolyte interface for 4-HO-TEMPO redox reactions. • The different binders significantly influenced the hydrophilicity and the wet surface area of electrode. • This simple modification method can effectively improve the performance of the RFB. [ABSTRACT FROM AUTHOR]

A novel and facile method by sewing low-cost fiber electrodes on paper is proposed to fabricate electrochemical paper-based analytical devices (ePADs). Prussian Blue (PB) and Ag/AgCl were deposited on carbon fibers to prepare the working and reference electrodes. The hydrophilic carbon fiber was employed as the counter electrode. All electrodes were sewed on the paper substrate. The linear voltammetry scanning (LSV) and physical characterization results showed that the physico-chemical characteristics of the prepared electrode were maintained after sewing. As a proof of concept, the ePAD fabricating by sewing was used to detect hydrogen peroxide (H 2 O 2). The limit of detection (LOD) achieved 0.9 µM and the ePAD possessed high anti-interference ability to a variety of common ions and biological molecules. Additionally, the robustness of the ePADs against bending (error 6.2 %) manifested that the ePAD had excellent practical applicability. The good reproducibility (3.65 %) displayed by the current responses confirmed that this strategy can be profitably adopted to easily assemble ePADs in a highly flexible manner. In addition, a user-friendly reagent-free ePAD was proposed to determine the content of H 2 O 2 in real water sample without treatment. The good recovery percentage (95.7–99.7 %) demonstrated the high feasibility of the reagent-free ePAD with facile carbon fiber-sewed electrodes in the detection of H 2 O 2 from complex water samples. These results confirm that the sewing method is feasible and promising. This work provides a new insight into fabrication of highly sensitive and highly selective ePADs with fiber electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Fibers and binder in the carbon paper have different oxidative stability. • Spatially-resolved VO2+ oxidation was tracked by Raman spectroelectrochemisrty. • Vanadium dimers formed preferentially at the oxygen-functionalized fiber surface. The elucidation of redox reaction mechanisms utilized in vanadium flow battery opens broad opportunities for targeted improvement of performance in specific power and energy efficiency. However, there is no unified agreement with regard to the catholyte reaction mechanism as common electrochemical methods such as cyclic voltammetry show general current-voltage response without distinguishing the various vanadium reaction intermediates involved in the redox reaction process. The literature describes several mechanisms that vary from electrode carbon composition, surface functionality, and electrolyte composition. Still, all proposed reaction pathways were derived from indirect models, and thus the introduction of an additional method for monitoring the speciation of vanadium moieties and for spatially resolving redox processes at the electrode/electrolyte interface is required for reliable validation of the reaction mechanism. Herein, we introduce a new spectroelectrochemical technique, which combines Raman spectroscopy with cyclic voltammetry as a powerful tool for deducing complex redox mechanisms at carbon paper electrodes. In particular, the vanadyl oxidation reaction mechanism was investigated on heated carbon paper with the help of in situ Raman Spectroelectrochemistry. Significant differences in the reactivity of carbon paper was found for electrodes activated at different temperatures and show that the fibers are more susceptible to oxidation, while the binder burns, which leads to a decrease in electrochemical active surface area. The monitoring of vanadyl oxidation showed two different reaction mechanisms on the fiber surface and the alternative one for the binder phase. Thus, this new spectroelectrochemical technique is an effective tool to track species transformation during redox reaction not only for catholyte in Vanadium Flow batteries but also for other systems. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we design a novel FeCo 2 S 4 @Ni(OH) 2 core-shell hollow nanotube arrays on carbon paper for superior capacitance of supercapacitors. FeCo 2 S 4 hollow nanotube arrays vertically grow on carbon paper via hydrothermal reaction served as a "core" to shorten the ion transport path, Ni(OH) 2 nanosheets modified on the hollow nanotube arrays based on constant voltage electrodeposition reveal outstanding pseudocapacitance characteristic. The ultrathin Ni(OH) 2 nanosheets act as a "shell" layered to expand the specific surface area, effectively increasing the active sites of the faraday reaction. The subtle heterogeneous synergistic effects significantly improve their electrochemical performance. The unique core-shell structure of FeCo 2 S 4 @Ni(OH) 2 displays a superior capacity of 239.72 mA h g−1 at 1 A g−1, even at 8 A g−1 still has a capacity of 128.0 mA h g−1, indicating the excellent rate performance. Significantly, the asymmetric supercapacitor assembled by the FeCo 2 S 4 @Ni(OH) 2 nanoarrays positive electrode and activated carbon (AC) negative electrode exhibits superior electrochemical performance with ultra-high energy density (55.33 Wh Kg−1 at 800 W kg−1) and power density (8000 W kg−1 at 15.78 Wh Kg−1). After 10000 charge-discharge cycles, the device still has capacitance retention of 93.8%. Therefore, FeCo 2 S 4 @Ni(OH) 2 nanoarrays can be widely used in high-performance supercapacitors as potential and promising electrode materials. Composition of FeCo 2 S 4 @Ni(OH) 2 //AC two-electrode supercapacitor with ultra-high electrochemical performance (55.33 Wh Kg−1 at 800 W kg−1) and still retains 93.8% capacitance after 10,000 cycles，Charging to 3.2 V in tens of seconds, the device can light up the circular blue LED for a period of time. Image 1 [ABSTRACT FROM AUTHOR]

The vanadium redox flow battery (VRFB) has emerged as a promising technology for large-scale storage of intermittent power generated from renewable energy sources due to its advantages such as scalability, high energy efficiency and low cost. In the current study, a three-dimensional(3D) Lattice Boltzmann model is developed to simulate the transport mechanisms of electrolyte flow, species and charge in the vanadium redox flow battery at the micro pore scale. An electrochemical model using the Butler-Volmer equation is used to provide species and charge coupling at the surface of active electrode. The detailed structure of the carbon paper electrode is obtained using X-ray Computed Tomography(CT). The new model developed in the paper is able to predict the local concentration of different species, over-potential and current density profiles under charge/discharge conditions. The simulated capillary pressure as a function of electrolyte volume fraction for electrolyte wetting process in carbon paper electrode is presented. Different wet surface area of carbon paper electrode correspond to different electrolyte volume fraction in pore space of electrode. The model is then used to investigate the effect of wetting area in carbon paper electrode on the performance of vanadium redox flow battery. It is found that the electrochemical performance of positive half cell is reduced with air bubbles trapped inside the electrode. [ABSTRACT FROM AUTHOR]

The direct electrochemical behaviour of carbohydrates at a nickel/carbon paper electrode with a novel fabrication method is investigated. The investigation is used for verification the feasibility of using monosaccharides and disaccharides in the application of fuel cell. The selected monosaccharides are glucose, fructose and galactose; the disaccharides are sucrose, maltose and lactose. The modified nickel/carbon paper electrode was prepared using a filtered cathodic vacuum arc technique. The morphology image of the nickel thin film on the carbon paper surface was characterized by scanning electron microscopy (SEM). The existence of nickel was verified by X-ray photoelectron spectroscopy (XPS). The contact angle measurement was also used to characterize the modified electrode. Cyclic voltammetry (CV) was employed to evaluate the electrochemical behaviour of monosaccharides and disaccharides in an alkaline aqueous solution. The modified electrode exhibits good electrocatalytic activities towards carbohydrates. In addition, the stability of the nickel/carbon paper electrode with six sugars was also investigated. The good catalytic effects of the nickel/carbon paper electrode allow for the use of carbohydrates as fuels in fuel cell applications. [ABSTRACT FROM AUTHOR]

Abstract: Nano-Si/(multi-wall carbon nanotube) (Si/MWCNT) composite paper was prepared as flexible electrode for lithium ion batteries by a simple filtration method using sodium carboxymethyl cellulose (CMC) as a dispersing/binding agent, followed by a thermal sintering process. Scanning electron microscopy (SEM) showed that nanosized Si particles were dispersed homogeneously and intertwined by the MWCNT throughout the whole paper electrode. After thermal sintering, Si/MWCNT paper electrode exhibited a significantly improved flexibility with a high Si content of 35.6wt% as compared with before sintering, and retained a specific capacity of 942mAhg−1 after 30 cycles with a capacity fade of 0.46%/cycle. [Copyright &y& Elsevier]

Abstract: Porous conducting carbon paper has been identified as the most suitable material to be used as a backing material for the fuel cell electrode. The surface of carbon fiber, the major constituent of the carbon paper was modified by: (1) removing the functional groups by heat cleaning process and (2) coating the non-functionalized carbon fiber with multi-walled carbon nanotubes (MWCNTs). This has a marked influence on the fiber–matrix interactions during later stages of processing of carbon paper that helped in controlling its various characteristic properties. Using the carbon paper formed with CNT coated carbon fiber as electrode, the maximum power density achieved from a unit fuel cell was found to be 783mW/cm2 as compared to 630mW/cm2 when the paper was formed with normal fiber. [Copyright &y& Elsevier]

• A columnar liquid-crystalline triazine-based dendrimer has been incorporated as Li-ion battery anode. • The additional 1% carbon filler (CNT paper) in the triazine-based anode successfully boost the battery performance. • Systematical spectroscopic studies reveal that Li+ insertion in triazine and piperazine functional groups plays an important role in the Li+ storage mechanism. • The charge storage evaluation and kinetical studies unleashed the role of carbon filler on boosting capacitive contribution and accelerating Li+ transport. Owing to their highly tunable molecular structure and chemical stability, dendrimers consisting of triazine and piperazine moieties have been investigated. The present work describes the electrochemical performance of a columnar liquid-crystalline triazine-based dendrimer containing the linker with diaminopropane (DAP) as a lithium-ion battery anode. To elucidate the impact of conductive carbon filler in the electrode, a tiny amount of carbon nanotube (CNT) paper has been incorporated in the DAP anode. The battery performance revealed that the DAP anode has shown a high specific capacity of up to 444 mA h g−1 at 0.5 A g−1 after 200 cycles. Surprisingly, with an additional 1% CNT, the Li+ storage capacity of the dendrimer-based composite anode (DAP/CNT1%) significantly enhanced up to 656 mA h g−1. To the best of our knowledge, this is the first time that a triazine-based dendrimer has been utilized as an anode material in conjunction with a small amount of CNT to further boost its energy-storing capabilities through a synergy of capacitive storage mechanisms and improve Li+ transport. The efficient lithium storage of DAP/CNT composite further shows its amenability as organic electrode material for next-generation organic Li-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

• An all-solid-state thin-layer laminated cell realized calibration-free coulometric determination of K+ ions. • The cell achieved complete mass transport of the target ion from a 1 mm3 drop of the aqueous sample. • An originally prepared conducting-polymer-dispersed ink was cast on the carbon electrode. • The cell allows the calibration-free determination of K+ ions in a 1 mm3 drop of ten-fold-diluted serum. Calibration-free coulometric determination of K+ ions was realized using an all-solid-state thin-layer laminated cell with a simple laminate structure. The fabricated cell consists of a Ag/AgCl electrode, a plastic spacer for positioning the aqueous sample solution, an organic ion-selective membrane, and a conducting polymer/carbon electrode. An originally prepared conducting-polymer-dispersed ink was cast on a conductive carbon sheet (a screen-printed graphite electrode or carbon paper) to fabricate the conducting polymer/carbon electrode. The cell achieved complete mass transport of the target ion from a 1 mm3 drop of the aqueous sample to the organic ion-selective membrane under a constant potential between the Ag/AgCl electrode and the conducting polymer/carbon electrode, which generated electrical current for enabling the ion transfer. The electric charge obtained by integrating the electric current was used to estimate the molar amount of the target ion in the sample drop. For tetraethylammonium cations (TEA+; 20–200 μmol dm−3), the evaluated molar amounts corresponded to 92%–94% of the initial mole amounts. The repeatability estimated using the same cell was ±4%–6%, and the device-to-device reproducibility was ±4% for five cells. In terms of K+-ion detection (0.1–0.8 mmol dm−3) in sample drops containing NaCl (14 mmol dm−3), the evaluated molar amounts corresponded to 86%–92% of the initial molar amounts, indicating the promise of the all-solid-state thin-layer laminated cell for achieving the calibration-free determination of K+ ions in a 1 mm3 drop of ten-fold-diluted serum. [Display omitted] [ABSTRACT FROM AUTHOR]

• Different carbon-based electrodes following a nature-inspired solution were tested by CV and EIS. • Glass-carbon electrodes (GCE) and carbon paper-based electrodes (CPE) with and without polytetrafluoroethylene (PTFE) were evaluated. • The electrodes' performance was assessed by employing the ferri/ferrocyanide ([Fe(CN) 6 ]3-/4−) electrochemical probe. • Surface properties of the commercial electrodes materials were evidenced from AFM and water contact angle measurements. • Best results were achieved with CPE without PTFE, given its hierarchical porous structure and absence of the insulating binder. Carbon electrodes are widely accepted as very versatile platforms, with applications ranging from electrocatalysis to sensors and other devices, like fuel cells and water electrolyzers. However, there are still difficulties given that over time, at high potentials, the oxidation of carbon materials (as a catalyst and/or catalyst support) can play a detrimental role, undermining the efficiency and stability of the electrochemical processes and devices performance. In this paper, it is reported the research work followed by resourcing to electrochemical analytical techniques, like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), along with complementary atomic force microscopy (AFM) and water contact angle (WCA) measurements. These techniques were used to characterise glass-type and paper-based carbon electrodes. On a nature-inspired solution, we took advantage of the different interfacial carbon-support hierarchical porous structures to boost the carbon electrocatalytic effect towards sensing the ferri/ferrocyanide redox couple ([Fe(CN) 6 ]3-/4−) in aqueous solution. It is shown that the best results were achieved with carbon paper electrodes without wet proofing, given its hierarchical porous structure and absence of the insulating binder. This research endeavors to contribute to the ongoing advancements in the field of electrochemical green energy conversion by exploring innovative approaches and materials, with the ultimate aim of developing carbon substrates that not only enhance performance but also promote environmental sustainability. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) is characterized by easy synthesis, high porosity and high nitrogen doping level. It has good application prospects as an negative electrode material for metal-ion batteries. However, graphitic carbon nitride (g-C 3 N 4) cannot be directly used as negative electrode material (NEMs) for lithium-ion batteries due to poor electrical conductivity and poor cycling performance. To solve this problem, in this paper, g-C 3 N 4 is synthesized on the surface of reduced graphene oxide by in situ synthesis method. The prepared rGO-g-C 3 N 4 composites have high surface capacitance process occupancy due to the presence of a large amount of pyridinic-N and pyrrolic-N, and various defects and pores generated during the synthesis process provide a large lithium-ion mobility rate for the rGO-g-C 3 N 4 composites. The rGO-g-C 3 N 4 composites have excellent electrochemical properties and excellent lithium storage performance, the capacity of 1 A/g after cycling 300 laps to maintain a high lithium storage capacity of 708.6 mAh/g, and is still in the rising state, even if the current density of 15 A/g under the cycle of 10,000 laps, the highest lithium storage capacity of up to can still be up to 423.6 mAh/g, and stabilized in the 306.8 mAh/g. This work provides a new idea for the preparation of new negative electrode materials with low cost and high capacity. [ABSTRACT FROM AUTHOR]

• Environmentally-friendly biochar inks for screen-printing are developed. • Fully printed electrochemical sensors based on biochar/ethylcellulose are optimized. • Novel electroanalytical platform for determination of paracetamol is elaborated. • Viability in electroanalysis of pharmaceutical formulations is demonstrated. Biochar is a material prepared by biomass pyrolysis, representing a more sustainable and efficient alternative to commonly used conventional carbon materials in electroanalysis. The aim of this paper is to point out that it can also show significant potential in the mass screen-printing production of miniaturized, low-cost, disposable and sensitive electrochemical sensors. Herein, a new generation of fully screen-printed electrochemical sensors is introduced, based on biochar/ethylcellulose-modified carbon working electrodes. The optimization in the sensor fabrication, involving the variability in the concentration of a binder and rheology modifier (ethylcellulose) and its impact on biochar inks from the viewpoint of viscoelasticity, printability and thermal stability, was performed to obtain the carbon-based electrochemical sensors with favourable robustness. The viability of these electrochemical sensors was demonstrated by the development and full validation of a new and sensitive differential pulse voltammetric method for the fast and reliable determination of paracetamol in pharmaceutical formulations. Within the method development, all necessary aspects, such as a study of the effect of ethylcellulose concentration, pH study of supporting electrolyte, selection of pulse parameters and analytical performance, were investigated. The obtained results allow us to predict the production and subsequent use of new, printable, cheap and environmentally friendly sensor platforms, which will exhibit convenient analytical performance with the possibility of commercialization. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical removal of bromate ions was performed with BDD electrodes in a two-compartment electrolytic reactor. Bromate ions removal and the production of Br− were observed and determined. The removal of bromate ions occurred at an applied bias potential of −0.45V (vs. SCE). And, the removal rate increased with the applied bias potential. Within 2h, nearly 90% of bromate ions were removed with the applied bias potential of −1.0V (vs. SCE). Effect of pH on bromate ions removal was slight. SO4 2− and Cl− ions inhibit the electrochemical reduction of bromate ions, which can be explained by the competitive adsorption of coexisting anions at the electrode surface with the bromate ions. In comparison, the graphite and carbon paper electrode exhibit low catalytic activities toward reduction removal of bromate ions under the same experimental conditions. A possible reason was proposed. [Copyright &y& Elsevier]

Enzyme-based amperometric biosensors measure target analyte concentrations through the transduction of enzymatically generated electrons into a detectable current at an electrode surface. To achieve efficient electron transfer, many such systems rely on the use of diffusive electron mediators or intricate, nanostructured electrode materials, which can limit applicability. Herein, we report on the development and characterization of enzyme-based glucose biosensors operating using a combination of intramolecular electron transfer and electron self-exchange through ferrocene-containing redox mediators covalently coupled directly to glucose oxidase (GOX). To accomplish this, we applied polymer-based protein engineering to grow poly( N -(3-dimethyl(ferrocenyl)methylammonium bromide)propyl acrylamide (pFcAc) via atom-transfer radical polymerization from initiator molecules attached to the GOX surface. The use of these GOX-pFcAc conjugates allowed the fabrication of simple, paper-based glucose biosensors through crosslinking with the carrier protein human serum albumin (HSA) within a viscous chitosan solution and drop casting onto carbon paper strips. Chit-GOX-pFcAc-HSA-carbon paper biosensors yielded a glucose sensitivity of 0.33 ± 0.01 μA mM −1 cm −2 and exhibited selectivity when challenged with other sugars. The ease of sensor fabrication further afforded a tailorable response through variation of GOX-pFcAc concentration upon crosslinking and drop casting. The reported approach shows the glucose sensing capabilities of a system that merges the characteristics of bioelectronics fabricated using redox-containing polymer networks with those based on the surface modification of enzymes with electron relays. [ABSTRACT FROM AUTHOR]

Enzyme-based biosensors have garnered intense research interest due to the catalytic properties and physiologic applicability of enzymes. However, the use of these biological catalysts also introduced persistent lifetime limiting stability issues that hinder device longevity. We report on the identification and understanding of sources of long-term stability loss within a glucose oxidase (GOX)-based biosensor. Through polymer-based protein engineering (PBPE), we grew poly( N -(3-dimethyl(ferrocenyl)methylammonium bromide)propyl acrylamide (pFcAc) directly from initiator sites at the GOX surface via atom-transfer radical polymerization. The resulting GOX-pFcAc conjugates were crosslinked along with human serum albumin (HSA) within chitosan (Chit)-containing solution and drop cast onto carbon paper strips. Chit-GOX-pFcAc-HSA-carbon paper biosensors generated current by intramolecular electron transfer and electron self-exchange through the GOX-pFcAc conjugates as well as through oxygen mediated electron transfer under varied cell potentials and solution conditions. A systematic characterization method identified the leading sources of instability within the enzyme-polymer conjugate system. We found that a physically crosslinked network prevented GOX leaching from the functionalized electrode. Pre-wetting the electrode also increased current outputs. A reduction in ferrocene-mediated current generation resulted from instability of the ferrocenium ion produced during operation. This issue could be solved through the use of freely diffusing ferrocene, which indicated a path toward improvement for enzyme-polymer conjugate systems with carefully engineered redox characteristics. [ABSTRACT FROM AUTHOR]

Further increasing the output power is important to develop next-generation supercapacitor. In recent years, many papers focus on the design of pore structure to improve high-rate performance of supercapacitor, but few reports devote attention to reducing the nanoscale size of carbon framework to reach an optimal ion transfer. In the present paper, a novel ultrathin carbon gauze was fabricated by a simple boiling-induced volume expansion method. This carbon gauze shows foam-like morphology that is composed of 7 nm-thick carbon sheets. In addition, owing to the loose stack of carbon sheets, lots of meso-/macropores are created. When used as electrode in supercapacitor, the ultrathin carbon sheets can effectively minimize the electrolyte transfer distance and meso-/macropores can accelerate ion transfer speed, and then carbon gauze exhibits an impressive high-rate supercapacitive performance. While the scan rate is raised from 0.02 to 0.5 V s −1 , the capacitance only reduces from 190 to 173 F g −1 , implying a retention of 91%, and even under an extremely high scan rate of 2.0 V s −1 , the cyclic voltammogram of carbon gauze still presents a symmetrically rectangular shape, revealing a considerable capacitance of 142 F g −1 (75% of the capacitance at 0.02 V s −1 ). [ABSTRACT FROM AUTHOR]

• This work studies the pore-scale reactive transfer behaviors in gradient electrode. • Results reveal the performance of electrode with different flow conditions. • Gradient electrode achieves the lowest total polarization loss at high flow rate. Porous electrodes are critical component of redox flow batteries (RFBs), that decide the fluid, species/charge transport and electrochemical reaction properties during the operation of RFBs. It is a potential way to elevate the performance of RFBs by applying the porous electrodes with gradient pore structures. However, it is still lack of a suitable numerical model to understand the reactive transport processes in the heterogeneous pore structures, thus to design and develop the optimal RFB electrodes. Using a lattice Boltzmann model, this work studies the pore-scale reactive transfer behaviors in a double-layer gradient electrode assembling as the negative side of deep eutectic solvents electrolyte-based vanadium-iron RFB, that consists of a graphite felt near the current collector side and a carbon paper near the membrane side. The numerical results reveal the galvanostatic discharging performance of double-layer electrode under the different electrolyte feeding modes and flow rates. Comparing with full flow-through feeding mode, the interdigitated flow feeding mode would give rise to serious inhomogeneity of electrolyte flowing at the low flow rate condition, thereby resulting in the sluggish convective mass transfer performance near the membrane side. Moreover, the total power loss of double-layer electrode is higher than that of the mono-layer carbon paper electrode within the low flow rate range. Conversely, the double-layer electrode with interdigitated flow mode can achieve the lowest total power loss than mono-layer electrodes at the high inlet flow rate. This work provides a new pathway to investigate the RFB power performance effected by the gradient porous structures of electrodes. [ABSTRACT FROM AUTHOR]

A novel redox flow battery based on soluble organic redox active material is attracting increasing research attention, which employs a family of molecules known as quinones. A three dimensional numerical model of the novel flow battery with a flow through electrode has been developed. The electric current density and the ion current density along the electrode thickness under different specific areas and different electrode conductivities are analyzed, accounting for the electrode thickness effect on the cell performance. It can be concluded that six layers of carbon paper is the most appropriate electrode thickness. More than six layers of carbon paper provides more surface area at the expense of higher ohmic resistance, which is not appropriate. Less carbon paper cannot provide enough specific active area. The flow fields in the x direction and z direction are analyzed to account for the electric current density distribution. The high current density at the junction of the land and channel for the flow through electrode cell is related to the flow field in z direction. The simulation results are well-fitted for the experiment data. In addition, we improve the previously existing electrolyte conductivity calculation model and demonstrate that accurate electrolyte conductivity values are required for accurate modeling of the experiment. The model is validated using data obtained from combining a quinone/hydroquinone couple with a Br2/Br − redox couple flow battery system. [ABSTRACT FROM AUTHOR]

• A natural cellulose derived fibrous WO 3 /carbon composite was fabricated. • The composite has a 3D structure with WO 3 microspheres anchored on the carbon fibers. • As an anodic material, the composite shows improved electrochemical performances. To meet the ever-growing demands over electrochemical energy storage, tungsten trioxide (WO 3) has aroused substantial attention as a promising anodic material for lithium-ion batteries due to its high theoretical capacity, abundant earth storage, and eco-friendliness. However, developing high-performance WO 3 -based electrodes is hampered by its restrictive conductivity and tremendous structural as well as the volumetric changes during the charge/discharge processes. Herein, a novel bio-inspired nanofibrous WO 3 /carbon composite was synthesized via a facile hydrothermal method employing pre-carbonized cellulose substrate (e.g., ordinary filter paper) as both the structural scaffold and the carbon source. The urchin-like WO 3 microspheres with diameters of 3–6 μm assembled by nanorods were uniformly anchored on the surfaces of the cellulose-derived carbon fibers. The three-dimensional network structure of the composite was beneficial in alleviating the volume expansion of WO 3 nanorods and enhanced the charge-transport kinetics of the electroactive materials. The composite with an optimized content of WO 3 (26.36 wt%) exhibited superior lithium storage properties with an initial discharge capacity of 1470 mAh g−1 and an extraordinary long-term cycling performance of 682 mAh g−1 capacity retention after 300 cycles at 100 mA g−1. Furthermore, cyclic voltammetry, ex-situ XRD, and SEM measurements for mechanism studies were carried out to yield deeper insights into the synergism in the WO 3 /carbon electrodes, revealing the predominance of reversible pseudocapacitive intercalation of lithium-ions during the electrochemical reaction inside the WO 3 /carbon anode. A natural cellulose derived WO 3 /carbon nanofibrous composite was fabricated, showing enhanced electrochemical performances as an anodic material for lithium-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Porous structures grown in situ increase the electrode contact area with the electrolyte, reduce ion diffusion distance, and enhance electrode material electrochemical properties. In this paper, we have adopted a dual-channel electrodeposition strategy with simultaneous electrodeposition and phosphorylation to construct metal-semiconductor contact heterostructures by depositing Ni@NiCo phosphate microspherical nanostructures directly on a copper foam (CF) (Ni@NiCoP/CF) framework at room temperature. The results show that Ni@NiCoP/CF has excellent electrochemical performance with a high specific capacity of 200 mAh g –1 at 1 A g –1, 147.2 mAh g –1 at 20 A g –1 and 93.6 % after 5000 cycles, showing excellent ration performances and cycling stability. In addition, the hybrid supercapacitor composed of Ni@NiCoP/CF as the positive electrode and activated carbon as the negative electrode achieves a high energy density of 48.7 Wh kg−1 at 874 W kg−1 and has excellent cycling stability with 113.23 % capacity retention after 30,000 charge/discharge cycles at a high current density of 10 A g –1. This study serves as a guide for the development of high-performance capacitor cathode materials with high electrochemical activity and capacity. [ABSTRACT FROM AUTHOR]

• The Co-Mordenite/Mesoporous Carbon modified Glassy Carbon Electrode (Co-MOR/MC-GCE) was presented. • The voltammetric method for the ultrasensitive determination of mesalazine (MES) was developed. • The nanomolar level of LOD was achieved without any preconcentration step. • The method was applied for the determination of MES in pharmaceutical, environmental, and biological samples. In this paper, an ultrasensitive and highly selective analytical method for the voltammetric determination of the anti-inflammatory drug mesalazine (MES) at the Co-exchanged mordenite/mesoporous carbon modified glassy carbon electrode (Co-MOR/MC-GCE) is presented. The combination of unique properties of zeolite and mesoporous carbon, affirmed by conducting morphology and textural parameters studies, resulted in the fabrication of the unique platform sensing, which exhibited a significant enhancement effect of MES oxidation peak current. In the voltammetric determination of mesalazine by the means of differential pulse voltammetry (DPV), univariate optimization stage of the instrumental parameters and the pH value of the supporting electrolyte was performed. In 0.04 mol L−1 Britton-Robinson buffer solution (pH 2.0), the oxidation peak of MES at 0.41 V vs. Ag | AgCl | 3 M KCl reference electrode revealed a linear response in the range of 0.99 – 99.01 µg L−1 (6.47·10−9 – 6.47·10−7 mol L−1) with the limit of detection (LOD) equal to 0.27 µg L−1 (1.76·10−9 mol L−1). The developed protocol was successfully applied for the direct determination of mesalazine in pharmaceuticals, environmental waters, and biological fluids (human urine and serum) with recovery of 103.4 – 119.3%. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Microfluidic vanadium redox fuel cells are membraneless and catalyst-free fuel cells comprising a microfluidic channel network with two porous carbon electrodes. The anolyte and catholyte for fuel cell operation are V(II) and V(V) in sulfuric acid based aqueous solution. In the present work, the electrochemical characteristics of the vanadium redox reactions are investigated on commonly used porous carbon paper electrodes and compared to a standard solid graphite electrode as baseline. Half-cell electrochemical impedance spectroscopy is applied to measure the overall ohmic resistance and resistivity of the electrodes. Kinetic parameters for both V(II) and V(V) discharging reactions are extracted from Tafel plots and compared for the different electrodes. Cyclic voltammetry techniques reveal that the redox reactions are irreversible and that the magnitudes of peak current density vary significantly for each electrode. The obtained kinetic parameters for the carbon paper are implemented into a numerical simulation and the results show a good agreement with measured polarization curves from operation of a microfluidic vanadium redox fuel cell employing the same material as flow-through porous electrodes. Recommendations for microfluidic fuel cell design and operation are provided based on the measured trends. [Copyright &y& Elsevier]

Abstract: Oxidative protein damage is the most critical factor implicated in carcinogenesis and other disorders. However, the electrochemical detection of oxidative protein damage and the protections of protein from damage by antioxidants have been reported rarely. In this work, a novel, sensitive and inexpensive method for direct electrochemical detection of bovine serum albumin (BSA) damage in aqueous solutions is described. The simple electrochemical procedure has been constructed on the glassy carbon electrode (GCE) surface by BSA direct adsorption technique. Co(bpy)3 3+ was used as a redox indicator to monitor BSA damage induced by hydroxyl radical (h was produced from Fenton reaction. The simplest fabrication procedure and the most classic method of free radical production were used to research the protein damage, demonstrating obvious virtues of brachylogy, rigor and precise. The electrochemical behaviors of the underlying electrodes were characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Ultraviolet–visible (UV–vis) spectroscopy was used to verify the BSA damage with the universal index of the protein carbonyl group content. The optimizations of the Fe2+/H2O2 ratio and incubation time on BSA damage were explored. Moreover, the protections of BSA from damage by antioxidants were investigated. These conclusions demonstrated that the proposed method could be used to detect protein damage induced by Fenton reaction through a simple electrochemical approach. [Copyright &y& Elsevier]

Transition metal sulfides have been considered as the promising electroactive materials for the supercapacitors with high specific capacitances. Herein, cobalt sulfide foam (CSF) with three-dimensional (3D) porous hierarchical structure was controllably synthesized on the electrode by the facile electrochemical reduction of elemental sulfur in the precursor of sulfur incorporated polypyrrole (S/PPy) composite with a electrochemical reduction method followed with in-situ reacting with Co2+ ions in the electrolyte, and used for high-performance supercapacitors. Since such a CSF material provided smooth ion diffusion pathways for the fast ion transfer between electrode and electrolyte and simultaneously the anchoring of conductive PPy to the cross-linked cobalt sulfide (CoS) nanosheets enabled good electrical contact between the current collector and the active material for the fast electron transfer. By synergetic combination of these advantages, the optimum electrode delivered exceptional rate capability (84.8% capacity retention from 1 to 20 mA cm−2) and excellent cycling stability (86.8% capacity retention after 10000 cycles). An asymmetric supercapacitor assembled with the CSF as the positive electrode and activated carbon as the negative electrode displayed outstanding electrochemical performance. It is expected to provide a green and simple method for the preparation of transition metal sulfide-based electrodes for the practical energy storage. Image 1 • Cobalt sulfide foam (CSF) is fabricated by electrochemical reduction of sulfur. • CSF with 3D hierarchical structure provides unobstructed ion diffusion pathways. • PPy facilitates the electronic transportation between CoS and carbon paper. • Chemical bonding between PPy and CoS enables cycling stability of electrode. [ABSTRACT FROM AUTHOR]

This paper reports on the long-term performance of electrochemical capacitor operating in 1 mol⋅L−1 KI solution subjected to two ageing protocols, i.e., galvanostatic cycling and potentiostatic floating. Ageing tests have been performed at similar voltage conditions (1.5 V), estimated from the coulombic and energetic efficiency as well as the self-discharge analysis. The end-of-life criterion (80% of initial capacitance retained) was the same for both procedures. The influence of the ageing methodology on the structural and textural changes in electrode material has been discussed. The results obtained allowed for failure mechanisms description in the floating tests in comparison to traditional galvanostatic cycling. It has been stated that de facto the structural changes do not diminish the long-time performance. Notwithstanding, it has been found that galvanostatic cycling has a definitely stronger and detrimental impact on the carbon structure. Interestingly, both ageing methodologies affect the electrode porosity in a similar way. The nitrogen adsorption measurements indicated that the specific surface area decrease correlates with the capacitance fade. Changes observed in the pore size distribution allowed us to conclude that the porosity of both electrodes is blocked by adsorbed and/or deposited species. It looks that floating causes higher pore clogging especially for positive electrode. • Different ageing mechanism was proposed for capacitor failure during cycling and floating. • Decrease of electrode porosity after ageing tests was significant especially for (+) electrodes. • Iodide species were confined in both electrodes. • Electrochemical capacitor with a redox active electrolyte (I-/I 2) shows moderate self-discharge for optimal voltage. [ABSTRACT FROM AUTHOR]

Abstract Capacitive deionization (CDI) is a promising technology for water desalination. An excellent desorption rate guarantees re-adsorption performance of CDI electrode in the following cycles. In this paper, we reported for the first time that the use of half-wave rectified alternating current (HWAC), a periodically changing electric field, improved electrodesorption in CDIs. Up to 90% of adsorbed NaCl can be released from activated carbon electrodes after HWAC (1.2 V, 1 kHz, 90 min) than 78% of direct current (DC, 1.2 V) powered systems, corresponding to a 79% current efficiency than 71% of DC. This was attributed to the elimination of capacitance in pores as well as the agitation of ions by the periodically changing electric field. Energy consumption per unit charge release decreased by 68% from 145 ± 11 J/(mmol e−) of DC to 46 ± 3 J/(mmol e−) of HWAC. Electrodesorption of MgSO 4 and the mixture of NaCl/MgSO 4 have similar results, indicating that the energy-saving strategy of HWAC was not affected by ionic charge or radius. These findings demonstrated that HWAC was a highly efficient waveform for maximizing the ion desorption from porous electrodes with a low energy requirement. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the electrochemical reactivity of boron doped diamond (BDD) electrodes. A comparative study has been carried out to show the influence of the presence of graphitic micro-domains upon the surface of these films. Those graphitic domains are sometimes present on as-grown boron doped diamond electrodes. The effect of doping a pure Csp3 diamond electrode is established by highly oriented pyrolytic graphite (HOPG) abrasion onto the diamond surface. In order to establish the effect of doping on a pure Csp3 diamond electrode, the amount of graphitic domains was increased by means of HOPG crystals grafted onto the BDD surface. Indeed that method allows the enrichment of the Csp2 contribution of the electrode. The presence of graphitic domains can be correlatively associated with the presence of kinetically active redox sites. The electrochemical reactivity of boron doped diamond electrodes shows a distribution of kinetic constants on the whole surface of the electrode corresponding to different active sites. In this paper, we have studied by cyclic voltammetry and electrochemical impedance spectroscopy the kinetics parameters of the ferri/ferrocyanide redox couple in KCl electrolyte. A method is proposed to diagnose the presence of graphitic domains on diamond electrodes, and an electrochemical “pulse cleaning” procedure is proposed to remove them. [Copyright &y& Elsevier]

• A simple label-free immunosensor for the detection of SARS-CoV-2 spike S1 protein. • Gelatin as biocompatible support suitable for further modifications with protein A and antibodies. • Gelatin improves the electrochemical stability of the supporting screen-printed carbon electrode. • Sensitive and linear operation in the clinically-relevant range. • Excellent limit of detection of 1.2 pM. The persistent nature of the SARS-CoV-2 virus, characterized by its large-scale periodical recurrence and high infectivity, has imposed an increasing demand for rapid and frequent tests. This paper presents a simple, disposable, sensitive, and selective label-free sensor for impedimetric detection of the virus Spike S1 protein. We modified a screen-printed carbon electrode with gelatin as the biocompatible support to deposit a protein A layer, acting as the structure-directing agent for subsequent site-induced binding of antibodies. We thoroughly investigated the main design factors, such as gelatin deposition, protein A and antibody concentrations, incubation time, BSA blocking time, followed by the analytical performance studies using the Spike S1 protein in phosphate-buffered saline (PBS) and artificial nasopharyngeal fluid (ANF). The immunosensor exhibited an excellent linear impedimetric response for Spike S1 in the clinically-relevant range of 0.001 - 10 μg mL−1 (13 pM - 130 nM), along with very low limits of detection of 169 pg mL−1 (2.2 pM) in PBS and 90 pg mL−1 (1.2 pM) in ANF. Together with favorable stability, repeatability, and selectivity, the newly developed immunosensor can be designated for its point-of-need application. [Display omitted] [ABSTRACT FROM AUTHOR]

For device fabrication, materials needs to satisfy 3Es (economical, environment friendly and easy to prepare) along with technical characteristics. Present paper reports an electrolyte synthesized by modifying potato starch by solution cast technique which is easy to synthesize, stretchable, bendable and twistable low cost (∼ INR 15/cm 2 ) free standing electrolyte film having wide electrochemical stability window (ESW ∼ 2.4 V), low equivalent series resistance (ESR ∼ 1.7 Ω) and small ion relaxation time (15 μs). Supercapacitors are fabricated using this electrolyte with two different electrodes (teflon coated carbon cloth and anodized aluminium). With laboratory prepared anodized Al as electrode, the electrochemical stability window is >4 V, ESR is <2 Ω and capacitance of ∼mF is obtained. Approximately −80° phase angle is obtained which remains constant from 1 Hz to 10 kHz range which covers the frequency requirement of ac line filtering application. The coulombic efficiency estimated from charging/discharging curves have values > 98% which approximately remains constant in studied number of cycle. All these indicate that prepared electrolyte is a potential candidate for electrochemical device applications. [ABSTRACT FROM AUTHOR]

The binder-free all-carbonaceous-component electrode was constructed by directly growing electroactive materials of nitrogen-doped carbon (NDC) on the substrate material of carbon paper (CP). The nitrogen-enriched polyaniline could be converted into NDC nanowires to cover on the surface of CP through electro-polymerization and carbonization processes. The polyaniline-derivated NDC electroactive material exhibits high capacity of 404.0 F g −1 at 1.0 A g −1 . The superior capacitance results from the good electron-donor properties of heterocyclic nitrogen distributed in the carbon skeleton and reversible redox reactivity of exocyclic nitrogen-containing functional groups at the edge of carbon skeleton. A low capacity decay of 22% indicates high rate capability when current density increases from 1.0 to 10 A g −1 . A high capacity retention ratio of 95.8% after 5000 cycles at 10.0 A g −1 presents good cycling stability. A symmetrical solid-state supercapacitor was constructed using NDC/CP electrode and polyvinyl alcohol-H 2 SO 4 gel electrolyte. The device delivers a specific capacitance of 187.1 F g −1 at 1.0 A g −1 , an energy density of 66.54 Wh kg −1 at the power density of 0.8 kW kg −1 , the capacity retention ratio of 94.1% after 5000 cycles at 5.0 A g −1 and an output voltage of 1.6 V, which is comparable to the reported state-of-the-art carbon-based supercapacitor. The all-carbonaceous-component electrode presents promising application in electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

Oxygen functional groups are one of the most important subjects in the study of electrochemical properties of carbon materials which not only can change the wettability, conductivity and pore size distributions of carbon materials, but also can occur redox reactions. In the electrode materials of carbon-based supercapacitors, the oxygen functional groups have been widely used to improve the capacitive performance. In this paper, we systematically analyzed the reasons for the increase of the capacity that promoted by oxygen functional groups in the charge∕discharge cycling tests and the mechanism how the pseudocapacitance is provided by the oxygen functional groups in the acid/alkaline aqueous electrolyte. In addition, we in more depth discussed the effect of the oxygen functional groups in electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Performance and durability of lithium-ion batteries highly rely on local conditions inside electrodes during operation. In this paper, local physical conditions inside a standard graphite electrode are explored at various C-rate and mass-loading with a physic-based model, validated with electrochemical experiments. The typical equilibrium potential curve of graphite controls strongly the intercalation heterogeneity along thickness and this heterogeneity is maximal for state of charge corresponding to regions of flat equilibrium potential. Indeed, a flat equilibrium potential promotes lithiation disparities along thickness, whereas a variable equilibrium potential enhances a quick return to a homogeneous lithiated electrode. Current and mass loading affect proportionally these heterogeneities, which are linked with a decrease in cell performance. A correlation between heterogeneities and equivalent resistances interpolated from galvanostatic discharge is found. Pathway resistances calculated from simulation outputs indicate preferential locations of intercalation under operation, depending on the difference between the local and global equilibrium potential of the graphite electrode. [ABSTRACT FROM AUTHOR]

In this paper, a lithium-ion full battery based on a high quality graphitized graphene anode and a high capacity, high rate Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 cathode was reported. After carefully designing the cell and improving the initial Coulombic efficiency of the anode, electrochemical performances such as cycling life (500 stable cycles at 1C rate), rate capability(a capacity of 115 mAh g −1 at 10C) and energy density(about 180 Wh kg −1 at 1C rate and a moderate operating voltage) can be achieved, making the battery very promising for powering hybrid electrical vehicles (HEVs) or electric vehicles (EVs). [ABSTRACT FROM AUTHOR]

The iron precursor of lithium iron phosphate (LiFePO 4 ) is highly prone to oxidation to Fe 3+ during the hydrothermal synthesis. The Fe 3+ impurities in LiFePO 4 restrict the conduction path of Li + ions in LiFePO 4 , which negatively affect the cell performance. In this paper, we report that ferrocenecarboxylic acid possessing an extremely stable Fe 2+ species and as carbon source has been used successfully to suppress Fe 3+ impurities in LiFePO 4 . The X-ray diffraction results reveal that Li 2 CO 3 first reacts with (NH 4 ) 2 HPO 4 to form Li 3 PO 4 at low temperatures, which above 160 °C further reacts with ferrocenecarboxylic acid to give LiFePO 4 . The infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and elemental analysis results show that the carbon sources during calcination of LiFePO 4 are derived from polymers through sequential [4 + 2] cycloaddition reactions of cyclopentadiene and 1,3-cyclopentadiene-1-carboxylic acid during decomposition of ferrocenecarboxylic acid. The electron paramagnetic resonance results show that the percentage of Fe 3+ in the synthesized LiFePO 4 is as low as 0.5 mol%. A plausible reaction mechanism for the hydrothermal synthesis of LiFePO 4 is also proposed. The as-synthesized LiFePO 4 shows an orthorhombic olivine with a discharge capacity of 158 mAh g −1 at a discharge rate of 0.1C. The cell also shows excellent C-rate and cycle-life performances. [ABSTRACT FROM AUTHOR]

This paper discussed in details the impact of binder polyvynilidene fluoride (PVDF) concentrations (5, 10 and 20 wt%) and pressures (∼382 ∼ 891 ∼ 1783 and ∼2547 MPa) for the fabrication of electrodes based on Carbon nanofibers (CNFs) for supercapcitors. The surface area, pore size distribution and morphology were characterized by Brunauer–Emmett–Teller (BET) method and SEM. The decrease in specific surface area was about 31% and pore volume 14.6% with increase in PVDF concentration from 5 to 20 wt% at ∼891 MPa pressure. The assembled electrodes were tested with two electrode system in aqueous electrolyte. The specific capacitance was 80 F/g for lowest concentration of PVDF (5 wt%) and decreased about 28.3% with increase concentrations at same pressure ∼891 MPa. In comparing the effect of pressure on specific capacitance, it increases about 38% for (PVDF, 10 wt%; pressure ∼1783 MPa) from (PVDF, 10 wt%; pressure ∼891 MPa); their corresponding power density 24502 W/kg at energy density of 6.8 Wh/Kg and 19886 W/kg at energy density energy of 3.8 Wh/kg. ESR values increase from 0.3 to 1.9 Ω with increase in PVDF concentration and decrease again to 0.5 Ω with increase in pressure. The results show optimal conditions are 10 wt% of PVDF and higher pressure of ∼891 MPa. [ABSTRACT FROM AUTHOR]

In this paper, high performance supercapacitor based on electrochemical reduced graphene oxide (ERGO)-polyaniline (PANI) nanocomposite film was prepared in facile two steps. ERGO sheets synthesized on surface of glassy carbon electrode (GCE) by an effective and environment-friendly electrochemical reduction of graphene oxide (GO), followed PANI formed on ERGO surface via cyclic voltammetry electrodeposition at potential window −0.20 to 0.80 V at a scan rate of 50 mV s −1 . Electrochemical results indicate that ERGO-PANI nanocomposites exhibit a good capacitance performance with maximum specific capacitance of 1084 Fg −1 , and high specific energy density of 53.12 Wh kg −1 with specific power density of 500.61 W kg −1 at a current density of 3.22 mA cm −2 in 1 M H 2 SO 4 aqueous solution. Improved electrochemical performance of the nanocomposites arises from synergistic combination of electrically conductive ERGO and highly capacitive behavior of PANI. Therefore, the ERGO-PANI nanocomposite electrodes are promising candidate for application in energy storage devices. Moreover, the products have been successfully characterized by X-ray diffraction (XRD), Fourier transformation spectroscopy (FT-IR), scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and atomic force microscopy (AFM). [ABSTRACT FROM AUTHOR]

In this paper, the selective and sensitive determination of hydrogen peroxide (H 2 O 2 ) at physiological pH using silver nanoparticles-zinc-metal organic framework (AgNPs-Zn-MOF) modified glassy carbon (GC) electrode was described. Initially, the Zn-MOF was synthesized by hydrothermal method and then incorporated with AgNPs capped tannic acid. The AgNPs-Zn-MOF was characterized by fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The SEM image shows that the AgNPs in Zn-MOF were spherical in shape with an average size of ∼50 nm. Then, the synthesized AgNPs-Zn-MOF was modified on GC electrode by drop casting and the resulting modified electrode was characterized by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS). The CV of AgNPs-Zn-MOF modified electrode exhibits a sharp anodic peak at +0.20 V corresponding to the oxidation of Ag 0 to Ag + and a subsequent reduction peak at −0.50 V corresponding to Ag + to Ag 0 . Further, the electrocatalytic activity of the AgNPs-Zn-MOF modified electrode was examined by studying the reduction of H 2 O 2 . It exhibits a sharp reduction peak for H 2 O 2 at −0.67 V with a current of −21 μA whereas no response was observed at GC, GC/Zn-MOF and GC/TA-AgNPs modified electrodes. The current response of H 2 O 2 was increased linearly while increasing its concentration from 1 μM to 5 mM with a correlation coefficient of 0.9915 and a limit of detection was found to be 67 nM (S/N = 3). The practical application of the present method was demonstrated by determining H 2 O 2 in milk, human urine and blood serum samples. [ABSTRACT FROM AUTHOR]

The conventional enhancement in capacitive performance that only relies on electrode materials is limited. Here, based on the system-level design principle, we explore the possibility of enhancing capacitance through both electrode and electrolyte. A novel and ultrahigh-performance asymmetric supercapacitor has been fabricated using two redox electrode systems. The positive electrode system consists of graphene supported Co(OH) 2 nanosheet (Co(OH) 2 /GNS) electrode and mixed KOH and K 3 Fe(CN) 6 aqueous electrolyte. And the negative electrode system comprises carbon fiber paper supported activated carbon (AC/CFP) electrode in mixed KOH and p-phenylenediamine (PPD) aqueous electrolyte. The novel asymmetric supercapacitor exhibits a significantly improved capacitive performance (specific capacitance of 204.5 Fg −1 , operational voltage of 2.0 V) in comparison with that of the conventional asymmetric supercapacitor (66.8 Fg −1 , 1.5 V) fabricated without redox electrolyte. The improvement is attributed high reversibility and conductivity of electrode materials and redox electrolyte, as well as the synergistic effect between the two electrode systems, resulting in a ultrahigh energy density (114.5 Whkg −1 at a power density of 1000 Wkg −1 ), excellent power density (4000 Wkg −1 at an energy density of 31.6 Whkg −1 ) and long-term cycling stability (after 20000 cycles, initial capacitance remains well). These encouraging results afford a facile and efficient way to fabricate ultrahigh-performance supercapacitors for the increasing demands on the energy storage devices. [ABSTRACT FROM AUTHOR]

The development of alternative anode materials out of flexible composite nanofibers has seen a growing interest. In this paper, binary carbon nanofiber electrodes of SnO 2 /NiO and Sn nanoparticles are produced using a scalable technique, Forcespinning (FS), and subsequent thermal treatment (carbonization). The Sn/C composite nanofibers were porous and flexible, while the SnO 2 /NiO composite nanofibers had “hairy-like” particles and pores on the fiber strands. The nanofiber preparation process involved the FS of Sn/PAN and SnO 2 /NiO/PAN solution precursors into nanofibers and subsequent stabilization in air at 280 ° C and calcination at 800 °C under an inert atmosphere. The flexible composite nanofibers were directly used as working electrodes in lithium-ion batteries without a current collector, conducting additives, or binder. The electrochemical performance of the SnO 2 /NiO/C and Sn/C composite fiber anodes showed a comparable cycle performance of about 675 mAhg −1 after 100 cycles. However, the SnO 2 /NiO/C electrode exhibited a better rate performance than the Sn/C composite anode and was able to recover its capacity after charging with a higher current density. A postmortem analysis of the composite nanofiber electrode after the aging process revealed a heavily passivated electrode from the electrolyte decomposition by-products. The synthesis and processing methods used to produce these composite nanofibers clearly were a factor for the high rate capability and excellent cycle performance of these binary composite electrodes, largely on the account of the unique structure and properties of the composite nanofibers. [ABSTRACT FROM AUTHOR]

In the last two decades, tremendous work has been investigating the electro-reduction of metal oxide cathodes in what is known as the FFC-Cambridge process. This paper explores the electrolyte changes that occur during the electro-deoxidation of metal oxides. The investigation takes niobium oxide as a case study and subjects a Nb 2 O 5 cathode to a constant potential difference of 2.5V between the cathode and carbon anode during the in- situ recording of the cyclic voltammetry of the electrolyte on a glassy carbon electrode. The deoxidation of the cathode supplies oxygen ions that increase the oxygen content of the electrolyte, even in the very early stage of the process. We could detect many non-Faradic processes and increase the electrolyte electronic and ionic conductivity a few hours after starting the electro-deoxidation due to the reduction of CaO. It was also possible to detect partial dissolution of the cathode in the electrolyte and back deposition of Nb on the current collector. The dissolved niobium ions can combine with the oxide ion in the melt to form a negatively charged complex which can be discharged on the anode to form a thick ceramic layer. The electrolyte changes were also investigated using electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

• Layered molybdenum disulfide (2D-MoS 2) nanosheets of different size, < L >, and number of layers, < N >, were prepared via liquid cascade centrifugation (LCC). • Dopamine (DA) and riboflavin (RF) were tested for the first time to investigate the role of < N > and < L > of MoS 2 nanosheets. • The electro-oxidation of RF was found to be largely promoted on the 2D-MoS 2 -based electrode with the smaller lateral size and minor number of layers. In this paper, layered molybdenum disulfide (2D-MoS 2) nanosheets of different size and number of layers were prepared via liquid cascade centrifugation (LCC) and their microstructural, morphological and electrochemical characteristics for the detection of dopamine (DA) and riboflavin (RF) were investigated. The microstructural and morphological characteristics of 2D-MoS 2 nanosheets obtained at different centrifugation rates were evaluated by UV-Vis, Raman spectroscopy, and SEM analysis. The 2D-MoS 2 nanosheets obtained showed a monotonic decrease of average lateral sheet size < L > and number of layers < N > with the increase of the centrifugation speed. Screen printed carbon electrodes (SPCE) were modified by drop casting on their surfaces 2D-MoS 2 nanosheets from aqueous dispersions. The electrochemical properties of the modified 2D-MoS 2 /SPCE were assessed by electrical impedance spectroscopy and cyclic voltammetry in [Fe (CN) 6 ]3−/4− redox probe. DA and RF were tested to investigate the role of < N > and < L > of MoS 2 nanosheets in the electrochemical sensing of these two biomolecules. Results have shown no significant variations in the electrochemical parameters for DA sensing using the different modified electrodes. In contrast, the electro-oxidation of RF was found to be largely promoted on the 2D-MoS 2 -based electrode with smaller lateral size and minor number of layers, demonstrating the feasibility of tuning the electrochemical properties of 2D-MoS 2 nanosheets by modifying their geometric features. The study proposes LCC as an alternative promising technique for preparing nanomaterials with enhanced performances for developing electrochemical sensors for biomolecules. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper reports on the performance of the supercapacitor operating in aqueous acetic acid salts. Lithium, sodium and magnesium acetate aqueous solutions at various concentrations have been selected as electrolytes. Maximum operational voltage and the overall capacitor performance have been determined by several electrochemical techniques. Floating and galvanostatic charge/discharge tests proved the promising performance at high voltages (1.5 V); the capacitance values have been retained at more than 80% of initial value for all tested electrolytes. Additionally, due to the the ability to operate at high voltages, the maximum energy obtained in the system with 0.5 mol L −1 CH 3 COONa is more than two times higher than with 6 mol L −1 KOH, i.e., conventional aqueous capacitor. Taking into account a mild character of the electrolytes used, a novel concept of eco-friendly energy storage device has been proposed. [ABSTRACT FROM AUTHOR]

Ultra-microporosity and heteroatom-doping have been proved to be desired for carbon electrode materials of advanced supercapacitors. In this paper, dual N, S-doped carbon materials with high-developed ultra-micopores (∼0.70 nm) are prepared by direct carbonization of potassium salts of m-amionphenol-m-mecaptophenol co-resin. The morphology, structure and surface properties of the carbon materials are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption, X-ray photoelectron spectroscopy (XPS), and Energy dispersive spectroscopy (EDS). It was found that the reactant ratio of phenols play an important role on the microscopy morphology, pore texture and heteroatom-doping of carbon materials. The potassium ions mono-dispersed in phenolic resins as a form of O − K + deliver a homogenous “ in-situ self-activation ”, thus created developed ultra-microporosity with high uniformity, connectivity and short pore length. Due to the synergy effect of tailored ultra-microporosity and N, S, O-doping, the SNC-3:1-600 carbon shows a high specific capacitance of 250 F g −1 , good capacitance retention of 61% in the range of 0.2–20 A g −1 , low relaxation time constant of 0.71 s in KOH electrolyte. The present preparation strategy is attractive and inspiring for preparation of tunable N, S-doped carbon materials for advanced supercapacitors. [ABSTRACT FROM AUTHOR]

In this paper, novel ε-MnO 2 microspheres with uniform flaky texture were synthesized by a precursor conversion method. Basing on this material, a novel ε-MnO 2 microspheres/chitosan/GCE (glassy carbon electrode) electrochemical sensor prepared by a simple physical deposit method was developed for the ultrasensitive determination of Ponceau 4R. The proposed electrochemical sensor exhibits remarkable electrocatalytic activity towards Ponceau 4R, suggesting a potentially detailed reaction mechanism catalyzed by ε-MnO 2 and demonstrating a wide linear detection range from 0.005 to 1000 μmol dm −3 and a low detection limit of 0.1 nmol dm −3 (S/N = 3) for Ponceau 4R. The sensor also shows promising selectivity, stability and reproducibility and finally, is applied to determine Ponceau 4R in real samples, giving satisfactory results. [ABSTRACT FROM AUTHOR]

We report in this paper an original way to covalently bind the macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane (cyclam), through diazonium salt chemistry, on the surface of carbon screen-printed electrodes (SPEs). The in situ synthesis of the diazonium salt obtained from the amine precursor derived from the cyclam and its electrografting are described. X-ray Photoelectron Spectroscopy was used to characterize this functionalized surface. Owing to the strong cyclam–Cu(II) affinity, the so called SPE-cyclam can be used as electrochemical sensors for Cu(II) determination at trace levels. The influence of electroanalysis parameters such as the accumulation time and the pH of the medium were investigated. An interference study was carried out with numerous metallic cations and few interference was found for Cu(II) quantification. The described method provided a limit of detection and a limit of quantification of 1.3 × 10 −8 M and 4.0 × 10 −8 M, respectively. Interference study and performances show that SPE-cyclam could be considered as efficient sensors for environmental analysis. [ABSTRACT FROM AUTHOR]

The work reported in this paper demonstrates for the first time that graphene modified glassy carbon electrode (Gr/GC) show remarkable electrocatalysis towards Pu(IV)/Pu(III) redox reaction and the results were compared with that of single-walled carbon nanotubes modified GC (SWCNTs/GC) and glassy carbon (GC) electrodes. Graphene catalyzes the exchange of current of the Pu(IV)/Pu(III) couple by reducing both the anodic and cathodic overpotentials. The Gr/GC electrode shows higher peak currents (i p ) and smaller peak potential separation (ΔE p ) values than the SWCNTs/GC and GC electrodes. The heterogeneous electron transfer rate constants ( k s ), charge transfer coefficients (α) and the diffusion coefficients (D) involved in the electrocatalytic redox reaction were determined. Our observations show that graphene is best electrocatalytic material among both the SWCNTs and GC to study Pu(IV)/Pu(III) redox reaction. [ABSTRACT FROM AUTHOR]

Hollow spheres structured materials have been intensively pursued due to their unique properties for energy storage. In this paper, hollow-in-hollow carbon spheres (HIHCS) with a multi-shelled structure were successfully synthesized using a facile hard-templating procedure. When evaluated as anode material for lithium-ion batteries, the resultant HIHCS anode exhibited superior capacity and cycling stability than HCS. It could deliver reversible capacities of 937, 481, 401, 304 and 236 mAh g −1 at current densities of 0.1 A g −1 , 1 A g −1 , 2 A g −1 , 5 A g −1 and 10 A g −1 , respectively. And capacity fading is not apparent in 500 cycles at 5 A g −1 . The excellent performance of the HIHCS anode is ascribed to its unique hollow-in-hollow structure and high specific surface area. [ABSTRACT FROM AUTHOR]