Carbon Black Electrodes Research Articles

Highly Selective Hydrogen Peroxide Electrosynthesis on Carbon: In Situ Interface Engineering with Surfactants

Summary In situ modulation of surface reaction is a powerful approach to drive high-yield H2O2 electrosynthesis on metal-free carbon. Here, we discover that cationic surfactants can work efficiently as an in situ kinetic promoter for the oxygen-to-peroxide reaction on a carbon black electrode, achieving a peroxide yield above 90% (up to 95.2%) across a >0.8 V window in alkaline media, the best among reported H2O2 electrocatalysts. Our characterizations and kinetic model analysis show that the high peroxide selectivity is attributable to surface carboxylates (–COO−) with weak peroxide binding under a Coulombic pull imposed by an adsorbed cationic layer. Although surface carbonyls (–C=O) also participate in the peroxide synthesis, they exhibit strong binding to peroxide and promote on-site reduction at moderate-to-high overpotential. At only a minute amount of cationic surfactant, a chronoamperometry experiment with a carbonyl-free system can deliver a peroxide production at a sustainably high selectivity (∼96%) over 10 h.

Woven Structure for Flexible Capacitive Pressure Sensors

Flexible and stretchable capacitive pressure sensors have been developed in recent years due to their potential applications in health monitoring, robot skins, body activity measurements and so on. In order to enhance sensor sensitivity, researchers have changed structure of the dielectric of parallel plate capacitive sensor . Here we enhance the sensor sensitivities by changing electrode composition and explore the use of a woven electrode structure sensor with silver coated nylon yarn and EcoflexTM. The woven structure enhanced sensitivity 2.3 times relative to a simple cross-grid geometry (sensitivity was 0.003 kPa-1). Furthermore, it is also observed that the sensor with the woven electrode also had better repeatability and showed less creep than a device using carbon black electrodes. The woven structure of the electrodes enabled the device to be compliant, despite the presence of the stiff nylon fibres – thereby enabling good sensitivity without the creep seen in softer electrodes.

Probing the degradation of carbon black electrodes in the presence of chloride by electrochemical impedance spectroscopy

The influence of the presence of chloride ions (Cl−) on the electrochemical stability of a porous carbon black electrode was examined. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), we have observed that the durability of this porous carbon layer, similar to those used in fuel cells and supercapacitors, is altered in the presence of chloride. The presence of as little as 1 mM chloride leads to a substantial reduction in electrode capacitance and an increase in the total resistance of the porous layer, which will impact performance in electrochemical energy applications. The effect is more pronounced at higher chloride concentrations.

Electrocatalysis of Hydrogen Peroxide Generation Using Oxygen-Fed Gas Diffusion Electrodes Made of Carbon Black Modified with Quinone Compounds

Hydrogen peroxide (H2O2) is one of the most popular and widely used oxidants. Among the wide range of synthesis techniques used for the production of H2O2; the electrochemical method allows the use of gas diffusion electrodes to generate H2O2 without limiting the low solubility of O2 in water. The present work reports the modification of carbon black with quinone, where the generation of H2O2 occurs in an electrochemical/chemical mechanism. The results obtained by this technique were found to be highly promising. The use of the organic compound 1,2-dihydroxyanthraquinone to modify carbon black electrode resulted in greater production of H2O2. Carbon black electrode modified with 1% of 1,2-dihydroxyanthraquinone yielded 298 mg L−1 of H2O2 at the end of 90 min of experiment, reaching an electrical efficiency of approximately 25.5%. Based on the findings of this study, H2O2 generation is found to be directly associated with the chemical structure of the carbon modifier and not solely related to the presence of quinone groups.

Chiral voltammetric sensor for warfarin enantiomers based on carbon black paste electrode modified by 3,4,9,10-perylenetetracarboxylic acid

A chiral electrochemical sensor based on carbon black paste electrode (CBPE), consisting of graphitized carbon black powder Carboblack C modified by nanoclusters of 3,4,9,10-perylenetetracarboxylic acid (PTCA) for the selective recognition and determination of warfarin (WA) enantiomers is described in this work. The spontaneous appearance of two-dimensional space group during self-assembly by an external induction of PTCA nanoclusters provides their chirality. It was found that the CBPE modified by PTCA afforded specific interaction with WA enantiomers and acted as a chiral selector, which affected the current and peak potential change. CBPE modified by PTCA was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The electrochemical and analytical characteristics of the sensor, and conditions of the voltammogram registration were studied by differential pulse voltammetry (DPV). The experimental results indicate a linear correlation between the peak current of warfarin enantiomers and their concentration in the range from 5 μM to 0.16 mM, leading to a detection limit of 3.09 μM and 4.02 μM for R- and S-WA, respectively. The potential ability of proposed electrode for WA enantiomer determinations has been evaluated by analyzing human urine and blood plasma with a recovery ranging from 97.1% to 102.9%. The present sensor can determine ratio of WA isomer's in enantiomeric mixture.

Feasibility of a Nano‐Carbon Black Paste Electrode for Simultaneous Voltammetric Determination of Antioxidants in Food Samples and Biodiesel in the Presence of Surfactant

AbstractIn this work, a simple and low‐cost method was developed for the simultaneous determination of the antioxidants tert‐butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA) in the presence of the cationic surfactant CPB by square wave voltammetry (SWV) technique using a carbon black paste electrode (CBPE). The performance of the method was investigated by varying parameters such as pH, electrolyte, and type and concentration of surfactant. Under the optimum conditions of 0.2 mol L−1 phosphate buffer (pH 7.0), 600.0 μmol L−1 of cetylpyridinium bromide surfactant and SWV operating parameters optimized through the Doehlert matrix, the method presented low limits of quantification for TBHQ and BHA (0.23 and 0.26 μmol L−1, respectively) and high precision in successive measurements. The proposed method was applied in mayonnaise, margarine and biodiesel and the accuracy of method was checked by the HPLC technique.

Fabrication of multi-walled carbon nanotubes and carbon black co-modified graphite felt cathode for amoxicillin removal by electrochemical advanced oxidation processes under mild pH condition.

Hydrogen peroxide (H2O2) electrogenerated via two-electron oxygen reduction reaction at cathode plays an important role in electrochemical advanced oxidation processes for organic pollutants removal from wastewater. Herein, multi-walled carbon nanotubes and carbon black co-modified graphite felt electrode (MWCNTs-CB/GF) was prepared as an efficient cathode for H2O2 electrogeneration and amoxicillin removal by anodic oxidation with hydrogen peroxide (AO-H2O2) and electro-Fenton (EF) under mild pH condition. Besides, the physicochemical and electrochemical properties of MWCNTs-CB/GF were characterized by scanning electron microscopy, N2 adsorption and desorption experiment, contact angle measurement, X-ray photoelectron spectroscopy, and linear sweep voltammetry. Compared with GF, MWCNTs-CB/GF showed a higher H2O2 generation of 309.0mgL-1 with a current efficiency of 60.9% (after 120min) and more effective amoxicillin removal efficiencies of 97.5% (after 120min) and 98.7% (after 30min) in AO-H2O2 and EF (with 0.5mM Fe2+) processes, under the condition of current density 12mAcm-2 and initial pH5.5. Meanwhile, the TOC removal efficiency was 45.2% during EF process after 120min. Anodic oxidation, H2O2 oxidation, and methanol capture indicated that ∙OH generated via electro-activation reaction at MWCNTs-CB/GF and Fenton reaction in solution played the dominant role in amoxicillin removal. Moreover, the TOC removal was associated with ∙OH generated during Fenton reaction in the solution. The major intermediates of AMX degradation by EF process were identified using LC-MS and the possible degradation pathways were proposed containing of β-lactam ring opening, hydroxylation reaction, decarboxylation reaction, methyl groups in the thiazolidine ring oxidation reaction, bond cleavage, and rearrangement processes. All of the above results proved that MWCNTs-CB/GF was an excellent cathode for AMX degradation under mild pH condition.

A Chiral Voltammetric Sensor Based on a Paste Electrode Modified by Cyanuric Acid for the Recognition and Determination of Tyrosine Enantiomers

An enantioselective voltammetric sensor based on graphitized carbon black (Carboblack C) paste electrode modified by cyanuric acid (CA) was developed for the selective recognition and determination of tyrosine (Tyr) enantiomers. The sensor preferably recognizes D-Tyr because of steric differences between the Tyr enantiomers and nanocavities of CA supramolecules. Using cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and polarimetry, the conditions for modifying Carboblack C with cyanuric acid were optimized and the electrochemical characteristics of the sensor and the conditions for recording voltammograms were studied. The performance of the sensor was estimated under the conditions of differential pulse voltammetry. The proposed sensor was used to recognize and determine the L- and D-enantiomers of tyrosine in a mixture and in samples of urine and human blood plasma. Using molecular dynamics simulation, the features of the interaction of tyrosine enantiomers with CA supramolecules are considered.

Effect of actuation parameters and environment on the breakdown voltage of silicone dielectric elastomer films

This paper presents results on dielectric breakdown studies for silicone dielectric elastomer (DE) membranes. Dielectric breakdown is a crucial property for the characterization of DE actuator behaviour. Here, we particularly focus on the effect of environmental parameters on the breakdown field, using a recently designed novel test stand for automatic testing of multiple measurement points per sample in a climate chamber. We present an extensive study about the influence of temperature, humidity, and water content on the breakdown field of DEs under indoor environmental conditions. Additionally, the effect of actuation parameters, such as various stretch-ratios, as well as the influence of screen-printed carbon black electrodes, is systematically investigated. The study indicates slightly higher breakdown fields with increasing temperatures but negligible influence of humidity and water content changes. Samples with printed electrodes show significantly lower breakdown fields whereas the increase of stretch ratio resulted in significantly higher breakdown fields.

Evolution of the Solid-Electrolyte Interphase on Carbonaceous Anodes Visualized by Atomic-Resolution Cryogenic Electron Microscopy.

The stability of modern lithium-ion batteries depends critically on an effective solid-electrolyte interphase (SEI), a passivation layer that forms on the carbonaceous negative electrode as a result of electrolyte reduction. However, a nanoscopic understanding of how the SEI evolves with battery aging remains limited due to the difficulty in characterizing the structural and chemical properties of this sensitive interphase. In this work, we image the SEI on carbon black negative electrodes using cryogenic transmission electron microscopy (cryo-TEM) and track its evolution during cycling. We find that a thin, primarily amorphous SEI nucleates on the first cycle, which further evolves into one of two distinct SEI morphologies upon further cycling: (1) a compact SEI, with a high concentration of inorganic components that effectively passivates the negative electrode; and (2) an extended SEI spanning hundreds of nanometers. This extended SEI grows on particles that lack a compact SEI and consists primarily of alkyl carbonates. The diversity in observed SEI morphologies suggests that SEI growth is a highly heterogeneous process. The simultaneous emergence of these distinct SEI morphologies highlights the necessity of effective passivation by the SEI, as large-scale extended SEI growths negatively impact lithium-ion transport, contribute to capacity loss, and may accelerate battery failure.

Expansion of the urea electrocatalytic oxidation window by adsorbed nickel ions

The electrocatalytic oxidation of urea using Ni-based catalysts is able to oxidize urea at high rates, reaching hundreds of mA cm−2 depending on electrode and solution properties. Most of the demonstrated systems, however, report a drop-off in current ~ 0.3 V positive of the Ni2+/Ni3+ redox transition resulting in a dramatic decrease of activity. The drop-off limits the electrochemical window available for urea decomposition. To overcome this narrow window, Ni2+ ions are herein adsorbed onto carbon black electrodes cohesively bound with Nafion. The resulting electrodes are electrochemically tested for urea electro-oxidation activity whereby their cyclic voltammograms display no drop-off in activity up to 1.5 V positive of the Ni2+/Ni3+ transition. The oxidation currents of the adsorbed Ni2+ electrodes demonstrate urea decomposition rates nearly identical to Ni-metal films, and impedance measurements show similar charge transfer limitations. Electrodes are monitored after electrochemical cycling with atomic force microscopy to reveal that adsorbed species coalesce into surface particles, which behave like bulk Ni(OH)2, implying that the commonly observed drop-off in current may be due to structural characteristics of Ni(OH)2 and NiOOH. The simplicity of the adsorption process and its ability to widen the electrochemical window for urea oxidation allows new substrates to be incorporated into urea degradation systems without sacrificing high urea oxidation rates.

Laccase stabilized on β-D-glucan films on the surface of carbon black/gold nanoparticles: A new platform for electrochemical biosensing

In this study, (1→3)(1→6)-β-D-glucan (botryosphaeran) from Botryosphaeria rhodina MAMB-05 was used, for the first time, to immobilize laccase on a carbon black paste electrode modified with gold nanoparticles. The physicochemical characterization of the proposed laccase-biosensor was performed using transmission electron microscopy and electrochemical impedance spectroscopy. The performance of this novel bio-device was evaluated by choosing hydroquinone as a typical model of a phenolic compound. For hydroquinone determination, experimental variables such as enzyme concentration, pH and operational parameters of the electroanalytical technique were optimized. From square-wave voltammograms, a linear dependence between the cathodic current peak and the hydroquinone concentration was observed within the range 2.00–56.5μmolL−1, with a theoretical detection limit of 0.474μmolL−1. The proposed method was successfully applied to determine hydroquinone in dermatological cream, and samples from biological and environmental niches. The proposed biosensor device presented good selectivity in the presence of uric acid, various inorganic ions, as well as other phenolic compounds, demonstrating the potential application of this biosensing platform in complex matrices. Operational and analytical stability of the laccase biosensor were evaluated, and demonstrated good intra-day (SD=0.3%) and inter-day (SD=3.4%) repeatability and long storage stability (SD=4.9%).

PVA Hydrogel Electrolyte and Porous Polyisoprene Carbon Nanostructure Composite Based Pressure Sensitive Supercapacitor

Narrow operational voltage window can be considered as one of the greatest limitations for aqueous polymer electrolytes. Using freeze-thaw hydrogel preparation method we have synthesized wider potential window electrolytic polyvinyl alcohol (PVA)/Na2SO4 and PVA/K2SO4 electrolytes. Supercapacitors (SC) have been assembled using novel porous polyisoprene and carbon black composite electrodes. Our SC exhibit pressure sensitive properties therefore this effect is deeper explored here, giving explanation for capacitance increase during pressure application. It is found that up to 2 MPa the capacitance increases due to greater interface between electrode and electrolyte.

Interaction of vanadium species with a functionalized graphite electrode: A combined theoretical and experimental study for flow battery applications

Vanadium redox flow battery (VRFB) is one of the most promising large-scale energy storage system; however, a widespread VRFB development is still limited by the poor electrochemical activity of graphite electrodes and a poor understanding of redox reactions occurring at electrode/electrolyte interface.In this work, DFT was performed to study the first solvation shell structure of all vanadium ions and to investigate the reactivity of modified graphite electrodes toward the V2+/V3+ redox species. The results suggest that the presence of oxygen and nitrogen functionalities at the electrode edges provides more active sites for adsorption of the V2+/V3+ redox couple, and therefore improve electron transfer kinetics.These results have been experimentally validated by means of Cyclic Voltammetry and Electrochemical Impedance Spectroscopy with carbon black electrode having different density of oxygen and nitrogen-containing surface groups.

Electrochemical Carbon Dioxide Reduction in Methanol at Cu and Cu2O-Deposited Carbon Black Electrodes

The electrochemical reduction of carbon dioxide in methanol was investigated with Cu and Cu2O-supported carbon black (Vulcan XC-72) nanoparticle electrodes. Herein, Cu or a Cu2O-deposited carbon black catalyst has been synthesized by the reduction method for a Cu ion, and the drop-casting method was applied for the fabrication of a modified carbon black electrode. A catalyst ink solution was fabricated by dispersing the catalyst particles, and the catalyst ink was added onto the carbon plate. The pH of suspension was effective for controlling the Cu species for the metallic copper and the Cu2O species deposited on the carbon black. Without the deposition of Cu, only CO and methyl formate were produced in the electrochemical CO2 reduction, and the production of hydrocarbons could be scarcely observed. In contrast, hydrocarbons were formed by using Cu or Cu2O-deposited carbon black electrodes. The maximum Faraday efficiency of hydrocarbons was 40.3% (26.9% of methane and 13.4% of ethylene) at −1.9 V on the Cu2O-deposited carbon black catalyst. On the contrary, hydrogen evolution could be depressed to 34.7% under the condition.

Electrochemical Kinetics of SEI Growth on Carbon Black: Part II. Modeling

Mathematical models of capacity fade can reduce the time and cost of lithium-ion battery development and deployment, and growth of the solid-electrolyte interphase (SEI) is a major source of capacity fade. Experiments in Part I reveal nonlinear voltage dependence and strong charge-discharge asymmetry in SEI growth on carbon black negative electrodes, which is not captured by previous models. Here, we present a theoretical model for the electrochemical kinetics of SEI growth coupled to lithium intercalation, which accurately predicts experimental results with few adjustable parameters. The key hypothesis is that the initial SEI is a mixed ion-electron conductor, and its electronic conductivity varies approximately with the square of the local lithium concentration, consistent with hopping conduction of electrons along percolating networks. By including a lithium-ion concentration dependence for the electronic conductivity in the SEI, the bulk SEI thus modulates the overpotential and exchange current of the electrolyte reduction reaction. As a result, SEI growth is promoted during lithiation but suppressed during delithiation. This new insight establishes the fundamental electrochemistry of SEI growth kinetics. Our model improves upon existing models by introducing the effects of electrochemical SEI growth and its dependence on potential, current magnitude, and current direction in predicting capacity fade.

Highly Stretchable Capacitive Sensor with Printed Carbon Black Electrodes on Barium Titanate Elastomer Composite.

Wearable electronics and soft robotics are emerging fields utilizing soft and stretchable sensors for a variety of wearable applications. In this paper, the fabrication of a highly stretchable capacitive sensor with a printed carbon black/Ecoflex interdigital capacitor is presented. The highly stretchable capacitive sensor was fabricated on a substrate made from barium titanate–EcoflexTM 00-30 composite, and could withstand stretching up to 100%. The designed highly stretchable capacitive sensor was robust, and showed good repeatability and consistency when stretched and relaxed for over 1000 cycles.

Hybrid Graphene Ribbon/Carbon Electrodes for High‐Performance Energy Storage

AbstractThe utility of supercapacitors for both fixed and portable energy storage would be greatly enhanced if their energy density could be increased while maintaining their high power density, fast charging time, and low cost. This study describes a simple, solution‐phase, scalable modification of carbon materials by a covalently bonded “brush” of hydrogen‐terminated graphene ribbons (GRs) with layer thicknesses of 2–20 nm, resulting in a 20–100 times increase in the areal capacitance of the unmodified electrode surface. On a flat sp2 carbon surface modified by GRs, the capacitance exceeds 1200 µF cm−2 in 0.1 m H2SO4 due to a distinct type of pseudocapacitance during constant current charge/discharge cycling. Modification of high surface area carbon black electrodes with GRs yields capacitances of 950–1890 F g−1, power densities >40 W g−1, and minimal change in capacitance during 1500 charge/discharge cycles at 20 A g−1. A capacitance of 1890 F g−1 affords an energy density of 318 Wh kg−1 operating at 1.1 V and 590 Wh kg−1 at 1.5 V. The projected energy density of a hybrid GR/carbon supercapacitor greatly exceeds the current 10 Wh kg−1 for commercial supercapacitors and approaches that of lithium ion batteries.

Flow-Electrode Capacitive Deionization (FCDI) Using Suspensions of 2D Materials As Electrodes

The increasing shortage of potable water in many part of the world is leading the development of various approaches to water purification, with desalination of sea water the prime target. The most common approach to desalination is reverse osmosis (RO), being used in 65% of currently installed plants[1], but its high costs due to the use of membranes, leading to high-energy requirements, is pushing the desalination industry to find other solutions. An alternative to the high-energy requirements of RO is a method called capacitive deionization (CDI). In this process, two porous electrodes are arranged parallel to one to the other, letting brackish water flow between them. When a voltage is applied, the ions from the feed water migrate to the surface of the electrodes and are adsorbed capacitively, reducing the overall concentration of salts in the water stream. When the voltage is removed, or reversed, the ions desorb from the surface of the electrodes, resulting in a by-product of this process, brine. One of the greatest advantages of this system is that the applied energy can be recovered during the discharge step, just like an electrochemical capacitor, that is used to store energy by means of a pair of electrodes[2]. There are a number of recent reports in the literature describing an innovative CDI technique that focuses on improving the operation of these desalination systems. A suspended electrode material flowing in a path carved on the current collector plays the same role as the porous carbon electrodes fixed on the current collector in a typical CDI process, and this has been termed “flow-electrode capacitive deionization (FCDI)”[3].The flow operates continuously by providing fresh flow electrodes with increased ion capacitance, showing a continuous desalination behaviour and high desalting efficiency that originates from this. In this study, we have tested FCDI systems using graphene and other 2D materials in suspension, as well as optimizing the FCDI system parameters, to try to improve the desalination performance of the system. The goal is to treat feed water with high salinity, close to that of seawater (35 g/L approximately). Studies of FCDI to date have used activated carbon and carbon black suspensions [4,5,6,7,8,9,10]. Graphene and 2D materials are expected to improve the overall desalination capacity of FCDI systems because of their high theoretical surface area and superior electrical conductivity. In the case of traditional CDI setups, graphene was able to increase the salt adsorption capacity 2.3 times[11], compared to previous studies made on activated carbon and carbon black electrodes.

Design of Magnetoelectrocatalysts for the Hydrogen Evolution Reaction

Recent evidence highlights a magnetic effect on electron transfer processes for the hydrogen evolution reaction (HER) [1]. To further evaluate these observations from Trasatti’s data, studies of various diamagnetic electrodes under magnetic modification were undertaken. Here, results for magnetically modified carbon black electrodes are presented. Electrodes are modified by drop casting a suspension of Nafion and carbon black onto a glassy carbon electrode. Electrodes are magnetically modified on inclusion of magnetized microparticles. HER is undertaken voltammetrically at these electrodes and evaluated for impacts on the HER rates under magnetic modification. Magnetically enhanced electron transfer rates has broad impacts on electron transfer theory and electrocatalyst design. Here, implications for design of magnetoelectrocatalysts are presented.