Carbon Electrode Materials Research Articles

The application of plasma technology for the preparation of supercapacitor electrode materials.

With the rapidly growing demand for clean energy and energy interconnection, there is an urgent need for rapid and high-capacity energy storage technologies to realize large-scale energy storage, transfer energy, and establish the energy internet. Supercapacitors, which have advantages such as high specific capacitance, fast charging and discharging rates, and long cycle lifetimes, are being widely used in electric vehicles, information technology, aerospace, and other fields. The performance of supercapacitors is crucially dependent on electrode materials. These can be categorized into electric double-layer capacitors and pseudocapacitors, primarily made from carbon and transition metal oxides, respectively. However, effectively monitoring the physicochemical properties of electrode materials during preparation and processing is challenging, which limits the improvement of supercapacitors' performance. Plasma materials preparation technology can effectively affect the materials preparation processing by energetic electrons, ions, free radicals, and multiple effects in plasma, which are easily manipulated by operation parameters. Therefore, plasma material preparation technology is considered a promising method to precisely monitor the physicochemical and electrochemical properties of energy storage materials and has been widely studied. This paper provides an overview of plasma materials preparation mechanisms, and details of the plasma technology application in the preparation of transition metal hybrids, carbon, and composite electrode materials, as well as a comparison with traditional methods. In conclusion, the advantages, challenges, and research directions of plasma materials preparation technology in the field of electrode materials preparation are summarized.

Natural tea polyphenol functionalized graphene anode for simultaneous power production and degradation of methyl orange dye in microbial fuel cells.

The microbial fuel cell (MFCs) has dual functions, capable of achieving dye decolorization and synchronous power generation. Despite these advantages, the MFCs have faced challenges related to low electron transfer efficiencies and limited dye treatment capacity in wastewater applications. This work introduces an innovative approach by employing reduced graphene oxide-modified carbon cloth (TP-RGO@CC) anodes, utilizing tea polyphenols as the reducing agent. This modification significantly enhances the hydrophilicity and biocompatibility of the anodes. The MFC equipped with the TP-RGO@CC anode demonstrated a remarkable increase in the maximum power density, reaching 773.9 mW m-2, representing a 22% improvement over the plain carbon cloth electrode. The decolorization rate of methyl orange (50 mg L-1, pH 7) reached 99% within 48 h. Biodiversity analysis revealed that the TP-RGO@CC anode selectively enriched electrogens producing and organic matter-degrading bacteria, promoting a dual mechanism of dye decolorization, degradation, and simultaneous electro-production at the anode. This work highlights advanced anode materials that excel in effective pollutant removal, energy conversion, and biomass reuse.

Living Plant-Assisted Recycling of Nano Gold into Murray Porous Carbon Electrode Materials

Based on the enrichment potential of living plants for nanoparticles, this paper develops a new strategy to utilize Murray’s law in plants to removal various shapes of gold nanoparticles and...

Tailoring a hierarchical porous carbon electrode from carbon black via 3D diatomite morphology control for enhanced electrochemical performance.

Carbon black, a nano-porous material usually derived from the pyrolysis of waste tyres possesses varied particle sizes and morphology making it a viable material for several engineering applications. However, the high tendency for CB to agglomerate remains a challenge. To address this, bio-templating has been employed to produce a nanostructured porous carbon electrode material for supercapacitor applications using diatomite as a template. Diatomite-synthesized activated carbon (DSAC) was fabricated through a three-step process involving acid treatment of diatomite, thermal activation of carbon black, and bio-template synthesis. The resulting material was thoroughly characterized using XRD, Raman spectroscopy, BET analysis, and SEM imaging. Its electrochemical properties were assessed through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The DSAC material exhibited a high specific surface area of 266.867 m2 g-1, pore volume of 0.6606 cm3 g-1, and mean pore radius of 1.8943 nm. The electrochemical evaluation revealed that DSAC demonstrates excellent electrochemical performance, achieving a high specific capacitance of 630.18 F g-1 and retaining 94.29% capacitance after 5000 cycles at 1 A g-1. The DSAC electrode is eco-friendly and a promising candidate for supercapacitor applications.

Extending the lifetime of vanadium redox flow batteries by reactivation of carbon electrode materials.

The degradation and aging of carbon felt electrodes is a main reason for the performance loss of Vanadium Redox Flow Batteries over extended operation time. In this study, the chemical mechanisms for carbon electrode degradation are investigated and distinct differences in the degradation mechanisms on positive and negative electrodes have been revealed. A combination of surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Electrochemical Impedance Spectroscopy (EIS) was applied for this purpose. In addition to understanding the chemical and physical alterations of the aged electrodes, a thermal method for reactivating aged electrodes was developed. The reactivation process was successfully applied on artificially aged electrodes as well as on electrodes from a real-world industrial vanadium redox flow battery system. The aforementioned analysis methods provided insight and understanding into the chemical mechanisms of the reactivation procedure. By applying the reactivation method, the lifetime of vanadium redox flow batteries can be significantly extended.

Binder-free MoSe/MMSe composite and onion-derived activated carbon electrode materials for high-performance hybrid supercapacitors

MoSe/MMSe composite electrode materials were prepared on Ni foam via a facile hydrothermal technique. The composite electrode showed superior electrochemical performanc with ultra-long cycling stability.

Surface modification of a biomass-derived self-supported carbon nano network as an emerging platform for advanced field emitter devices and supercapacitor applications.

Herein, a self-supported carbon network is designed through the sole pyrolysis of Carica papaya seeds (biomass) without any activation agent, demonstrating their field emission and supercapacitor applications. The pyrolysis of seeds in an argon atmosphere leads to the formation of interconnected, rod-like structures. Furthermore, the hydrofluoric acid treatment not only removed impurities, but also resulted in the formation of CaF2 nanocrystals with the addition of F-doping. From the field emission studies, the turn-on field values defined at an emission current density of ∼10 μA cm-2 were found to be ∼2.16 and 1.21 V μm-1 for the as-prepared carbon and F-doped carbon, respectively. Notably, F-doped carbon exhibits a high emission current density of ∼9.49 mA cm-2 and has been drawn at an applied electric field of ∼2.29 V μm-1. Supercapacitor studies were carried out to demonstrate the multi-functionality of the prepared materials. The F-doped carbon electrode material exhibits the highest specific capacitance of 234 F g-1 at 0.5 A g-1. To demonstrate the actual supercapacitor application, the HFC//HFC symmetric coin cell supercapacitor device was assembled. The overall multifunctional applicability of the fabricated hybrid structures provides a futuristic approach to field emission and energy storage applications.

Electrochemical measurement of ruthenium oxide quantum dots synthesized at room temperature

Electrochemical energy storage has evolved into one of the most significant areas of current research to meet the escalating energy demands of contemporary society. Apart from the depletion of conventional sources of energy, the emission of hazardous chemicals is dangerous to the environment and human health as well. Among various electrochemical energy storage systems, the supercapacitor is emerging rapidly because of its elevated lifetime, flexibility, and light weight in various industrial areas. Ruthenium oxide (RuO2) is one of the most promising nanomaterials, with several applications in catalysts, sensors, microelectronics and other fields. Among numerous applications, ruthenium oxide is considered a promising candidate for electrode material for supercapacitors owing to its fast redox kinetics, low resistivity and high thermal and mechanical stabilities. Nowadays, researchers are increasingly turning to the biosynthesis of nanoparticles in order to establish clean, economical, and efficient synthesis techniques. In the present report, we have mycologically synthesised RuO2 quantum dots (RuO2 QDs), and different characterization techniques have been employed for the conformational nature of the quantum dots. Further, electrochemical studies have investigated the electrochemical potential of the mycologically synthesised RuO2 QDs utilising cyclic voltammetric measurements. The specific capacitance of RuO2 QDs coated on carbon cloth electrodes was 230 Fg−1 at a scan rate of 5.0 Ag−1 and the capacitance retention was found to be 95.8 % at the end of the 1000th charge-discharge cycle. The working electrodes derived from RuO2 QDs has rendered corrosion resistance in H2SO4 up to 0.16 M. A working model is also put to the test to find out the feasibility of QDs in practical application.

Rational Design of Ni-Doped V2O5@3D Ni Core/Shell Composites for High-Voltage and High-Rate Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) have significant potential for large energy storage systems because of their high energy density, cost-effectiveness and environmental friendliness. However, the limited voltage window, poor reaction kinetics and structural instability of cathode materials are current bottlenecks which contain the further development of ZIBs. In this work, we rationally design a Ni-doped V2O5@3D Ni core/shell composite on a carbon cloth electrode (Ni-V2O5@3D Ni@CC) by growing Ni-V2O5 on free-standing 3D Ni metal nanonets for high-voltage and high-capacity ZIBs. Impressively, embedded Ni doping increases the interlayer spacing of V2O5, extending the working voltage and improving the zinc-ion (Zn302+) reaction kinetics of the cathode materials; at the same time, the 3D structure, with its high specific surface area and superior electronic conductivity, aids in fast Zn302+ transport. Consequently, the as-designed Ni-V2O5@3D Ni@CC cathodes can operate within a wide voltage window from 0.3 to 1.8 V vs. Zn30/Zn302+ and deliver a high capacity of 270 mAh g-1 (~1050 mAh cm-3) at a high current density of 0.8 A g-1. In addition, reversible Zn2+ (de)incorporation reaction mechanisms in the Ni-V2O5@3D Ni@CC cathodes are investigated through multiple characterization methods (SEM, TEM, XRD, XPS, etc.). As a result, we achieved significant progress toward practical applications of ZIBs.

Scalable synthesis of N, O co-doped hierarchical porous carbon for high energy density supercapacitors

Rational design of hierarchical porous architecture with abundant pseudocapacitive sites is highly desirable for carbon electrode materials. However, the lengthy production process and high economic input limit its broader application. Herein, we successfully prepared N, O co-doped hierarchical porous carbon (NOHC) through hydrothermal carbonization (HTC) of chitin biomass with the assist of NH4Cl and subsequent carbonization with NaNH2. The optimal NOHC600 exhibits a remarkable hierarchical porous structure and an ultrahigh specific surface area (SSA) of 2555 m2 g−1. Furthermore, it showcases a significant content of N, O co-doping, thereby providing abundant defects and additional active sites for ion adsorption. The aforementioned characteristics ensure outstanding capacitance performance of NOHC600. In the three-electrode system, NOHC600 exhibits a remarkable specific capacitance of up to 455 F g−1 at a current density of 0.5 A g-1. The symmetric supercapacitors (SCs) based on NOHC600 achieve an impressive energy density of 30.4 Wh kg−1 at a power density of 180 W kg−1. Moreover, the all-solid-state NOHC600 microsupercapacitors (MSCs) demonstrate an exceptional areal capacitance of 78.2 mF cm−2 and an areal energy density of up to 10.8 μWh cm−2. Accordingly, this facile and scalable strategy shows a great potential for producing high-heteroatom-doped porous carbon materials from chitin biomass, which can be applied in practical energy-related applications.

Tungsten oxide nanostructures for all-vanadium redox flow battery: Enhancing the V(II)/(VIII) reaction and inhibiting H2 evolution

Vanadium redox flow batteries (VRFBs) offer remarkable performance capabilities for renewable energy power plants. However, the kinetics of the VRFBs' redox reactions are slow and the efficiency is low due to parasitic reactions such as the hydrogen evolution reaction (HER). In this work, to overcome these limitations, the effect of modifying the carbon cloth electrode with tungsten oxide nanowires, nanoflakes, and nanospheres prepared was elucidated for the negative half-cell reaction V(II)/V(III). The physical and chemical properties of those nanostructures were characterized using FESEM, XPS, XRD, FTIR, and contact angle measurements. The effect of the catalyst loading and structure, pH and composition of the synthesis solution, and the presence of binder on catalytic activity was evaluated using CV and EIS. The results showed that the effective loading of all three structures is ~2 mg/cm2, with all of the structures showing a significant enhancement of the V(II)/(VIII) reaction kinetics in comparison to the untreated carbon cloth and greater stability than the thermally treated carbon cloth. The tungsten oxide nanostructures prepared at pH 2 showed the best catalytic activity, with the suppression of hydrogen evolution reaction (HER) being inversely proportional to the number of defects. Tungsten oxide nanoflakes prepared at pH 2 using water as a solvent exhibited the optimum balance between promoting the V(II)/(VIII) reaction kinetics and suppressing the HER. The performance evaluation in a two-electrodes setup of all‑vanadium RFB revealed that the WNFs structure have the highest charge/discharge capacity and energy efficiency at a relatively high current density of 60 mA/cm2 due to its improved kinetics.

Coal tar pitch-derived porous carbon prepared in deep eutectic spinning solution via electrospinning for supercapacitor electrodes

Developing a novel preparation strategy for the fabrication of high-performance porous carbon electrode materials is still the focus of current research. Herein, O/N doped coal tar pitch (CTP)-based porous carbon with a fishnet-like structure is prepared via the electrospinning technology. CTP is used as a carbon source and ChCl/phenol deep eutectic solvent (DES) is used as a spinning solution directly, and not any polymer is added. The complexes obtained by electrospinning are then activated by a small amount of K3C6H5O7 and get the porous carbon. Specifically, the DES has a specific viscosity and can be used not only as a solvent to improve the spinnability of CTP, but also as N source and act as a multifunctional solution. The electrospinning technology constructs the macropores and mesopores, while K3C6H5O7 can make micropores and even ultra-micropores in the prepared carbon material. Benefiting from the constructive hierarchical pore channels and abundant heteroatoms doping, the prepared porous carbon electrode possesses a high specific capacitance of 202 F g−1 even when reaching commercial loading. Simultaneously, a novel K3C6H5O7/glycol/acetonitrile DES gel electrolyte is synthesized, and an extended working voltage (2.2 V) can be achieved. The fabricated capacitor has large energy density of 23.9 Wh kg−1, and can still operate normally in a wide temperature range (-25 ∼ 100 °C). The multifunctionality of DES uncovers the feasibility of preparation of porous carbon using DES as the spinning solution directly, and may expect to prepare other carbon materials using the proposed strategy with different carbon precursors.

Electrochemical Direct Air Capture of Carbon Dioxide by a Redox-Mediated Salt Splitting Process

Direct air capture of carbon dioxide is an important emerging direction for electrochemical separation technology. Carbon dioxide removal has a critical role to play in the coming century as a complement to deep decarbonization efforts, because removal may offset emissions we cannot avoid, such as agriculture for food security. Direct air capture might even be used to decrease the atmospheric carbon dioxide level if the value at which it stabilizes is deemed too high. Electrochemical methods allow us to power a carbon removal device directly by carbon-free electricity. Here, we present a salt splitting process, based on bipolar membrane electrodialysis, which begins with a neutral electrolyte (e.g. KCl), and creates a strong base (e.g., KOH) and a strong acid (e.g., HCl). The base may then be used to absorb carbon dioxide from ambient air; the acid is then used to extract the carbon dioxide by recombining with the base, reversing the salt splitting process. The process is driven by iron(II/III) hexacyanide redox on carbon cloth electrodes, which is kinetically facile and contributes relatively little to the cell voltage.Energy required for redox-mediated salt splitting depends on contributions from water dissociation in the bipolar membrane, ohmic resistances in ion exchange membranes and electrolyte layers, and electrode reactions. We show that the largest contribution to the energy required comes from the bipolar membrane, motivating further research on bipolar membrane development. We also discuss the role of ion exchange membranes in this system: these membranes must provide high ion conductivity while providing selectivity against leakage of acid and base products. Several commercial membranes were screened for conductivity and water content, and their electrodialysis performance is compared. Finally, we use technoeconomic modeling to assess how electrodialysis operating conditions and electrolyte composition affect energy, land, and water demands of a continuously operating direct air capture process, with redox-mediated salt splitting as the centerpiece. Figure 1

Electrochemical Analysis and Quantification of Anodic Oxidation on Activated Carbon Cloth Electrodes through Cyclic Voltammetry

Capacitive Deionization (CDI) has applications ranging from water purification to biofuels processing. For CDI to be a viable scalable technology, electrode stability is critical. In extended experiments the activated carbon cloth (ACC), used for the electrode, has been previously observed to degrade as a result of surface oxidation reactions. Carbon cloth oxidation can reduce the surface area and alter the pore structure, in turn reducing the adsorption capacity. While the behavior of oxidation is known, a reliable method of quantifying the extent of degradation is lacking. To quantify it, cyclic voltammetry was explored to measure the capacitance of pristine and oxidized carbon cloth samples. A three-electrode electrochemical cell was used to quantify capacitance of activated carbon cloth in 1M NaCl solution. The specific capacitance of carbon cloth that underwent anodic oxidation was lower than cathodic and pristine carbon cloth. Further tests analyzed the change in the severity of the anodic degradation on whether the initial CDI separations were performed on organic or inorganic ions. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) was utilized to verify and quantify surface oxidation. Cyclic voltammetry is demonstrated as a simple and reliable method for analyzing and quantifying anodic oxidation on activated carbon cloth electrodes in CDI stacks.

Low-Cost and Scalable Electrodes for Anodic Production of Hydrogen Peroxide Via 2e- Water Oxidation

Hydrogen peroxide (H2O2) is a crucial chemical that is widely utilized in various industrial processes. The conventional anthraquinone process for H2O2 production has limitations in terms of energy consumption, high costs, and waste generation [1]. An alternative, greener and more sustainable approach is the electrochemical production of H2O2 from oxygen and water using renewable energy. Our research group has been extensively investigating the two electron (2e-) water oxidation reaction (WOR) for production of H2O2 using various electrode materials, including metal oxides, commercial carbon materials, and boron-doped diamond (BDD) [2, 3]. We also investigated the role of carbonate ions (HCO3 - and CO3 2-) in the process of water oxidation to H2O2. The enhancing effect e of CO3 2- ions on anodic H2O2 production was studied in a continuous flow reactor, where the optimal flow rate, process configuration and cell design, and chemical stabilizer were determined. Among other parameters, chemical composition and pH regime of the electrolyte were found to be crucial.Recently, we explored the use of graphite bipolar plates (BPP) as a low-cost alternative to BDD electrodes for anodic H2O2 generation [4]. Three different commercial BPPs with varying fluoropolymer content were examined, and a correlation was found between fluoropolymer content and H2O2 generation. In that study we found that a BPP sample with high fluoropolymer content resulted in a stable H2O2 production for up to 100 hours at a current density of 200 mA cm–2, with a constant faradaic efficiency of 40%. The results demonstrate that low-cost commercial carbon electrode materials can selectively oxidize water to H2O2, enabling economically viable technical applications of anodic H2O2 production.

In situ biosynthesized polyphosphate nanoparticles/reduced graphene oxide composite electrode for highly sensitive detection of heavy metal ions

The development of an effective sensing platform is critical for the electrochemical detection of heavy metal ions (HMIs) in water. In this study, we fabricated a newly designed sensor through the in situ assembly of reduced graphene oxide (rGO) and polyphosphate nanoparticles (polyP NPs) on a carbon cloth electrode via microorganism-mediated green biochemical processes. The characterization results revealed that the rGO produced via microbial reduction had a three-dimensional porous structure, serving as an exceptional scaffold for hosting polyP NPs, and the polyP NPs were evenly distributed on the rGO network. In terms of detecting HMIs, the numerous functional groups of polyP NPs play a major role in the coordination with the cations. This electrochemical sensor, based on polyP NPs/rGO, enabled the individual and simultaneous determination of lead ion (Pb2+) and copper ion (Cu2+) with detection limits of 1.6 nM and 0.9 nM, respectively. Additionally, the electrode exhibited outstanding selectivity for the target analytes in the presence of multiple interfering metal ions. The fabricated sensor was successfully used to determine Pb2+/Cu2+ in water samples with satisfactory recovery rates ranging from 92.16% to 104.89%. This study establishes a facile, cost-effective, and environmentally friendly microbial approach for the synthesis of electrode materials and the detection of environmental pollutants.

3-Dimensional porous carbon derived from waste aucklandia lappa straw for high-performance liquid and all-solid-state supercapacitors

Efficient and sustainable biochar as electrode material is the key to constructing portably green energy storage equipment. Using waste aucklandia lappa straw as carbon precursor, biomass porous carbon was prepared by high temperature carbonization and KOH activation. The 3-dimensional porous carbon material was obtained by optimizing the proportion of activator, which has a high specific surface area (2427 m2 g−1), abundant pore structure and substantially high specific capacitance (up to 431.35 F g−1 at 0.5 A g−1). The assembled symmetrical supercapacitor exhibits a wide voltage range of 0–2.0 V and a high energy density of 36.51 Wh kg−1 in 1 M Na2SO4 electrolyte. The all-solid-state supercapacitor with PVA/KOH gel as electrolyte has high response frequency and phase angle, which can provide high specific capacitance of 340.98 F g−1 and energy density of 19.59 Wh kg−1 at 0.5 A g−1. The capacitance retention rate is 89.47% after 10,000 cycles. Aucklandia lappa straw-derived porous carbon electrode material is an ideal candidate for the preparation of high-performance supercapacitor.

Structural and surface engineering promotes Zn-ion energy storage capability of commercial carbon cloth

Aqueous Zn-ion hybrid supercapacitors (AZHSCs) combining the advantages of high-energy batteries and high-power supercapacitors see a bright future, but they still suffer from the poor capacity of carbonic cathodes. Herein, a functionalized porous carbon cloth (denoted as FPCC) electrode is demonstrated based on commercial carbon cloth (denoted as CC) tuning by structural and surface engineering. The constructed exfoliated porous carbon layer and the negatively charged functionalized interface not only increase the electrical double layer capacitance but also favor the chemical adsorption of Zn2+ to obtain additional pseudocapacitance. Consequently, the FPCC electrode delivers a high capacity of 0.16 mAh cm−2 at 4 mA cm−2, which is 923.8 times higher than CC, and a long cycle life (85.0% capacity retention after 30 000 cycles). More importantly, the Zn//FPCC AZHSC possesses an impressive energy density (3.3 mWh cm−3) and power density (240 mW cm−3), superior to many advanced batteries and supercapacitors. The quasi-solid-state device is also assembled as a demo. This modification strategy may provide new opportunities for high-performance AZHSCs.

N/S co-doped carbon electrode material made from saponin pod skin for sodium ion battery with high performance

Waste biomass material derived carbon has become an important energy storage material which is easily available, inexpensive and environmentally friendly. However, it is a major challenge to develop ultra-high specific capacity and stable anode materials based on biomass carbon materials (BCMs). In this work, saponin pod skin was doped with thiourea through a simple hydrothermal process, followed by being sintered in one step to obtain simultaneously N and S elements co-doped porous carbon anode material for sodium ion batteries (SIBs). The active sites and layer spacing of the original pure BCM have been altered, which are conducive to the promotion of ion/electron transport. The half battery (Na/electrolyte/C) has a specific capacity of 259 mAh g‐−1 at 0.1 A g−1 maintaining a specific capacitance of 238 mAh g−1 after 250 cycles, meanwhile it could reach a potential capacity of 239 mAh g−1 at 1.0 A g−1 which maintaining a specific capacity of 120 mAh g−1 after 1000 cycles. This research provides new strategy for the development of novel biomass-derived carbon materials as anode materials for high-performance SIBs.

Electrochemical Residence Time Distribution as a Diagnostic Tool for Redox Flow Batteries

The fluid dynamic and electrochemical performance of redox flow batteries (RFBs) stems from the relationship between the flow field and the porous electrode, whose interplay determines how active species move and react during device operation. While characterization techniques, such as residence time distribution, offer insights into species mobility within a reactive volume for a traditional chemical reactor, electrochemical reactors also enable simultaneous measurement of the redox reactions, unlocking another dimension of analysis. Herein, we demonstrate how potentiodynamic measurements, using injections of electrolyte examined through moment analysis, can provide electrode-specific performance scaling relationships across a matrix of carbon paper and cloth electrodes with flow through and interdigitated flow fields. We further combine experimental campaigns with multiphysics simulations to demonstrate how electrode surface area can be estimated with this technique, which we then validate with activated and unactivated commercial carbon cloth electrodes. These studies reveal the multiscale observations that potentiodynamic measurements afford, augmenting existing electrochemical techniques for holistic electrochemical reactor diagnostics.