Graphite Felt Research Articles

Fluorine-Doped Graphene Oxide-Modified Graphite Felt Cathode for Hydrogen Peroxide Generation

Electrochemical oxygen reduction via the two-electron pathway (2e-ORR) is an emerging method for producing H2O2. It is cleaner, safer, and more convenient compared to the anthraquinone process. Graphite felt is one of the cathode candidates for large-scale cells due to its excellent mechanical properties. However, commercial graphite felt often fails to achieve the desired hydrogen-peroxide yield because of its low catalytic selectivity for the 2e-ORR pathway. Fluorine-doped carbon materials are expected to enhance 2e-ORR selectivity. This is because the electronic structure of carbon atoms adjacent to fluorine atoms may facilitate the production of hydrogen peroxide while hindering its further reduction. In this study, fluorine-doped graphene oxide (FGO) was prepared by the hydrothermal method. Subsequently, graphite felt modified with FGO was fabricated and used as the cathode for H2O2 production. The results indicated that in alkaline media, the graphite felt modified with FGO achieved a catalytic selectivity of 93% and a generation rate of 8.91 mg cm⁻2 h⁻¹. In comparison, commercial graphite felt had a catalytic selectivity of 75% and a generation rate of 2.10 mg cm⁻2 h⁻¹. Moreover, graphite felt modified by FGO also exhibited excellent electrocatalytic performance for H2O2 generation in neutral media. This research provides a fundamental study to promote the application of graphite felt in the environmentally friendly electrocatalytic production of hydrogen peroxide in industries.

Electrochemical investigations of decorated graphite felt electrodes with Nafion/TiO2 nanoparticles for vanadium redox flow battery: Improving electro-catalytic characteristics

The present study aimed to investigate the effect of Nafion/TiO2 nanoparticles as an electrocatalyst on the electrochemical behavior of graphite felt (GF) electrodes in a vanadium redox flow battery. Various electrochemical tests, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV), were conducted to assess the performance of these electrodes at different concentrations of nanoparticles (2-4 g L-1). Additionally, X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy were employed to analyze the chemical composition, bonding, and morphology of the decorated electrodes, respectively. The CV results revealed several effects of TiO2 nanoparticles on the GF electrode, such as increased peak intensity and shifted peak sites. As the concentration of nanoparticles increased, the peak intensity rose by up to 44%. Moreover, the potentials of the decorated electrodes shifted towards the favorable side compared to the GF electrode, with changes ranging from 18 to 84%. Overall, the optimal concentration of TiO2 nanoparticles (3 g L-1) exhibited excellent electrode performance, characterized by the highest calculated diffusion coefficient, greater reversibility, enhanced electron transfer kinetics, improved stability, lower over-potential, and the lowest activation energy for redox reactions. EIS results demonstrated a significant decrease in polarization resistance (67.2-70.8%) for the decorated electrodes. Furthermore, LSV measurements indicated that the utilization of nano-electrocatalysts effectively inhibited hydrogen evolution at negative potentials.

“Rigid-Flexible” structured polyimine/graphite felt composites with excellent fire Resistance, electromagnetic shielding and recyclability

With the development of the electronic information, the conductive polymers with high electromagnetic interference (EMI) shielding effectiveness has become a research point. The polyimine material that forms a cross-linking network can rapidly achieve bond exchange at high temperatures, which is becoming a potential substrate for carbon loaded materials. In this work, a novel composite material is successfully prepared by incorporating cost-effective graphite felt (GF) with excellent electrical properties into a biobased polyimine network. Leveraging the exchange properties of dynamic imine bond (−C = N-), the two substrates can be separated by acidolysis, enabling a recycle of the GF efficiently. The electromagnetic shielding effectiveness (EMI SE) of the composite material in the X-band (8.2–12.4 GHz) reaches approximately 46 dB. Additionally, the introduction of highly fire-resistant graphite material significantly enhances the flame retardancy of the composite by reducing the peak heat release rate (HRR) by 47.1 %, which improves the fire safety in complex electromagnetic environments. Herein, we broaden the application of polyimine/graphite composites in the electronic information field and provide a new strategy for the preparation of environmentally friendly composite materials.

A solar thermoelectric system by temperature difference for efficient removal of chromium (VI) in water and soil

In this work, we designed and developed a facile solar thermoelectric generator (STEG)-based system and a new electrokinetic remediation (EKR) system, which consists of main electrodes and unenergized auxiliary electrodes. The prepared nanocomposite was investigated for the effectiveness of the STEG+PANI-CNT/GF system in remediating Cr-contaminated. Photothermal performance test were applied in order to examine this STEG could export a power density of 365.56mW/dm2 and output potential of 801mV at the temperature difference of 50 ℃. Thus the STEG could be used as the power to construct a Cr(VI) removal system using polyaniline (PANI) film/carbon nanotubes (CNT) modified graphite felt (GF) electrode (PANI-CNT/GF) as cathode and graphite rod as anode. The as-prepared STEG+PANI-CNT/GF system exhibited a significant Cr(VI) removal efficiency (96.2% in water) through electromigration, electro-adsorption and electroreduction. Moreover, a multi auxiliary electrodes (AEs) system (STEG+PANI-CNT/GF+AEs) with six PANI-CNT/GF auxiliary electrodes was constructed in remediating Cr(VI)-contaminated soil, showing Cr(VI) removal efficiency of 16.7-60.1% higher than that of STEG+PANI-CNT/GF. The PANI-CNT/GF auxiliary electrodes could bind Cr(VI) and adjust electric field distribution, contributing to adsorption and reduction of Cr(VI). Consequently, this work provides a promoting approach for heavy metals removal in future application.

Levofloxacin degradation in electro-Fenton system with FeMn@GF composite electrode

In this work, a one-step solvent-thermal approach was used to synthesize an Mn-doped Fe3O4 modified graphite felt (GF) composite electrode material (FeMn@GF), which was then used as the cathode in an Electro-Fenton (EF) system. The levofloxacin (LEV) in wastewater can be successfully removed by the EF system, which can produce and activate H2O2 in situ. The successful fabrication of the FeMn@GF composite electrode was confirmed by employing the characterization techniques of Scanning Electron Microscope, X-ray Diffraction, and X-ray Photoelectron Spectroscopy. Additionally, the electrochemical performance test was conducted. The FeMn@GF composite electrode demonstrated a greater electrochemical activity and a more robust electronic transmission ability. The LEV degradation experiment demonstrated reached 98.9 % that under ambient temperature conditions, within 120 minutes, given initial LEV concentration of 20 mg·L −1, Na2SO4 concentration of 50 mM, applied voltage of 3.0 V, initial pH value of 3, and aeration rate of 3.0 L·min −1.The highest leaching quantities of Fe and Mn were 1.294 mg·L−1 and 0.675 mg·L−1, respectively, while the removal effectiveness of LEV remained at 85.2 % after five cycles. Experiments using radical quenching revealed that the main active species were ·OH. The reaction mechanism of the EF system with FeMn@GF as the cathode (FeMn@GF-EF) and the degradation pathway of LEV were investigated.

Enhancing Organic Pollutant Degradation Efficiency through a Photocatalysis-Electro-Fenton System via MoS2 Crystal Morphology Regulation.

A photocatalysis-electro-Fenton (PEF) system was constructed via molybdenum disulfide (MoS2) to remove tetracycline (TC) without an external oxidant supply and solution pH adjustment. In the system, original graphite felt (GF) was used as a cathode, from which H2O2 was in situ generated continuously under power. MoS2 was motivated by visible light to facilitate the cycle of Fe2+/Fe3+, enhancing the Fenton process to produce •OH. The experimental results showed that the system can increase the degradation rate of pollutants by more than 5 times. Moreover, the quenching and electron paramagnetic resonance (EPR) tests demonstrated that •OH was the dominant active species. X-ray photoelectron spectroscopy (XPS) characterization, Mo concentration, and cycle experiments proved the excellent catalytic activity and chemical stability of MoS2. It is worth mentioning that the photocatalytic performances of different morphologies of MoS2 (flower, flake, and radar) were compared. As a result, flower-like MoS2 exhibited a much superior photoresponse than flake and radar, which could accelerate the Fe2+/Fe3+ cycle further effectively. These findings highlight the morphology-performance relationship of MoS2 under a PEF system and the mechanisms of contaminant degradation, which is of great significance for developing photoelectric Fenton technology.

Enhancing Vanadium Redox Flow Battery Performance with ZIF-67-Derived Cobalt-Based Electrode Materials.

Vanadium redox flow batteries (VRFBs) have emerged as a promising energy storage solution for stabilizing power grids integrated with renewable energy sources. In this study, we synthesized and evaluated a series of zeolitic imidazolate framework-67 (ZIF-67) derivatives as electrode materials for VRFBs, aiming to enhance electrochemical performance. Four materials-Co/NC-700, Co/NC-800, Co3O4-350, and Co3O4-450-were prepared through thermal decomposition under different conditions and coated onto graphite felt (GF) electrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses confirmed the structural integrity and distribution of the active materials. Electrochemical evaluations revealed that electrodes with ZIF-67-derived coatings exhibited significantly lower charge transfer resistance (Rct) and higher energy efficiency (EE) compared to uncoated GF electrodes. Co/NC-800//GF delivered the highest energy efficiency and discharge capacity among the tested configurations, maintaining stable performance over 100 charge-discharge cycles. These results indicate that Co/NC-800 holds great potential for use in VRFBs due to its superior electrochemical activity, stability, and scalability.

Indium Nanoparticle‐Decorated Graphite Felt Electrodes for Efficient and Long‐Cycle Zinc‐Bromine Flow Batteries

AbstractZinc‐bromine flow batteries (ZBFBs) offer the potential for large‐scale, low‐cost energy storage; however, zinc dendrite formation on the electrodes presents challenges such as short‐circuiting and diminished performance. Herein, an indium nanoparticle‐decorated graphite felt composite electrode for ZBFBs is proposed to mitigate zinc dendrite formation, improve performance, and prolong operational longevity. Using a facile in situ electrodeposition method, indium nanoparticles are uniformly and densely distributed on the carbon fiber surface, demonstrating exceptional efficacy in regulating zinc deposition. Thus, a higher prevalence of Zn (002) crystal planes and a smoother and more compact surface morphology are obtained, compared with those of thermally treated graphite felt. Furthermore, integration of the composite electrode into the negative side of a ZBFB yielded substantial improvements in cell performance, achieving an energy efficiency of 66.83% ± 0.45% at 120 mA cm−2, significantly surpassing the performance of batteries utilizing thermally treated graphite felt (52.64% ± 1.50%). Notably, the cycle life of the battery is extended by more than five‐fold with the composite electrode, underscoring the remarkable zinc deposition‐regulating capabilities of the indium nanoparticles.

Self-Assembled Blossom-Shaped NiCo2S4 Nanosheets In Situ Deposited Electrodes: Possessing High Reactivity and Selectivity for Bromine-Based Flow Batteries.

Bromine-based flow batteries (Br-FBs) are emerging rapidly due to their high energy density and wide potential window for renewable energy storage systems. Nevertheless, the sluggish kinetics of the Br2/Br- reaction on the electrode is considered to be the main challenge contributing to the poor performance of Br-FBs. Herein, we report self-assembled blossom-shaped NiCo2S4 nanosheets, enabling in situ growth on graphite felt (GF) via a one-step hydrothermal method. In the prepared NiCo2S4-GF, the gaps formed by the nanosheets restrict bromine diffusion, the sulfuretted blossom-shaped structure provides active sites with bromine adsorption capacity, and the synergistic effect of Ni and Co accelerates the electron transfer rate, which allow the electrode to exhibit excellent electrocatalytic activity compared to commercial GF, CoS-GF, and NiS-GF. Moreover, NiCo2S4-GF demonstrates unique selectivity for enhancing the Br2/Br- redox reaction compared to the bimetallic oxide of NiCo2O4-GF. Consequently, the zinc-bromine flow battery (ZBFB) with NiCo2S4-GF achieves an energy efficiency of 80.16%, which is 16.18% higher than that of the battery with commercialized GF at a current density of 60 mA cm-2, as well as a maximum power density of 260.75 mW cm-2 at 280 mA cm-2. The effective enhancement of the performance of ZBFB suggests that NiCo2S4-GF possesses great application potential in Br-FBs.

Comparative Analysis of Thermal Activation on Felts and Continuous Carbon Filament Electrodes for Vanadium Redox Flow Batteries

AbstractThermal treatments are commonly used to improve electrode kinetics in vanadium redox flow batteries (VRFB). The impact of the widely adopted thermal treatment—400 °C for least 24 hours—was investigated on polyacrylonitrile (PAN)‐based continuous carbon filaments (tows) and compared to PAN‐based graphite felts. Surface properties were assessed with scanning electron microscopy (SEM), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS) and wettability measurements. The electrode activity was investigated via electrochemical impedance spectroscopy (EIS). Charge‐transfer resistances and the constant phase element parameters related to the electric double layer were determined, revealing a correlation between enhanced electrode activity and increased double layer across all electrodes. An 8‐hour 400 °C thermal treatment was sufficient to improve electrode activity for tows, whereas felts required longer durations, up to 24 hours, attributed to differences in the carbonization process employed for each material, with the tows undergoing continuous processing and the felts following a batch process. Three‐electrode half‐cell EIS measurements were conducted to elucidate positive and negative electrode contributions. Activated continuous carbon filament electrodes exhibited consistent electrode activities in both the catholyte (VO2+/VO2+) and anolyte (V3+/V2+), whereas the electrochemical activity of felts was limited by the electrode deactivation in the anolyte.

Highly Electrocatalytic Activity of Micro and Nanocomposite Phase Engineering of MoO3−x@K3PW12O40 Decorated on Graphite Felt for High-Performance VRFB

Highly Electrocatalytic Activity of Micro and Nanocomposite Phase Engineering of MoO3−x@K3PW12O40 Decorated on Graphite Felt for High-Performance VRFB

Functionalized Metal-Organic Framework for NADH Regeneration by Hydrogen in a Redox Flow Bioreactor.

The electrochemical regeneration of reduced nicotinamide adenine dinucleotide (NADH) using [Rh(Cp*)(bpy)Cl]+ holds significant promise for the industrial synthesis of chiral chemicals. However, challenges persist due to the high consumption of NADH and the limited efficiency of its cyclic regeneration, which currently hinder widespread application. To address these obstacles, based on in-situ growth of 3D ordered metal-organic framework (NU-1000) on the surface of graphite felt, [Rh(Cp*)(bpy)Cl]+ were immobilized on the Zr6 nodes of NU-1000 by solvent-assisted ligand incorporation (SALI), and applied in a flow bioreactor. Moreover, we employ a gas diffusion electrode (GDE) to oxidize H2, providing a clean proton source for the electrochemical regeneration of NADH. Consequently, highly efficient enzymatic electrocatalytic synthesis of L-lactate was achieved when coupled with L-lactate dehydrogenases (LDH) as a model reaction, and the total turnover number (TTN) reached 19600 and 1750 for [Rh(Cp*)(bpy)Cl]+ and NAD+ after 48 h, corresponding to a high turnover frequency (TOF) of 2350 h-1 and 210 h-1 for [Rh(Cp*)(bpy)Cl]+ and NAD+, respectively. This work provides new insights for the construction of efficient enzymatic electrosynthesis systems in industrial production.

Enhancement in the performance of a vanadium-manganese redox flow battery using electrospun carbon metal-based electrode catalysts

This study investigates the performance of both a vanadium/manganese redox flow battery (V/Mn RFB) and an all-vanadium redox flow battery (VRFB), employing carbon metal fabrics (CMFs) prepared through electrospinning followed by carbonization. Noteworthy advancements are observed in both systems upon coupling CMFs with thermally treated graphite felt (GF) electrodes. Nearly doubled peak power density and 50 % higher capacity utilization over 150 charge/discharge cycles at 75 mA cm−2 are achieved for the V/Mn RFB with the incorporation of CMFs alongside graphite felt as catalysts. The VRFB demonstrates notable enhancements too, achieving approximately 200 cycles at a current density of 80 mA cm−2, with high efficiencies (85 %) and electrolyte utilization (79 %) when CMFs are used in combination with graphite felts. These advancements may facilitate pilot-scale testing and integration of the V/Mn RFB for the employment in the renewable energy storage sector and grid-balancing studies.

Mesoporous graphite felt electrode prepared via thermal oxidative etching on all-vanadium redox flow batteries

Mesoporous graphite felt electrode prepared via thermal oxidative etching on all-vanadium redox flow batteries

Exploring the potential of graphite felt electrodes for electrochemical sensing of bisphenol A: An experimental and computational study

Considering the seriously detrimental effects of bisphenol A (BPA) on human beings and environment, efforts have been devoted to search for its effective and efficient electrochemical detection. This study explores the potential of Polyacrylonitrile (PAN)- and Rayon-based graphite felts for electrochemical sensing of BPA. Effect of thermal treatment on the physicochemical and electrochemical properties of the graphite felts (GF) is also comprehensively investigated. The felts were thermally activated to increase the hydrophilicity and then characterized by Fourier transform infra-red (FT-IR) spectroscopy, Raman spectrometry, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and electrochemical methods. Furthermore, the electrochemical behavior of BPA was investigated on the graphite felt electrodes in phosphate buffer solution using cyclic voltammetry (CV) technique. Electrochemical measurements using cyclic voltammetry revealed the superior activity of thermally activated PAN-based GF (T-PGF) as an electroactive substrate for BPA sensing. Under optimized conditions, the CV response of T-PGF towards BPA showed two linear relationships within concentration ranges of 1–100 µM and 100–1000 µM and low limit of detection (0.13 µM at S/N = 3). The experimental results were also validated by density functional theory (DFT) studies. Compared with other sensing substrates for BPA such as glassy carbon electrode, GF with a simple surface modification by thermal treatment appears as a promising and reliable method for rapid detection of BPA and will help in its removal and mitigate its harmful effects.

Next‐Generation Ultrathin Lightweight Electrode for pH‐Universal Aqueous Flow Batteries

AbstractAqueous flow batteries (AFBs) are promising long‐duration energy storage system owing to intrinsic safety, inherent scalability, and ultralong cycle life. However, due to the thicker (3–5 mm) and heavier (300–600 g m−2) nature, the current used graphite felt (GF) electrodes still limit the volume/weight power density of AFBs. Herein, a lightweight (≈50 g m−2) and ultrathin (≈0.3 mm) carbon microtube electrode (CME) is proposed derived from a scalable one‐step carbonization of commercial cotton cloth. The unique loose woven structure composed of carbon microtube endows CME with excellent conductivity, abundant active sites, and enhanced electrolyte transport performance, thereby significantly reducing polarization in working AFBs. As a consequence, CME demonstrates excellent cycling performance in pH‐universal AFBs, including acidic vanadium flow battery (maximum power density of 632.2 mW cm−2), neutral Zn‐I2 flow battery (750 cycles with average Coulombic efficiency of 99.6%), and alkaline Zn‐Fe flow battery (energy efficiency over 70% at 200 mA cm−2). More importantly, the estimated price of CME is only 5% of GF (≈3 vs ≈60 $ m−2). Therefore, it is reasonably anticipated that the lightweight and ultrathin CME may emerge as the next generation electrode for AFBs.

Bismuth nanosheets guided zinc deposition enabled long-life aqueous zinc-based flow batteries

The poor cycling durability and low Coulombic efficiency (CE) of zinc (Zn) anodes substantially restrict their further development, which should be attributed to the severe uneven plating and hydrogen evolution reaction (HER) across the repeated plating/stripping processes. Herein, bismuth nanosheets decorated graphite felt (BiNS/GF) is constructed for Zn anode via galvanic replacement reaction. BiNS/GF affords more robust Zn nucleation sites, lower Zn nucleation overpotential and higher HER overpotential to guide even and dense Zn deposition. In addition, a total internal reflection imaging method is employed to detect micro-bubbles generated by HER on the electrode surface, revealing that BiNS prevents the formation of micro-bubbles and thus avoids dead Zn caused by unstable Zn deposition. As a proof of concept, BiNS/GF exhibits an average CE of 99.2 % in 300 cycles and a peak power density of 295.2 mW cm−2 at a current density of 380 mA cm−2 in aqueous neutral zinc-iron flow batteries. Therefore, it is reasonably anticipated that the BiNS/GF may emerge as suitable electrode for other aqueous zinc-based flow batteries.

Bismuth Single Atoms Regulated Graphite Felt Electrode Boosting High Power Density Vanadium Flow Batteries.

Vanadium flow batteries (VFBs) are considered one of the most promising candidates for large-scale energy storage. However, VFBs suffer from relatively low power density due to severe electrochemical polarization. Herein, we report Bi single atoms supported by an N-doped carbon-regulated graphite felt electrode (Bi SAs/NC@GF) with high electrocatalytic activity and stability, owing to the greatly improved active sites and optimized Bi-N4 configuration. Electrochemical in situ characterization and theoretical calculations elucidate the desolvation process and specific inner sphere reaction mechanism of [V(H2O)6]3+/[V(H2O)6]2+. As a result, a VFB single cell assembled with Bi SAs/NC@GF achieves a much higher energy efficiency of 81.1% at 240 mA cm-2 than NC@GF (70.5%). Moreover, a 5 kW VFB stack equipped with Bi SAs/NC@GF is assembled for the first time and ran stably for over 400 cycles. This work confirms that a single-atom catalyst is efficient for scalable VFBs with high power density and low cost.

Endogenously doped mixed-oxide CoO/Co2O3 in ZIF-derived carbon deposited on graphite felt for electrochemical oxidation of pharmaceutics

Some of the important goals in the development of the electro-Fenton (EF) process are to increase the performance of the electrodes while reducing their size as an alternative for expensive electrodes, expanding the active pH range, and also generating reactive oxygen species (ROSs) directly without using other homo/heterogeneous catalysts. This work modified graphite felt (GF) using a rapid and in-situ synthesis with Co/Zn doped mixed-metal ZIF. After calcination, various physicochemical analyses, including XRD, SEM, and XPS, confirmed that a carbonic material doped with mixed-oxide CoO/Co2O3 is embedded on the surface of GF fibers. LSV analysis showed that the modification significantly improved the electrode activity for O2 reduction. The modified CoZnCal-GF electrode showed good performance and higher kinetics in the EF process. It removed 87% of rifampin (RIF) in a short period of 30 min without any homo/heterogeneous catalysts. The selected conditions for this process were 1.0 V, 40 mg/L, and 5.6 for applied voltage, initial RIF concentration, and pH, respectively. The non-radical species 1O2 showed the most important role in removing RIF. LC-MS analysis was performed, and while confirming the complete removal of RIF, it was used to investigate the degradation pathway and identify the produced intermediates.

Composite Modified Graphite Felt Anode for Iron–Chromium Redox Flow Battery

The iron–chromium redox flow battery (ICRFB) has a wide range of applications in the field of new energy storage due to its low cost and environmental protection. Graphite felt (GF) is often used as the electrode. However, the hydrophilicity and electrochemical activity of GF are poor, and its reaction reversibility to Cr3+/Cr2+ is worse than Fe2+/Fe3+, which leads to the hydrogen evolution side reaction of the negative electrode and affects the efficiency of the battery. In this study, the optimal composite modified GF (Bi-Bio-GF-O) electrode was prepared by using the optimal pomelo peel powder modified GF (Bio-GF-O) as the matrix and further introducing Bi3+. The electrochemical performance and material characterization of the modified electrode were analyzed. In addition, using Bio-GF-O as the positive electrode and Bi-Bio-GF-O as the negative electrode, the high efficiency of ICRFB is realized, and the capacity attenuation is minimal. When the current density is 100 mA·cm−2, after 100 cycles, the coulomb efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) were 97.83%, 85.21%, and 83.36%, respectively. In this paper, the use of pomelo peel powder and Bi3+ composite modified GF not only promotes the electrochemical performance and reaction reversibility of the negative electrode but also improves the performance of ICRFB. Moreover, the cost of the method is controllable, and the process is simple.