Search Results (24)

A series of Cu-MnO_x/GF catalytic electrodes, with graphite felt (GF) pretreated via microwave modification as the catalyst carrier, were prepared under various hydrothermal conditions and characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and Raman spectroscopy. The catalytic oxidation activity of catalytic Cu-MnO_x/GF electrodes toward toluene was evaluated in an all-solid-state electrocatalytic device under mild operating conditions. The evaluation results demonstrated that the microwave-modified catalytic electrode exhibited high electrocatalytic activity toward toluene oxidation, with Cu-MnO_x/700W-GF exhibiting significantly higher catalytic activity, indicating that an increase in catalyst loading capacity can promote the removal of toluene. Only CO₂ and CO were detected, with no other intermediates observed in the reaction process. Moreover, the catalytic effect was significantly affected by the relative humidity. The catalytic oxidation of toluene can be fully realized under a certain humidity, indicating that the conversion of H₂O to strongly oxidizing ·OH on the catalytic electrode is a key step in this reaction. Full article

The design parameters of large-scale iron-chromium redox flow batteries (ICRFB) encompass a wide range of internal and external operational conditions, including electrodes, membranes, flow rate, and temperature, among others. Among these factors, the intrinsic structures of graphite felt (GF) and carbon cloth (CC) play a pivotal role in determining the overall working conditions of ICRFBs. This study systematically investigates the multifaceted relationship between the intrinsic structure of the GF and CC and their impact on the operational performance of ICRFBs. The fundamental difference between the two types of electrodes lies in the intrinsic structure space available in them for electrolyte penetration. A systematic analysis of the structure–activity relation between the electrodes and the initial internal resistance, as well as the operating temperature of the cell, was performed. Additionally, the influence of the electrode structure on critical parameters, including the flow rate, membrane selection (Nafion 212 and Nafion 115), and performance of electrodeposition catalysts (bismuth and indium), is examined in detail. Under varying operating conditions, the intrinsic structures of GF and CC turn out to be a crucial factor, providing a robust basis for electrode selection and performance optimization in large-scale ICRFB systems. Full article

In our investigation, we unveil a novel, eco-friendly, and cost-effective method for crafting a bio-derived electrode using discarded cotton fabric via a carbonization procedure, marking its inaugural application in a vanadium redox flow battery (VRFB). Our findings showcase the superior reaction surface area, heightened carbon content, and enhanced catalytic prowess for vanadium reactions exhibited by this carbonized waste cloth (CWC) electrode compared to commercially treated graphite felt (TT-GF). Therefore, the VRFB system equipped with these custom electrodes surpasses its treated graphite felt counterpart (61% at an equivalent current) and achieves an impressive voltage efficiency of 70% at a current density of 100 mA cm⁻². Notably, energy efficiency sees a notable uptick from 58% to 67% under the same current density conditions. These compelling outcomes underscore the immense potential of the carbonized waste cotton cloth electrode for widespread integration in VRFB installations at scale. Full article

The integration of intermittent renewable energy sources into the energy supply has driven the need for large-scale energy storage technologies. Vanadium redox flow batteries (VRFBs) are considered promising due to their long lifespan, high safety, and flexible design. However, the graphite felt (GF) electrode, a critical component of VRFBs, faces challenges due to the scarcity of active sites, leading to low electrochemical activity. Herein, we developed a bismuth nanoparticle uniformly modified graphite felt (Bi-GF) electrode using a bismuth oxide-mediated hydrothermal pyrolysis method. The Bi-GF electrode demonstrated significantly improved electrochemical performance, with higher peak current densities and lower charge transfer resistance than those of the pristine GF. VRFBs utilizing Bi-GF electrodes achieved a charge-discharge capacity exceeding 700 mAh at 200 mA/cm², with a voltage efficiency above 84%, an energy efficiency of 83.05%, and an electrolyte utilization rate exceeding 70%. This work provides new insights into the design and development of efficient electrodes, which is of great significance for improving the efficiency and reducing the cost of VRFBs. Full article

Glyphosate (GH) wastewater potentially poses hazards to human health and the aquatic environment, due to its persistence and toxicity. A highly superhydrophilic and stable graphite felt (GF)/polydopamine (PDA)/titanium dioxide nanotubes (TiO₂-NT)/SnO₂/Ru anode was fabricated and characterized for the degradation of glyphosate wastewater. Compared to control anodes, the GF/PDA/TiO₂-NT/SnO₂/Ru anode exhibited the highest removal efficiency (near to 100%) and a yield of phosphate ions of 76.51%, with the lowest energy consumption (0.088 Wh/L) for degrading 0.59 mM glyphosate (GH) at 7 mA/cm² in 30 min. The exceptional activity of the anode may be attributed to the co-activation of lattice oxygen in TiO₂-NT and SnO₂ by coupled Ru, resulting in a significant amount of •O₂⁻ and oxygen vacancies as active sites for glyphosate degradation. After electrolysis, small molecular acids and inorganic ions were obtained, with hydroxylation and dephosphorization as the main degradation pathways. Eight cycles of experiments confirmed that Ru doping prominently enhanced the stability of the GF/PDA/TiO₂-NT/SnO₂/Ru anode due to its high oxygenophilicity and electron-rich ability, which promoted the generation and utilization efficiency of active free radicals and defects-associated oxygen. Therefore, this study introduces an effective strategy for efficiently co-activating lattice oxygen in SnO₂ and TiO₂-NT on graphite felt to eliminate persistent organophosphorus pesticides. Full article

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 (R_ct) 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. Full article

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. Full article

Iron redox flow batteries (IRFBs) are cost-efficient RFBs that have the potential to develop low-cost grid energy storage. Electrode kinetics are pivotal in defining the cycle life and energy efficiency of the battery. In this study, graphite felt (GF) is heat-treated at 400, 500 and 600 °C, and its physicochemical and electrochemical properties are studied using XPS, FESEM, Raman and cyclic voltammetry. Surface morphology and structural changes suggest that GF heat-treated at 500 °C for 6 h exhibits acceptable thermal stability while accessing the benefits of heat treatment. Specific capacitance was calculated for assessing the wettability and electrochemical properties of pristine and treated electrodes. The 600 °C GF has the highest specific capacitance of 34.8 Fg⁻¹ at 100 mV s⁻¹, but the 500 °C GF showed the best battery performance. The good battery performance of the 500 °C GF is attributed to the presence of oxygen functionalities and the absence of thermal degradation during heat treatment. The battery consisting of 500 °C GF electrodes offered the highest voltage efficiency of ~74%, Coulombic efficiency of ~94%, and energy efficiency of ~70% at 20 mA cm⁻². Energy efficiency increased by 7% in a battery consisting of heat-treated GF in comparison to pristine GF. The battery is capable of operating for 100 charge–discharge cycles with an average energy efficiency of ~ 67% for over 100 cycles. Full article

Electrodes are one of the key components that influence the performance of all-vanadium redox flow batteries (VRFBs). A porous graphite felt with modified fiber surfaces that can provide a high specific activation surface is preferred as the electrode of a VRFB. In this study, a simple binder-free approach is developed for preparing stable carbon nanotube modified graphite felt electrodes (CNT-GFs). Heat-treated graphite felt electrodes (H-GFs) are dip-coated using CNT homogeneous solution. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results conclude that CNT-GFs have less resistance, better reaction currents, and reversibility as compared to H-GF. Cell performances showed that CNT-GFs significantly improve the performance of a VRFB, especially for the CNT-GF served in the positive side of the VRFB. CNT presence increases the electrochemical properties of the graphite electrode; as a result, reaction kinetics for both VO₂⁺/VO²⁺ and V³⁺/V²⁺ are improved. Positive CNT-GF (P-CNT-GF) configured VRFB exhibits voltage efficiency, coulombic efficiency, and energy efficiency of 85%, 97%, and 82%, respectively, at the operating current density of 100 mA cm⁻². At high current density of 200 mA cm⁻², the VRFB with P-CNT-GF shows 73%, 98%, and 72% of the voltage, coulombic, and energy efficiencies, respectively. The energy efficiency of the CNT-GF is 6% higher when compared with that of B-H-GF. The VRFB with CNT-GF can provide stable performance for 300 cycles at 200 mA cm⁻². Full article

The vanadium redox flow battery (VRFB) has been regarded as one of the best potential stationary electrochemical storage systems for its design flexibility, long cycle life, high efficiency, and high safety; it is usually utilized to resolve the fluctuations and intermittent nature of renewable energy sources. As one of the critical components of VRFBs to provide the reaction sites for redox couples, an ideal electrode should possess excellent chemical and electrochemical stability, conductivity, and a low price, as well as good reaction kinetics, hydrophilicity, and electrochemical activity, in order to satisfy the requirements for high-performance VRFBs. However, the most commonly used electrode material, a carbonous felt electrode, such as graphite felt (GF) or carbon felt (CF), suffers from relatively inferior kinetic reversibility and poor catalytic activity toward the V²⁺/V³⁺ and VO²⁺/VO₂⁺ redox couples, limiting the operation of VRFBs at low current density. Therefore, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. Here, we give a brief review of recent progress in the modification methods of carbonous felt electrodes, such as surface treatment, the deposition of low-cost metal oxides, the doping of nonmetal elements, and complexation with nanostructured carbon materials. Thus, we give new insights into the relationships between the structure and the electrochemical performance, and provide some perspectives for the future development of VRFBs. Through a comprehensive analysis, it is found that the increase in the surface area and active sites are two decisive factors that enhance the performance of carbonous felt electrodes. Based on the varied structural and electrochemical characterizations, the relationship between the surface nature and electrochemical activity, as well as the mechanism of the modified carbon felt electrodes, is also discussed. Full article

The use of flow batteries for energy storage has attracted considerable attention with the increased use of renewable resources. It is well known that the performance of a flow battery depends, among other factors, on the properties of the electrodes, which are generally composed of graphite felt (GF). In this work, thermal, chemical and plasma treatments have been employed to modify the surface of the graphite felt to improve the electrochemical activity of the redox flow cell. The influence of the variables of each of these processes on the generation of surface functional groups and on changes in the obtained surface area have been examined. In this work, the kinetics of redox reactions relevant to the VO²⁺/VO₂⁺ reaction have been studied with these treated electrodes and the relationship between the nature of the surface and electrochemical activity of the GF is discussed. As a result, an enhanced electrochemical performance (reduction over 200 mV of the separation between anodic and cathodic peaks and 110 mV of the onset potential) in comparison to the untreated GF is obtained for those GF treatments with low oxygenated groups concentration. Full article

Vanadium redox flow battery (VRFB) is one of the most promising technologies for grid-scale energy storage applications because of its numerous attractive features. In this study, metal-organic frameworks (MOF)-derived catalysts (MDC) are fabricated using carbonization techniques at different sintering temperatures. Zirconium-based MOF-derived catalyst annealed at 900 °C exhibits the best electrochemical activity toward VO²⁺/VO₂⁺ redox couple among all samples. Furthermore, the charge-discharge test confirms that the energy efficiency (EE) of the VRFB assembled with MOF-derived catalyst modified graphite felt (MDC-GF-900) is 3.9% more efficient than the VRFB using the pristine graphite felt at 100 mA cm⁻². Moreover, MDC-GF-900 reveals 31% and 107% higher capacity than the pristine GF at 80 and 100 mA cm⁻², respectively. The excellent performance of MDC-GF-900 results from the existence of oxygen-containing groups active sites, graphite structure with high conductivity embedded with zirconium oxide, and high specific surface area, which are critical points for promoting the vanadium redox reactions. Because of these advantages, MDC-GF-900 also possesses superior stability performance, which shows no decline of EE even after 100 cycles at 100 mA cm⁻². Full article

In an all-vanadium redox flow battery (VRFB), redox reaction occurs on the fiber surface of the graphite felts. Therefore, the VRFB performance highly depends on the characteristics of the graphite felts. Although atmospheric pressure plasma jets (APPJs) have been applied for surface modification of graphite felt electrode in VRFBs for the enhancement of electrochemical reactivity, the influence of APPJ plasma reactivity and working temperature (by changing the flow rate) on the VRFB performance is still unknown. In this work, the performance of the graphite felts with different APPJ plasma reactivity and working temperatures, changed by varying the flow rates (the conditions are denoted as APPJ temperatures hereafter), was analyzed and compared with those treated with sulfuric acid. X-ray photoelectron spectroscopy (XPS) indicated that the APPJ treatment led to an increase in O-/N-containing functional groups on the GF surface to ~21.0% as compared to ~15.0% for untreated GF and 18.0% for H₂SO₄-treated GF. Scanning electron microscopy (SEM) indicated that the surface morphology of graphite felt electrodes was still smooth, and no visible changes were detected after oxidation in the sulfuric acid or after APPJ treatment. The polarization measurements indicated that the APPJ treatment increased the limiting current densities from 0.56 A·cm⁻² for the GFs treated by H₂SO₄ to 0.64, 0.68, and 0.64 A·cm⁻², respectively, for the GFs APPJ-treated at 450, 550, and 650 °C, as well as reduced the activation overpotential when compared with the H₂SO₄-treated electrode. The electrochemical charge/discharge measurements showed that the APPJ treatment temperature of 550 °C gave the highest energy efficiency of 83.5% as compared to 72.0% with the H₂SO₄ treatment. Full article

In this study, a simple and environment-friendly method of preparing activated graphite felt (GF) for a vanadium redox flow battery (VRFB) by depositing the vanadium precursor on the GF surface and calcining vanadium oxide was explored. The intermediate material, VO₂, generated carbon oxidation during the calcination. In contrast to the normal etching method, this method was simple and without a pickling process. On the surface of the activated GF, multiple pores and increased roughness were noted after the calcination temperature and surface area of the activated GF reached 350 °C to 400 °C and 17.11 m²/g, respectively. Additionally, the polarization of the activated GF decreased with resistance to the charge transfer at 0.27 Ω. After a single-cell test at current density of 150 mA/cm² was performed, the capacity utilization and the capacity retention after 50 cycles reached 70% and 84%, respectively. These results indicated the potential use of activated GF as an VRFB electrode. Full article

The intrinsic hydrophobicity of graphite felt (GF) is typically altered for the purpose of the surface wettability and providing active sites for the enhancement of electrochemical performance. In this work, commercial GF is used as the electrodes. The GF electrode with a coated-polydopamine catalyst is achieved to enhance the electrocatalytic activity of GF for the redox reaction of vanadium ions in vanadium redox flow battery (VRFB). Materials characteristics proved that a facile coating via atmospheric pressure plasma jet (APPJ) to alter the surface superhydrophilicity and to deposit polydopamine on GF for providing the more active sites is feasibly achieved. Due to the synergistic effects of the presence of more active sites on the superhydrophilic surface of modified electrodes, the electrochemical performance toward VO²⁺/VO₂⁺ reaction was evidently improved. We believed that using the APPJ technique as a coating method for electrocatalyst preparation offers the oxygen-containing functional groups on the substrate surface on giving a hydrogen bonding with the grafted functional polymeric materials. Full article