Next Article in Journal
Innovative Research and Applications in Hydrodynamics and Flow Control
Previous Article in Journal
Pressure Capacity Assessment of L-PBF-Produced Microchannel Heat Exchangers
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Inventions
Volume 9
Issue 5
10.3390/inventions9050098
inventions-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

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

by
Sheng Wu
1,
Haotian Zhu
1,*,
Enrui Bai
1,
Chongyang Xu
1,
Xiaoyin Xie
2,* and
Chuanyu Sun
3,*
1
Yantai Research Institute, Harbin Engineering University, Yantai 264003, China
2
School of Chemistry and Chemical Technology, Hubei Polytechnic University, Huangshi 435003, China
3
School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China
*
Authors to whom correspondence should be addressed.
Inventions 2024, 9(5), 98; https://doi.org/10.3390/inventions9050098
Submission received: 9 August 2024 / Revised: 30 August 2024 / Accepted: 3 September 2024 / Published: 9 September 2024
(This article belongs to the Special Issue Advanced Electrode Material for Electrochemical Production Conversion and Storage of Energy)
Browse Figures
Versions Notes

Abstract

:
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.

1. Introduction

With the development of human society, a large amount of CO2 is emitted into the atmosphere with the inflammation of fossil fuels, resulting in global climate change, which has become an urgent problem to be solved. An important solution is to increase the application of new energy sources, including wind energy, solar energy, and wave energy [1]. However, due to the randomness and intermittency of environmental factors, it is difficult for new energy to generate electricity continuously and stably. Therefore, in the large-scale grid connection of new energy generation, in order to prevent the power grid from being impacted, a large amount of energy is wasted [2], thus the development of energy storage technology has become the key to realizing the large-scale application of new energy [3]. Redox flow battery (RFB) is efficient, cheap, safe, and stable, and has broad application prospects in the field of new energy storage [4]. In 1974, Thaler of the NASA Lewis Research Center proposed the concept of ICRFB [5], and in 1987, M Skyllas Kazacos et al. proposed the vanadium redox battery (VRFB) [6]. At present, VRFB is the most commercially developed RFB energy storage technology [7,8]. However, due to the scarcity of vanadium, it is difficult to further reduce the cost of VRFB [9,10]. ICRFB has the characteristics of low cost, wide temperature adaptability, and environmental friendliness [4,11]. Therefore, the ICRFB with lower cost has received extensive attention from researchers again in recent years [11,12,13].
GF with low cost and good conductivity is often used as the electrode of ICRFB [14,15,16] and super capacitor [17]. However, the hydrophilicity and electrochemical activity of GF are poor, resulting in an insufficient number of reactive sites on the electrode. Moreover, the reversibility of GF to Cr3+/Cr2+ is poor, and the reaction rate is slower than Fe2+/Fe3+, which is prone to hydrogen evolution side reactions and affects the battery efficiency [18]. The above two points have hindered the application of ICRFB. Therefore, the study of electrode materials with controllable cost, easy preparation, and excellent performance is of great significance to improve the performance of ICRFB and promote its commercial application. In the existing studies, scholars have proposed many methods of electrode modification, which can effectively enhance the specific surface area of the electrode by changing the morphology of the electrode surface through heat treatment [19], acid, etc., [16] or biomass modification [20]. These three methods can also introduce more oxygen-containing functional groups on the surface of the electrode so as to improve the hydrophilicity. The above two changes can increase the number of reactive sites on the electrode surface, thereby effectively improving the electrochemical activity of the electrode [16,19,20]. Another modification method is to deposit metal nanoparticles or metal oxides on the surface of the electrode to improve the catalytic activity of the electrode for redox reactions. Su used In3+ to modify the PAN-GF electrode. The results showed that the PAN-GF electrode modified by In3+ of 0.2 M had the best electrochemical performance [21]. Ren used KMnO4 to modify the GF electrode, and the results showed that the introduced MnOx could adsorb the active substances in the solution. Moreover, the discharge capacity and energy efficiency of the optimal modified GF electrode were 41% and 21% higher than that of the GF electrode, respectively [22]. Zhang deposited metal bismuth (Bi) on the GF negative electrode, effectively improving the reaction reversibility of Cr3+/Cr2+ on the negative electrode [23,24]. Che used amorphous bismuth nanoparticles (NPS) and N dopants to modify the GF electrode. The optimal energy efficiency of the modified GF electrode reached 85.8% at 60 mA·cm−2 [25]. For the negative electrode of the battery, combined with the above two modification methods of increasing electrode specific surface area, hydrophilicity, and introducing the metal catalyst to modify GF, it is promising to enhance the reversibility of the negative electrode for Cr3+/Cr2+ while promoting the electrochemical activity. Nevertheless, few related studies have been reported for the ICRFB applications.
In this paper, for the negative electrode of ICRFB, based on the existing research, Bio-GF-O [26] was used as the matrix, and Bi3+ was introduced by soaking and drying. Then, the optimal BiCl3 concentration in the preparation process was determined, and the optimal composite modified graphite felt (Bi-Bio-GF-O) negative electrode was prepared. After analyzing the reversibility of redox reactions and electrochemical activity, the surface morphology, structure, element composition, and hydrophilicity were characterized. Finally, using Bio-GF-O as the positive and Bi-Bio-GF-O as the negative electrode, high-efficiency ICRFB is realized. Under various current densities, the efficiency of ICRFB assembled with Bi-Bio-GF-O as the negative electrode was higher than that of other ICRFBs. When the current density was 100 mA·cm−2, the CE of ICRFB with Bi-Bio-GF-O as the negative electrode was 97.83%, VE was 85.21%, EE was 83.36% after 100 cycles, and its capacity attenuation was the smallest.

2. Methods and Materials

First, before preparing the composite modified GF electrode, a certain amount of Bio-GF-O was prepared according to the previous research content [26]. Cut several groups of GF samples into the dimension of 5.0 × 5.0 cm (carbon content ≥ 99.9%, bulk density: 0.12~0.13 g cm−3, thickness: 3 mm, Gansu Haoshi Carbon Fiber Co., Ltd., Baiyin, China) and rinse with deionized water for three times. Then, the GF samples were immersed in ethanol for 10 min, and they were taken out and rinsed with deionized water for half an hour, and finally dried in a vacuum oven (Yixin Scientific Instrument Factory, Shanghai, China) for 6 h at 80 °C. A total of 15.0 g of the treated pomelo peel powder [26] was mixed with 200.0 mL of deionized water and 10.0 mL of 0.3 M sucrose solution. The acquired mixture was agitated and ultrasonically for 10 min, respectively, to form slurry. The GF sample was immersed in the slurry for 5 min, and it was dried in the vacuum oven for 6 h at 80 °C. After the samples were taken out, they were pyrolyzed at 1050 °C for 3 h in an N2 atmosphere in a tubular furnace. The obtained samples were recorded as Bio-GF-O.
After that, Bi3+ was further introduced into Bio-GF-O, and the prepared Bio-GF-O was washed with deionized water. The carbon debris on the surface of the sample was washed off and then dried in a vacuum oven for 6 h at 80 °C, and later it was taken out. Meanwhile, the electronic analytical balance was used to weigh three groups of BiCl3 drugs with different masses, which were fully dissolved in three groups of 200 mL of 3 M HCl solution, so that the concentration of Bi3+ in the solution was 0.1, 0.2, and 0.3 M, respectively. The prepared Bio-GF-O electrodes were divided into three groups. They were soaked in HCl and different concentrations of BiCl3 for 6 h and dried in a vacuum oven for 6 h at 80 °C, and it was finally taken out and labeled as Bi-Bio-GF.
To observe the surface morphology of the modified electrode, scanning electron microscopy (SEM, JEOL JSM-7610F, Tokyo, Japan) was employed. For element mapping analysis, the energy dispersive spectrometer (EDS, JEOL JSM-7610F, Tokyo, Japan) was adopted. Raman spectroscopy (Horiba Jobin Yvon LabRAM HR800, Paris, French) was used to evaluate the order degree of the crystal structure of the sample. X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific K-Alpha, Waltham, MA, USA) and X-ray diffraction (XRD, Bruker D8 advance, Billerica, MA, USA) were used to study the chemical information on the surface of the electrode. The static contact angle (SCA, DataPhysics OCA20, Filderstadt, Germany) was measured to assess the hydrophilicity of the electrode.
The electrochemical performance of the modified electrode was detected by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) of the electrochemical workstation (CHI760E, CH Instrument, Shanghai, China). The electrolyte was a mixture of 1 M FeCl2 + 1 M CrCl3 + 3 M HCl [27]. The EIS test was conducted in a standard double-electrode system at room temperature. The comparison electrode was a platinum sheet with a specification of 1.0 cm × 1.0 cm, and the working electrode is 1.5 cm × 2.0 cm. During the test, the AC voltage amplitude is set as 5 mV, and the scanning frequency changes from 0.01 Hz to 100 kHz. A CV test is conducted in a standard three-electrode system at room temperature. In addition to the working electrode and the comparison electrode, a reference electrode composed of saturated calomel electrode (SCE) and KCl salt bridge is also required. During the test, the scanning window is limited to 0 V~0.8 V and −0.8 V~0 V. To make the curve change trend more obvious and the comparative analysis more significant, the potential scanning rate is set as 1 mV·s−1 [26].
The battery testing system (CT3002K, Blue Electron, Wuhan, China) is employed to test the ICFRB cell (Chuxin Technology Co., Ltd., Wuhan, China). There are three groups in total. The gradient current density of the charge discharge test and the constant current density cycle of the charge discharge test are completed for each group. The first group used GF as positive and negative electrodes; the second group used Bio-GF-O as positive and negative electrodes. The third group used Bio-GF-O as the positive electrode and Bi-Bio-GF-O as the negative electrode. The entire battery system except for the peristaltic pump is located in a thermostat at 65 °C. The electrolyte is still a mixed solution [27], consisting of 35 mL in the catholyte and anolyte storage tanks, respectively. The specification of the ion exchange membrane is 6.0 cm × 6.0 cm (Nafion 212, DuPont, Wilmington, NC, USA). The electrode was cut into a square with a side length of 5.0 cm. The cut-off voltage of battery discharging and charging is 0.8 V and 1.2 V. The current density range for the charge–discharge cycling is between 40 and 140 mA·cm−2, the interval is 20 mA·cm−2, and the battery charges and discharges for 5 cycles at each current density. The current density of the long-term charge–discharge cycling is 100 mA·cm−2. On the premise that the battery performance conditions are met, 100 cycles of charge–discharge operations are performed on the battery to test the cycle stability of ICRFB under different electrode composition schemes.

3. Results

The preparation of the Bi-Bio-GF-O electrode and the application of ICRFB are shown in Figure 1. The single cell structure of ICRFB is shown in Figure 2, which, from inside to outside, successively includes the membrane, GF electrode, flow frame, bipolar plate, collecting plate, and fastening plate.
Table 1 summarizes and compares the performance of single-cell ICRFB with various electrode compositions. The results show that the ICRFB in the Bi-Bio-GF-O group has the highest CE, VE, and EE. Although its charge discharge efficiency is slightly lower than that of the ICRFB in the Bio-GF-O group, the capacity decay rate is significantly lower than that of the ICRFB in the Bio-GF-O group. Therefore, it can be determined that Bi-Bio-GF-O is a better anode material.

4. Discussion

The electrochemical features of GF, Bio-GF-O and Bi-Bio-GF were studied according to CV curves, and the optimal Bi3+ concentration for the preparation of Bi-Bio-GF-O was determined. The CV curve with a scan window of −0.8 V~0 V reflects the reactivity of the anode to Cr3+/Cr2+, while the scan window of −0.8 V~0 V reflects the reactivity of the cathode to Fe2+/Fe3+. First of all, in Figure 3a, for the negative electrode, since the redox reaction of Cr3+/Cr2+ on the GF electrode is less reversible than Fe2+/Fe3+, the reduction peak of the GF electrode is not as obvious as the oxidation peak. Although the Ipa (106.7 mA) of the Bio-GF-O electrode was higher than that of the GF electrode (56.2 mA), the reduction peak of the Bio-GF-O electrode became more difficult to observe after the modification of pomelo peel powder. When Bi3+ was further introduced into Bio-GF-O, the reduction peak potential of the prepared Bi-Bio-GF electrode increased significantly, the position of the peak moved to the right, and the Ipc also increased. Due to the obvious increase in the reduction peak potential, the ∆Ep of the three groups of Bi-Bio-GF decreased significantly, indicating that the oxidation-reduction reaction of Cr3+/Cr2+ was more likely to occur on the electrode surface after the introduction of Bi3+. According to Table 2, in the three groups of Bi-Bio-GF, the ∆Ep of Bi-Bio-GF-0.2M is 0.119 V, which is less than the ∆Ep of the GF electrode (0.296 V); Ipa and Ipc were 119.5 mA and −148.9 mA, respectively, which were higher than those of the GF electrode (56.2 mA and −56.6 mA). Moreover, the absolute value of Ipa/Ipc of Bi-Bio-GF-0.2M is the closest to 1, which indicates that Bi-Bio-GF-0.2M has the best reversibility of Cr3+/Cr2+ [28], so the optimal Bi3+ concentration in the process of preparing the composite modified electrode is determined to be 0.2 M, and Bi-Bio-GF-0.2M is Bi-Bio-GF-O. Comparing the negative CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O (Figure 3b), it can be seen that Bi-Bio-GF-O has larger Ipa and Ipc and smaller ∆Ep, which is a better negative material for batteries.
For the positive electrode, in Figure 3c, the peak current of Bio-GF-O electrode (Ipa = 171.3 mA, Ipc = −163.4 mA) is larger than that of GF electrode (Ipa = 121.5 mA, Ipc = −127.4 mA), and the absolute value of Ipa/Ipc also approaches 1, indicating that the electrochemical activity of Bio-GF-O as cathode is higher than that of GF. Moreover, Bio-GF-O has good reversibility for Fe2+/Fe3+ redox reactions. The reduction peak potential of the Bi-Bio-GF electrode decreased significantly, the peak position moved to the left, and the Ipc also decreased. At the same time, the oxidation peak on the CV curve disappeared. The reason is that the introduction of bismuth catalyst is not conducive to improving the electrochemical activity of the Fe2+/Fe3+ redox reaction [29]. By comparing the negative CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O (Figure 3d), it can be seen that Bio-GF-O is a better cathode material for batteries.
The charge transfer resistance (Rct) in the redox reaction process is evaluated according to the EIS diagram and its fitting results. Wherein, Rs represents the intrinsic resistance of the system, Rct represents charge transfer resistance, Cpe represents double-layer capacitance of electrode/electrolyte liquid interface, and W0 represents Warburg impedance. The Nyquist diagram is divided into two parts, including the semicircular part (high-frequency section) and the linear part (low-frequency section), which, respectively, represent the charge transfer at the electrode/electrolyte interface and the diffusion of redox active substances [30,31,32]. Rct can be estimated from the semicircular diameter [33]. As shown in Figure 4, the impedance spectrum is fitted according to the equivalent circuit. The data with -cal are the fitting calculation results, and the data with -msd are the EIS experimental test results. The results show that the radius of the high-frequency semicircular part of the Bio-GF-O electrode is smaller than that of the GF electrode, while the radius of the high-frequency semicircular part of the Bi-Bio-GF-O electrode is the smallest. As shown in Table 3, the Rct (2.422 Ω) of the Bio-GF-O electrode is less than that of GF electrode (2.961 Ω), and the Rct (0.57 Ω) of the Bi-Bio-GF-O electrode is the smallest, far less than the first two. This shows that compared with the GF electrode, Bio-GF-O and Bi-Bio-GF-O electrodes have smaller polarization resistance in the mixed electrolyte, and the performance of the Bi-Bio-GF-O electrode is better.
The surface morphologies of GF, Bio-GF-O and Bi-Bio-GF-O were studied by scanning electron microscopy. According to Figure 5a,d, the GF electrode is composed of disordered graphite fibers, which is beneficial to increase the porosity of the electrode surface and then increase the reactive active sites compared with the ordered structure; However, the surface of the fiber is relatively smooth, which is not conducive to increasing the specific surface area of the electrode. According to Figure 5b,e, after the Bio-GF-O electrode was modified by pomelo peel powder and high temperature in the N2 atmosphere, the gullies on the graphite fiber surface were more obvious and uneven, and the surface was uniformly encapsulated with a stratum of biomass nanoparticles exhibiting a heterogeneous distribution. This modification is anticipated to augment the specific surface area of the Bio-GF-O electrode, thereby enhancing its electrochemical performance. From Figure 5c,f, crystalline bulges were observed on the Bi-Bio-GF-O electrode surface. These crystals were BiCl3 crystals naturally precipitated during the drying process when preparing Bi-Bio-GF-O. It is worth noting that some precipitated BiCl3 crystals can also be seen on the relatively internal graphite fiber, implying that the preparation method of Bi-Bio-GF-O, which is fully soaked and then dried, can uniformly and deeply introduce Bi3+.
The elemental compositions of GF (Figure 6a,b), Bio-GF-O (Figure 6c,d), and Bi-Bio-GF-O (Figure 6e–h) were preliminarily analyzed by energy dispersive spectroscopy. The results showed that more O elements were enriched on the biomass particles that adhered to the Bio-GF-O surface, and these O elements came from the oxygen-containing functional groups in the biomass particles. For Bi-Bio-GF-O, Bi is enriched on the crystalline bulge adhered to the electrode surface, which is consistent with the analysis results of SEM images. It can be proved that the modification method adopted in this study effectively introduces Bi on the electrode surface.
The chemical elements of GF, Bio-GF-O, and Bi-Bio-GF-O were further determined by XPS analysis, and the oxygen-containing functional groups and Bi elements incorporated into the modified electrode were determined. From Figure 7a, the XPS spectrum of Bio-GF-O shows a stronger O1s signal than that of GF, which indicates that there are larger quantities of oxygen-containing functional groups in Bio-GF-O. The O1s signal of Bi-Bio-GF-O is the strongest and shows a strong Bi4f signal, which indicates that a huge amount of Bi elements are incorporated into the surface of Bi-Bio-GF-O and confirms the conclusion that Bi2O3 is produced during electrode drying.
In the Raman spectrum, the three electrodes have two manifest characteristic peaks at 1597 and 1353 cm−1, corresponding to the G and D band, respectively [34]. The D-band arises from the vibrational modes associated with sp3 hybridized carbon atoms or other structural irregularities at disordered grain boundaries, whereas the G-band is attributed to the in-plane tensile vibrations of sp2 hybridized carbon atoms that are interconnected within the carbon lattice (Figure 7b) [35]. The ID/IG values of Bi-Bio-GF-O (1.46) and Bio-GF-O (1.43) were higher than GF (1.28), which indicated that the quantity of defective carbon/edge carbon increased, heteroatoms increased, and the crystal structure order decreased after biomass modification and composite modification.
The crystal structures of GF, Bio-GF-O, and Bi-Bio-GF-O were studied by XRD and Raman spectroscopy. According to XRD analysis, first of all, after biomass modification, the main structure of the Bio-GF-O electrode is still graphite. From Figure 7c, GF and Bio-GF-O both show wide peaks at 43.0° and 25.5°, which are attributed to the (100) and (002) planes of graphite [36,37,38]. For Bi-Bio-GF-O, besides the characteristic peaks of (110) and (002) crystal planes, there are more characteristic peaks. Among them, the characteristic peaks at 26.21°, 36.85°, 48.54°, 55.37°, 60.79°, and 63.21° represent the (012), (104), (202), (024), (116), and (122) crystal planes of hexagonal system Bi (JCPDS No. 44–1246). Other characteristic peaks correspond to some crystal planes of Bi2O3 (JCPDS No. 45–1344), which indicates that BiCl3 crystals are precipitated on the Bi-Bio-GF-O electrode surface during the drying process, and a small amount of Bi2O3 is also produced during this process. Moreover, the characteristic peaks of (110) and (002) crystal planes representing graphite shifted to the left, which was caused by the introduction of BiCl3 crystal on the electrode surface.
The static contact angle (SCA) was used to characterize the change in hydrophilicity of electrode materials. SCA refers to the angle that comes into being when the liquid phase is sandwiched between the solid–liquid and gas–liquid interface at the gas–liquid-solid three-phase junction on the solid surface. The smaller the SCA, the better the hydrophilicity of the electrode sample. From Figure 8a–c, the SCA of Bio-GF-O (135.827°) is smaller than that of GF (153.977°), which indicates that the hydrophilicity of Bio-GF-O is better because higher amounts of oxygen-containing functional groups are located in the biomass particles on the Bio-GF-O surface. The SCA (127.515°) of Bi-Bio-GF-O is the smallest because more O elements are introduced into the Bi2O3 on its surface.
The performance of ICRFB with different electrodes was compared. In the battery test diagram, the GF curve refers to GF as positive and negative electrodes; the Bio-GF-O curve refers to Bio-GF-O as positive and negative electrodes; and the Bi-Bio-GF-O curve indicates that Bio-GF-O is used as the positive electrode and Bi-Bio-GF-O as the negative electrode. First, the charge and discharge capacities of the batteries in each group were tested. According to Figure 9a, when the current density was 100 mA·cm−2, the performance of Bio-GF-O (charge capacity was 631 mAh, discharge capacity was 601 mAh) and Bi-Bio-GF-O (charge capacity was 584 mAh, discharge capacity was 534 mAh) were better than those of the GF group (charge capacity was 253 mAh, discharge capacity was 208 mAh). The charge and discharge capacity of Bi-Bio-GF-O was lower than that of Bio-GF-O because the voltage changed faster when the charge and discharge voltage were close to the cut-off voltage. The gradient tests of three groups of ICRFBs with different current densities were carried out. After calculation, the electrolyte utilization rate of the GF group charging was 18.88%, Bio-GF-O was 39.85%, and Bi-Bio-GF-O was 47.09%.
From Figure 9b−d, when the current density rises from 40 mA·cm−2 to 140 mA·cm−2 at an interval of 20 mA·cm−2, the VE and EE of the battery decrease, and CE increases. Nevertheless, the EE and CE of the GF group exhibited pronounced fluctuations, which were attributed to the concurrent side reactions involving hydrogen evolution occurring on the GF [26]. It can be seen that the ICRFB assembled with Bio-GF-O significantly reduced the fluctuation caused by the side reactions involving hydrogen evolution and effectively improved the VE, EE and CE of the battery. Although the stability of the Bi-Bio-GF-O group decreased slightly, this scheme further improved the efficiency of ICRFB. After gradient cycling, under the low current density of 40 mA·cm−2, the VE, EE, and CE of the battery were 93.72%, 88.97%, and 94.93%, respectively.
On the basis of the above three groups of ICRFBs, an additional control group was added. The control group used Bio-GF-O as the cathode and anode of the battery but added 5 mmol/L of BiCl3 to the negative electrolyte, which was recorded as Bio-GF-O (Bi). Relevant studies show that Bi3+ with this concentration is directly added to the anode electrolyte, which can better catalyze the oxidation-reduction reaction of the anode [39]. The four ICRFBs were cyclic charging and discharging at 100 mA·cm−2. From Figure 10a,b, the attenuation speed of the GF group began to slow down after nearly 20 cycles, and it was unable to stabilize the cycle for 100 times. After nearly 60 cycles, the battery capacity was 70 mAh, which had been attenuated to the point that it could not continue to support the cyclic charge and discharge. In the Bio-GF-O group, the decay rate of capacity was slower during 100 cycles, and the charging capacity was still 124 mAh after 100 cycles. The discharge capacity is 120 mAh, which is very close to the charging capacity. The main reasons for the capacity attenuation include the side reaction of hydrogen evolution, the transmembrane migration of ions, and the increase in internal resistance caused by the increase in charge and discharge times. Bio-GF-O group ICRFB can be cycled for 100 times, indicating that the side reaction of hydrogen evolution on the Bio-GF-O electrode is reduced. The capacity of the Bi-Bio-GF-O group decreased rapidly at the initial stage of the cycle. But after about 20 times, the attenuation rate began to slow down. After about 60 times, the capacity of the Bio-GF-O group was always higher than that of the Bio-GF-O group, and it was more stable. After 100 cycles, the charging capacity was still 160 mAh, and the discharge capacity was 157 mAh; they are both higher than the Bio-GF-O group. Moreover, in comparison to the control group of Bio-GF-O (Bi), the decay rate of the capacity of the Bi-Bio-GF-O group was slower, indicating that the preparation method of Bi-Bio-GF-O, which was fully soaked and then dried, was better than the modification scheme of adding Bi3+ directly into the negative electrolyte and could retain the catalytic effect of Bi on Cr3+/Cr2+ redox reactions to a greater extent after multiple cycles.
The battery efficiency of the above four groups of ICRFBs during the cyclic test at 100 mA·cm−2 is recorded. From Figure 11a–c, After 57 cycles, the CE, VE, and EE of the GF group were 91.04%, 71.80%, and 65.37%, respectively. The CE, VE, and EE of Bio-GF-O group were higher than those of the GF group during the cycle. After 100 cycles, the CE, VE, and EE of the battery were 96.42%, 78.50%, and 75.69%, respectively. After 100 cycles, the Bi-Bio-GF-O battery maintained the highest efficiency among the four ICRFBs, the CE and EE were more stable than those in the control group. This result once again proves that the preparation method of Bi-Bio-GF-O can make the catalytic effect of Bi on Cr3+/Cr2+ redox reactions more stable. This is because Bi can only be sedimented on the electrode surface during the charging process by adding Bi3+ only to the negative electrolyte, which is not deep enough. Moreover, due to the single internal channel structure of the stack and the flow direction of the electrolyte, Bi deposited at the inlet will be more than that at the outlet, which is difficult to deposit evenly. The preparation method of Bi-Bio-GF-O, which is fully soaked and then dried, makes it easier to deposit more Bi3+ on the Bi-Bio-GF-O. After 100 cycles, the CE, VE, and EE of the Bi-Bio-GF-O battery were 97.83%, 85.21%, and 83.36%, respectively.

5. Conclusions

In conclusion, this paper investigated a cost-effective, effective, and simple approach to modifying the GF anode. Firstly, GF was modified by pomelo peel powder, and then Bi3+ was introduced by soaking and drying, and the optimal concentration of BiCl3 in the preparation process was determined. The electrochemical activity of the modified Bi-Bio-GF-O anode was better than that of the GF and Bio-GF-O anodes, and it showed an obvious electrocatalytic effect on the Cr3+/Cr2+ redox reaction. The battery test outcomes demonstrate that the performance of ICRFB with Bi-Bio-GF-O is better. The CE, VE, and EE of ICRFB assembled with Bi-Bio-GF-O group were higher in the gradient current density charge discharge test of 40 mA·cm−2~140 mA·cm−2 with an interval of 20 mA·cm−2 and the cyclic charge discharge test of 100 mA·cm−2. At the end of the cycle, the EE of ICRFB in Bi-Bio-GF-O group was 83.36%, 17.99% higher than that of GF and 7.67% higher than that of Bio-GF-O group, and the capacity attenuation of ICRFB in Bi-Bio-GF-O group was smaller. In addition, compared with the modification scheme of adding BiCl3 directly to the electrolyte, the preparation method of Bi-Bio-GF-O, which is fully soaked and then dried, can deposit more Bi3+ on the surface of the negative electrode and adhere more deeply, making the effect of improving battery capacity and efficiency more stable. We believe that this modification method of battery anode is conducive to promoting the commercial application of ICRFB.

Author Contributions

Conceptualization, H.Z., S.W. and X.X.; methodology, H.Z. and S.W.; software, H.Z.; validation, H.Z., S.W. and C.X.; formal analysis, H.Z. and C.S.; investigation, H.Z. and E.B.; resources, S.W., X.X. and C.S.; data curation, H.Z.; writing—original draft preparation, H.Z.; writing—review and editing, C.S.; visualization, H.Z.; supervision, S.W. and X.X.; project administration, S.W. and X.X.; funding acquisition, S.W. and X.X. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Key R&D Program of China No. 2022YFB4200704; Hubei Provincial Key R&D Program Projects, NO.: 2023DJC187 and Hubei Provincial Natural Science Foundation Project, NO.: 2024AFD003.

Data Availability Statement

The datasets presented in this article are not readily available because the data are part of an ongoing study. Requests to access the datasets should be directed to the authors on request.

Acknowledgments

The author would like to first express his gratitude to Harbin Engineering University for the opportunity to study this topic. The author would also like to extend his sincere appreciation to other co-authors for their support. Besides, we gratefully thank Wuhan Chuxin Technology Co., Ltd. for providing us with technical and equipment support.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Yang, Z.; Zhang, M.; Liu, L.; Zhou, D. Can renewable energy investment reduce carbon dioxide emissions? Evidence from scale and structure. Energy Econ. 2022, 112, 106181. [Google Scholar] [CrossRef]
  2. Wang, R.; Yang, W.; Li, X.; Zhao, Z.; Zhang, S. Day-ahead multi-objective optimal operation of Wind–PV–Pumped Storage hybrid system considering carbon emissions. Energy Rep. 2022, 8, 1270–1279. [Google Scholar] [CrossRef]
  3. Zhao, H.; Xu, J.; Xu, K.; Sun, J.; Wang, Y. Optimal Allocation Method of Source and Storage Capacity of PV-Hydrogen Zero Carbon Emission Microgrid Considering the Usage Cost of Energy Storage Equipment. Energies 2022, 15, 4916. [Google Scholar] [CrossRef]
  4. Zhang, H.; Sun, C. Cost-effective iron-based aqueous redox flow batteries for large-scale energy storage application: A review. J. Power Sources 2021, 493, 229445. [Google Scholar] [CrossRef]
  5. Thaller, L.H. Electrically Rechargeable REDOX Flow Cell. U.S. Patent 3,996,064, 7 December 1976. [Google Scholar]
  6. Skyllas-Kazacos, M.; Grossmith, F. Efficient Vanadium Redox Flow Cell. J. Electrochem. Soc. 1987, 134, 2950–2953. [Google Scholar] [CrossRef]
  7. Skyllas-Kazacos, M. Review-Highlights of UNSW All-Vanadium Redox Battery Development: 1983 to Present. J. Electrochem. Soc. 2022, 169, 070513. [Google Scholar] [CrossRef]
  8. Chakrabarti, M.H.; Hajimolana, S.A.; Mjalli, F.S.; Saleem, M.; Mustafa, I. Redox Flow Battery for Energy Storage. Arab. J. Sci. Eng. 2012, 38, 723–739. [Google Scholar] [CrossRef]
  9. Zhang, H.; Lu, W.; Li, X. Progress and Perspectives of Flow Battery Technologies. Electrochem. Energy Rev. 2019, 2, 492–506. [Google Scholar] [CrossRef]
  10. Sun, C.; Negro, E.; Nale, A.; Pagot, G.; Vezzù, K.; Zawodzinski, T.A.; Meda, L.; Gambaro, C.; Di Noto, V. An efficient barrier toward vanadium crossover in redox flow batteries: The bilayer [Nafion/(WO3)x] hybrid inorganic-organic membrane. Electrochim. Acta 2021, 378, 138133. [Google Scholar] [CrossRef]
  11. Li, B.; Liu, J. Progress and directions in low-cost redox-flow batteries for large-scale energy storage. Natl. Sci. Rev. 2017, 4, 91–105. [Google Scholar] [CrossRef]
  12. Xie, C.; Yan, H.; Song, Y.; Song, Y.; Yan, C.; Tang, A. Catalyzing anode Cr2+/Cr3+ redox chemistry with bimetallic electrocatalyst for high-performance iron–chromium flow batteries. J. Power Sources 2023, 564, 232860. [Google Scholar] [CrossRef]
  13. Su, Y.; Ren, H.L.; Zhao, S.; Chen, N.; Li, J.Q.; Li, C.W.; Wang, X.M. Analysis of the influence of high-entropy oxide optimized electrolyte on the electrochemical performance of iron chromium flow batteries. Ceram. Int. 2023, 49, 30443–30451. [Google Scholar] [CrossRef]
  14. Zhang, H.; Chen, N.; Sun, C.; Luo, X. Investigations on physicochemical properties and electrochemical performance of graphite felt and carbon felt for iron-chromium redox flow battery. Int. J. Energy Res. 2020, 44, 3839–3853. [Google Scholar] [CrossRef]
  15. Castañeda, L.F.; Walsh, F.C.; Nava, J.L.; de León, C.P. Graphite felt as a versatile electrode material: Properties, reaction environment, performance and applications. Electrochim. Acta 2017, 258, 1115–1139. [Google Scholar] [CrossRef]
  16. Chen, N.; Zhang, H.; Luo, X.D.; Sun, C.Y. SiO2-decorated graphite felt electrode by silicic acid etching for iron-chromium redox flow battery. Electrochim. Acta 2020, 336, 135646. [Google Scholar] [CrossRef]
  17. Poudel, M.B.; Kim, A.R.; Ramakrishan, S.; Logeshwaran, N.; Ramasamy, S.K.; Kim, H.J.; Yoo, D.J. Integrating the essence of metal organic framework-derived ZnCoTe–N–C/MoS2 cathode and ZnCo-NPS-N-CNT as anode for high-energy density hybrid supercapacitors. Compos. Part. B Eng. 2022, 247, 110339. [Google Scholar] [CrossRef]
  18. Wong, A.A.; Aziz, M.J. Method for Comparing Porous Carbon Electrode Performance in Redox Flow Batteries. J. Electrochem. Soc. 2020, 167, 110542. [Google Scholar] [CrossRef]
  19. Kil, D.; Lee, H.J.; Park, S.; Kim, S.; Kim, H. Synthesis of Activated Graphite Felts Using Short-Term Ozone/Heat Treatment for Vanadium Redox Flow Batteries. J. Electrochem. Soc. 2017, 164, A3011–A3017. [Google Scholar] [CrossRef]
  20. Hu, Z.; Miao, Z.; Xu, Z.; Zhu, X.; Zhong, F.; Ding, M.; Wang, J.; Xie, X.; Jia, C.; Liu, J. Carbon felt electrode modified by lotus seed shells for high-performance vanadium redox flow battery. Chem. Eng. J. 2022, 450, 138377. [Google Scholar] [CrossRef]
  21. Su, Y.; Chen, N.; Ren, H.L.; Guo, L.L.; Li, Z.; Wang, X.M. Preparation and Properties of Indium Ion Modified Graphite Felt Composite Electrode. Front. Chem. 2022, 10, 899287. [Google Scholar] [CrossRef]
  22. Ren, H.; Su, Y.; Zhao, S.; Chen, N.; Li, C.; Wang, X.; Li, B. Study on the performance of MnOx modified graphite felts as electrodes for iron-chromium redox flow battery obtained by permanganic acid etching. J. Energy Storage 2024, 75, 109592. [Google Scholar] [CrossRef]
  23. Zhang, H.; Tan, Y.; Li, J.; Xue, B. Studies on properties of rayon- and polyacrylonitrile-based graphite felt electrodes affecting Fe/Cr redox flow battery performance. Electrochim. Acta 2017, 248, 603–613. [Google Scholar] [CrossRef]
  24. Chen, S.; Sun, C.; Zhang, H.; Yu, H.; Wang, W. Electrochemical Deposition of Bismuth on Graphite Felt Electrodes: Influence on Negative Half-Cell Reactions in Vanadium Redox Flow Batteries. Appl. Sci. 2024, 14, 3316. [Google Scholar] [CrossRef]
  25. Che, H.X.; Gao, Y.F.; Yang, J.H.; Hong, S.; Hao, L.D.; Xu, L.; Taimoor, S.; Robertson, A.W.; Sun, Z.Y. Bismuth nanoparticles anchored on N-doped graphite felts to give stable and efficient iron-chromium redox flow batteries. New Carbon Mater. 2024, 39, 131–141. [Google Scholar] [CrossRef]
  26. Zhu, H.; Bai, E.; Sun, C.; Liu, G.; Zhang, Z.; Xie, X.; Xu, C.; Wu, S. Biomass pomelo peel modified graphite felt electrode for iron-chromium redox flow battery. J. Mater. Sci. 2023, 58, 17313–17325. [Google Scholar] [CrossRef]
  27. Wang, S.; Xu, Z.; Wu, X.; Zhao, H.; Zhao, J.; Liu, J.; Yan, C.; Fan, X. Analyses and optimization of electrolyte concentration on the electrochemical performance of iron-chromium flow battery. Appl. Energy 2020, 271, 115252. [Google Scholar] [CrossRef]
  28. Johnson, D.A.; Reid, M.A. Chemical and Electrochemical Behavior of the Cr(III)/Cr(II) Half-Cell in the Iron-Chromium Redox Energy Storage System. J. Electrochem. Soc. 1985, 132, 1058–1062. [Google Scholar] [CrossRef]
  29. Xu, Q.; Wang, S.; Xu, C.; Chen, X.; Zeng, S.; Li, C.; Zhou, Y.; Zhou, T.; Niu, Y. Synergistic effect of electrode defect regulation and Bi catalyst deposition on the performance of iron–chromium redox flow battery. Chin. Chem. Lett. 2023, 34, 108188. [Google Scholar] [CrossRef]
  30. Cheng, Y.; Cui, W.; Wang, L.; Peng, C.; Wang, S.; Wang, Y. Vitrification and Crystallization of Phase-Separated Metallic Liquid. Metals 2017, 7, 73. [Google Scholar] [CrossRef]
  31. Haripriya, M.; Manimekala, T.; Dharmalingam, G.; Minakshi, M.; Sivasubramanian, R. Asymmetric Supercapacitors Based on ZnCo2O4 Nanohexagons and Orange Peel Derived Activated Carbon Electrodes. Chem.–Asian J. 2024, 19, e202400202. [Google Scholar] [CrossRef]
  32. Vasudevan, S.; Tharani, D.S.; Manickam, M.; Sivasubramanian, R. A sol–gel derived LaCoO3 perovskite as an electrocatalyst for Al–air batteries. Dalton Trans 2024, 53, 3713–3721. [Google Scholar] [CrossRef] [PubMed]
  33. Xia, L.; Zhang, Q.; Wu, C.; Liu, Y.; Ding, M.; Ye, J.; Cheng, Y.; Jia, C. Graphene coated carbon felt as a high-performance electrode for all vanadium redox flow batteries. Surf. Coat. Technol. 2019, 358, 153–158. [Google Scholar] [CrossRef]
  34. Langner, J.; Bruns, M.; Dixon, D.; Nefedov, A.; Wöll, C.; Scheiba, F.; Ehrenberg, H.; Roth, C.; Melke, J. Surface properties and graphitization of polyacrylonitrile based fiber electrodes affecting the negative half-cell reaction in vanadium redox flow batteries. J. Power Sources 2016, 321, 210–218. [Google Scholar] [CrossRef]
  35. Su, J.; Zhao, Y.; Xi, J. Phosphorus-doped carbon nitride as powerful electrocatalyst for high-power vanadium flow battery. Electrochim. Acta 2018, 286, 22–28. [Google Scholar] [CrossRef]
  36. Cecchetti, M.; Casalegno, A.; Zago, M. Local potential measurement through reference electrodes in vanadium redox flow batteries: Evaluation of overpotentials and electrolytes imbalance. J. Power Sources 2018, 400, 218–224. [Google Scholar] [CrossRef]
  37. Wei, L.; Zhao, T.; Zhao, G.; An, L.; Zeng, L. A high-performance carbon nanoparticle-decorated graphite felt electrode for vanadium redox flow batteries. Appl. Energy 2016, 176, 74–79. [Google Scholar] [CrossRef]
  38. Xiong, Y.; Jin, L.; Yang, H.; Li, Y.; Hu, H. Insight into the aromatic ring structures of a low-rank coal by step-wise oxidation degradation. Fuel Process. Technol. 2020, 210, 106563. [Google Scholar] [CrossRef]
  39. Zeng, Y.; Zhou, X.; Zeng, L.; Yan, X.; Zhao, T. Performance enhancement of iron-chromium redox flow batteries by employing interdigitated flow fields. J. Power Sources 2016, 327, 258–264. [Google Scholar] [CrossRef]
Inventions 09 00098 g001
Figure 1. Preparation of Bi-Bio-GF-O electrode and application of ICRFB.
Figure 1. Preparation of Bi-Bio-GF-O electrode and application of ICRFB.
Inventions 09 00098 g001
Inventions 09 00098 g002
Figure 2. The single cell structure of ICRFB.
Figure 2. The single cell structure of ICRFB.
Inventions 09 00098 g002
Inventions 09 00098 g003
Figure 3. (a) CV curves of GF, Bio-GF-O, and different Bi-Bio-GFs at −0.8~0 V (b) CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O at −0.8~0 V (c) CV curves of GF, Bio-GF-O, and different Bi-Bio-GFs at 0~0.8 V (d) CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O at 0~0.8 V.
Figure 3. (a) CV curves of GF, Bio-GF-O, and different Bi-Bio-GFs at −0.8~0 V (b) CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O at −0.8~0 V (c) CV curves of GF, Bio-GF-O, and different Bi-Bio-GFs at 0~0.8 V (d) CV curves of GF, Bio-GF-O, and Bi-Bio-GF-O at 0~0.8 V.
Inventions 09 00098 g003
Inventions 09 00098 g004
Figure 4. EIS curve (before cycle test) of GF, Bio-GF-O, and Bi-Bio-GF-O at open circuit voltage.
Figure 4. EIS curve (before cycle test) of GF, Bio-GF-O, and Bi-Bio-GF-O at open circuit voltage.
Inventions 09 00098 g004
Inventions 09 00098 g005
Figure 5. (a) SEM image of GF, (b) SEM image of Bio-GF-O, (c) SEM image of Bi-Bio-GF-O at 1000 times (d) SEM image of GF, (e) SEM image of Bio-GF-O, (f) SEM image of Bi-Bio-GF-O at 5000 times. The scale bar is in the lower left corner of the figure. Specifically, its length is 10 μm (a–c) and 1 μm (d–f).
Figure 5. (a) SEM image of GF, (b) SEM image of Bio-GF-O, (c) SEM image of Bi-Bio-GF-O at 1000 times (d) SEM image of GF, (e) SEM image of Bio-GF-O, (f) SEM image of Bi-Bio-GF-O at 5000 times. The scale bar is in the lower left corner of the figure. Specifically, its length is 10 μm (a–c) and 1 μm (d–f).
Inventions 09 00098 g005
Inventions 09 00098 g006
Figure 6. (a) SEM image, (b) O, N, C mapping of GF. (c) SEM image, (d) O, N, C mapping of Bio-GF-O. (e) SEM image, (f) Bi, O, N, C mapping, (g) O mapping, (h) Bi mapping of Bi-Bio-GF-O. The scale bar is in the lower left corner of the figure. Specifically, its length is 10 μm.
Figure 6. (a) SEM image, (b) O, N, C mapping of GF. (c) SEM image, (d) O, N, C mapping of Bio-GF-O. (e) SEM image, (f) Bi, O, N, C mapping, (g) O mapping, (h) Bi mapping of Bi-Bio-GF-O. The scale bar is in the lower left corner of the figure. Specifically, its length is 10 μm.
Inventions 09 00098 g006
Inventions 09 00098 g007
Figure 7. (a) XPS survey spectra, (b) Raman spectra, (c) XRD patterns of GF, Bio-GF-O and Bi-Bio-GF-O.
Figure 7. (a) XPS survey spectra, (b) Raman spectra, (c) XRD patterns of GF, Bio-GF-O and Bi-Bio-GF-O.
Inventions 09 00098 g007
Inventions 09 00098 g008
Figure 8. (a) SCA of GF. (b) SCA of Bio-GF-O. (c) SCA of Bi-Bio-GF-O.
Figure 8. (a) SCA of GF. (b) SCA of Bio-GF-O. (c) SCA of Bi-Bio-GF-O.
Inventions 09 00098 g008
Inventions 09 00098 g009
Figure 9. (a) The charge/discharge voltage profiles. (b) Voltage efficiency, (c) Energy efficiency, (d) Coulombic efficiency of GF, Bio-GF-O and Bi-Bio-GF-O ICRFBs during gradient current density charging and discharging.
Figure 9. (a) The charge/discharge voltage profiles. (b) Voltage efficiency, (c) Energy efficiency, (d) Coulombic efficiency of GF, Bio-GF-O and Bi-Bio-GF-O ICRFBs during gradient current density charging and discharging.
Inventions 09 00098 g009
Inventions 09 00098 g010
Figure 10. (a) Charge capacity, (b) Discharge capacity of the four ICRFBs during cyclic charge and discharge.
Figure 10. (a) Charge capacity, (b) Discharge capacity of the four ICRFBs during cyclic charge and discharge.
Inventions 09 00098 g010
Inventions 09 00098 g011
Figure 11. (a) Coulombic efficiency, (b) Voltage efficiency, (c) Energy efficiency of the four ICRFBs during cyclic charge and discharge.
Figure 11. (a) Coulombic efficiency, (b) Voltage efficiency, (c) Energy efficiency of the four ICRFBs during cyclic charge and discharge.
Inventions 09 00098 g011
Table 1. Performance of single cell ICRFB with various electrode compositions.
Table 1. Performance of single cell ICRFB with various electrode compositions.
ElectrodesCE (%)VE (%)EE (%)Charge/Discharge Capacity (mAh)
GF91.0471.8065.37253/208
Bio-GF-O96.4278.5075.69631/601
Bio-GF-O cathode &
Bi-Bio-GF-O anode		97.8385.2183.36584/534
Table 2. Parameters of CV curves for GF, Bio-GF-O, and different Bi-Bio-GFs at −0.8~0 V.
Table 2. Parameters of CV curves for GF, Bio-GF-O, and different Bi-Bio-GFs at −0.8~0 V.
Electrodes∆Ep (V)Ipa (mA)Ipc (mA)Ipa/Ipc
GF0.29656.2−56.6−0.992
Bio-GF-O/106.7//
Bi -Bio-GF-0.1M0.01337.9−95.0−0.399
Bi -Bio-GF-0.2M0.119119.5−148.9−0.803
Bi -Bio-GF-0.3M0.162124.2−180.6−0.688
Table 3. Parameters of EIS curves for GF, Bio-GF-O at open circuit voltage.
Table 3. Parameters of EIS curves for GF, Bio-GF-O at open circuit voltage.
ElectrodesRs (Ω)CPE (F)Rct (Ω)W0 (F)
GF6.1551.245 × 10−52.9619.416 × 10−2
Bio-GF-O4.4361.230 × 10−52.4222.454 × 10−1
Bi-Bio-GF-O2.4611.203 × 10−40.5708.872 × 10−2
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wu, S.; Zhu, H.; Bai, E.; Xu, C.; Xie, X.; Sun, C. Composite Modified Graphite Felt Anode for Iron–Chromium Redox Flow Battery. Inventions 2024, 9, 98. https://doi.org/10.3390/inventions9050098

AMA Style

Wu S, Zhu H, Bai E, Xu C, Xie X, Sun C. Composite Modified Graphite Felt Anode for Iron–Chromium Redox Flow Battery. Inventions. 2024; 9(5):98. https://doi.org/10.3390/inventions9050098

Chicago/Turabian Style

Wu, Sheng, Haotian Zhu, Enrui Bai, Chongyang Xu, Xiaoyin Xie, and Chuanyu Sun. 2024. "Composite Modified Graphite Felt Anode for Iron–Chromium Redox Flow Battery" Inventions 9, no. 5: 98. https://doi.org/10.3390/inventions9050098

APA Style

Wu, S., Zhu, H., Bai, E., Xu, C., Xie, X., & Sun, C. (2024). Composite Modified Graphite Felt Anode for Iron–Chromium Redox Flow Battery. Inventions, 9(5), 98. https://doi.org/10.3390/inventions9050098

Article Metrics

Back to TopTop