Polypyrrole-coated hierarchical porous composites nanoarchitectures for advanced solid-state flexible hybrid devices

As a storage battery suitable for leveling output of renewable energy, a redox flow battery with features such as long life and high safety has attracted attention. Since a redox flow battery uses a pump for the electrolyte circulation, it is necessary to supply the electrolyte with keeping the pressure drop as small as possible. Mench et al. reported that the interdigitated design (IDD) of electrolyte flow fields can maintain lower pressure drop than the conventionally-used flow through design (FTD) (1). Some studies have reported that carbon paper electrodes show better cell performance with the serpentine design of electrolyte flow fields than carbon felt electrodes that have been widely used until now (2). In this study, by using the carbon felt electrode, I-V performance and pressure loss with two kinds of flow designs, the IDD and the FTD, were compared, and the influence of the flow designs on the cell performance was examined. In addition, the performance for the IDD was also compared with that using carbon paper electrode, and the influence of type of porous carbon electrode was investigated in the IDD. Furthermore, we tried to improve the cell performance by applying the combination of carbon felt and carbon paper electrodes with the IDD. Figure 1 shows schematic views of the FTD and the IDD. In the FTD, the electrolyte flows uniformly through the porous electrode, as shown in Figure 1(a), and reacts on the surface of carbon electrode. In the IDD, the electrolyte flows from the inlet flow path of the channel, dives into the porous electrode, and exits to the outlet flow path, as in Figures 1(b) and (c). In this study, two kinds of electrodes, carbon felt and carbon paper, were used, and the reaction area was 21.6cm2 (4.6cm × 4.7cm). The carbon felt with a thickness of 3.1mm was compressed to 2.0 mm, and four carbon papers with the thickness of 1.1mm (0.28mm × 4) were compressed to 0.85mm. Figure 2 shows the I-V characteristics with the FTD and the IDD. The SOCs are 40 and 80%, and the flow rate is 30mL/min. It was confirmed that the performance with the FTD is higher than that with the IDD with the same flow rate. Figure 3 shows the relationship between the pressure drop and the flow rate of the electrolyte using various flow fields. In the case of the FTD, the pressure loss for the carbon paper electrode with lower porosity becomes larger than that of the carbon felt electrode. In the case of the IDD, small pressure loss can be maintained regardless of the type of electrode. The IDD is suitable for upsizing because of small pressure loss, but the I-V characteristics with the IDD is inferior to that with the FTD with the same flow rate of the electrolyte, as described above. Therefore, it is necessary to improve the I-V performance of the IDD with keeping the pressure loss low. In this study, we tried to optimize the electrode structure by combining the two types of electrodes having opposite properties. The carbon paper electrode having a low porosity has an advantage that the surface area can be secured even if it is thin. On the other hand, the carbon felt electrode having a small pressure loss has an advantage that it can suppress the pump power. Figure 4 shows results of the I-V measurement with the IDD using four types of electrode structures. In addition to the previous structures, the combination of carbon paper and felt, and two 4.0mm thick two carbon felts are compared. In the combination, one carbon paper was stacked on one carbon felt electrode at the current collector side. In the case with the combination structure, the I-V performance is improved compared to that with the carbon felt electrode. The pressure loss can be also maintained small. This suggests that combination of various types of carbon electrode is effective to improve the cell performance with the ID. Detailed investigations on the mechanism and further improvements of the cell performance with the IDD will be conducted. Reference (1) M. M. Mench, et al. , Journal of Power Sources, 302, 369 (2016). (2) T. J. Schmidt, et al. , ECS Trans., 57, 535 (2018). Figure 1

Single fibre electrode measurements – A versatile strategy for assessing the non-uniform kinetics at carbon felt electrodes

Cerium, a unique rare earth element, possesses a relatively high abundance, low cost, and high redox voltage, making it an attractive candidate for redox flow batteries. However, the sluggish kinetics and corrosion nature of the Ce3+/Ce4+ electrolyte result in overpotential and degradation of carbon felt (CF) electrodes, which hinders the development of cerium‐based flow batteries. Therefore, it is essential to develop an electrode with high catalytic activity and corrosion resistance to the Ce3+/Ce4+ electrolyte. Herein, a TiC/TiO2 coated carbon felt (TiC/TiO2‐CF) electrode is proposed. Remarkably, the TiC/TiO2 coating effectively minimizes the exposure of the CF to the highly corrosive cerium electrolyte, consequently enhancing the electrode's corrosion resistance. Additionally, X‐ray photoelectron spectroscopy and high‐resolution transmission electron microscopy characterizations reveal the formation of a heterojunction between TiC and TiO2, which significantly enhances the redox reaction kinetics of the Ce3+/Ce4+ redox couple. Eventually, the practical application of TiC/TiO2‐CF catalytic electrode in a Ce–Fe flow battery is demonstrated. This study sheds light on the synthesis conditions of the TiC/TiO2‐CF electrode, elucidates its heterojunction structure, and presents a novel Ce–Fe flow battery system.

Polysulfide/ferricyanide flow batteries (S/Fe RFBs), with the advantages of abundant earth reservation, low cost, high safety, and environmental friendliness, have attracted significant interest and demonstrated noteworthy potential for practical applications. However, the battery performance, including the energy efficiency (EE), voltage efficiency (VE), and power density of the S/Fe RFBs, remains low owing to the slow redox kinetics of polysulfide ions. To address these concerns, WS 2 was selected as the booster and deposited on a commercial carbon felt electrode (WS 2 –CF) to stimulate the redox reactions of polysulfide ions. With better hydrophilicity and smaller charge‐transfer resistance, WS 2 –CF exhibits enhanced electrochemical activity toward polysulfide redox reactions. Consequently, the battery performance of S/Fe RFB with WS 2 –CF as the anode has been improved, with EE of 84%, VE of 84%, and a peak power density of 175.7 mW·cm −2 , which are all higher than the cell only with the bare carbon felt (CF) as electrodes (76%, 77%, and 155.8 mW·cm −2 , respectively). Furthermore, the cycling life of the S/Fe RFB with WS 2 –CF has been prolonged to 2200 cycles with a capacity retention of 96% at 40 mA·cm −2 because of the good stability of WS 2 –CF as the anode. Contrarily, under the same conditions, the S/Fe RFB without WS 2 –CF terminated after 1500 cycles with a fast capacity decay. The successful utilization of WS 2 as a booster on an electrode provides an efficient strategy for obtaining advanced S/Fe RFBs for practical applications.

We present a study of vanadium electrochemistry in porous electrodes with and without sodium dodecyl sulfate (SDS) additives present. Carbon paper and felt electrodes are compared. Carbon felt electrodes are the de facto standard in flow batteries. There are significant differences in the electronic conductivity of these media. The carbon paper has a much higher conductivity than the felt, which has an electronic conductivity similar to the ionic conductivity of the electrolytes used. The latter fact motivates an extension of available theory for polarization curve fitting to explicitly include both electronic and ionic contributions in the porous electrode. We demonstrate agreement between our model and an existing model evaluated at the limit where electrode conductivity is significantly greater than electrolyte conductivity. Our model uses the product of the electrode surface area per volume ratio and the heterogeneous electron transfer rate constant, and the Damköhler number as fitting parameters for carbon paper and felt electrodes. We discuss the effect of SDS additives on kinetics in the context of the cation hydration shell for the vanadium ions. To this point, we apply Marcus-Hush-Chidsey formalism to our porous electrode model to quantify reorganization energies obtained through polarization curve fitting. This work was supported as part of the Breakthrough Electrolytes for Energy Storage (BEES2), an Energy Frontier Research Center funded by the United States. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0019409.

Ammonia gas treatments of varying temperature were performed on carbon felt electrodes in this study. Their physical and electrochemical properties were investigated.Carbon felt electrodes are often used in vanadium redox flow batteries (VRFBs). Without processing, carbon felt has poor wettability which frustrates electrochemical activity. This material must be modified to improve performance, which has been historically accomplished with thermal treatments ostensibly to promote oxygen functional groups, although this has been the subject of debate as morphological impacts have also been observed. [1-3] Many attempts have been made to improve performance of carbon felt in VRFBs, but some of the more successful modifications have resulted in an increase in the specific surface area. [4-6] Previous research at the University of Tennessee Knoxville suggests edge sites play a role in improving performance. Preliminary experiments on carbon felt performed by this lab with ammonia at high temperatures have shown promising results. Additional experiments were performed at 900°C by varying length of treatment time, finding four hours to be optimal. [3] New experiments have been done to investigate the kinetic effects of temperature.For these experiments, commercially available carbon felts (SIGRACELL® GFD3 by SGL Carbon, Meitingen, Germany) were modified by exposure to flowing ammonia gas through a furnace at (500°C, 700°C, 900°C, and 1100°C) varying temperatures for four hours. The samples were tested in a single-cell flow battery using cyclic voltammetry (CV), polarization curves, and electrochemical impedance spectroscopy (EIS). This treatment results in a significant increase in electrochemical surface area and performance.The physical properties were characterized using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and Raman spectroscopy. This was done to study the mechanism and kinetic effects of ammonia on the carbon felt material as temperature increases during the treatment itself. Samples treated at the highest temperatures exhibited a notable loss of mass, which is observed in the SEM images in Figure 1. This resulted in a significant increase in edge sites and active surface area, along with a substantial increase in cell performance, which was achieved with the ammonia-modified carbon felts described in this work, with over three times the current density at 80% voltage efficiency compared to untreated felt. Sun, B. and M. Skyllas-Kazacos, Modification of graphite electrode materials for vanadium redox flow battery application—I. Thermal treatment.Electrochimica Acta, 1992. 37(7): p. 1253-1260.Pezeshki, A.M., "Impedance-Resolved Performance and Durability in Redox Flow Batteries. " PhD diss., University of Tennessee, 2016.Gass, K., High Performance Vanadium Redox Flow Battery Electrodes. [manuscript under submission], 2021.Lu, W., et al., High-performance porous uncharged membranes for vanadium flow battery applications created by tuning cohesive and swelling forces.Energy & Environmental Science, 2016. 9(7): p. 2319-2325.Zhou, X.L., et al., A high-performance dual-scale porous electrode for vanadium redox flow batteries.Journal of Power Sources, 2016. 325: p. 329-336.Wei, L., et al., Highly catalytic hollow Ti3C2Tx MXene spheres decorated graphite felt electrode for vanadium redox flow batteries.Energy Storage Materials, 2020. 25: p. 885-892. Figure 1. SEM images at 30,000X magnification of carbon felt electrodes: a) untreated, b) 4 hours NH3 treated at 500°C, c) 4 hours NH3 treated at 700°C, d) 4 hours NH3 treated at 1100°C. Scale was identical for all micrographs Figure 1

Vanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO2+/VO2 + and V2+/V3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm−2, which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm−2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%.

A high-performance carbon felt electrode for all-vanadium redox flow battery (VRFB) systems is prepared via low-temperature atmospheric pressure plasma treatment in air to improve the hydrophilicity and surface area of bare carbon felt of polyacrylonitrile and increase the contact potential between vanadium ions, so as to reduce the overpotential generated by the electrochemical reaction gap. Brunauer-Emmett-Teller (BET) surface area of the modified carbon felt is, significantly, five times higher than that of the pristine felt. The modified carbon felt exhibits higher energy efficiency (EE) and voltage efficiency (VE) in a single cell VRFB test at the constant current density of 160 mA cm−2, and also maintains good performance at low temperatures. Moreover, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis results show that the resistance between electrolyte and carbon felt electrode decreased. As a result, owing to the increased reactivity of the vanadium ion on the treated carbon felt, the efficiency of the VRFB with the plasma-modified carbon felt is much higher and demonstrates better capacity under a 100-cycle constant current charge-discharge test.

Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells

Vanadium acetylacetonate [(V(acac)3] is being used as model redox species for the study of non-aqueous redox flow battery (NAqRFB). The redox species present reversible redox reactions for both V+2/V+3 (i.e. the negolyte ca. -1.75 V vs Ag/Ag+) and V+3/V+4 (i.e. posolyte ca. 0.45 V vs Ag/Ag+). The same discharge state V+3 of this electrolyte can be used on both sides of the half cell. The latter and the fact it dissolves easily in an organic solvent, besides its commercial availability at a fair price makes it a promising candidate for future commercial versions of non-aqueous redox flow batteries.Nonetheless, merits are usually accompanied by some demerits. Vanadium has four valency states starting from V+2 to V+5; for the V-NAqRFB only three oxidations states are desirable V+2, V3+, and V4+ thus the formation of V5+ is unwanted. To avoid this oxidation state, typically the battery open circuit potential is kept below 2.27 V. Another downside of this electrolyte refers to its sensitivity towards a moisture/oxygen-enriched environment. The presence of moisture/oxygen in the environment triggers a non-reversible reaction which leads to the formation of VO(acac)2 at the positive electrode. VO(acac)2 irreversible formation causes rapid battery capacity loss due to its parasitic and increased concentration on the electrolyte. Therefore, the electrolyte must be kept in an inert atmosphere such as dry nitrogen. Nonetheless, it was observed that even by maintaining a strictly controlled saturation of the electrolyte with inert gas, the stability of the batteries was still rather negligible. Components such as the electrodes (carbon felts, CF) could also represent a major source for the oxygen-enriched surface. Many oxidation pre-treatments such as chemical exfoliation (H2SO4) and thermal oxidation under airflow at 450 °C are commonly performed on CFs to increase their wettability and performance in aqueous all vanadium redox flow cells. Nonetheless, these kind of pre-treatments might not be suitable for the system here in the study due to the beforehand mentioned reasons. The latter served as the main motivation for this study.Initially, cyclic voltammetry (CV) was performed using a three-electrode configuration cell and a glassy carbon as the working electrode. The addition of few DI water drop s (0.005% or 50 ppm) and the electrolyte saturation with O2 caused the immediate disappearance of redox species peaks (V2+/V3+ redox couple) and the appearance of additional peaks which indicated a strong influence for the reaction shift towards the formation of parasitic VO(acac)2. V+3/V+4 redox couple was also degraded significantly after 0.05% (500 ppm). Thus, keeping a dry and oxygen-free atmosphere is of utmost importance for maintaining a stable battery operation. Interestingly, it was found that the reversibility of species on top of the WE depends on the exposure time to oxygen. The effect is negligible up to 20 minutes of oxygen saturation but extremely critical over 4 hours as even upon saturating the electrolyte with an inert gas again, the adsorption of the active species was less effective and non-reversible (much lower anodic current peaks and much wider apart oxidation/reduction peaks).The carbon felt electrodes used for the aqueous vanadium redox flow battery, even with no treatment have already oxygen functional groups which serve as the reaction sites for the vanadium redox reaction in the aqueous electrolyte. Hydrogen is known as a powerful reducing agent and so might be employed to remove these oxygen functionalities. Therefore, the impact of different pre-treatments on the carbon felts morphology and performance for the V-NAqRFB was assessed. Mainly, the effect of solely adding a pre-oxygen heat treatment (referred to as PO) to a pristine carbon felt from SGL (4.6GFD), a hydrogen treatment (PH), and a combination of oxygen followed by a hydrogen treatment (POH) to completely remove all previously formed heteroatoms, were tested, each for 10 hours at 400 °C. For comparison purposes, a pristine electrode (P) was also used. Then upon, the electrochemical surface area of each CF was pre-screened by leading CV measurements and the hydrogen treatment followed by an oxygen heat treatment (POH) appeared to be the best solution to increase the number of active sites on the CF structure. Morphological characterization was performed on all electrodes using SEM and FTIR. Later, these CFs were used in NAqRFB-cell for battery cycling, impedance spectroscopy, and polarization measurements. The co-relation of the results highlighted that POH is performing better in the V(acac)3 based non-aqueous electrolyte. Besides, solely conducting a pre-oxygen heat treatment on the CFs condemns the performance of the battery, as expected. The results are shown in the attached figure. Figure 1

Electro-conductive carbon felt (CF) material is composed by bonding together different lengths of carbon filaments resulting in a porous structure with a significant internal surface that facilitates enhanced electrochemical reactions. Owing to its excellent electrical properties, CF is found in numerous electrochemical applications, such as electrodes in redox flow batteries, fuel cells, and electrochemical desalination apparatus. CF electro-conductivity mostly arises from the close contact between the surface of two electrodes and the long carbon fibers located between them. Electrical conductivity can be improved by a moderate pressing of the CF between conducting electrodes. There exist large amounts of experimental data regarding CF electro-conductivity. However, there is a lack of analytical theoretical models explaining the CF electrical characteristics and the effects of compression. Moreover, CF electrodes in electrochemical cells are immersed in different electrolytes that affect the interconnections of fibers and their contacts with electrodes, which in turn influence conductivity. In this paper, we investigated both the role of CF compression, as well as the impact of electrolyte characteristics on electro-conductivity. The article presents results of measurements, mathematical analysis of CF electrical properties, and a theoretical analytical explanation of the CF electrical conductivity which was done by a stochastic description of carbon filaments disposition inside a CF frame.

Traditional vanadium batteries use pure sulfuric acid as electrolyte, but H2SO4 does not absorb enough vanadium ions to make the electrolyte an efficient energy source. This study investigates the effect of hydroxylation process on electrochemical and operational properties of carbon felt electrode in VOSO4 solution with an optimized supporting electrolyte (a mixture of six parts HCl and 2.5 parts H2SO4). Carbon felt electrode was hydroxylated with mixed acids of H2SO4 and HNO3 in a stainless steel autoclave for 6 h. Then thermal treatment of electrode was performed at 400 oC for 5h. Obtained results of cyclic voltammograms showed that when the carbon felt was hydroxylated, both oxidation and reduction peak currents were increased remarkably and the peak potential separation is decreased from 356 mV to 246 mV, suggesting that the electrochemical activity and the kinetic reversibility on HCF electrode were improved compared to the pristine one. According to results of electrochemical impedance spectra, charge transfer resistance (Rct) was calculated to be 648 Ω for pristine carbon felt. The obtained Rct at hydroxylated electrode (176 Ω) shows a decrease of about 73 % in Rct. Charge-discharge profiles of two cells assembled with the pristine carbon felt (cell A), and hydroxylated carbon felt (cell B) showed that energy, voltage and coulombic efficiencies were significantly improved by using the hydroxylated electrodes inside the cell of vanadium redox flow battery.

Nitrogen (N) and phosphorous (P) co-doped carbon felt is proposed as a promising electrode for enhancing VO2+/VO2 + redox reactions. Nitrogen and phosphorous can be simultaneously incorporated onto the carbon felt through straightforward synthesis method using aniline and triphenylphosphine as N and P source. The successful incorporation of nitrogen and phosphorous functional groups onto the carbon felt surface can be confirmed by X-ray photoelectron spectroscopy analysis. Compared to the carbon felt electrode doped solely with nitrogen or phosphorous functional groups on its surface, the electrochemical activity of the proposed carbon felt electrode towards slow redox reactions of VO2+/VO2 + can be greatly enhanced owing to the synergistic effects of the nitrogen and phosphorous functional groups. Consequently, VRFB cell assembled with N, P co-doped carbon felt electrode exhibits much stable cycle performance accompanied by highly improved energy efficiencies of 84.94 and 84.33% in the 1st and 50th cycle, respectively.

Carbon felt electrodes are used as electrode material in VRFB. The main reasons to use carbon felt electrodes are their corrosion resistance in acidic electrolyte, high overpotential towards hydrogen evolution reaction and low material costs. Different origins of degradation can be related to dynamic cycling conditions or to possible side reactions. Chemical degradation or aging on the other hand can be caused by simple contact with the electrolyte. The static aging and the dynamic degradation of heat-treated carbon felt electrodes in all-Vanadium redox flow battery systems were investigated by different electrochemical and analytical methods. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to determine the performance loss of the carbon-based electrodes. Different characterization methods, such as scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were applied to study cause and effects of material’s degradation. Chemical aging was found to take place during the first 6 days of mere contact with the electrolyte (1.6 M V3+/4+, 2 M H2SO4, 0.05 M H3PO4). Both, the charge transfer resistance and the diffusion resistance increased with time. Electrochemical degradation was observed for 50 charge and discharge cycles of a 10 cm2 cell with flow-through design and 100 mL of electrolyte. The half-cell potentials shifted towards more negative potentials with an increasing amount of cycles. Chemical aging and electrochemical degradation have a strong impact on the negative half-cell. XPS and SEM reveal that the main reason for the observed performance loss is a decrease of electrochemically active surface area (ECSA) due to the oxidation of the carbon felt to CO and CO2. The durability of the electrodes was increased by introducing bismuth coated electrodes in the negative half-cell. Bismuth was deposited on the carbon felt with a pulse deposition protocol out of an aqueous solution. Charge and discharge experiments exhibited a more stable performance compared to pure carbon felt electrodes. The half-cell potentials remained constant during cycling but the overall cell resistance was higher, because the electrical conductivity of bismuth is lower compared to graphitic carbon.

Rapid development of portable electronic devices promotes the demand for high performance and durability of micro power sources. As a new kind of portable power sources, microfluidic fuel cells (MFFC) utilize the parallel laminar flow to separate the fuel and the oxidant naturally without a proton exchange membrane (PEM) in traditional PEM fuel cells. As a result, a series of problems related to the PEM such as high cost, complicated water management and degradation of membrane can be eliminated. Therefore, microfluidic fuel cells have been paid more and more attention recently and are gradually becoming one of the promising micro portable power sources. Previous studies on microfluidic fuel cells showed that due to a relatively high oxygen concentration and diffusivity of oxygen in the air, using an air-breathing cathode could alleviate the oxygen transfer limitation in traditional microfluidic fuel cells which used dissolved oxygen as oxidant. As a result, the performance could be improved by the air-breathing cathode. However, the mass transfer at the anode still limits the cell performance. To further enhance the microfluidic fuel cell performance, a porous flow-through anode could be used to achieve the convective transport of the fuel to the electrode, resulting in reduction of the concentration boundary layer thickness at the planar electrode surface. However, in most studies of microfluidic fuel cells with porous flow-through electrodes, the two-dimensional porous carbon paper was used at the anode. As a common electrode material, the three-dimensional porous carbon felt with large porosity and specific surface area is expected to further improve the microfluidic fuel cell performance. In this study, an air-breathing microfluidic fuel cell with a carbon felt flow-through anode was fabricated and compared with the microfluidic fuel cell with a carbon paper anode. The micro morphology of electrode surface was characterized by a scanning electron microscopy (SEM). The electrochemical and cell performances were tested in acidic and alkaline conditions. The mass transport and performance characteristics of the microfluidic fuel cell with the carbon felt flow-through anode were further studied in alkaline condition. The experimental results showed that catalysts were better-distributed on the carbon felt electrode surface than that on the carbon paper electrode surface. The electrochemical performance of carbon felt electrode was superior to carbon paper electrode both in acidic and alkaline conditions because of its inherent three-dimensional porous structure. In acidic condition, the optimal power density and maximum current density of the microfluidic fuel cell with carbon felt anode were 1.8 and 2.8 times than that of the microfluidic fuel cell with carbon paper anode density, respectively. In alkaline condition, the optimal power density and the maximum current density of microfluidic fuel cell with carbon felt anode were 35.1 mW/cm2 and 192.9 mA/cm2, which were 5.2 and 7 times than that of the microfluidic fuel cell with carbon paper anode. Moreover, the cell performance under alkaline condition increased with an increase in the fuel and electrolyte flow rate and then remained almost the same, while it increased at first and then decreased as the fuel concentration, electrolyte and supporting electrolyte concentration increased.