Anodic Charge Transfer Resistance Research Articles

Impact of biocatalytic behavior of Shewanella sp. through electron transfer processes on effective treatment of beer brewing wastewater in a microbial fuel cell and power generation

AbstractThis study examines the performance of a microbial fuel cell (MFC) utilizing Shewanella bacteria through electrochemical impedance spectroscopy (EIS). Exo‐electrogen bacteria are key agents in an MFC. Shewanella sp. as a common exo‐electrogen bacteria can transfer electrons from the cell surface through different electron transfer mechanisms. In this work, EIS was used to probe the effects of biofilms of Shewanella sp. and the solution of 10% V/V Shewanella on the MFC performance. This research investigates the effects of both microbial biofilms and Shewanella bacterial solutions on MFC efficacy. Findings revealed that biofilm formation on the anode surface significantly reduces anode charge transfer resistance, thereby enhancing power generation. Notably, a 10% Shewanella solution resulted in a 25% higher power density compared to the biofilm. Furthermore, the MFC demonstrated up to 80% chemical oxygen demand removal efficiency in treating brewery wastewater. The study underscores the viability of Shewanella bacterial solutions as an efficient alternative to biofilms, emphasizing their role in improving MFC performance and wastewater treatment efficiency.

Multiwalled-Carbon-Nanotube-Modified Li2ZnTi3O8 as Anode with Improved Cycling Stability and Rate Capability for Lithium-Ion Batteries

Due to its better electronic conductivity and larger lithium intercalation capacity, a multiwalled-carbon-nanotube (MWCNT)-modified Li2ZnTi3O8 (LZTO) has significant potential for use as an anode material for Li-ion batteries. The rapid and affordable ball-mill-aided solid state approach is used to synthesize LZTO with MWCNT-modified Li2ZnTi3O8 (LZTO@MWCNTs). Electrochemical performance tests of the anode material were carried out using cyclic voltammetry (CV), galvanostatic charge-discharge measurement, and electrochemical impedance spectroscopy (EIS). The CV experiments reveal that the LZTO@MWCNT electrode has a lower anodic and cathodic peak potential difference (0.184 V) than the LZTO electrode (0.211 V) and LZTO@MWCNT electrode has better electrochemical reversibility than that of pristine electrode after five cycles utilizing the same procedure. LZTO@ MWCNTs anode material has a higher charge-discharge capacity than LZTO anode material at 0.1–5 C rates. After 100 cycles, the initial discharge capacities of LZTO@MWCNT electrode are 227 and 142 mAh g−1 at the 1C–5C rate, respectively, whereas the initial discharge capacities of LZTO electrode are only144 and 28 mAh g−1 in the same condition. The charge transfer and SEI resistance of the LZTO anode are 19.31 and 62.74 ohms, respectively, after 30 cycles at 1C, according to the EIS data. Additionally, the values for the LZTO@MWCNTs anode are 7.93 and 12.06 ohms for charge transfer and SEI resistance, respectively.

Enhanced bioelectricity generation in thermophilic microbial fuel cell with lignocellulose as an electron donor by resazurin-mediated electron transfer

Microbial fuel cell (MFC) with lignocellulose as an electron donor is considered a sustainable biorefinery. However, low lignocellulose degradation and energy output restrict the scale of application. Herein, the extracellular electron transfer (EET) capacity of Acetivibrio thermocellus DSM 1313 with lignocellulose as substrate was shown to be mediated by the self-produced flavin, and its intracellular electron transfer went through the whole respiratory chain. Thermophilic MFC with resazurin exhibited an increase in the open circuit voltage by 37.78%, and a 2.60 folds increase in power density of 77.85 mW/m2, respectively. Differential pulse voltammetry and electrochemical impedance spectroscopy analysis indicated that resazurin decreased the solution and anode charge transfer resistance, and enhanced the extracellular electrochemical activity. Furthermore, resazurin resulted in a lower redox potential, allowing preferential electron transfer to resazurin rather than flavin. This research establishes a resazurin-mediated thermophilic MFC with lignocellulose as substrate, which provides novel idea on the biomass refinery.

A Study on Effect of Ionomer Content on Catalyst Ink Property and PEM Water Electrolyzer Performance

Producing hydrogen from water electrolysis with renewable electricity is essential for a carbon-free and environment-friendly economy. Proton exchange membrane (PEM) water electrolysis has advantages over other types of water electrolysis technologies with respect to compact system, high purity H2, high current density operation, better safety and reliability etc. Catalyst coated membrane (CCM) is the core of the membrane electrode assembly (MEA) and PEM water electrolyzer [1]. The CCMs are prepared by depositing catalyst inks onto the polymer electrolyte membrane. The composition of the catalyst inks plays an important role in determining the CCM and PEMWE performance.Catalyst ink is prepared from catalyst, ionomer and solvent. Commonly used is IrOx as catalyst, Nafion solution as ionomer (binder and proton conductivity path), and a mixture of organic solvent and water as solvent. One of the key parameters determining the CCM performance is the ionomer content in the catalyst layer.A wide range of ionomer content was reported in the literature, ranging from 2 to 30wt%. Xu et al. reported an optimal value of 25 wt% ionomer content using Ru0.7Ir0.3O2 [1]. The same Nafion content was used by Su et al. with IrO2 [2]. Bernt and Gasteiger found 11.6 wt% ionomer content showed the best performance with IrO2/TiO2 [3]. Ma et al. concluded that 30 wt% ionomer content was the best using Ir black [4]. P. Holzapfel et al [5] and S. Khandavali et al [6] used 2 wt% of ionomer content in their studies with IrO2. The large variability of the ionomer content indicates that there is a need on fundamental understanding of the effect of ionomer content for PEMWE applications.Catalyst ink properties may affect the catalyst layer structure and further PEMWE performance. S. Khandavali et al. studied the rheology and microstructure of the catalyst inks [7]. However, no further steps were presented such as fabricating CCMs using the ink and testing the CCMs in PEMWE. How the ink properties affect the catalyst layer structure, and further the PEMWE performance are not studied to our knowledge. In this work, a study on effect of ionomer content on catalyst ink property and further PEMWE performance is presented.In this work, catalyst ink was prepared from a mixture of isopropanol and water (1:1), Nafion solution, and IrO2. Inks with Nafion concentrations ranging from 1.0 wt. % to 20 wt. % were investigated. Ink properties such as viscosity, Zeta-potential and average particle size were studied. Properties of CCMs developed from the inks by directly coating the catalyst ink on Nafion membrane using ultrasonic spray were also investigated.The CCMs prepared from inks with 5.0, 7.0, 8.5 and 10% Nafion were tested in PEM water electrolyzer single cell at 80oC and ambient pressure. The CCM with the 7.0% Nafion shows the highest performance, while the 5.0% Nafion shows the lowest. The 8.5 and 10% Nafion CCMs show slightly lower performance than the 7.0%. The PEMWE was diagnosed with AC impedance. Fig. 1 presents the EIS spectra of the four CCMs in PEMWE obtained at 50 mA.cm-2. It can be seen that other than the CCM with 5.0% Nafion, all other 3 CCMs showed similar spectra. This is in agreement with the polarization curves. Impedance data fitting using the modified Randles equivalent circuit (solid lines in Fig. 1) shows that the 5.0% Nafion demonstrated the highest anode charge transfer resistance (oxygen evolution reaction (OER)) and the 7.0% shows the lowest value. Correlation of the ink properties with the PEMWE performance will be presented.References Xu, K. Scott, Int. J. Hydrogen Energy, 35 (2010) 12029 – 12037Su, B. J. Bladergroen, V. Linkov, S. Pasupathi, S. Ji, Int. J. Hydrogen Energy, 36 (2011) 1615081 – 15088Bernt, H. Gasteiger, J. Electrochem. Soc., 163 (11) (2016) F3179 – F3189Ma, S. Sui, Y. Zhai, Int. J. Hydrogen Energy, 34 (2009) 678 – 684Holzapfel, M. Bühler, C. V. Pham, F. Hegge, T. Böhm, D. McLaughlin, M. Breitwieser, S. Thiele, Electrochem. Commun. 110 (2020) 106640Buhler, P. Holzapfel, D. McLaughlin, S. Thiele, J. Electrochem. Soc., 166 (14) (2019) F1070 – F1078Khandavali, J. H. Park, N. N. Nariuki, S. F. Zaccarine, S. Pylypenko, D. J. Myers, M. Ulsh, S. A. Mauger, ACS Appl. Mater. Interfaces, 11 (2019) 45068 – 45079 Figure 1

Effects of 1-pyrrolidinedithiocarbamate and 2,5-dimercapto-1,3,4-thiadiazole on lead corrosion behavior in chloride medium

The adsorption and corrosion protection of 1-pyrrolidinedithiocarbamate (PDTC) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on bare Pb were investigated. Surface analyses revealed that for high concentration (i.e 10 mM), the organic molecules are strongly adsorbed on Pb surface. In 30 g.L-1 NaCl, Pb corrosion current was highly decreased and anodic passivation was very efficient. EIS measurements and simulations enabled to evaluate organic films thickness, anodic charge transfer resistance Rta and metal/film interface resistivity ρ0. Efficient Pb corrosion protection was confirmed. Results obtained from Young and power law models showed that EIS parameters are not much dependent on the chosen analytical expression.

Novel electrocatalysts for ethylene glycol oxidation based on functionalized phosphates of bimetals Mn/Ni: Morphology, crystallinity, and electrocatalytic performance

Novel bimetallic phosphates of Mn&Ni were investigated in this study as low-cost phosphate electrodes for ethylene glycol (EG) electrooxidation at high pH (2.0 M NaOH aqueous medium). The investigated electrocatalyst was chemically prepared by two preparation methods: reflux (MnNiPh-Re) and sol-gel (MnNiPh-SG). The as-designed MnNiPh-Re and MnNiPh-SG materials were physiochemically investigated by different techniques to describe the morphology and the impact of the preparation method on its morphology besides crystallinity and chemistry. Interestingly, the preparation method significantly affects the observed morphology. In the case of the sol-gel method, the MnNiPh-SG material has nanocubes characteristics with heterogeneous orientation and exhibits micro sheets in case of reflux strategy made up of super-thin sheets having nanoscale in their thickness and connected to create a different thickness sheet. The electrocatalytic performance of MnNiPh-Re and MnNiPh-SG as working electrodes for EG oxidation was investigated in terms of anodic current density and charge transfer resistance. Interestingly, the anodic current density of the suggested phosphate electrode was increased from 0.018 mA/cm2 to 5.73 mA/cm2 because of only introducing EG to the supporting electrolyte. The fabricated MnNiPh-SG has better EG oxidation if compared with MnNiPh-Re at different EG contents from 0.0 M to 1.0 M Additionally, the improvement of the charge transfer resistances and anodic current density confirms the successful electrocatalytic oxidation of EG over the presented MnNiPh-SG.

Simultaneous Anaerobic Ammonium Oxidation and Electricity Generation in Microbial Fuel Cell: Performance and Electrochemical Characteristics

In this study, a microbial fuel cell (MFC) that can achieve simultaneous anode anaerobic ammonium oxidation (anammox) and electricity generation (anode anammox MFC) by high-effective anammox bacteria fed with purely inorganic nitrogen media was constructed. As the influent concentrations of ammonium (NH4+-N) and nitrite (NO2−-N) gradually increased from 25 to 250 mg/L and 33–330 mg/L, the removal efficiencies of NH4+-N, NO2−-N and TN were over 90%, 90% and 80%, respectively, and the maximum volumetric nitrogen removal rate reached 3.01 ± 0.27 kgN/(m3·d). The maximum voltage and maximum power density were 225.48 ± 10.71 mV and 1308.23 ± 40.38 mW/m3, respectively. Substrate inhibition took place at high nitrogen concentrations (NH4+-N = 300 mg/L, NO2−-N = 396 mg/L). Electricity production performance significantly depended upon the nitrogen removal rate under different nitrogen concentrations. The reported low coulombic efficiency (CE, 4.09–5.99%) may be due to severe anodic polarization. The anode charge transfer resistance accounted for about 90% of the anode resistance. The anode process was the bottleneck for energy recovery and should be further optimized in anode anammox MFCs. The high nitrogen removal efficiency with certain electricity recovery potential in the MFCs suggested that anode anammox MFCs may be used in energy sustainable nitrogen-containing wastewater treatment.

Electrocatalysis of Methanol Oxidation in Alkaline Electrolytes over Novel Amorphous Fe/Ni Biphosphate Material Prepared by Different Techniques.

In this work, novel phosphate materials based on bimetallic character (Fe and Ni) were introduced by different chemical fabrication methods, the reflux method (FeNiP-R) and the sol–gel technique (FeNiP-S), and evaluated as non-precious electrodes for methanol electrooxidation in KOH electrolytes. The designed FeNiP-R and FeNiP-S samples were investigated using different characterization techniques, namely TEM, SEM, XPS, BET, DLS, and FT-IR, to describe the impact of the fabrication technique on the chemistry, morphology, and surface area. The characterization techniques indicate the successful fabrication of nanoscale-sized particles with higher agglomeration by the sol–gel technique compared with the reflux strategy. After that, the electrochemical efficiency of the fabricated FeNiP-R and FeNiP-S as electrodes for electrocatalytic methanol oxidation was studied through cyclic voltammetry (CV) at different methanol concentrations and scan rates in addition to impedance analysis and chronoamperometric techniques. From electrochemical analyses, a sharp improvement in the obtained current values was observed in both electrodes, FeNiP-R and FeNiP-S. During the MeOH electrooxidation over FeNiP-S, the current value was improved from 0.14 mA/cm2 at 0.402 V to 2.67 mA/cm2 at 0.619 V, which is around 109 times the current density value (0.0243 mA/cm2 at 0.62 V) found in the absence of MeOH. The designed FeNiP-R electrode showed an improved electrocatalytic character compared with FeNiP-S at different methanol concentrations up to 80 mmol/L. The enhancement of the anodic current density and charge transfer resistance indicates the methanol electrooxidation over the designed bimetallic Fe/Ni-phosphates.

2D layered structure-supported imidazole-based metal-organic framework for enhancing the power generation performance of microbial fuel cells

By self-assembly of imidazole-based ZIF67 in the two-dimensional (2D) MXene layer, A bio-compatible and bio-electrocatalytic anode combed of a metal organic framework (MOF) and MXene was created on the carbon felt by self-assembly of imidazole-based zeolite imidazolate framework-67 (ZIF67) in the 2D MXene layer. The maximum power density of the microbial fuel cells (MFCs) with Ti3C2-ZIF67/CF is 5.7 ± 0.12 W m−3 higher than that of Ti3C2/CF (4.07 ± 0.06 W m−3), ZIF67/CF (2.5 ± 0.04 W m−3) and CF (2.1 ± 0.1 W m−3). The charge transfer resistance of the composite anode (9.7 Ω) in the MFC is much lower than those of the Ti3C2 (15.3 Ω), ZIF67 (34.3 Ω) and CF (18.6 Ω) anodes. This enhancement was achieved because the composite combined the advantages of each component, including MXene's conductivity and hydrophilic and MOF's biocompatibility. Meanwhile, the composite anode accelerated the rate of the extracellular electron transfer (EET) between the anode and the microbes. Moreover, the high throughput sequencing technology reveals that the composite possessed good colonization of microorganisms and high biodiversity, with the microbial community playing an efficient synergistic role in facilitating electricity generation. Consequently, the Ti3C2-ZIF67 composite exhibited excellent bio-electrochemical performance as an anode material. This work not only expands the application of MXene in the bio-electrochemical system but also provides ideas for the development of MXene-based materials for MFCs.

Fast‐Charging Electrolyte: A Multiple Additives Strategy with 1,3,2‐Dioxathiolane 2,2‐Dioxide and Lithium Difluorophosphate for Commercial Graphite/LiFePO4 Pouch Battery

AbstractSafe fast‐charging lithium‐ion batteries (LIBs) can be achieved by using LiFePO4 electrode and optimized electrolyte for the rapid development of electric vehicles. However, conventional carbonate electrolyte suffers resistive solid electrolyte interphase (SEI) that hampering the fast‐charging for LIBs. Herein, a multiple additive strategy, the combination of 1,3,2‐Dioxathiolane 2,2‐dioxide (DTD) and lithium difluorophosphate (DFP), is proposed to optimize the electrode interface for graphite (Gr)/LiFePO4(LFP) pouch cells under fast‐charging. Combining DTD with DFP can significantly reduce the charge transfer resistance of anode and greatly extend the lifespan of cells with >2400 cycles at a 2 C rate, which is much better than that of baseline and single additive based electrolytes with <1000 cycles. Further mechanistic studies revealed that proper sulfurized and phosphatized species are involved in the SEI film, which stabilizes lithium carbonate in the middle of SEI to avoid being attacked by Lewis acids. Multiple additive strategies optimize the interfacial structure and provide valuable guidance for the development of safe fast‐charging engineering.

One-pot fabrication of N-doped hierarchical porous carbon derived from sponge for lithium-ion battery

As the consumption of battery materials and the waste from commercial polyurethane (PU) sponges continue to increase, this study introduces a way to recycle PU sponges and use them as a source of anode material in lithium-ion batteries (LIBs). The recycled PU sponge was carbonized to grant it electrical conductivity before applying it as an anode active material, and the particles of carbonized PU sponge (CPUS) were obtained through this process. The CPUS anode displays competitive electrochemical performance because the CPUS particles have hierarchical porous structures and also due to the presence of heteroatoms derived from the PU sponge skeleton. It shows a stable cycle, the capacity obtained is stable for 100 cycles with average capacities of 445 and 490 mAh/g at RT and 50 °C, respectively. Additionally, the charge transfer resistance of the CPUS anode is lower than that of the conventional graphite anode. These results indicate that CPUS is a promising anode material for use in the sustainable development of LIBs.

Effect of chloride ions on the corrosion behavior of carbon steel in an iron bacteria system.

Reclaimed water used as circulating cooling water can effectively relieve water stress, but the corrosion problem in it is very prominent. In particular, Cl− and iron bacteria (IB) are important influencing factors of corrosion behavior in a circulating water environment, and both of them often coexist in circulating water systems, so it is crucial to study their synergistic effects. This paper investigated the effect of Cl− on the corrosion behavior of carbon steel in the IB system by use of weight loss measurements, electro-chemistry and X-ray photoelectron spectroscopy (XPS). In the first 1–9 days of the experiment, the increase of Cl− concentration led to an increase of corrosion rate and a decrease of anode potential and charge transfer resistance at the interface. The corrosion rate of the 4ClIB condition reached 0.45 mm a−1 in the 1st day, which was 1.47 and 1.15 times that of 3ClIB and 1ClIB, and its anode potential was 22.6% and 33.8% lower than that of 3ClIB and 1ClIB. This indicates that a higher concentration of Cl− made the anodic reaction easier and the corrosion more severe. However, after 9 days, a decline in the corrosion rate was recorded at similarly high Cl− concentrations. On the 15th day, the corrosion rates for 3ClIB and 4ClIB were 7.0% and 15.6% lower compared to the 1ClIB condition. At this stage, the anode potential and film resistance had increased significantly, to become the dominant factors controlling the corrosion reaction. On the 15th day, the βa values of 1ClIB, 3ClIB and 4ClIB were 1.2, 1.5 and 1.7 times higher than those of the 1st day, and the highest Rb value of 1592.1 Ω cm2 was obtained for the 4ClIB condition, which was 1.9 times higher than that of Rct. In the early stage of corrosion, the surface of the carbon steel was enriched in Cl− due to their high concentration, and the Cl− could easily destroy the developing corrosion product film and promote the generation of Fe2+. At the same early stage, the growth of IB was enhanced, and the metabolism of IB was promoting local corrosion. However, in the later stage of corrosion, biofilms had an increasing effect on corrosion. A high concentration of Cl− accelerated biofilm growth and densified the corrosion product layer which subsequently hindered the anodic reaction and thus inhibited corrosion.

Silver nanoparticles conjugated MnFe-based Prussian blue analogue for voltammetric and impedimetric bioaptasensing of amifostine (ethyol).

A novel bioaptasensing-based electrochemical method for determination of amifostine (AMF) is proposed. The electrochemical aptasensor is based on modification of a glassy carbon electrode with a nanocomposite consisting of silver nanoparticles @ MnFe Prussian blue analogue nanospheres (AgNPs@MnFePBA NS), followed by immobilization of aptamer via Ag-N bonds (aptamer/AgNPs@MnFePBA NS/GCE). Experimental parameters including pH, incubation time, and aptamer concentrations were optimized. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetric (DPV) techniques were utilized to quantify AMF. The anodic peak current (∆Ipa) and charge transfer resistance (∆Rct) differences increase in the presence of AMF. Under the optimal conditions, using the redox probe, the electrochemical aptasensor exhibited linear ranges of 0.34-45nmolL-1 and 0.69-45nmolL-1 with LODs of 0.11nmolL-1 and 0.23nmolL-1 for EIS and DPV, respectively. The aptasensor was used to determine AMF in human plasma and in the presence of interfering species with recoveries and RSDs in the range 97.8-103.2% and 2.2-4.2%, respectively. Graphical abstract.

A Novel Reference Electrode for EIS Measurements in Sodium-Ion Batteries

Electrochemical impedance spectroscopy (EIS) is a powerful and non-invasive technique to gain valuable insights into the lithium or sodium intercalation kinetics via monitoring of the associated resistances.[1,2,3] To date, the measurement of symmetrical cells is the most commonly used approach to differentiate between the contributions of anode and cathode to the full-cell impedance. However, this method requires the reassembly of two identically treated anodes and cathodes from (aged) full-cells into a symmetric cell. Therefore, disassembly and reassembly of numerous cells is needed to perform state-of-charge (SOC) and/or state-of-life dependent EIS analyses. On the other hand, simultaneous in-situ measurement of the anode and cathode impedance can be achieved via incorporation of a micro-reference electrode (µ-RE) within the cell setup. Solchenbach et al. [4] and others [5] have shown such a µ-RE has to fulfill the following fundamental requirements: (a) its potential has to be stable within the measuring time of the impedance spectrum, (b) it has to be located centrally between anode and cathode, and (c) its cross-sectional dimensions have to be small compared to the distance between the electrodes. In this talk, we will introduce a novel micro-reference electrode for sodium-ion batteries based on an insulated tin wire with a diameter of ≈75 mm, further on referred to as Tin Wire Reference Electrode (TWRE), which is electrochemically alloyed with sodium after cell assembly from either the working or the counter electrode in order to receive a stable reference potential. This TWRE enables measuring the impedance response of sodium-based active materials in-situ during cycling. Since hard carbons (HCs) currently are the most promising candidates as anode materials for emerging sodium ion batteries (SIBs),[3,6] we will present data on the impedance evolution of a commercial HC anode as a function of SOC during sodiation and desodiation (see Figure 1). By comparing in-situ EIS data with impedance measurements performed using the symmetrical cell approach, we will prove that reliable impedance responses can be obtained in-situ. Figure 1a exemplary shows two in-situ impedance spectra of a HC anode in a Nyquist plot representation, one measured directly after cell assembly and sodiation of the tin wire (0% SOC, black) and the other measured after sodiation of the HC anode to 300 mAh/g (ca. 100% SOC, green). The former displays a transmission-line like behavior with a 45° line at high frequencies and a largely capacitive behavior at low frequencies. From the impedance response collected at close to 100% SOC, the HC anode charge transfer resistance (RCT) can be quantified by fitting the semi-circle in the Nyquist plot with an R/Q element. Figure 1b depicts the RCT-values of the HC anode measured at various state-of-charge levels during sodiation and desodiation, showing continuously decreasing RCT values upon Na intercalation. These findings will be compared to the magnitude and the evolution of the cell resistances for the lithiation of the same HC, and implications on the rate capability originating therefrom will be discussed.

Submission of “Electric power generation from sediment microbial fuel cells with graphite rod array anode”

Sediment microbial fuel cells (SMFCs) illustrated great potential for powering environmental sensors and bioremediation of sediments. In the present study, array anodes for SMFCs were fabricated with graphite rods as anode material and stainless steel plate as electric current collector to make it inconvenient to in situ settle down and not feasible for large-scale application. The results demonstrated that maximum power of 89.4 μW was obtained from three graphite rods, twice of 43.3 μW for two graphite rods. Electrochemical impedance spectroscopy revealed that three graphite rods resulted in anodic resistance of 61.2 Ω, relative to 76.0 Ω of two graphite rods. It was probably caused by the parallel connection of the graphite rods, as well as more biomass which could reduce the charge transfer resistance of the biofilm anode. The presently designed array configuration possesses the advantages of easy to enlarge the surface area, decrease in anodic resistance because of the parallel connection of each graphite rod, and convenience to berry into sediment by gravity. Therefore, the as prepared array node would be an effective method to fabricate large-scale SMFC and make it easy to in situ applicate in natural sediments. Keywords: Array anode, Electric power generation, Graphite rod, Sediment microbial fuel cell, Stainless steel plate

The construction of rod-like polypyrrole network on hard magnetic porous textile anodes for microbial fuel cells with ultra-high output power density

This study attempts to prompt the formation of microorganism films on flexible textile-based anodes and enhances the performance of living microorganisms by introducing magnetic properties to the anodes. A magnetic and electrically conductive anode for a microbial fuel cell is designed and fabricated by encapsulating uniformly dispersed SrFe12O19 nanoparticles into the poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers and forming a three-dimensional (3D) polypyrrole (PPy) network on the surface of flexible composite nanofiber based fabric. A dual-chamber MFC equipped with the magnetized anode shows a maximum power density of 3317 mW m−2, which is significantly larger than that of the non-magnetized anode (2471 mW m−2). This study demonstrates that the hard-magnetic anode providing an inherent magnetic field can greatly promote bio-electrochemical reaction rates of E. coli, and decrease the anode charge transfer resistance in a MFC system.

A Novel Sediment Microbial Fuel Cell Based Sensor for On‐Line and in situ Monitoring Copper Shock in Water

AbstractTo online and in situ monitor the heavy metal shock in water, a novel sediment microbial fuel cell based sensor was developed with anode being inserted into flooded soil and cathode submerged in overlaying water. Immediately after CuSO4 solutions were added into the overlaying water, the voltage signal generated by the sensor reached a peak and the increment from baseline voltage to peak voltage increased linearly with Cu2+ concentrations up to 160 mg L−1. After Cu2+ shock, charge transfer resistance (Rct) of anode and cathode was determined by using electrochemical impedance spectroscopy. Soil DNA and RNA was extracted and 16S rRNA and 16S rRNA gene of dominant exoelectrogenic bacteria (Geobacter and Clostridium) was quantified. Result showed that Cu2+ shock decreased cathodic charge transfer resistance (Rct) but did not affect anodic Rct. The addition of 320 mg L−1 Cu2+ significantly reduced abundance and activity of Geobacter and Clostridium in surface soil (0–3 cm in depth) but had no effect on exoelectrogenic bacteria in deeper soil. Moreover, baseline voltage was stable after Cu2+ shock. The result indicates that the sensor could online and in situ monitor Cu2+ shock which increased voltage signal by promoting cathodic reaction without dramatically inhibiting exoelectrogenic bacteria.

Effect of iron doped Zinc oxide nanoparticles coating in the anode on current generation in microbial electrochemical cells

In this study, Iron doped Zinc oxide (FeZnO) nanoparticles (NPs) were synthesized and coated on carbon paper electrode. The NPs and NPs coated electrode physicochemical, antimicrobial, antibiofilm traits and MFC performances were investigated. The characterization results depicted that FeZnO NPs were hexagonal rod shape with hexagonal phase structure in size of 90–100 nm have 59 m2/g surface area. Antibiofilm results indicates concentration of 5 mg/L of NPs shows 39 and 42% inhibition for Lysinibacillus Sphaericus and Bacillus safensis. The antibacterial assay confirmed that test organism was more resistant against NPs and coated electrode. Impedance analysis of NPs coated anode shown decreased anodic charge transfer resistance. The MFC results confirmed that power density was increased for NPs coated electrode (134.7 mW/m2) as compared to uncoated electrode. Cyclic Voltammetry analysis reported that exoelectrogenesis was promoted by NPs. The NPs coated and bare electrode COD removal efficiency were found to be 72.8 and 63.8%.

Experimental characterization of high-temperature proton exchange membrane fuel cells under CO- and methane-containing hydrogen-rich gases

The objective of this work is to study a high-temperature proton exchange membrane fuel cell using CO- and methane-containing hydrogen-rich gases because of the advantages of high operating temperature and the growing feasibility of using natural gases or methane as the sources of hydrogen-rich reformate gases. According to the experimental results, it is suggested that the fuel cell be operated at 180 °C under reformate gases with high CO concentrations to avoid not only a significant decrease in performance, but also severe potential oscillations. In addition, the anode oxidation reaction is more sensitive to the temperature than the cathode reduction reaction under CO-containing H2. On the other hand, the effects of methane in the reformate gas on the fuel cell can be ignored because the existence of methane causes neither a decrease in the cell performance nor an increase in the anodic charge transfer resistance. Thus, the CO concentration and operating temperature are still the two dominant parameters with regard to the cell performance under CO- and methane-containing hydrogen-rich gases.

Effect of Wall Boundary Layer Thickness on Power Performance of a Recirculation Microbial Fuel Cell

Hydrodynamic boundary layer is a significant phenomenon occurring in a flow through a bluff body, and this includes the flow motion and mass transfer. Thus, it could affect the biofilm formation and the mass transfer of substrates in microbial fuel cells (MFCs). Therefore, understanding the role of hydrodynamic boundary layer thicknesses in MFCs is truly important. In this study, three hydrodynamic boundary layers of thickness 1.6, 4.1, and 5 cm were applied to the recirculation mode membrane-less MFC to investigate the electricity production performance. The results showed that the thin hydrodynamic boundary could enhance the voltage output of MFC due to the strong shear rate effect. Thus, a maximum voltage of 22 mV was obtained in the MFC with a hydrodynamic boundary layer thickness of 1.6 cm, and this voltage output obtained was 11 times higher than that of MFC with 5 cm hydrodynamic boundary layer thickness. Moreover, the charge transfer resistance of anode decreased with decreasing hydrodynamic boundary layer thickness. The charge transfer resistance of MFC with hydrodynamic boundary layer of thickness 1.6 cm was 39 Ω, which was 0.79 times lesser than that of MFC with 5 cm thickness. These observations would be useful for enhancing the performance of recirculation mode MFCs.