Iron Oxide Electrodes Research Articles

Nanostructured 3D Mesoporous α-Fe2O3 Nano-Cubes As a High-Performance Electrode for Supercapacitors

Development of energy storage devices of high energy density and long cycle life is one of the pressing needs of electronic devices. Pseudo-capacitors with iron oxide electrodes show promising energy storage devices because they are economical and safe, but have poor conductivity and stability. To achieve an improved electrochemical performance such as shorter ion-diffusion path, faster ion accessibility, and higher conductivity, a rationally design of electrode material is highly desirable. Here, we shed the light on how three-dimensional (3D) Nano porous networked α-Fe2O3 nano-cubes serves as a supercapacitor electrode. Here we show the high specific capacitance and long-life supercapacitor anode by developing a hierarchical three-dimensional α-Fe2O3 nano-cubes. KOH is used as an aqueous electrolyte. The synthesized annealed nano-cubes (PNC) have high surface areas of 5.127m2/g. The annealed Hematite (α-Fe2O3) NC show good thermodynamic stability with high reversible redox activity. The half-cell anode based on this nanostructure give rise to a high specific capacitance value of ~520F/g at a current density of 1 A/g and ~90% of the capacitance can be retained at 2 A/g after 1000 redox cycles (indicates the good cyclic stability). The present work demonstrates that binder and conductive additive-free 3D Nano porous electrodes open up a new avenue to fabricate high surface area electrodes for improved charge storage performance. These performance features are superior among those reported for iron oxide-based supercapacitors. High specific capacitance value, stable cycling, and facile preparation make Hematite NC(α-Fe2O3) an excellent material for use as supercapacitor electrodes.

Synthesis and electrochemical properties of -Fe2O3 particles for energy storage devices

In this study, we fabricated α-Fe2O3 materials via a facile hydrothermal route to use as the active material for iron-based battery anode. The particle size of α-Fe2O3 is in a range of a few hundreds of nanometers to a few micrometers. The structural characteristics and particle size of the synthesized iron oxides were studied via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of iron oxide electrode was investigated by cyclic voltammetry (CV). The distribution of iron species was observed by Energy dispersive X-ray spectroscopy (EDS) measurement. Carbon was used as additive to improve the conductivity of α-Fe2O3/C composite electrode. The electrochemical measurements revealed that the prepared α-Fe2O3 particles provided the good cyclability. The EDS showed that iron species were dispersed on the carbon surface during discharge-discharge through the electrochemical dissolution-deposition process of iron.

Asymmetric Supercapacitors Using Porous Carbons and Iron Oxide Electrodes Derived from a Single Fe Metal-Organic Framework (MIL-100 (Fe)).

MOF-derived carbon (MDC) and metal oxide (MDMO) are superior materials for supercapacitor electrodes due to their high specific capacitances, which can be attributed to their high porosity, specific surface area (SSA), and pore volume. To improve the electrochemical performance, the environmentally friendly and industrially producible MIL-100 (Fe) was prepared using three different Fe sources through hydrothermal synthesis. MDC-A with micro- and mesopores and MDC-B with micropores were synthesized through carbonization and an HCl washing process, and MDMO (α-Fe2O3) was obtained by a simple sintering in air. The electrochemical properties in a three-electrode system using a 6 M KOH electrolyte were investigated. These novel MDC and MDMO were applied to an asymmetric supercapacitor (ASC) system to overcome the disadvantages of traditional supercapacitors, enhancing energy density, power density, and cyclic performance. High SSA materials (MDC-A nitrate and MDMO iron) were selected for negative and positive electrode material to fabricate ASC with KOH/PVP gel electrolyte. As-fabricated ASC resulted in high specific capacitance 127.4 Fg-1 at 0.1 Ag-1 and 48.0 Fg-1 at 3 Ag-1, respectively, and delivered superior energy density (25.5 Wh/kg) at a power density 60 W/kg. The charging/discharging cycling test was also conducted, indicating 90.1% stability after 5000 cycles. These results indicate that ASC with MDC and MDMO derived from MIL-100 (Fe) has promising potential in high-performance energy storage devices.

Multi‐Stage Porous Nickel–Iron Oxide Electrode for High Current Alkaline Water Electrolysis

AbstractAlkaline water electrolysis (AWE) is the promising technical pathway of large‐scale green hydrogen production. The sluggish oxygen evolution reaction seriously hampers the water decomposition reaction kinetics for AWE, especially at high current density above 500 mA cm−2. It is closely related with bubbles removal dynamic performance of porous electrodes. In this study, the multi‐stage porous nickel–iron oxide electrode is prepared by a two‐step electro‐deposition method. The electrode shows good oxygen evolution reaction performance at high current densitiy of 1000 mA cm−2, which is attributed to both the good electro‐catalytic performance of NiFeOx with nano‐cone structure and good bubbles removal performance of porous Ni interlayer with the curved pore channels. Bubbles motion inside the pore channels is deeply analyzed by Lattice Boltzmann simulation of gas–liquid two‐phase flows, combining with the experiments. The results indicate that bubbles motion speed is faster in curved pore channels than that in straight pore channels due to the role of bubble buoyancy. It illuminates the effects of pore channel curvature on bubbles motion for porous electrodes prepared by electro‐deposition. It provides the possibility of designing porous electrodes with both good electro‐catalytic performance and good bubbles removal performance by the electro‐deposition method, from the view of industrial applications.

New α-NaFeO2 synthesis route for green sodium-ion batteries

New technologies have been investigated to replace the use of lithium and cobalt ions, raw materials of the cathode active material of lithium-ion batteries. Among the emerging technologies stands out one that uses sodium (Na+) and iron ions. Sodium iron oxide (NaFeO2) has polymorphism, with only the α phase being active for the reversible deintercalation of sodium ions, so this phase has potential application as an electroactive material in green sodium-ion batteries. The novel synthesis of α-sodium iron oxide through the sol–gel route, which provides a material with small particles and high crystallinity, is described in this work. Through X-ray diffraction and Rietveld refinement, it was found that the initial chelating agent/metals ratio affects the concentration of the α and β phases at the end of the synthetic route. The α-sodium iron oxide, obtained with an appropriate chelating agent/metals ratio, showed high purity and crystallinity. A discharge capacity of approximately 110 mAh/g was achieved when the α-sodium iron oxide electrode, obtained through the sol–gel route, was cycled from 1.00 to 4.00 V against sodium ions/sodium (Na), corresponding to the intercalation of approximately 0.5 sodium ions of the Na1−x FeO2 formula. The success of the synthesis of the α-sodium iron oxide phase can lower the cost and ensure the economic viability of green sodium-ion batteries.

Elucidation of cube-like red iron oxide @ carbon nanofiber composite as an anode material for high performance lithium‐ion storage

Herein, a red iron oxide @ carbon fiber (RIO@CF) composite is prepared via a simple and effective single hydrothermal and calcination process. The physico-chemical characteristics of as-prepared electrode active materials are examined by X-ray photoelectron spectroscopy, high resolution field emission-scanning electron microscopy and field emission-tunneling electron microscopy analyses. When used as the anode material in the Li-ion battery, as-prepared RIO@CF composite have shown a specific capacity of 1138 mAh g−1 after 150 cycles with a capacity retention of 86% at a current density of 100 mA g−1. Moreover, a specific capacity of 825 mAh g−1 is achieved in the first cycle at a current density of about 5000 mA g−1. Thus, when compared to the pristine nano-cube-like red iron oxide (RIO) electrode material, the RIO@CF composite electrode exhibits an outstanding cyclic stability and rate capacity. This electrochemical enhancement facilitates effective lithium ion transport into the RIO@CF composite electrode, thus improving the electrical conductivity. In addition, the application of a homogeneous carbon fiber coating can provide effective contact between the electrode surface and the electrolyte to further benefit the electrochemical performance.

Optical and electrochemical properties of iron oxide and hydroxide nanofibers synthesized using new template-free hydrothermal method

We report the effect of hydrothermal synthesis conditions on the morphological, optical and electrochemical properties of as-prepared iron oxide (γ-Fe2O3) and hydroxide (α-FeOOH) nanostructures. The physico-chemical identification of these Fe-based nanostructures using X-ray diffraction, scanning/transmission electron microscopy, porosity and Raman spectroscopy analyses revealed a temperature-depended phase transformation. A maghemite and goethite iron-based nanostructured formation was observed in nanorod and trigonal nanofiber shape-like morphology with mean diameters ranging from 32 to 50 nm. The textural analysis of the nanofibers confirmed mesoporosity with a specific surface area of ~ 129 m2 g−1 (in γ-Fe2O3) and 23 m2 g−1 (in α-FeOOH). The electrochemical performance of the iron oxide and hydroxide nanofiber electrodes with and without the addition of activated carbon (AC) was also investigated. The sample electrodes composed of γ-Fe2O3, γ-Fe2O3/AC, α-FeOOH and α-FeOOH/AC showed remarkable specific capacities of 164 mAh g−1, 330 mAh g−1, 51 mAh g−1 and 69 mAh g−1 at 1 A g−1 gravimetric current. The influence of the phase transformation linked to the synthesis temperature, and the inclusion of an electric double-layer AC material into the nanofibers clearly demonstrates an enhancement in their energy-storage capability. Furthermore, the Fe-based nanofibers exhibited excellent cycling stability with good capacity retention of 73% and 99.8%, respectively, after 2000 cycles at a high 30 A g−1 gravimetric current as well as low resistance obtained by impedance spectroscopy analysis. The implication of the results depicts the potential of adopting these γ-Fe2O3 nanorods as suitable material electrodes in electrochemical energy-storage devices.

3D Porous iron oxide/carbon with large surface area as advanced anode materials for lithium-ion batteries

Nanostructures have received great attention to improve the performance of lithium-ion batteries, due to their advantages in dealing with critical issues associated with large volume change, low electrical conductivity, and slow rate of Li+ diffusion. To realize large lithium storage capacity and excellent rate capability of iron oxide electrode. Carbon-modified three-dimensional porous iron oxide was prepared by chemical reaction with in situ formation of templating agent followed by the calcination is reported herein. Benefit from the regulation of the number of pores in the precursor, part of Fe is oxidized to Fe3O4 and part of Fe is peroxidized to Fe2O3, thus forming Fe2O3/Fe3O4 heterostructure during oxidation process. Attributed to its unique structural feature, the 3D Fe2O3/Fe3O4-C heterostructure electrode for the anode of lithium-ion batteries exhibits outstanding rate capability, i.e., 911.4, 797.9, 736.3, 597.8, and 402.6 mAh g−1 at 0.3, 1.0, 2.0, 5.0, and 10.0 A g−1, respectively, and high reversible capacity, i.e., 929.1 mAh g−1 at a low current density of 300 mA g−1.

Construction of cobaltous oxide/nickel–iron oxide electrodes with great cycle stability and high energy density for advanced asymmetry supercapacitor

Cobaltous oxide/nickel–iron oxide (Co3O4/NiFe2O4) hybrids were fabricated via a template-free hydrothermal route with cyclodextrin as a reactor and a further two-step annealing treatment in an air atmosphere. The hybrid is composed of many small nanoparticles with a particle size distribution range from 20 to 50 nm. The hybrid combined the advantages of Co3O4 and NiFe2O4 nanoparticles, presenting enhanced electrochemical properties than its single component. The Co3O4/NiFe2O4 (0.6:1) hybrid electrode exhibited the highest specific capacitance and great electrochemical cycle stability (over 90.7% of total capacitance at 2 A g−1 after 1000 cycles and still kept 84.6% at 5 A g−1 after 5000 cycles). This may be ascribed to the common contribution of each component, which not only provided good electronic conductivity for efficient charge transfer but also a stable structure for better ions diffusion. A Co3O4/NiFe2O4//AC asymmetry supercapacitor was assembled and manifested the highest energy density of 76.0 Wh kg−1 at a power density of 859.7 W kg−1 and still kept 37.3 Wh kg−1 at the highest power density of 6.0 kW kg−1. This work indicated that the Co3O4/NiFe2O4 hybrid should be a potential active material for the electrochemical application.

Architecting hierarchical shell porosity of hollow prussian blue-derived iron oxide for enhanced Li storage.

Delicate architecture of active material enables improving the performacne of lithium ion batteries. Environmental-friendly Fe2 O3 anode has high theoretical specific capacity (1007 mAh g-1 ) in lithium ion batteries, but suffers from structural collapsing and poor electronic conductivity. Herein, we design an unique hierarchical iron oxide by regulating the initial precursor prussian blue and targeting hollow-shell structures with full consideration of temperature controls. Among them, Fe2 O3 with a sheet-crossing structure at 650°C, affords obvious advantages of improved electronic conductivity, short ionic diffusion length, prevented particle agglomeration, and buffer volume change. Thus, we achieve a superior discharge specific capacity of 611 mAh g-1 at 500 mA g-1 . Regulating hierarchical structure of prussian blue-assisted oxides enables effectively enchancing Li storge performance. LAY DESCRIPTION: Nanoparticle self-assembly, one of bottom-up methods is often used to prepare hollow hierarchical structures, whereas it suffers from low productivity and insufficient stability. Hence, we designed a unique hierarchical iron oxide by top-down method with regulating the initial precursor PB and targeting hollow-shell structures through full consideration of temperature controls. Delicate architecture of active material enables improving the performacne of lithium ion batteries. Environmental-friendly Fe2 O3 anode has high theoretical specific capacity (1007 mAh g-1 ) in lithium ion batteries, but suffers from structural collapsing and poor electronic conductivity. Hence, we prepared Prussian Blue (PB) materials with different sizes and calcined them at different temperatures. We found that no matter what the size of PB, the sheet-crossing morphology appeared at 650°C, and the interlaced morphology was the key to improve the performance of lithium batteries. If the size of PB precursor is too large or too small, it has adverse effects on lithium batteries. Only when the size and calcination temperature of PB precursor reach the optimum state, the best performance can be obtained. The calcination PB-K-3 at 650°C has a unique hierarchical structure of sheet-crossing. An obvious advantages include the prevention of particle agglomeration, short ionic diffusion lengths, and buffering volume changes. As a consequence, 611 mAh g-1 was obtained at the current density of 500 mA g-1 . In addition, we observed the structural changes of electrode plates at different reaction potentials, according to the reaction equation of Fe2 O3 +xLi+ +xe→Lix Fe2 O3 . With the proceeding charge process, the voltage increases from 0.01 to 3 V, the lithium ions gradually comes out of the iron oxide electrode surface. Whereas the discharging process reverses the aforementioned phenomena. Even if the changing volumes, however, the shape of cubic blocks for the PB-K-3 is preserved at different potentials. Taking these advantages into account, our designed MOFs-derived struture was an effective way to prepare hollow hierarchical structure with enhanced Li storage performacne. Such work is expected to facilitate the design of new electrode structure of lithium batteries.

Electrochemical properties of Fe2O3/AB based composite electrodes in alkaline solution

To find a suitable material for Fe-air battery anode, Fe2O3 nanoparticles (nm) and microparticles (µm) were used as active materials and Acetylene Black carbon (AB) as additive to prepare Fe2O3/AB composites. The effect of grain size of iron oxide particles and additives on the electrochemical behavior of Fe2O3/AB composite electrodes in alkaline solution have been investigated using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS) measurements. Iron oxide nanoparticles provided better cyclability than iron oxide microparticles. Impedance of electrode increased during cycling but the nm-Fe2O3/AB electrode gave smaller resistance than µm-Fe2O3/AB one. The additives showed strongly effects on the electrochemical behaviors of iron oxide electrodes. The AB additive enhanced the electric conductivity of Fe2O3/AB electrode and thus increased the redox reaction rate of iron oxide while K2S interacted and broke down the passive layer leading to improved cyclability and giving higher capacity for Fe2O3/AB electrodes.

Highly Efficient Sodium Storage in Iron Oxide Nanotube Arrays Enabled by Built-In Electric Field.

High-power sodium-ion batteries capable of charging and discharging rapidly and durably are eagerly demanded to replace current lithium-ion batteries. However, poor activity and instable cycling of common sodium anode materials represent a huge barrier for practical deployment. A smart design of ordered nanotube arrays of iron oxide (Fe2 O3 ) is presented as efficient sodium anode, simply enabled by surface sulfurization. The resulted heterostructure of oxide and sulfide spontaneously develops a built-in electric field, which reduces the activation energy and accelerates charge transport significantly. Benefiting from the synergy of ordered architecture and built-in electric field, such arrays exhibit a large reversible capacity, a superior rate capability, and a high retention of 91% up to 200 cycles at a high rate of 5 A g-1 , outperforming most reported iron oxide electrodes. Furthermore, full cells based on the Fe2 O3 array anode and the Na0.67 (Mn0.67 Ni0.23 Mg0.1 )O2 cathode deliver a specific energy of 142 Wh kg-1 at a power density of 330 W kg-1 (based on both active electrodes), demonstrating a great potential in practical application. This material design may open a new door in engineering efficient anode based on earth-abundant materials.

In situ Mössbauer analysis of bacterial iron-oxide nano-particles for lithium-ion battery

Nanometric amorphous iron-based oxides of bacterial origin show a great potential as an Fe3+/Fe0 conversion anode material for lithium-ion batteries. By means of in situ Mossbauer spectroscopy, chemical states of Fe ions were examined under the discharge-charge process of the bacterial iron-oxide electrode in a lithium-ion half-cell. As for the first discharge process, the successive reduction of Fe3+ → Fe2+ → Fe0 occurred in the electrode as a function of the cell voltage. While on the charge process, Fe0 in the electrode was oxidized directly to Fe3+ without going through Fe2+.

Toward Low-Cost and Sustainable Supercapacitor Electrode Processing: Simultaneous Carbon Grafting and Coating of Mixed-Valence Metal Oxides by Fast Annealing.

There is a rapid market growth for supercapacitors and batteries based on new materials and production strategies that minimize their cost, end-of-life environmental impact, and waste management. Herein, mixed-valence iron oxide (FeOx) and manganese oxide (Mn3O4) and FeOx-carbon black (FeOx-CB) electrodes with excellent pseudocapacitive behavior in 1 M Na2SO4 are produced by a one-step thermal annealing. Due to the in situ grafted carbon black, the FeOx-CB shows a high pseudocapacitance of 408 mF cm−2 (or 128 F g−1), and Mn3O4 after activation shows high pseudocapacitance of 480 mF cm−2 (192 F g−1). The asymmetric supercapacitor based on FeOx-CB and activated-Mn3O4 shows a capacitance of 260 mF cm−2 at 100 mHz and a cycling stability of 97.4% over 800 cycles. Furthermore, due to its facile redox reactions, the supercapacitor can be voltammetrically cycled up to a high rate of 2,000 mV s−1 without a significant distortion of the voltammograms. Overall, our data indicate the feasibility of developing high-performance supercapacitors based on mixed-valence iron and manganese oxide electrodes in a single step.

Modulated anodization synthesis of Sn-doped iron oxide with enhanced solar water splitting performance

Modulated anodization synthesis is introduced here for the fabrication of porous Sn-doped iron oxide. Continuous square-wave modulation consisting of highly positive (+50 to +80 V range) and slightly negative potentials (−2 to −10 V range) at 100 Hz allowed the etching anodization of the metallic Fe foil and incorporation of Sn-dopant from the fluoride anion–containing electrolyte, respectively. Compared with the undoped iron oxide, the surface-enriched Sn-dopant (in the form of Sn4+) alleviates the trapping and recombination of surface holes, while enhancing the hole transfer at the surface states. As such, the overpotential for photoelectrochemical (PEC) water oxidation was reduced by 110 mV and photocurrent density doubled. The incorporation of Co-Pi co-catalyst further improved the hole transfer efficiency, resulting in further reduction in overpotential by another 330 mV with respect to the bare Sn-doped iron oxide and significant improvement in photocurrent density at potentials below +1.23 V vs. reversible hydrogen electrode. Lastly, the iron oxide electrodes exhibit highly stable PEC water oxidation with no degradation in activity throughout the 10 h assessment under simulated solar irradiation and Faradaic efficiency of 90%. We envisage that the modulated anodization technique can be conveniently incorporated for a wide range of other dopants in search of efficient solar water splitting electrodes.

Electrocatalytic Water Reduction Beginning with a {Fe(NO)2}10-Reduced Dinitrosyliron Complex: Identification of Nitrogen-Doped FeO x(OH) y as a Real Heterogeneous Catalyst.

Electron paramagnetic resonance, IR, single-crystal X-ray diffraction, and density functional theory computation reveal that the electronic structure of α-diimine-coordinated {Fe(NO)2}10-reduced dinitrosyliron complexes (DNICs) may best be described as [{Fe(NO)2}10-L•], with the added electron residing mainly on the α-diimine ligand framework. The combination of electrochemistry, gas chromatography, Fourier transform infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy-energy-dispersive X-ray studies demonstrates that the cathodic potential promotes/triggers the transformation of an α-diimine-coordinated {Fe(NO)2}10-reduced DNIC into a particulate deposit on the electrode, and electrodeposited-film electrodes, CFeO and CFeNO, are kinetically dominant electrocatalysts responsible for hydrogen evolution reaction (HER) from water with quantitative Faradaic efficiency. In comparison with the CFeO electrode reaching a current density of 10 mA/cm2 with an overpotential of 333 mV for HER, the nitrogen-doped iron oxide electrode, CFeNO, requires 147 mV of overpotential to achieve a current density of 10 mA/cm2 in a 1 M NaOH aqueous solution. The CFeNO electrode exhibits higher kinetic efficiency (Tafel slope of 59 mV/dec) than the CFeO electrode (Tafel slope of 122 mV/dec) in alkaline conditions. As opposed to high Rct (74.3 Ω) displayed by the CFeO electrode, the smaller charge-transfer resistance ( Rct) of the CFeNO electrode (34.0 Ω) demonstrated that the better HER catalytic activity may be ascribed to the incorporation of nitrogen into iron oxide architecture, which increases the surface roughness and electroconductivity of the CFeNO electrode (56.9% iron content and nitrogen electron-donating effect) and improves HER catalysis by polarizing the incoming water molecule (acting as a proton tray). This result implicates that a (NH4)2SO4-assisted nitrogen-doping strategy is a direct and effective method to realize synergistic regulation of the reaction dynamics, catalytically active sites and electronic conductivity, endowing this nitrogen-doped material CFeNO electrode as a promising HER electrocatalyst under alkaline conditions.

Fe3O4 anodes for lithium batteries: Production techniques and general applications

Iron oxides, such as Fe 3 O 4 , are putative anode materials for rechargeable lithium-ion batteries (LIBs). LIBs are extensively used as power sources for electronics. They typically consist of cells, with each cell built out of a lithium cathode and a graphite anode. However, graphite anodes suffer from the disadvantages of significant density, large volume, low energy density, and inferior safety levels. Iron oxides seem to be a promising substitute to the currently used graphite anodes due to their high capacity, extensive availability, good stability, and environmental tolerance. Nevertheless, several hurdles prevent their market expansion, such as inferior electronic/ionic conductivity, large volume changes, poor cycling performance, and low coulombic efficiency. Using Fe 3 O 4 seems to be one alternative to address these challenges. This review will cover the current state of development of iron oxide electrodes with respect to design, production techniques, and general applications.

Morphology engineering of electro-deposited iron oxides for aqueous rechargeable Ni/Fe battery applications

Aqueous rechargeable Ni/Fe batteries possess potential advantages for large-scale energy storage applications due to their low cost, high safety and fast ion diffusions in electrolyte. However, the electrochemical performance of the iron-based anode is still far from ideal due to particle aggregations. Herein, we carry out the morphology engineering on the iron oxide active materials via a facile electrochemical method to improve its charge storage capability. The morphology transition from zero-dimensional particles to one-dimensional nanorods is realized by tuning the electrolyte composition, while subsequent annealing treatment results in further morphology modification into 3D interconnected nanoparticles (10–20 nm). The hierarchical structure allows facile ion and electron transfers, and the large surface provides various active sites for the charge storage conversion reaction. As a result, even at the high current density of 2 A g−1 (∼6C rate), the iron oxide electrode can still deliver a high specific capacity of 184 mAh g−1. At the same time, the morphology integrity and stability of the electrode leads to a good cycle life, with 87.5% capacity retained upon 5000 cycles. The Ni/Fe full cell assembled with the iron oxide anode and a Ni-Co double hydroxide cathode exhibits a good energy density of 82.3 Wh kg−1 at the power density of 3.3 kW kg−1. Our fundamental study would provide new insights for the electro-deposition of iron-based materials and endow new opportunities for the fabrication of high-performance iron-based electrodes for energy storage systems.

Microbial nanowires and electroactive biofilms.

Geobacter bacteria are the only microorganisms known to produce conductive appendages or pili to electronically connect cells to extracellular electron acceptors such as iron oxide minerals and uranium. The conductive pili also promote cell-cell aggregation and the formation of electroactive biofilms. The hallmark of these electroactive biofilms is electronic heterogeneity, mediated by coordinated interactions between the conductive pili and matrix-associated cytochromes. Collectively, the matrix-associated electron carriers discharge respiratory electrons from cells in multilayered biofilms to electron-accepting surfaces such as iron oxide coatings and electrodes poised at a metabolically oxidizable potential. The presence of pilus nanowires in the electroactive biofilms also promotes the immobilization and reduction of soluble metals, even when present at toxic concentrations. This review summarizes current knowledge about the composition of the electroactive biofilm matrix and the mechanisms that allow the wired Geobacter biofilms to generate electrical currents and participate in metal redox transformations.

Enhancing the Supercapacitive Properties of Iron Oxide Electrode through Cu2+-doping: Cathodic Electrosynthesis and Characterization

Enhancing the Supercapacitive Properties of Iron Oxide Electrode through Cu2+-doping: Cathodic Electrosynthesis and Characterization