Carbon Fiber Electrodes Research Articles

Investigating the Activity of Carbon Fiber Electrode for Electricity Generation from Waste Potatoes in a Single-Chambered Microbial Fuel Cell

Microbial fuel cells (MFCs), a technology that converts chemical energy into electrical energy, have been regarded as the most suitable method for sustainable energy production. However, most MFCs generate a low power output, limiting their large-scale industrial applications. Here, we introduce a high-performancesingle-chambered microbial fuel cell (SCMFC) based on carbon fiber anode and zinc oxide nanoparticle (ZnO NP)-fabricated copper cathode. Furthermore, best optimized conditions of temperature, pH, substrate, external resistance, and cathode fabrication were also considered to evaluate the performance of this SCMFC in treating potato wastewater along with bioenergy production. Results indicated that chemical oxygen demand (COD) could be effectively removed (80%) and maximum voltage, current density, and power density were 1.58 V, 0.235 mA/cm2, and 0.3714 mW/cm2, respectively. Hence, the SCMFC used in this study has a higher potential to treat potato wastewater along with high power production.

Conductive Metal-Organic Framework Microelectrodes Regulated by Conjugated Molecular Wires for Monitoring of Dopamine in the Mouse Brain.

Herein, we demonstrated a strategy to regulate the conductive metal-organic framework (MOF) surface, by the conjugated molecule wires for selective and sensitive determination of dopamine (DA) in the live brain. The MOFs were decorated at the carbon fiber electrode deposited by Au nanoleaves as the upper electric transducer to provide rich electrocatalytic sites for electron transfer of neurochemicals at the electrode surface, leading to greatly enhanced sensitivity for detection of neurochemicals. On the other hand, the conjugated molecular wire, 4-(thiophen-3-ylethynyl)-benzaldehyde (RP1), was synthesized and assembled as an underlying bridge to regulate the electrochemical processes at the MOF-based electrode, specifically decreasing the reaction Gibbs free energy of DA oxidation, thus selectively promoting the heterogeneous electron transfer of DA from the MOF layer to the electrode surface. Owing to the electrocatalytic activity for DA oxidation, the present microsensor exhibited high selectivity for real-time tracking of DA in a good linear relationship in the range of 0.004-0.4 μM with a detection limit of 1 nM. Eventually, this functionalized electrode was successfully applied for in vivo monitoring of DA in mouse brains with Parkinson's disease (PD) model. The results indicated that the levels of DA were obviously decreased in both acute and subacute PD models. Moreover, the level of DA strongly depended on the amount of uric acid (UA), a physiological antioxidant, which rose as the UA amount was lower than 200 mg kg-1 but was downregulated again after treatment by a higher amount of UA.

Multielectrode Arrays as a Means to Study Exocytosis in Human Platelets

Platelets are probably the most accessible human cells to study exocytosis by amperometry. These cell fragments accumulate biological amines, serotonin in particular, using similar if not the same mechanisms as those employed by sympathetic, serotoninergic, and histaminergic neurons. Thus, platelets have been widely recognized as a model system to study certain neurological and psychiatric diseases. Platelets release serotonin by exocytosis, a process that entails the fusion of a secretory vesicle to the plasma membrane and that can be monitored directly by classic single cell amperometry using carbon fiber electrodes. However, this is a tedious technique because any given platelet releases only 4-8 secretory δ-granules. Here, we introduce and validate a diamond-based multielectrode array (MEA) device for the high-throughput study of exocytosis by human platelets. This is probably the first reported study of human tissue using an MEA, demonstrating that they are very interesting laboratory tools to assess alterations to exocytosis in neuropsychiatric diseases. Moreover, these devices constitute a valuable platform for the rapid testing of novel drugs that act on secretory pathways in human tissues.

Selective heterogeneous capture and release of actinides using carborane-functionalized electrodes.

We report the heterogenization of molecular, electrochemically switchable ortho-substituted carboranes (POCb, POCb-Pyr) for selective metal capture. Films of POCb and POCb-Pyr on glassy carbon and carbon fiber (CF) electrodes demonstrated heterogeneous electrochemical behaviour that was enhanced by the inclusion of single-walled carbon nanotubes (CNTs). Galvanostatically charged CF|CNT|POCb and CF|CNT|POCb-Pyr electrodes selectively captured and released actinides (Th4+, UO22+) from mixed solutions containing alkali (Cs+), lanthanide (Nd3+, Sm3+) and actinide (Th4+, UO22+) metal ions.

Self-standing TiC-modified carbon fibre electrodes derived from cellulose and their use as an ultrahigh efficiency lithium metal anode

A self-standing three-dimensional TiC-modified carbon fibre (TiC@C) network has been fabricated by carbothermal reduction and demonstrated to be effective as a host for a dendrite-free metallic lithium anode.

Uricase Crowding via Polyelectrolyte Layers Coacervation for Carbon Fiber-Based Electrochemical Detection of Uric Acid.

Urate oxidase (UOx) surrounded by synthetic macromolecules, such as polyethyleneimine (PEI), poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) is a convenient model of redox-active biomacromolecules in a crowded environment and could display high enzymatic activity towards uric acid, an important marker of COVID-19 patients. In this work, the carbon fiber electrode was modified with Prussian blue (PB) redox mediator, UOx layer, and a layer-by-layer assembled polyelectrolyte film, which forms a complex coacervate consisting of a weakly charged polyelectrolyte (PEI or PAH) and a highly charged one (PSS). The film deposition process was controlled by cyclic voltammetry and scanning electron microscopy coupled with energy-dispersive X-ray analysis (at the stage of PB deposition) and through quartz crystal microbalance technique (at latter stages) revealed uniform distribution of the polyelectrolyte layers. Variation of the polyelectrolyte film composition derived the following statements. (1) There is a linear correlation between electrochemical signal and concentration of uric acid in the range of 10-4-10-6 M. (2) An increase in the number of polyelectrolyte layers provides more reproducible values for uric acid concentration in real urine samples of SARS-CoV-2 patients measured by electrochemical enzyme assay, which are comparable to those of spectrophotometric assay. (3) The PAH/UOx/PSS/(PAH/PSS)2-coated carbon fiber electrode displays the highest sensitivity towards uric acid. (4) There is a high enzyme activity of UOx immobilized into the hydrogel nanolayer (values of the Michaelis-Menten constant are up to 2 μM) and, consequently, high affinity to uric acid.

Sensitive electrochemical sensing platform based on Au nanoflower-integrated carbon fiber for detecting interleukin-6 in human serum

Prostate cancer (PCa) is the most prevalent cancer worldwide, with a high mortality rate. The early and accurate detection of PCa is critical in reducing mortality and saving lives. Timely diagnosis can improve the chances of successful treatment using advanced technologies. In recent years, nanomaterial-based electrochemical sensing strategies have been adopted in clinical diagnosis, as they allow sensitive early-biomarker detections to be converged with a cost-effective electronic readout system. Herein, we present a flexible electrochemical immunosensor platform for detecting interleukin-6 (IL-6) based on an Au-integrated flexible carbon fiber (Au/CF) electrode prepared via electrodeposition and chemically modified to capture IL-6 antibodies. Several techniques are used to analyze the prepared Au/CF composite electrodes to confirm their morphology, structure, and elemental composition. Under optimum conditions, the fabricated immunosensor exhibits a wide linear dynamic ranging from 1 fg/mL to 1 μg/mL and a low detection limit of 0.056 fg/mL, with a sensitivity of 62.17 μA/(fg mL−1). The proposed fiber-based immunosensor is used to quantify the concentration of IL-6 in serum samples from clinical PCa patients (T3b and T4 stages), and the results are validated using the commercial Meso Scale Diagnostics (MSD) V-Plex method. The acceptable results yielded by the proposed immunosensor indicate that it can serve as a new platform to realize highly sensitive and cost-effective diagnostic strategies for the early diagnosis of PCa.

A novel embedded all-solid-state composite structural supercapacitor based on activated carbon fiber electrode and carbon fiber reinforced polymer matrix

Composite structural supercapacitors (CSSs), that provide both mechanical and electrochemical properties, have great potential for applications in electric vehicles, unmanned aerial vehicles and portable electronic devices with reduced overall system weight and volume. In this paper, a novel composite structural supercapacitor device is designed and fabricated, mainly consisting of energy storage units (flexible devices) and a structural unit (carbon fiber reinforced polymer, CFRP). KOH activated carbon cloth (ACC) and PVA-KOH gel electrolyte are selected as the electrode and electrolyte of the energy storage units, respectively. The specific capacitance, energy density and power density of 1:1 ACC-CSS reach 88 mF⋅g−1, 9.9 mWh⋅kg−1 and 445.5 mW⋅kg−1, respectively. Meanwhile, the flexural strength, flexural modulus and shear strength of 1:1 ACC-CSS achieve 230 MPa, 21 GPa and 8.75 MPa, respectively. In addition, the excellent stability of electrochemical performance of 1:1 ACC-CSS under various external loads is verified by electrochemical three-point bending, electrochemical tensile and electrochemical tensile fatigue tests as well. Experimental results show that even after mechanical failure, 1:1 ACC-CSS can still maintain its electrochemical performance. The combination of good electrochemical and mechanical properties of 1:1 ACC-CSS makes it a promising and competitive candidate for the development of composite structural energy storage devices.

Multifunctional structural composite supercapacitors based on MnO2-nanowhiskers decorated carbon fibers

We report the concept of stiff, strong, and lightweight multifunctional composites that can perform as a structural composite supercapacitor. The self-assembly of Manganese Dioxide (MnO2) nanowhiskers decorated carbon fiber (MO-CF fiber) composites enabled improvement in surface area, electrical conductivity, and a high number of active sites of the carbon fiber electrodes, thereby, exhibiting excellent charge storage capacity for the composite supercapacitors. The MO-CF-integrated composites achieved a specific capacitance of 1.1 F g−1, which is a 120-fold increase compared with neat carbon fiber–based supercapacitors. Moreover, the composite supercapacitor device showed an energy density of 2.45 W h kg−1. The fabricated device also achieved a capacitance of 1.71 F g−1 and an energy density of 3.8 Wh kg−1 in a 3 M NaCl solution. With an exceptional increase in its electrochemical properties, the MO-CF-based composite also maintained its mechanical properties, exhibiting an increase in tensile strength up to 123.6 MPa. Additionally, we demonstrated the feasibility of using a MO-CF composite as a structural supercapacitor by illuminating an LED.

Binder-free La(OH)3 supported activated carbon fiber electrode with N-doped C layer for efficient phosphate electrosorption

Binder-free La(OH)3 supported activated carbon fiber (ACF) electrode with modification of N-doped C layer (named LNA) was developed for phosphate (P) electrosorption. The optimum electrosorption of P on LNA was achieved at pH = 4 and voltage = 4 V. The electrosorption capacity was 6.5 times that without voltage, and adsorption rate also increased by 9 times. The presence of 0.1 mol/L inorganic anions improved the electrosorption efficiency in the order of Cl->NO3–>SO42->HCO3–>CO32–. The regeneration study revealed that LNA still exhibited a high electrosorption capacity (29.91 mg/g) after 5 cycles. The mechanism of phosphate electrosorption of LNA was analyzed by kinetics, isotherms, FTIR and XPS, etc. The adsorption kinetics followed the pseudo-second-order model, and the adsorption equilibrium data were well described by the Langmuir isotherm. The Langmuir maximum electrosorption capacity of LNA was 70.66 mg/g. The electrosorption of phosphate was controlled by ion exchange, electrostatic attraction and the formation of surface complexes. N-doped C layer affected the local electronic structure of La and strengthened the interaction with lanthanum hydroxide, promoting the electrosorption of phosphate. The results demonstrated that LNA is a promising electrosorption material for efficient phosphate recovery.

Enhanced Cl– electrosorptive performance of activated carbon fibre via modification by TiO2 and polyaniline

Chloride ions in reclaimed water are the main contributors to corrosion of pipelines. In this study, titanium dioxide (TiO2)-and polyaniline (PANI)-modified activated carbon fibre (ACF) electrodes were prepared using the sol–gel method and in situ polymerisation, and their Cl– electrosorptive performance in simulated reclaimed water was extensively investigated. The prepared materials were characterised using X-ray diffraction, scanning electron microscopy, N2 adsorption, and Fourier-transform infrared spectroscopy. The experimental results indicated that the optimal Cl– removal rate from the ACF/TiO2/PANI electrode reached 85.34% when the calcination temperature of TiO2 was 400 °C and the polymerisation concentration of PANI was 0.02 mol·L−1. This study demonstrated that the ACF/TiO2/PANI electrode showed an excellent equilibrium adsorption capacity of 17.1 mg·g−1, which was 1.4 times that of the parent ACF. The superior performance was attributed to the modification of TiO2 and PANI, which considerably improved the hydrophilicity, conductivity, and physical adsorption capacity of the electrode. Consequently, the electrosorption rate and adsorption capacity were enhanced. In addition, the prepared ACF/TiO2/PANI electrode exhibited a high Cl– removal rate of 80.42% (adsorption capacity of 16.88 mg·g−1) in actual reclaimed water. Based on these results, the electrosorption kinetics and mechanism of the prepared ACF/TiO2/PANI electrode were analysed further.

Dopamine Release Impairments Accompany Locomotor and Cognitive Deficiencies in Rotenone-Treated Parkinson's Disease Model Zebrafish.

In this work, we carried out neurochemical and behavioral analysis of zebrafish (Danio rerio) treated with rotenone, an agent used to chemically induce a syndrome resembling Parkinson's disease (PD). Dopamine release, measured with fast-scan cyclic voltammetry (FSCV) at carbon-fiber electrodes in acutely harvested whole brains, was about 30% of that found in controls. Uptake, represented by the first order rate constant (k) and the half-life (t1/2) determined by nonlinear regression modeling of the stimulated release plots, was also diminished. Behavioral analysis revealed that rotenone treatment increased the time required for zebrafish to reach a reward within a maze by more than 50% and caused fish to select the wrong pathway, suggesting that latent learning was impaired. Additionally, zebrafish treated with rotenone suffered from diminished locomotor activity, swimming shorter distances with lower mean velocity and acceleration. Thus, the neurochemical and behavioral approaches, as applied, were able to resolve rotenone-induced differences in key parameters. This approach may be effective for screening therapies in this and other models of neurodegeneration.

A Survey of Catalytic Materials for Ammonia Electrooxidation to Nitrite and Nitrate.

Studies of the ammonia oxidation reaction (AOR) for the synthesis of nitrite and nitrate (NO2/3 - ) have been limited to a small number of catalytic materials, majorly Pt based. As the demand for nitrate-based products such as fertilisers continues to grow, exploration of alternative catalysts is needed. Herein, 19 metals immobilised as particles on carbon fibre electrodes were tested for their catalytic activity for the ammonia electrooxidation to NO2/3 - under alkaline conditions (0.1 m KOH). Nickel-based electrodes showed the highest overall NO2/3 - yield with a rate of 5.0±1.0 nmol s-1 cm-2 , to which nitrate contributed 62±8 %. Cu was the only catalyst that enabled formation of nitrate, at a rate of 1.0±0.4 nmol s-1 cm-2 , with undetectable amounts of nitrite produced. Previously unexplored in this context, Fe and Ag also showed promise and provided new insights into the mechanisms of the process. Ag-based electrodes showed strong indications of activity towards NH3 oxidation in electrochemical measurements but produced relatively low NO2/3 - yields, suggesting the formation of alternate oxidation products. NO2/3 - production over Fe-based electrodes required the presence of dissolved O2 and was more efficient than with Ni on longer timescales. These results highlight the complexity of the AOR mechanism and provide a broad set of catalytic activity and nitrate versus nitrite yield data, which might guide future development of a practical process for the distributed sustainable production of nitrates and nitrites at low and medium scales.

Flexible carbon fiber/reduced-TiO2 composites for constructing remarkable performance supercapacitors

In this paper, we synthesize honeycomb structure titanium dioxide (TiO2) grafted with carbon fiber (CF) composites (CF/TiO2) for flexible supercapacitors (SCs), which evidently boosts specific surface areas (SSA) of CF. In addition, we put forward an effective strategy for enhancing conductivity of TiO2 relying on construction of oxygen defects in NaBH4 solution. Amazingly, the reduced-TiO2 supporting on CF electrode (CF/R–TiO2) obtains from optimum conditions (2 M 4h) and exhibits the highest specific capacitance of 115.2 F g−1 at 1200 mA g−1, suggesting ultra-utilization of R–TiO2 for SC. Interestingly, its capacitance retention still remains 98.37% after 10000 cycles, which declares prominent cycling stability. Furthermore, we conduct density functional theory (DFT) analysis to reveal the enhancement mechanism of R–TiO2. With the reduction process, Fermi energy (EF) can obviously move conduction band (CB), which indicates increments of electronic conductivity of TiO2. Moreover, the aqueous symmetric SC based on CF/R–TiO2 (CF/R–TiO2-SC) expresses a high energy density of 49.6 Wh kg−1 at a power density of 1440 W kg−1. Meanwhile, the all-solid-state flexible supercapacitor (CF/R–TiO2-AFSC) further presents favorable flexibility in tested bending angles. Our results demonstrate that CF/R–TiO2 is provided with introduction of oxygen defects and honeycomb structure, which might have tremendous potential for SC.

In situ electrodeposition of bismuth oxide nanowires @MWNT on the carbon fiber microelectrode for the sensitively electrochemical detection of folic acid

A microminiaturized electrochemical device, BiO@CNW/CFE was fabricated based on the in situ co-electrodeposition of bismuth oxide nanowires (BiNWs) and multi-walled carbon nanotubes (MWNTs) on the surface of carbon fiber electrode (CFE). The nanostructure of BiNWs could bind MWNTs on the surface of CFE during the precipitation of bismuth at the potential of −1.1 V. The vimineous nanostructure of BiO@CNW improved the surface area and electrochemical activity of the microelectrode. With the low background noise, folic acid (FA) can be detected sensitively by BiO@CNW/CFE based on the electrochemical reduction via the method of square wave voltammetry. The linear range of FA in sodium acetate-acetic acid buffer was achieved in the range of 5.00 nM–200 nM, the detection limit was estimated to be 0.63 nM. The recoveries of FA in human serum and artificial cerebral spinal fluid were between 99% and 103%, which indicates BiO@CNW/CFE was a reliable sensor for the detection of FA in biological samples.

Coupling hybrid membrane capacitive deionization (HMCDI) with electric-enhanced direct contact membrane distillation (EE-DCMD) for lithium/cobalt separation and concentration

The increasing usage of electronic devices has added up the generation of spent LiCoO2 (LCO) batteries. Hence there is an urgency to develop high-efficiency and environmentally-friendly approaches for LCO electrode recycling by Li+/Co2+ ion-separation and concentration. In this work, an ion-sieving membrane with a lamellar structure was fabricated by self-assembling MXene nanosheets on a hydrophilic PTFE membrane, and the interlayer spacing between 2D MXene pieces was adjusted by doping a certain amount of polyvinyl alcohol (PVA). Such ion-sieving membrane was inserted between cation exchange membrane (CEM) and activated carbon fiber (ACF) electrode, forming a hybrid membrane capacitive deionization (HMCDI) system to enhance the ion-separating performance. The artificial Li+/Co2+ mixed solution was firstly treated by the HMCDI process with a separating factor over 6. The Li-enriched HMCDI effluent was further concentrated and purified using an electric-enhanced direct contact membrane distillation (EE-DCMD) system, providing an ion-concentrating effect over 40-folds and a Co2+ removal rate over 99 %. On this basis, a membrane-based LCO battery recycling pathway was proposed, showing advantages in energy conservation, zero liquid discharging, and chemical agent saving. Moreover, the mechanism of ion-separating in the HMCDI system was elucidated in terms of energy barrier and Li+ selective adsorption. The mechanism of anti-fouling and ion-separating in EE-DCMD was discussed based on the interfacial electrochemical reactions and transmembrane mass transfer. We believe this study can a provide new insight into ion separation and concentration, which was promising in LCO battery recycling.

Ultraprecise Real-Time Monitoring of Single Cells in Tumors in Response to Metal Ion-Mediated RNA Delivery.

With the deepening of cancer clinical research, miRNAs provide new ideas for molecular diagnosis and treatment of tumors. Improving the molecular delivery efficiency of miRNA is the key to the success of miRNA therapy. We have established self-assembly diagnosis and treatment technologies that can be used to achieve accurate targeting and "cargo" delivery at the cellular level. This technology builds a miRNA (let-7a) delivery system based on metal precursor [Au(III) and Fe(II)]-mediated tumor microenvironmental response to realize the self-assembly of Au&Fe-miRNA complexes for precise real-time imaging of tumor cells and targeted therapy. To accurately measure the changes in reactive oxygen species during complex formation in real time at the single-cell level, we employed small-size nanoscale devices as analytical tools. This study proposes an electrochemical sensor based on carbon fiber electrodes for ultraprecise and multiple monitoring of metal-ion-mediated miRNA delivery systems, precisely realizing targeted tracking of tumors and effective intervention inhibition.

Integrating Co3O4 nanocubes on MXene anchored CFE for improved electrocatalytic activity: Freestanding flexible electrode for glucose sensing

Developing facile strategies to construct free-standing flexible electrodes with extremely sensitive and stable electrochemical response towards analytes is of huge demand and it is still highly challenging. Herein, we design a unique and cost-effective hybrid electrode comprising of cobalt oxide (Co3O4) directly grown on highly conducting MXene based carbon fiber electrode (CFE) as a self-standing electrode using a simple hydrothermal-annealing method, where MXene nanosheets on electrode support facilitate the growth of uniform-sized Co3O4 nanocubes. Our results demonstrate that the synergetic effects of conductive MXene support and catalytically active Co3O4 nanocubes provide a superior response towards glucose oxidation in an alkaline medium (0.1 M KOH). The resultant Co3O4/MXene@CFE demonstrates remarkable sensitivity (19.3 μA mM−1 cm−2), wide linear range (0.05 μM to 7.44 mM) and lower detection limits (10 nM), thus providing excellent selectivity over interfering species and good electrochemical stability for an extended shelf-life. Therefore, the obtained self-standing Co3O4/MXene@CFE flexible electrode establishes a promising platform for glucose oxidation and it could be envisioned for the highly sensitive detection of various target molecules for their widespread applications in clinical diagnosis and health care monitoring.

Effect of Oxygen-Containing Groups on Electrochemical and Marine Electric Field Response Properties of Carbon Fiber Electrode

Electric field response of carbon fiber sensor in sea water can be tuned up through modification of molecules or groups on its surface, which plays an important role in its high sensitivity and stability. Herein, high performance carbon fiber electrodes with different oxygen-containing functional groups were prepared by electrochemical oxidation coupled with electrochemical reduction, and their electric field response and electrochemical performances of electrodes are investigated. The results show that the electrochemical oxidation and reduction obviously alter the dominant contents of carbonyl, hydroxyl and carboxyl groups. Among them, carbonyl group has positive effects for paired carbon fiber electrode on its electrode potential stability and its distortion rate of electric field response curves, hydroxyl group makes the paired carbon fiber electrode more sensitive to weak electric field. Carboxyl group has negative effects on the electrode potential stability due to its high activity, but its larger specific capacitance and smaller charge transfer resistance are simultaneously obtained. The detailed relationship between the dominant oxygen-containing carbon fiber electrode and its electric field response is first reported systematically, and it will shed some light on the design of fast-stable and highly sensitive marine electric field electrodes.

Development of Compact Readout Device for Neural Observation System using Fluorescence Imaging and Fast-scan Cyclic Voltammetry.

A readout device for a dual-functional neural observation system is presented. The authors separately developed the reading operation of an implantable CMOS image sensor and a setup for fast-scan cyclic voltammetry and implemented them together in a microcontroller-based device. The developed imaging readout device with a size of [Formula: see text] can reach the highest reading rate of 160 fps with a 120×268 pixel image sensor. The voltammetry function was verified through an experiment using commercial carbon fiber electrodes in phosphate-buffered saline. When the imaging is sequentially operated with 400 V/s-scan rate voltammetry from -0.4 to 1.3 V, the system can operate at up to 60 fps. With this system, calcium imaging and dopamine recording in a freely behaving mouse can be achieved together in a simpler manner. This study aims to be the basis for the development of an implantable multi-functional sensor.