Carbon Fiber Substrate Research Articles

Narrow Pressure Stability Window of Gas Diffusion Electrodes Limits the Scale-Up of CO2 Electrolyzers.

Electrochemical CO2 reduction is a promising process to store intermittent renewable energy in the form of chemical bonds and to meet the demand for hydrocarbon chemicals without relying on fossil fuels. Researchers in the field have used gas diffusion electrodes (GDEs) to supply CO2 to the catalyst layer from the gas phase. This approach allows us to bypass mass transfer limitations imposed by the limited solubility and diffusion of CO2 in the liquid phase at a laboratory scale. However, at a larger scale, pressure differences across the porous gas diffusion layer can occur. This can lead to flooding and electrolyte breakthrough, which can decrease performance. The aim of this study is to understand the effects of the GDE structure on flooding behavior and CO2 reduction performance. We approach the problem by preparing GDEs from commercial substrates with a range of structural parameters (carbon fiber structure, thickness, and cracks). We then determined the liquid breakthrough pressure and measured the Faradaic efficiency for CO at an industrially relevant current density. We found that there is a trade-off between flooding resistance and mass transfer capabilities that limits the maximum GDE height of a flow-by electrolyzer. This trade-off depends strongly on the thickness and the structure of the carbon fiber substrate. We propose a design strategy for a hierarchically structured GDE, which might offer a pathway to an industrial scale by avoiding the trade-off between flooding resistance and CO2 reduction performance.

Utilization of Si/SiOx/Al2O3 materials from recycled solar cells for a high-performance lithium-ion battery anode

Si/SiOx/Al2O3 composites obtained from recycled solar cells are integrated with modified carbon fiber substrates, forming a high-performance lithium-ion battery anode.

Conducting Polymer Based Enzyme Electrodes Fabricated by Invertase and Polyphenol Oxidase

Novel carbon fiber enzyme electrodes were constructed and evaluated. Fabrication of electrodes was performed via electrochemical deposition of a conducting matrice composed of polythiophene and polypyrrole (PTh–PPy) onto carbon fiber substrates. The enzyme was entrapped into the matrix during electropolymerization. Resultant biosensors represented higher kinetic parameters, Vmax and Km, in comparison to PPy matrice, which are 2.471 ± 0.150 mol min1- electrode1- and 30.60 ± 5.30 mM for invertase, 0.056 ± 0.012 mol min1- electrode1- and 842.00 ± 37.50 mM for polyphenol oxidase respectively. Optimum pH and temperature of the immobilized enzyme within PTh–PPy composite indicates that this matrice provides a more protective environment. The detection limit (LOD) of polyphenols was obtained as 0.037 mg mL1-. Polyphenol oxidase enzyme electrodes were proved to be used for the determination of polyphenolic substances in real samples and the results were confirmed by the Folin-Ciocalteau method

Research on the Phase Transition Process of Sessile Droplet on Carbon Fiber Cold Surface

Abstract The droplet phase transition process on the cold surface of a T300 carbon fiber substrate was studied by observing the droplet freezing process. Through the construction of visualized experimental device, the change in the droplet phase transition time under different experimental conditions, the progression of the solid–liquid interface during the phase transition process, the droplet deformation rate, and the ratio of growth of the interface height after the phase interface appears were experimentally obtained. The influence of different surface temperatures and different droplet volumes on the phase transition process was investigated. The experimental results show that the phase interface shows an irregular profile during the phase transition of the sessile droplet on the cold surface of the carbon fiber substrate; it presents a wave shape early and a smooth concave shape later. The influence of droplet volume on the phase transition time is not a proportional relationship. The height of the solid–liquid phase interface during the droplet phase transition process first grows rapidly, then slowly, and then fast once again. In other words, the growth rate of the phase interface is relatively fast when the phase transition has just occurred and then when the bulged tip is formed. At different cold surface temperatures, the droplet deformation rate with a volume of 10 µL on the carbon fiber substrate is basically the same, which is about 32.4%, within an uncertainty of about 1%, and it is higher than the contrast substrate. However, the influence of gravity factor is important in determining the droplet deformation rate for different droplet volumes.

Li-doped ZnO nanowires on flexible carbon fibers as highly efficient hybrid antibacterial structures

In this paper, Li-doped ZnO nanowires were grown on flexible carbon fiber substrates by hydrothermal route to create hybrid antibacterial structures. We have reported the synthesis, characterization and antibacterial activity of these hybrid structures which are made up of ZnO nanowires incorporated with various amounts of Li (0.3%, 0.5%, 1%, 3%, and 5%). Structural, morphological, optical, and elemental properties of the samples were scrutinized by using X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), respectively. The antibacterial effect of the hybrid structures against Escherichia coli and Staphylococcus aureus was tested by colony counting method. From the results, the antibacterial effect of Li-doped ZnO/CF against both E. coli and S. aureus was observed to considerably high in all samples. It was also seen that the Li addition significantly improves the antibacterial effect of ZnO nanowires. Doping ZnO with 3% Li resulted in best antibacterial efficiency on both E. coli (99.3% inhibition) and S. aureus (98.7% inhibition) among all samples.

Recent advances in ZnO nanostructures and their future perspective

This review addresses the recent developments of the processing of ZnO nanostructures (NSs) and characterizations of the developed NSs by various techniques, mainly hydrothermal technique. This article discussed various kinds of ZnO NSs such as wires, rods, flowers, dumbbells, spheres, particles and combs created by hydrothermal process on carbon fibre substrate. ZnO likely has the wealthiest group of NSs among all materials, both in structures and properties. The NSs could have novel applications in sensors, transducers, optoelectronics, and biomedical sciences. This article moreover studies the distinctive NSs of ZnO created by the different procedures and upgrades in the mechanical, electrical and thermal properties of the subsequent progressive composites. ZnO NSs processed on any substrate makes a hierarchical structure and can altogether enhance the specific properties in the final nanocomposites. Article also discussed the potential of ZnO NSs for fiber reinforced nanocomposites, focusing on the most used techniques used for the creation of ZnO NSs reinforced hierarchical composites and surveys the potential for another age of cutting edge multifunctional materials. Recent concepts used for improving or synthesizing other distinctive NSs having tailored properties are also explained in the article.

Photocatalytic Degradation of Methylene Blue Using Zinc Oxide Nanorods Grown on Activated Carbon Fibers

In this work, the synthesis, characterization, and photocatalytic performance of zinc oxide/activated carbon fiber nanocomposites prepared by hydrothermal method were investigated. Zinc oxide nanoparticles (ZnO-NP) were deposited as seeds on porous activated carbon fiber (ACF) substrates. Then, zinc oxide nanorods (ZnO-NR) were successfully grown on the seeds and assembled on the fibers’ surface in various patterns to form ZnO-NR/ACF nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, UV–vis diffuse reflectance spectra (DRS), and Brunauer–Emmett–Teller (BET) surface area analysis. SEM images showed that brush-like and flower-like ZnO-NR patterns were grown uniformly on the ACF surface with sizes depending on the ZnO-NP concentration, growth time, and temperature. The FTIR spectrum confirmed the presence of the major vibration bands, especially the absorption peaks representing the vibration modes of the COOH (C = O and C = C) functional group. Adsorption and photocatalytic activities of the synthesized catalytic adsorbents were compared using methylene blue (MB) as the model pollutant under UV irradiation. ZnO-NR/ACF nanocomposites showed excellent photocatalytic activity (~99% degradation of MB in 2 h) compared with that of bare ZnO-NR and ACF. Additionally, a recycling experiment demonstrated the stability of the catalyst; the catalytic degradation ratio of ZnO-NR/ACF reached more than 90% after five successive runs and possessed strong adsorption capacity and high photocatalytic ability. The enhanced photocatalytic activities may be related to the effects of the relatively high surface area, enhanced UV-light absorption, and decrease of charge carrier recombination resulting from the synergetic adsorption–photocatalytic degradation effect of ZnO and ACF.

Mechanical property deterioration and defect repair factors of carbon fibers during the continuous growth of carbon nanotubes by chemical vapor deposition

The continuous growth of carbon nanotubes (CNTs) was realized on the surface of moving carbon fiber substrate by chemical vapor deposition (CVD). The changes in the microstructure of the catalyst precursor reduction and the catalyzed growth of CNTs during the continuous process were tracked, and the factors causing the deterioration of mechanical properties and the increase of tensile strength were discussed. The formation of catalyst nanoparticles invaded the surface of carbon fibers, cutting off the continuous graphite layer and causing a loose graphite structure. With the catalyzed growth of CNTs which have good crystallinity, the graphite cross-links between their roots and the fiber surface repaired the defects generated by the catalyst. Due to the repair of surface defects by carbon source decomposition and interface CNTs during CVD process, the tensile strength of CNTs/carbon fiber reinforcement is increased by 8.55% compared with the raw carbon fibers. This research helps to grow CNTs uniformly on the surface of carbon fibers to prepare a large number of composite reinforcements, and can maintain or even improve the overall mechanical properties.

Investigation of Electrolyte-Dependent Carbonate Formation on Gas Diffusion Electrodes for CO2 Electrolysis.

The electrochemical reduction of CO2 (ECO2R) is a promising method for reducing CO2 emissions and producing carbon-neutral fuels if long-term durability of electrodes can be achieved by identifying and addressing electrode degradation mechanisms. This work investigates the degradation of gas diffusion electrodes (GDEs) in a flowing, alkaline CO2 electrolyzer via the formation of carbonate deposits on the GDE surface. These carbonate deposits were found to impede electrode performance after only 6 h of operation at current densities ranging from -50 to -200 mA cm-2. The rate of carbonate deposit formation on the GDE surface was determined to increase with increasing electrolyte molarity and became more prevalent in K+-containing as opposed to Cs+-containing electrolytes. Electrolyte composition and concentration also had significant effects on the morphology, distribution, and surface coverage of the carbonate deposits. For example, carbonates formed in K+-containing electrolytes formed concentrated deposit regions of varying morphology on the GDE surface, while those formed in Cs+-containing electrolytes appeared as small crystals, well dispersed across the electrode surface. Both deposits occluding the catalyst layer surface and those found within the microporous layer and carbon fiber substrate of the electrode were found to diminish performance in ECO2R, leading to rapid loss of CO production after ∼50% of the catalyst layer surface was occluded. Additionally, carbonate deposits reduced GDE hydrophobicity, leading to increased flooding and internal deposits within the GDE substrate. Electrolyte engineering-based solutions are suggested for improved GDE durability in future work.

Synthesis and electrochemical performance of an electroactive nitrogen-doping SnO2nanoarray supported on carbon fiber

An electroactive nitrogen-doping tin dioxide nanorod array (N-SnO2NRA) is designed as an effective energy-storage electrode material for supercapacitor applications. N-SnO2supported on a carbon fiber substrate is prepared using SnCl4as a precursor through hydrolysis, hydrothermal growth, and an NH3-nitriding process. Electroactive N-SnO2is formed by an N-doping reaction between Sn(OH)4and NH3, revealing a high nitrogen-doping level of 12.5% in N-SnO2. N-SnO2/carbon fiber reveals a lower ohmic resistance and charge transfer resistance than SnO2/carbon fiber, which is consistent with its higher current response and lower voltage drop in electrochemical measurements. N-SnO2NRA has an independent nanoarray structure and a small side length of a quadrangular nanorod, contributing to a more accessible interspace, reactive sites, and feasible electrolyte ion diffusion. The N-SnO2/carbon fiber NRA electrode shows higher specific capacitance (105.4 F g−1at 0.5 A g−1) and rate capacitance retention (45.0% from 0.5 to 5 A g−1) than a SnO2/carbon fiber NRA electrode (58.6 F g−1, 38.4%). Significantly, the cycling capacitance retention after 2000 cycles increases from 78.1% of SnO2/carbon fiber to 98.8% of N-SnO2/carbon fiber, presenting a superior electrochemical cycling stability. The N-SnO2supercapacitor maintains stable power working at an output voltage of 1.6 V. The specific capacitance decreases from 75.2 to 55.1 F g−1when the current density increases from 1 to 10 A g−1. The corresponding energy density decreases from 24.23 to 9.81 Wh kg−1, presenting a reasonable rate capability. So, the prepared N-SnO2nanorod array demonstrates superior capacitance performance for energy-storage applications.

Long-term cell culture and electrically in situ monitoring of living cells based on a polyaniline hydrogel sensor.

Accurate, in situ and long-term electrically monitoring of cell development plays an important role in cell study, which brings in challenges in terms of biocompatibility, processability, and sensing capability of electrochemical sensors. Based on biocompatible conductive polyaniline (PAni) hydrogels, we constructed a flexible sensor with flexible carbon cloth for electrical analysis of living cells. The carbon fiber substrate modified with conductive PAni hydrogels was selected as the electrode to promote the current collection of the sensor. The three dimensional nanostructured mesoporous matrix of PAni hydrogels is favorable for in situ generation of catalytic Pt nanoparticles and cell growth. With these hierarchically nanostructured features, the hydrogel electrochemical sensor was endowed with high sensitivity and selectivity in the detection of H2O2 (with a low detection limit of 1.6 μM in 0.01 M PBS and a wide linear range from 10 μM to 10 mM), and good biocompatibility for cell growth as long as 5 days. The accurate detection of H2O2 released from cells enabled us to differentiate the physiological states of cells and imitate the different stimuli-responsive behavior, which can provide real-time information on cell biological events. With outstanding biocompatibility, operability and repeatability, this strategy can be expanded to the fields of other biosensor fabrication and cell-related biomarker monitoring, which exhibits a broad application potential in bioanalysis catering to new generation sensors.

Cold atmospheric plasma jet applied for TiO2/carbon fiber composite biomaterial

AbstractIn the present work, Titanium dioxide (TiO2) micro–nanostructured thin films are deposited by a cold atmospheric plasma jet on carbon fiber substrates. The surface morphology, grain size, and structure phase of TiO2 thin films are investigated by scanning electron microscopic (SEM), X-ray diffraction (XRD), and Raman spectrum. As the discharge voltage increased from 5 to 15 kV, the size of these TiO2 particles decreased from 2 to 3 μm to less than 1 μm. The XRD and Raman spectroscopic results show TiO2 on the carbon fiber surface prepared by atmospheric plasma jet is at the mixture phase of anatase and rutile. We also investigated the adhesion and proliferation assays of MC3T3-E1 preosteoblasts on the samples. The surface with smaller TiO2 particles deposited on carbon fiber is more appropriate for attachment of preosteoblasts. Furthermore, the highest proliferation of MC3T3-E1 was found on a sample with smaller TiO2 particles after incubation. Our data suggest that the increased roughness fosters cell attachment and proliferation on the surface of TiO2/carbon fibers.

Electrochemical fabrication of carbon fiber-based nickel hydroxide/carbon nanotube composite electrodes for improved electro-oxidation of the urea present in alkaline solutions

A Ni(OH)2/carbon nanotube (CNT)/carbon fiber (CF) composite electrode was developed, and its electrode kinetics was investigated to improve its urea oxidation reaction (UOR) performance. The fabrication of the electrode was done using electrophoretic co-deposition combined with hydrothermal reaction. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used to examine the electrode properties, while cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) were used to study the electrode kinetics. The prepared catalyst that had a flake-like structure was an α phase Ni(OH)2 catalyst, which mixed well with the CNTs to form a composite layer on the CF substrate. The α-Ni(OH)2/CNT/CF electrode displayed satisfactory UOR performance because it had a higher oxidation current and a lower overpotential than those of either the α-Ni(OH)2/CF electrode or CF electrode. These improved properties of the α-Ni(OH)2/CNT/CF electrode can be because of the active and reversible Ni2+/Ni3+ redox reaction, which has high rate constant and anodic transfer coefficient, of the α-Ni(OH)2/CNT composite. Moreover, compared with α-Ni(OH)2/CF or CF electrodes, the α-Ni(OH)2/CNT/CF electrode has a low charge transfer resistance because of the increase in the reaction surface area and electrical conductivity caused by the CNTs. Overall, the composite electrode combines the advantages of the α-Ni(OH)2 catalyst, CNT conductive network, and CF current collector for improved UOR performance, which will be beneficial for urea pollution mitigation and H2 production.

Synthesis and growth mechanism of SiC/SiO2 nanochains by catalyst-free thermal evaporation method in Ar/CO atmosphere

SiC/SiO2 nanochains were synthesized on a carbon fiber substrate by a catalyst-free thermal evaporation method in the Ar/CO atmosphere. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the as-synthesized SiC/SiO2 nanochains are composed of single-crystalline SiC nanowires and amorphous SiO2 beads. The introduction of CO can promote the formation of SiO2, so that the SiC/SiO2 nanochains are subsequently formed during cooling. In addition, the photoluminescence spectrum of SiC/SiO2 nanochains showed a broad emission peak at around 350 nm, which is ascribed to the oxygen discrepancy in the SiO2 beads as well as the SiC/SiO2 interfacial effect. These findings can provide guidance for further study of the vapor growth of 1D SiC-based materials.

Effect of Pb(NO3)2 on Preparation and Properties of CF/β-PbO2 Electrodes for Zinc Electrowinning

In this study, the β-PbO2 active layer was deposited on the surface of the carbon fiber cloth by electrodeposition. The CF/β-PbO2 electrode was investigated by scanning electron microscopy (SEM), anodic polarization curves, Tafel curves, and a four-probe method. It was found that a uniform and flattened dense β-PbO2 active layer is obtained when the concentration of Pb(NO3)2 is 150 g l−1. The deposition quality of the active layer of β-PbO2 particles in the carbon fiber is affected by the concentration of Pb(NO3)2, thereby affecting the interfacial bonding strength between the active layer and the carbon fiber. The weightlessness rate of the carbon fiber substrate electrode materials with Pb(NO3)2 concentration of 150 g l−1 are the smallest. The interface resistivity of the CF/β-PbO2 electrode sample with Pb(NO3)2 concentration of 150 g l−1 is 6.71 × 10−5 Ω·m and is smallest. The CF/β-PbO2 electrode prepared under the 150 g l−1 has the smallest oxygen evolution potential and is 2.335 V. When the concentration of Pb(NO3)2 is 150 g l−1, the prepared CF/β-PbO2 electrode has the largest corrosion potential (1.085 V) and the minimum corrosion current (2.074 × 10−4 A · cm−2).

Enhanced Surface Energetics of CNT-Grafted Carbon Fibers for Superior Electrical and Mechanical Properties in CFRPs.

Surface enhancement of components is vital for achieving superior properties in a composite system. In this study, carbon nanotubes (CNTs) were grown on carbon fiber (CF) substrates to improve the surface area and, in turn, increase the adhesion between epoxy-resin and CFs. Nickel (Ni) was used as the catalyst in CNT growth, and was coated on CF sheets via the electroplating method. Surface energetics of CNT-grown CFs and their work of adhesion with epoxy resin were measured. SEM and TEM were used to analyze the morphology of the samples. After the optimization of surface energetics by catalyst weight ratio (15 wt.% Ni), CF-reinforced plastic (CFRP) samples were prepared using the hand lay-up method. To validate the effect of chemical vapor deposition (CVD)-grown CNTs on CFRP properties, samples were also prepared where CNT powder was added to epoxy prior to reinforcement with Ni-coated CFs. CFRP specimens were tested to determine their electrical resistivity, flexural strength, and ductility index. The electrical resistivity of CNT-grown CFRP was found to be about 9 and 2.3 times lower than those of as-received CFRP and CNT-added Ni-CFRP, respectively. Flexural strength of CNT-grown Ni-CFRP was enhanced by 52.9% of that of as-received CFRP. Interestingly, the ductility index in CNT-grown Ni-CFRP was 40% lower than that of CNT-added Ni-CFRP. This was attributed to the tip-growth formation of CNTs and the breakage of Ni coating.

(Invited) Developing Electrodes for Efficient Electroreduction of CO2 to Fuels or Chemicals

Using CO2 as a feedstock for the production of intermediates for fuels/chemicals such as formic acid, CO, ethylene, and ethanol via electroreduction is one of several approaches being explored to help reduce anthropogenic CO2 emissions. In addition to reducing CO2 by using some of it as feedstock, an additional amount of CO2 emissions potentially can be avoided by replacing today’s energy-intense thermo-catalytic processes with (close to) carbon neutral CO2 electrolysis technology. Over the past decade a variety of promising electrocatalysts have been identified for the selective conversion of CO2 to products such as CO, formic acid, ethylene, and ethanol under different operating conditions (see for example [1,2,3]). Various techno-economic analyses indicate that several of these catalyst exhibit sufficient activity and selectivity, provided they are stable over thousands of hours of operation (see for example [4]).This presentation will focus on structure-performance relationships of gas diffusion electrodes (GDEs), the type of electrodes often used in CO2 electrolysis cells. GDEs typically are comprised of three layers, a carbon fiber substrate (CFS) that provides lateral conductivity and structural stability, a micro-porous layer (MPL) that provides a barrier for the liquid electrolyte, and a catalyst layer (CL) that contains the catalyst. A variety of so-called gas diffusion layers comprised of a CFS covered by a MPL can be obtained commercially, and the catalyst layer can be applied to the MPL via painting or spray coating [5]. The electrochemical performance of a catalyst embedded onto a GDE depends on many factors including the exact composition and structure of each of the layers of the GDE, especially the catalyst layer (see for example [6]) and the micro-porous layer, MPL (see for example [7]). Also, structure-performance relationships of GDEs have been studied through computational models (see for example [8]). After an overview of key GDE structure and composition aspects as summarized above, the presentation will focus on studying the performance stability / durability of GDEs under electrolysis operation conditions (hundreds of mA/cm2). We have developed protocols for (accelerated) durability testing that include characterization of structure and composition before, during, and after hours of operation. These experiments revealed a number of degradation mechanisms, some of which are directly related to a drop in electrochemical performance. Understanding gained from studies such as these will allow for more stable / durable electrodes for CO2 electrolysis to be developed, thereby achieving the thousands of hours of performance needed to achieve economic feasibility.(1) S. Verma, X. Lu, S. Ma, R.I. Masel, P.J.A. Kenis, PhysChemChemPhys., 2016, 18 (10), 7075-7084. (2) S. Verma, Y. Hamasaki, C. Kim, W. Huang, S. Lu, H.R.M. Jhong, A.A. Gewirth, T. Fujigaya, N. Nakashima, P.J.A. Kenis, ACS Energy Lett., 2018, 3, 193-198. (3) T.T.H. Hoang, S. Verma, S. Ma, T.T. Fister, J. Timoshenko, A.I. Frenkel, P.J.A. Kenis, A.A. Gewirth, J. Am. Chem. Soc., 2018, 140, 5791-5797. (4) S. Verma, B. Kim, H.R. Jhong, S. Ma, P.J.A. Kenis, ChemSusChem, 2016, 9 (15), 1972-1979. (5) H.R.M. Jhong, F.R. Brushett, P.J.A. Kenis, Advanced Energy Materials, 2013, 3 (5), 589-599. (6) S Ma, R Luo, JI Gold, ZY Aaron, B Kim, P.J.A. Kenis, J. Materials Chemistry. A., 2016, 4 (22), 8573-8578. (7) B. Kim, F. Hillman, M. Ariyoshi, S. Fujikawa, P.J.A. Kenis, J. Power Sources, 2016, 312, 192-198. (8) K. Wu, E. Birgersson, B. Kim, P.J.A. Kenis, I.A. Karimi, J. Electrochem. Soc., 2015, 162 (1), F23-F32.

N2–H2 plasma functionalization of carbon fiber fabric for polyaniline grafting

AbstractCarbon fiber fabric was treated with radiofrequency plasma in a N2/H2 gas mixture to create functional groups with –NHx or –N, thus promoting conditions for polyaniline (PAni) grafting. The morphology and chemical structure of PAni on the carbon fiber surface were assessed by scanning electron microscopy and Raman spectroscopy, showing strong interactions between the PAni and the carbon fiber, especially for the 5‐min plasma‐treated substrate. The electrochemical activity of electrodes consisting of carbon fiber fabric and PAni was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy, which showed fast polarization response and lower charge transfer resistance for electrodes with better interactions between the PAni and the carbon fiber substrate, indicating the occurrence of grafting.

PANI//MoO3 Fiber-shaped Asymmetric Supercapacitors with Roll-type Configuration

An asymmetric fiber-shaped supercapacitor (FSC) with roll-type configuration, displaying high power and energy density characteristics, has been fabricated for energy storage in wearable devices. The positive and negative electrodes of the asymmetric FSC consist of polyaniline (PANI) and MoO3, respectively, and are deposited on a carbon fiber (CF) substrate using a chemical bath deposition method. A polyvinyl alcohol/H2SO4 gel is used as electrolyte, which also maintains the CF electrodes in fiber form. The asymmetric PANI//MoO3 roll-type FSC exhibits a wider potential range than its symmetric PANI//PANI counterpart, resulting in higher energy and power densities. The asymmetric PANI//MoO3 roll-type FSC shows an energy density of 67.51 µWh/cm3 with a power density of 59.71 mW/cm3 at a current of 10 mA, which is more than twice the energy density of symmetric PANI//PANI roll-type FSC (30.42 µWh/cm3 and 25.12 mW/cm3).

Singular properties of boron-doped diamond/carbon fiber composite as anode in Brilliant Green dye electrochemical degradation

Carbon fiber (CF) and boron doped diamond/carbon fiber (BDD/CF) were applied as anodes for the Brilliant Green dye electrochemical degradation process. CF substrates were obtained from polyacrylonitrile precursor heat treated at 1000 °C in a nitrogen atmosphere. BDD films were grown on CF substrates by hot filament chemical vapor deposition with boron source from an additional hydrogen line passing through a bubbler containing B2O3 dissolved in methanol solution with B/C ratio of 15,000 ppm. The electrodes were characterized by field emission gun-scanning electron microscopy images, Raman spectroscopy, and electrochemical impedance spectroscopy showing notable tridimensional characteristics besides their high diamond quality. They were applied to electrochemical degradation of Brilliant Green dye at different current densities using a concentration of 100 mg L−1. Their electrolysis efficiency was analyzed by UV/Vis spectrophotometry technique. The results showed that BDD/CF electrodes were efficient in the solution color removal, regardless of the current density value. BDD/CF electrode under the lowest current density of 10 mA·cm−2 presented the best performance with higher kinetic constant and color removal percentage associated to its low energetic consumption.