Anodic Deposition Research Articles

Anodic MnO2 deposition on Titanium Electrode Coated with Thermally Prepared Manganese Oxide

Zinc electrowinning uses an acidic zinc sulfate solution prepared from zinc ore, which contains some other metal ions such as Mn2+. The solution after zinc electrowinning goes back to the solution preparation process, in which the zinc concentration is recovered to the appropriate level, while that of Mn2+ is increased, if no Mn2+ is consumed by anodic deposition in electrowinning cell, which is possible with amorphous RuO2-Ta2O5/Ti anodes [1]. Therefore, the situation that Mn2+ concentration becomes high enough to recover Mn2+ as manganese oxide is expected, and it would resemble the commercial production process of EMD (Electrolytic Manganese Dioxide) that is famous as the positive electrode material of some batteries. For such a novel manganese recovering system in zinc electrowinning, the anode for deposition of MnO2 from zinc electrowinning solution is needed, with which MnO2 is deposited on and harvested from the anode that should be durable for the deposition and harvesting cycle. In this study, we prepared the titanium electrode covered with manganese oxide as the catalytic layer for MnO2 deposition from zinc electrowinning solution, and the obtained electrode was characterized by XRD, SEM, and EDX. The polarization measurement and continuous electrolysis of the anode in Mn2+ containing solutions were also performed to examine the obtained product on the anode and the current efficiency. The manganese oxide coated titanium electrode was prepared by thermal decomposition of the precursor solution containing Mn2+ painted on a titanium substrate which had been degreased in acetone and etched in 10% oxalic acid. The obtained electrode was analyzed by XRD, SEM, and EDX. The anodic polarization of the anode in H2SO4 solution with and without Mn2+ was examined by cyclic voltammetry with a conventional three-electrode cell equipped with a platinum plate counter electrode and an Ag/AgCl reference electrode in saturated KCl solution. Constant current electrolysis was also performed to obtain MnO2 on the anode, and the weight of the anode before and after the electrolysis was measured to know the amount of the product which was characterized by XRD. The electrolytic solution was 2 mol/L H2SO4 + MnSO4 and used at a temperature from 40 oC to 75 oC. The catalytic layer prepared by thermal decomposition was found to be Mn2O3 by XRD measurements. Constant current electrolysis with the anode was carried out under different conditions, in which the typical examples are 40 o C or 75 o C as the electrolyte temperature with electrolysis at 5 mA/cm2 for 30 min. For these conditions, the product on the anode was obtained with the increase of the anode’s weight by electrolysis, and the XRD results showed the diffraction pattern corresponding to MnO2, although the diffraction peak intensity was weak for the product obtained at 40 oC compared to that at 75 oC. The current efficiency for MnO2 deposition was calculated with the assumption that no oxygen evolution occurs, and the results were 17.5% at 40 oC and 70.6% at 75 oC. It was also found that the electrolyte was transparent before constant current electrolysis, which was unchanged by the electrolysis at 75 oC, while that became dark red at 40 oC, implying that Mn3 + is generated at 40 oC and the oxidation of Mn2+ to MnO2 is not completed. More detailed results on the effects of the electrolysis conditions on the obtained product and the current efficiency will be shown in this paper. This work was financially supported by “Kyoto Super Cluster Program” of Japan Science and Technology Agency (JST). Reference [1] T. Zhang, Ph.D. Thesis, Doshisha University (2015).

A Fully Regenerable Thermal Silver Ammonia Battery to Convert Low-Grade Waste Heat to Electricity

A vast amount of low-grade thermal energy (temperature < 130 ⁰C) is available globally at industrial plants and from solar and geothermal sources. Converting these sources of energy to electricity has drawn increasing attention in recent years. Solid-state thermoelectrics (SSTs) and liquid-based thermoelectrochemical systems (TECs) have been widely investigated as means of converting low-grade waste heat to electrical energy. However, despite much progress in both the methods, these systems have failed to produce high power densities, and have not been cost-effective. A recently developed thermally regenerative ammonia batteries (TRAB) showed a significantly higher power production (~12 times more) than both SSTs and TECs. In a TRAB, electrical power is obtained from the formation of metal ammine complexes, which are produced by adding ammonia to the anolyte, but not to the catholyte. After the cell discharges, ammonia is separated from the anolyte using a conventional technology, such as distillation with low-grade waste heat, and then added to the other electrolyte for the next discharge cycle. The previous TRAB based on copper electrodes and a copper salt electrolyte showed a relatively high power production. However, unbalanced rates of anode dissolution and deposition of copper on the cathode limited the use of copper in closed-loop cycles. To address the reversibility issue, a silver-based TRAB was developed as an alternative to the copper-based TRAB. With silver, the cathodic and anodic coulombic efficiencies of the TRAB were the same (~100%), resulting in a reversible system for converting low-grade waste heat into electricity over many successive cycles. The developed silver system produced a net maximum power density of 30 W m−2-electrode area, with a net energy production of 490 Wh m−3-anolyte in a flow cell with an optimal hydraulic retention time (HRT) of 2 s. Successive deposition and dissolution cycling (i.e., the electrode reversibility) showed the system was stable over a hundred cycles. An initial economic analysis of the system showed that the price of electricity produced based on materials costs was 1.8 times more than the average electricity price is the U.S. ($ 120 MWh−1), due primarily to the cost of the membrane as well as sliver. However, this could be reduced to $ 120 MWh−1 if the cost of a membrane used in the system could be reduced to $10 m–2. Other potential benefits, such as elimination of air pollution, and beneficial issues related to health and climate change were not included in the comparison. Although the cost of building and operation relative to energy production of Ag-TRAB is currently higher than that of conventional technologies, this approach could generate a cleaner method of electrical power generation using a waste source of heat if the commercial cost of ion exchange membranes could be significantly reduced.

Defective and “c-Disordered” Hortensia-like Layered MnOx as an Efficient Electrocatalyst for Water Oxidation at Neutral pH

The development of a highly active manganese-based water oxidation catalyst in the design of an ideal artificial photosynthetic device operating under neutral pH conditions remains a great challenge, due to the instability of pivotal Mn3+ intermediates. We report here defective and “c-disordered” layered manganese oxides (MnOx-300) formed on a fluorine-doped tin oxide electrode by constant anodic potential deposition and subsequent annealing, with a catalytic onset (0.25 mA/cm2) at an overpotential (η) of 280 mV and a benchmark catalytic current density of 1.0 mA/cm2 at an overpotential (η) of 330 mV under neutral pH (1 M potassium phosphate). Steady current density above 8.2 mA/cm2 was obtained during the electrolysis at 1.4 V versus the normal hydrogen electrode for 20 h. Insightful studies showed that the main contributing factors for the observed high activity of MnOx-300 are (i) a defective and randomly stacked layered structure, (ii) an increased degree of Jahn–Teller distorted Mn3+ in the MnO6 octa...

Ultrafine Silver Nanoparticles for Seeded Lithium Deposition toward Stable Lithium Metal Anode.

To exploit the high energy density of the lithium (Li) metal battery, it is imperative to address the dendrite growth and interface instability of the anode. 3D hosts for Li metal are expected to suppress the growth of Li dendrites. Heterogeneous seeds are effective in guiding Li deposition and realizing spatial control over Li nucleation. Herein, this study shows that ultrafine silver (Ag) nanoparticles, which are synthesized via a novel rapid Joule heating method, can serve as nanoseeds to direct the deposition of Li within the 3D host materials, resolving the problems of the Li metal anode. By optimizing the Joule heating method, ultrafine Ag nanoparticles (≈40 nm) are homogeneously anchored on carbon nanofibers. The Ag nanoseeds effectively reduce the nucleation overpotential of Li and guide the Li deposition in the 3D carbon matrix uniformly, free from the dendrites. A stable and reversible Li metal anode is achieved in virtue of the Ag nanoseeds in the 3D substrate, showing a low overpotential (≈0.025 V) for a long cycle life. The ultrafine nanoseeds achieved by rapid Joule heating render uniform deposition of Li metal anode in 3D hosts, promising a safe and long-life Li metal battery for high-energy applications.

NiS2/FeS Holey Film as Freestanding Electrode for High‐Performance Lithium Battery

AbstractIn this work, a freestanding NiS2/FeS holey film (HF) is prepared after electrochemical anodic and chemical vapor deposition treatments. With the combination of good electrical conductivity and holey structure, the NiS2/FeS HF presents superior electrochemical performance, due to the following reasons: (i) Porous structure of HF provides a large surface area and more active sites/channels/pathways to enhance the ion/mass diffusion. Moreover, the porous structure can reduce the damage from the volumetric expansion. (ii) The as‐prepared electrode combines the current collector (residual NiFe alloy) and active materials (sulfides) together, thus reducing the resistance of the electrode. Additionally, the good conductivity of HF can improve electron transport. (iii) Sulfides are more stable as active materials than sulfur, showing only a small capacity decay while retaining high cyclability performance. This work provides a promising way to develop high energy and stable electrode for Li‐S battery.

An Analytical Model for Investigations on the Stress Distribution in Planar Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFC) have evolved to successful energy conversion devices for many applications, e.g. auxiliary power units (APU) or combined heat power generation systems (CHP). However, operation conditions under elevated temperatures as well as repeated temperature changes imply extreme demands for the materials involved, questioning durability and reliability of these fuel cells. These properties are important criteria which are not yet resolved satisfyingly. Especially, the effect of internal stresses in cell components arising from thermal shocks or heat cycles on the lifetime of a SOFC still remains unsolved. The residual stress induced by the production process influence the strength of the cell, either. A determination of the stress state is essential to improve the strength of the fuel cells. An analytical model is presented to determine the residual stress distribution in planar SOFCs during the whole production process. The residual stress is generated due to deposition process (e.g. quenching in thermal spraying or sputtering) and the CTE mismatch due to cooling from deposition temperature to ambient temperature. This model is based on the analytical model proposed by Y.C. Tsui and T.W. Clyne, which was adapted to the production process of SOFCs [1]. The model formulations relate to planar geometries. As boundary conditions, the substrate is clamped at one end and is free to bend during the whole process. Linear elastic material behavior without temperature dependency was assumed for all materials. The intrinsic stress and the thermal stress are introduced layer-by-layer in progressively deposited coating systems. By adding one layer for each deposition step, the residual stress distribution in the specimen can be predicted. A schematic representation of the stress generation coming from both contributions is shown in figure 1. The intrinsic stress is considered in the anode layer and in the electrolyte layer, respectively. In the anode layer the intrinsic stress, which is in the tensile range, is caused by shrinkage due to sintering. However the intrinsic stress in the electrolyte layer is compressive. This is mainly due to ion bombardment on the surface during sputtering. Thermal stress due to CTE mismatch is calculated for the different production steps, which require different temperatures. The final total residual stress is obtained by adding the contributions of deposition and thermal stress. The investigated SOFC is a MSC type with a porous ferritic Cr-steel substrate, a Ni/YSZ anode layer and an 8YSZ electrolyte layer on top [2, 3]. A polished cross section is shown in figure 2. In this study, the influence of the cathode layer on the stress distribution is neglected due to the low mechanical stability of this layer. For validation purposes a numerical model was built by means of Finite Element Methods (FEM) and compared with the analytical results. In the framework of this study a sensitivity analysis was conducted with respect to the geometric parameters as well as the intrinsic stress. The calculated stress distribution is comparable to the numerical results. However, differences in terms of magnitude between the two models can be observed. After anode deposition, the total stress level is in the tensile range. This observation can be explained by the large tensile intrinsic stress, which dominates the compressive thermal stress. The electrolyte deposition results in large compressive stress in the electrolyte layer, which is a consequence of the compressive intrinsic stress, but still tensile stress remains in the anode layer. These insights lead to the conclusion that thermal stress due to CTE mismatch has minor influence on the residual stress in contrast to the intrinsic stress, which are determined by the production process. These observations hold for several parameter sets. A validation of the models with experimental results is planned in the future. Figure 1

Advances in Low Temperature Coatings for Solid Oxide Fuel Cell Components

In the development of solid-oxide fuel cells, coating technologies are essential to successful commercialization. Electrode coating technologies allow the cost-effective deposition of anode and cathodes on cell components at high volumes and high precision. Further, catalytic and corrosion resistant coatings for common steel alloys find application in gas delivery and fuel reforming components of the balance-of-plant. Such corrosion-resistant alloys are also combined with conductive and insulating oxide protective layers to making low-cost steel interconnectors corrosion-resistant at SOFC operating while maintaining low contact resistance and minimizing Cr volatilization. Many of the first generation coating technologies that have found commercial implementation were designed for cell and stack operating temperatures of 750°C and higher. By design, conductive coatings for steels provide low contributions to the overall stack resistance (ASR < 0.05 ohm-cm2) at these operating temperatures. However, as stack operating temperatures push to the 600°C range, new protective coatings are required that achieve similar resistances at lower temperatures. In this paper, Nexceris will report on the development of new formulations designed to meet these needs, based on our patented approaches. To complement these protective coatings, Nexceris has developed a suite of contact paste, insulating layer coatings and catalytic materials for SOFC stacks and balance of plant, all designed with the end-user needs in mind. Leveraging aerosol spray deposition approaches that have been scaled to commercial requirements, Nexceris can interleave these coatings to create uniquely functional interconnects, cells and reformer components. Examples of the flexibility of these coating approaches will be provided, with performance data.

Oxygen vacancies: Effective strategy to boost sodium storage of amorphous electrode materials

Oxygen vacancies (OVs) are reported for the first time as an effective strategy to boost the electrochemical performance for amorphous electrode materials of sodium-ion batteries (SIB). Amorphous SnO2 is used as a model anode material to demonstrate the significant impact of OVs because it has received much attention in the SIB field. Amorphous SnO2 ordered arrays are fabricated using the nanoimprinted anodic aluminum oxide (AAO) template and atomic layer deposition and OVs are confined in the material by annealing the arrays in the N2 atmosphere. The OVs-containing amorphous SnO2 ordered arrays, used as binder- and conductive additive-free anodes, exhibit high reversible capacity and good cycle life by retaining the capacities of 376 mAh g−1 after 100 cycles at 0.05Ag−1 and 220 mAh g−1 after 800 cycles at 1Ag−1. They also show great rate capability by delivering the capacities of 210 and 200 mAh g−1 at 10 and 20Ag−1, respectively. Electrochemical kinetic study reveals that the presence of OVs greatly enhances charge transfer/transport in the amorphous SnO2, thereby boosts the performance comparing with the OVs-free counterpart. This work highlights the importance of modulating defects in amorphous electrode materials toward promoted sodium storage.

Photoactive TiO2 Films Produced with Different Techniques in Anodic Spark Deposition Regime

Photoactive TiO₂ Films Produced with Different Techniques in Anodic Spark Deposition Regime

An Analytical Model for Investigations on the Stress Distribution in Planar Solid Oxide Fuel Cells

An analytical model is presented to determine the residual stress distribution in planar Solid Oxide Fuel Cells (SOFCs). Usually, the residual stress in SOFCs is generated due to deposition processes of several layers in the manufacturing route and the CTE mismatch due to cooling from deposition to ambient temperature. In this model the deposition as well as the thermal stress are considered in each layer. The final residual stress is obtained by adding the contributions of deposition and thermal stress. The investigated SOFC is an MSC type. After anode deposition, the total stress is in the tensile range. The electrolyte deposition results in large compressive stresses in the electrolyte but still tensile stress remains in the anode layer. This leads to the conclusion that thermal stress due to CTE mismatch has minor influence on the residual stress in contrast to the deposition stress. These observations hold for several parameter sets.

Advances in Low Temperature Coatings for Solid Oxide Fuel Cell Components

In the development of solid-oxide fuel cells, high-performance coatings are essential to successful commercialization. Electrode coating technologies allow the cost-effective deposition of anode and cathodes on cell components at high volumes and high precision. Further, catalytic and corrosion resistant coatings for common steel alloys find application in gas delivery and fuel reforming components of the balance-of-plant. Such corrosion-resistant alloys are also combined with conductive and insulating oxide protective layers to making low-cost steel interconnectors corrosion-resistant at SOFC operating while maintaining low contact resistance and minimizing Cr volatilization. Many of the first-generation coating technologies that have found commercial implementation were designed for cell and stack operating temperatures of 750 °C and higher. In this paper, Nexceris will report on the development of new formulations designed to meet the needs of lower operating temperature SOFCs.

VO2 Nanoflakes as the Cathode Material of Hybrid Magnesium-Lithium-Ion Batteries with High Energy Density.

The hybrid magnesium-lithium-ion batteries (MLIBs) combining the dendrite-free deposition of the Mg anode and the fast Li intercalation cathode are better alternatives to Li-ion batteries (LIBs) in large-scale power storage systems. In this article, we reported hybrid MLIBs assembled with the VO2 cathode, dendrite-free Mg anode, and the Mg-Li dual-salt electrolyte. Satisfactorily, the VO2 cathode delivered a stable plateau at about 1.75 V, and a high specific discharge capacity of 244.4 mA h g-1. To the best of our knowledge, the VO2 cathode displays the highest energy density of 427 Wh kg-1 among reported MLIBs in coin-type batteries. In addition, an excellent rate performance and a wide operating temperature window from 0 to 55 °C have been obtained. The combination of VO2 cathode, dual-salt electrolyte, and Mg anode would pave the way for the development of high energy density, safe, and low-cost batteries.

Effect of surface hydrophilicity on the supercapacitive performance of carbon paper

In this paper, the surface hydrophilicity of carbon paper was modified by use of Caro’s acid, and MnO2 electrodeposited on carbon paper (CP) or surface-modified carbon paper (SMCP) were prepared through an anodic electrochemical deposition method. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of CP, SMCP-30, SMCP-60, and SMCP-90 indicated that the peaks at 1054, 1214, 1722, and 3426 cm−1 correspond to the stretching vibrations of C–O, C–H, C=O, and –OH. Our study results show that with the extension period of oxidation treatment time, the corresponding content of these groups C–O, C–H, C=O, and –OH increased; then, their surface hydrophilic properties enhanced; and finally, their capacitances increased. This study results indicate that introducing these groups C–O, C–H, C=O, and –OH into the surface of electrode materials is an important strategy for improving their capacitances.

Strained W(SexS1–x)2 Nanoporous Films for Highly Efficient Hydrogen Evolution

A W(SexS1–x)2 nanoporous architecture (NPA) was developed by facile anodic and chemical vapor deposition treatments. The ternary W(SexS1–x)2 NPA offers significant advantages toward high-efficiency hydrogen generation: (i) Nanoporous morphology provides more electrochemically active sites to split water. (ii) Lattice mismatch and disordering in the mix-phased W(SexS1–x)2 film introduce more defects to enhance the catalytic activity. (iii) Conducting 1T phase formed in the strained W(SexS1–x)2 facilitates the electron transfer during catalytic reactions. Therefore, an onset overpotential of 45 mV and a Tafel slope of 59 mV dec–1 were achieved using the as-prepared W(SexS1–x)2 NPA.

Electrochemical synthesis of three-dimensional porous networks of nickel with different micro-nano structures for the fabrication of Ni/MnOx nanocomposites with enhanced supercapacitive performance

We have electrochemically synthesized 3D-porous Ni/MnOx nanocomposites for supercapacitor applications. 3D porous micro-nanostructured networks of nickel were prepared using hydrogen bubbles as a dynamic template at different deposition potentials and times. The prepared nickel films were used then as 3D-porous substrates for anodic deposition of manganese oxide nanostructures. The effects of deposition potential and time on the structure of the prepared nickel scaffolds and especially on the capacitive behavior of the subsequently fabricated 3D-porous Ni/MnOx nanocomposites were investigated. The results show that the areal capacitance and especially the rate capability of prepared Ni/MnOx nanocomposites have improved with increasing the deposition potential or optimizing the deposition time of nickel films in the nanocomposites. The prepared 3D-porous Ni/MnOx nanocomposite, in which the nickel scaffold has been deposited at the potential of −6V and duration of 90s, show almost the highest capacitive performance among all other prepared nanocomposites. This prepared nanocomposite, with the loading mass of 1.65mgcm−2, showed the high areal capacitance of 654mFcm−2 (396.4Fg−1) at the current density of 0.5mAcm−2 (0.3Ag−1) in 0.5M Na2SO4 solution. This nanocomposite also revealed the highest rate capability; the capacitance retention is about 63% (412mFcm−2) with increasing the discharge rate from 0.5 to 20mAcm−2, which is almost twice the observed amount of retention when the deposition potential of Ni films was −2V (31%) or their deposition time was 45s (34%). In addition, the prepared nanocomposite exhibited an outstanding cycling stability. The capacitance retention was about 98.91% after performing 2000 charge-discharge cycles.

Transient modeling of spent nuclear fuel electrorefining with liquid metal electrode

During the molten salt electrorefining of spent nuclear fuel, multiple phases such as oxide, solid metal, liquid metal, and molten salt often co-exist. Computational modeling can be a useful tool for understanding the reaction mechanism across the multiple phases. The new model has been developed and applied to a lab-scale electrorefining with liquid metal anode and solid cathode LiCl-KCl molten salt. The benchmark study predicts anodic dissolution and cathodic deposition of U and Pu with minor disagreements. In particular, the on-set of Pu deposition on the surface of the solid cathode is well estimated, which is important for the quality of U ingot and the safeguards of process. The underestimation of U deposition (∼6%) and the overestimation of Pu dissolution (∼7%) at the end of simulation are explained by unconsidered reaction species such as Np and Am from the liquid Cd anode, which overestimates the dissolution of Pu from the anode compared to the measured data. The sensitivity study also reveals the transition behaviors of electrochemical reactions for U and Pu on the solid cathode are changed by diffusion boundary layer thickness, transfer coefficients, and the difference of electrochemical potentials more sensitively than those of the liquid metal anode. For this specific experiment case, the thinner diffusion boundary layer improves the prediction of cathodic reactions particularly at the end of electrorefining.

Deposition of Ultrathin Cellulose Nanofibers Films As Bio-Implant Corrosion Coatings

The wide use of magnesium and magnesium-based alloys for bio-implant materials has so far been restricted due to the rapid corrosion rate of such materials under in-vivo conditions 1,2. Cellulose based coatings have previously been examined as coatings for magnesium materials although the use of TEMPO-oxidised nano-fibrillated cellulose (CNF-TEMPO) coatings has yet to be explored 3,4. The work outlines details of an investigation in to the effect that deposition method has on the coating characteristics. Three different methods were used to deposit CNF-TEMPO coatings including adsorption, spin coating and anodic electrophoretic deposition. The coatings were subsequent analysed using atomic force microscopy (AFM), ellipsometry and quartz crystal microbalance (QCM) to determine differences in nanotopographic surface roughness and hydrophilicity in particular. The ability of the EPD technique to deposit films from relative dilute solutions (0.01 to 0.1 wt-%) was demonstrated. Finally, samples of magnesium were coated and the corrosion properties of the ultrathin films were determined using a number of electrochemical techniques including linear sweep voltammetry, polarization and free corrosion measurements. Overall, the results show that CNF-TEMPO coatings produced using the EPD method offer a potential starting point for the next generation of biobased coatings for implant materials.

ELECTROPHORETIC DEPOSITION OF DISPERSED GRAPHITE AND ELECTROCHEMICAL PROPERTIES OF OBTAINED FILMS

The paper considers the problems of obtaining the new electrode materials used in the electric power sources. The electrode material was prepared by anodic electrophoretic deposition in an alkaline medium of graphite nanosized particles. Nanoscale carbon phase was obtained by graphite foil anodic polarization in sulfuric acid followed by ultrasonic dispersing of the obtained powder. Electrophoretic coatings were deposited on a stainless steel electrode at applied potentials in the range of 5-10 V. The dependence of the anodic current density and specific capacity of the deposited film is linear on the anode potential. The method of FT-IR spectroscopy to study the properties of the surface of the obtained film was used. It was shown that as a result of electrophoresis the sufficiently strong reduction of surface oxygen-containing groups represented mainly phenolic groups occurs. The optimal value of the potential for deposition of electrophoretic films - 5 V, for a given value after 5 min of electrophoresis formed film thickness is 430 nm with a minimum content of oxygen-containing surface groups. Electrochemical properties of the resulting films were determined with a cyclic voltammetry in an acidic medium. It was found that at value of the potential sweep rate of 20 mV/s the specific film capacity was 117 F/g.Forcitation:Bratkov I.V., Yudina T.F., Mel'nikov A.G., Ershova T.V., Filimonov D.A. Electrophoretic deposition of dispersed graphite and electrochemical properties of obtained films. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 3. P. 77-82.

Graphene/carbon nanotube hybrid as a multi-functional interfacial reinforcement for carbon fiber-reinforced composites

Abstract A graphene/carbon nanotube hybrid material stabilized in an aqueous medium, was coated on carbon fibers by anodic electrophoretic deposition. Chemically oxidized graphene, graphene oxide, was used as a stabilizing agent for dispersion of carbon nanotubes and as a transport medium for the graphene oxide/carbon nanotube hybrid during electrophoretic deposition. This hybrid coating increased the wettability and surface roughness of carbon fibers, which led to improved affinity between the carbon fibers and epoxy matrix. The resulting hybrid-coated carbon fiber-reinforced composites showed an enhancement of over 10% in the short beam strength compared to un-coated carbon fiber composites and demonstrated significantly improved through-thickness electrical conductivity (increase of over 1400%).

Ferroelectric BiFeO3/TiO2 nanotube heterostructures for enhanced photoelectrochemical performance

Ferroelectric based heterostructures have shown great promises in solar water splitting due to unique photoelectrochemical (PEC) properties including polarization-induced charge separation and tunable electrochemical surface reaction. A highly ordered ferroelectric BiFeO3/TiO2 nanotube (TNT) heterostructures were fabricated by anodic oxidation and pulsed laser deposition. The microscopic morphology, optical, and PEC properties of nanostructures were characterized. The BiFeO3/TNT photoelectrode is photoactive under visible light illumination, which exhibits higher photocurrent from greater water oxidation, compared with the pure TNT photoelectrode. The coating thickness of BiFeO3 strongly affected the photoelectrochemical properties. The enhanced PEC performance could be attributed to the effective charge separation and the favorable band bending for water oxidation, originating from ferroelectric polarization-related internal field.