Electrical Conductivity Of Electrode Research Articles

Dual electrode functioning lithiated nickel based for solid oxide fuel cell

Research into producing electrode materials has increasingly focused on addressing the issues of durability experienced by electrode materials. There is a new configuration developing for the growing SOFC market. Symmetrical solid oxide fuel cells (S-SOFC) are a very new and innovative kind of fuel cell. S-SOFCs may be made practical by integrating lithiated nickel oxide-based materials, which are often used for lithium-ion battery applications. Accordingly, the focus of these studies will be on fundamental research, in particular the characterisation and chemical performance of lithiated nickel doped ruthenium (abbreviated as LN1-xRxO2 (x = 0.1,0.2, and 0.3). The LNRO-based powder was analysed in both oxidising and reducing environments to replicate the operating conditions of a dual-functioning electrode. The screen-printed LNRO/SDC/LNRO symmetrical cell was then subjected to 2 h of heat treatment at 800 °C. Additionally, the electrode's electrical conductivity and EIS analysis were performed on the samples. In a oxidised environment (H2:N2 gas mixture), LNR1, LNR2, and LNR3 have activation energies of 0.08, 0.07, and 0.09 eV, respectively; in a reduced environment (humidified air), these values are 0.22, 0.13, and 0.18 eV. Meanwhile, the best sample LNR2′s ASR value, determined by EIS analysis, is 6.123 Ω cm2 in air and 2.250 Ω cm2 in a reduced environment at 800 °C. This result proved that the dopant used in LNR2 has great promise as an electrode for the S-SOFC application, which is more than merely a means to enhance SOFC performance.

PdCu bimetallic nanoparticles decorated on ordered mesoporous silica (SBA-15) /MWCNTs as superior electrocatalyst for hydrogen evolution reaction

In the present study, a novel electrocatalyst with excellent catalytic performance based on PdCu bimetallic nanoparticles (NPs) supported on ordered mesoporous silica and multi-walled carbon nanotubes (PdCu NPs/SBA-15-MWCNT) was prepared for electrochemical hydrogen evolution reaction (HER). For this purpose, low-cost mesoporous SBA-15 was synthesized using silica extracted from Stem Sweep Ash (SSA) as an economically attractive silica source. Mesoporous SBA-15 with unparalleled porous structure is a stable support for PdCu bimetallic NPs which prevents the accumulation of PdCu bimetallic NPs and improves its efficiency in the catalytic process. The main advantage of this strategy is low loading of bimetallic catalyst with high catalytic activity. The presence of both mesoporous SBA-15 and MWCNTs materials in PdCu/SBA15-MWCNTs/carbon paste electrode (CPE) increases the metallic active sites and the electrical conductivity of electrode which provides great performance for HER. PdCu/SBA15-MWCNTs-CPE provided small Tafel slope (45 mV dec−1), low onset potential (~-150 mV), high current density (−165.24 mA cm−2at -360 mV) and exchange current density (2.51 mA cm−2) with great durability for HER in H2SO4 solution. Analysis of kinetic data suggests that the electrocatalyst controls HER by the Volmer-Heyrovsky mechanism. In addition, studies showed that the presence of sodium dodecyl sulfate (SDS) in electrolyte can decrease the potential of HER and increase the current density.

Process Performance of High Energy Wire EDM

Wire EDM is increasingly used for the production of components in small and medium batch sizes. Due to the higher wear capacity and electrical conductivity of electrodes with larger diameters and its electrical properties, higher discharge energies can be realized. Thus, cutting rates can be increased and larger working gaps occur. However, a higher energy input in the material also has a significant impact on the surface integrity. Therefore, in this paper the process performance and surface integrity of a steel material machined by using a brass and coated wire with a standard wire diameter and a 0.4 mm diameter are compared.

WITHDRAWN: Electrochemical detection of heavy metals using carbon quantum dots modified with metal oxides

Abstract The high toxicity of chemical pollutants and its detrimental effects to the living organisms has led to significant public concern. Hence it is very much necessary to monitor the level of these toxic ions in the environment using an appropriate sensor. In order to detect the heavy metal such as lead, mercury, cadmium etc. in water, there exist a need to develop a novel sensing technology for more sensitivity and rapid detection. The use of classical methods for the detection of the toxic ions in water is both tedious and time consuming. Nanomaterial of carbon serve as a powerful tool in analyzing these heavy metal ions due to their selectivity and sensitivity to one cation, owing to their excellent photoluminescence and photophysical properties.In this present work ,green synthesis of carbon quantum dots was carried out using lemon juice and onion juice. These CQD’s were then doped with metal oxides such as bismuth oxide and zinc oxide. These metal oxide doped CQD’s improves the sensitivity and electrical conductivity of electrodes and hence increases the rate of electrochemical reaction. The carbon dots and metal oxide doped carbon dots were characterized using IR technique, UV –Visble spectroscopy and SEM. The sensing property of electrode towards heavy metal was investigated by modifying the electrode with CQD’s, CQD’s doped with metal oxide and anionic polymer (nafion).The cyclic voltammetric studies were carried out with glassy carbon electrode modified with CQD/Bi203/Nafion. The cyclic voltammograms obtained showed that glassy carbon electrode modified with CQD/Bi203/Nafion showed excellent sensing property towards lead.

Electrochemical performance enhancement by the partial reduction of NiFe2O4@g-C3N4 with core-shell hollow structure

Transition metal oxide NiFe2O4 has many advantages such as abundance in nature, easy availability, low toxicity and being environmentally friendly. However, it suffers from poor electrical conductivity which results in unsatisfactory electrochemical performance. In this work, the construction of NiFe2O4@g-C3N4 core-shell hollow spherical structure and the in-situ formation of Fe–Ni alloy have been achieved by facile hydrothermal method followed by annealing in 5%H2/95%Ar. The electrical conductivity of electrode has been greatly improved leading to a specific capacity of 85.3 mAh g−1 at 1 A g−1 and a 67.2% capacity retention at 20 A g−1. A hybrid device exhibits 19.5 Wh kg−1 in specific energy and 150.1 W kg−1 in specific power, and good cycling stability of 100% capacity retention after 10,000 cycles at 6 A g−1.

Mathematical Modelling of Material Removal Rate During Electric Discharge Machining Using Buckingham’s Pi-Theorem

In the present work an attempt has been made to model material removal rate (MRR) by using Buckingham’s Pi-theorem during electric discharge machining (EDM) of shape memory NiTi alloy. Machining of Ni-Ti alloyis mostly attempted by non- conventional methods of machining, and, especially by EDM, as this advance material imposes machinability issues when cut by conventional processes. However, EDM process has low material removal rate.In present investigation EDM of NiTi alloy is carried out using electrolytic copper toolon die sink type of electric discharge machine. The experimental-based mathematical model to predict MRR is developed varying process parameters such as gap current, pulse on time, pulse off time, voltage, workpiece electrical conductivity and tool electrode electrical conductivity during the experiments. The model developed using dimensional analysis and Buckingham pie theorempredicts the value of MRR close to the experimental observations with the accuracy of 91 % shows that the developed model could be used to predict MRR during EDM of NiTi alloy within the domain of the parameters selected in the present study.

Flower-like Bi4Ti3O12/Carbon nanotubes as reservoir and promoter of polysulfide for lithium sulfur battery

Lithium-sulfur battery (LSB) is considered as the candidate of the new generation of rechargeable power conservation equipment due to its preferable theoretical specific energy and theoretical energy density. However, LSB is constrained by their inherent shortcomings containing notorious shuttle effect and poor conductivity of sulfur and discharge products (Li2S/Li2S2). In order to overcome these obstacles, flower-shaped bismuth titanate embedded with carbon nanotubes (BTO/CNT) is designed as efficient sulfur host materials. The BTO/CNT composites can provide abundant voidage to support the sulfur, and its large contact surface can accelerate the catalytic transformation of lithiumsulfide. Importantly, bismuth titanate (BTO) as ferroelectric materials can spontaneously polarize to induce an inner electric field, which can not only accelerate the lithium polysulfides (LiPS) conversion due to its catalytic activity, but also enhance the chemical interaction for heteropolar LiPS based on the Lewis acid and bases interaction to alleviate the shuttle effect of LSB. Furthermore, the embedded CNT constructs a conductive network greatly improving electrode electrical conductivity. In view of these advantages, BTO/CNT as sulfur host delivers impressive cyclic stability with attenuation rate of 0.037% per cycle capacity over 1000 cycles with sulfur loading around 1.0 mg cm−2 at 1 C, suggesting enormous potential for excellent-performance Li–S batteries.

Three-Dimensional Heterostructured NiCoP@NiMn-Layered Double Hydroxide Arrays Supported on Ni Foam as a Bifunctional Electrocatalyst for Overall Water Splitting.

Herein, the rational design and preparation of three-dimensional heterostructured NiCoP@NiMn-layered double hydroxide arrays supported on Ni foam (NiCoP@NiMn LDH/NF) is reported as a new bifunctional water-splitting electrocatalyst with high performance. Prepared with facile hydrothermal reactions and phosphorization, the NiCoP@NiMn LDH/NF is simultaneously highly active toward oxygen evolution reaction (OER) (100, 300, and 600 mA cm-2 at overpotentials of 293, 315, and 327 mV, respectively) and hydrogen evolution reaction (HER) (100, 200, and 300 mA cm-2 at overpotentials of 116, 130, and 136 mV, respectively). Interestingly, with cell voltages of 1.519, 1.642, 1.671, and 1.687 V at 10, 100, 200, and 300 mA cm-2, respectively, for overall water splitting, this electrocatalyst achieves 95.2% faradaic efficiency for OER, suggesting a relatively high contribution of water splitting in the apparent current in spite of the existence of partial catalyst oxidation. The heterostructure arrays supported on Ni foam have some advantages, acting as a bifunctional water-splitting electrocatalyst: (1) heterostructured NCoP@NiMn LDH combines the intrinsic properties of individual NiCoP (excellent activity for HER) and NiMn LDH (high activity for OER) via the effective interface engineering between the two phases; (2) the NiCoP core material serves as a fast electron transfer channel to enhance the electrode's electrical conductivity; and (3) Ni foam with a three-dimensional-network structure as a support is beneficial to exposing more active sites and ensures efficient gas bubble release and electron/mass transfer.

Effect of pore shapes on the overall electrical conductivity of cathode material in Li-ion batteries

The paper focuses on the development and verification of a quantitative micromechanical model for evaluation of the overall electrical conductivity of electrodes in Li-ion batteries. Based on microstructural observations, the cathode is modeled as a multiphase composite consisting of PVDF/C matrix, spherical particles made of the active component Li(Ni1/3Co1/3Mn1/3)O2, oblate spheroidal graphite particles and concave pores. Effective electrical conductivity of such a multiphase material is evaluated using Maxwell homogenization techniques and compared with the experimental data available in literature. The agreement is generally very good and allow extraction of information about porous space geometry required for evaluation of other physical properties of the material.

An Ionic Polymer Actuator Capable of Simultaneously Improving Bandwidth and Blocking Force for Efficient Haptic Feedback

Recently, an ionic electroactive polymer (i-EAP) actuators are spotlighted in various fields because they provide a lot of advantages such as lightweight, flexibility, simple process, and low driving power. However, they suffer from low blocking force, displacement, and wide bandwidth that can be implemented under electric field for apply to various applications. In order to apply these i-EAP actuators to various applications, it is important to provide the optimum characteristics of the i-EAP actuator adaptive to the target application. Particularly, it is required to achieve high blocking force and displacement as well as wide actuation bandwidth for haptic feedback among the various applications. In this talk, we propose an ionic polymer actuator (IPA) with wide bandwidth of over 100Hz and high blocking force based on PEDOT:PSS electrode with additives and ionic polymer with fibrillary nanostructures for effective haptic feedback. In particular, we developed an actuator that improves the interfacial properties between electrodes and an ionic polymer as well as electrical conductivity of electrodes by simple and effective way through spray-coating of PEDOT: PSS solution with additives. As a result, the IPA was successfully operated with a large displacement up to 2.5mm at an operating frequency of 20mHz under an applied voltage of 2V. Further, the IPA shows large blocking force of 0.4mN at operating frequency of 1Hz. These our actuator is capable of driving up to a high frequency of 200Hz and shows an improved blocking force up to 0.4mN. We potentially believe our IPA will provide a rational guide to future haptic feedback.

Highly compressible 3-D hierarchical porous carbon nanotube/metal organic framework/polyaniline hybrid sponges supercapacitors

Optimization of the transport behaviors of ions and electrons is the key for the property improvement of supercapacitor, which are essentially controlled by the design of hierarchical porous structure and electrical conductive backbone, from nanoscale to microscale, respectively. However, such design requirements are very difficult to be satisfied simultaneously, because the generation of porosity would result to the detrimental effects on the electrical conductivity of electrode. In this study, we propose to prepare a hierarchical porous supercapacitor electrode, with a novel 3-D highly porous (with pore size in the range of 50-100 nm) carbon nanotube sponges (CNTS) as a conductive substrate for the successively deposition of metal organic frameworks (MOF) and polyaniline. The porous structure of the sponge is beneficial for precursor penetration and uniform deposition of MOF and polyaniline (PANI) on to the nanotubes. The highly porous CNTS not only provides conductive highway for electrons, but also channels for ions quick diffusion. The coated MOF offers extra ion storage reservoir, while PANI further wire the insulating MOF together. In addition, the composite structure does not require any conductive additives or mechanical binders and delivers excellent capacitance coupled with flexible, compressive, and have relatively high specific capacitance.

A core-sheath holey graphene/graphite composite fiber intercalated with MoS2 nanosheets for high-performance fiber supercapacitors

One-dimensional fiber-shaped supercapacitors have recently attracted lots of attention as a potential energy storage solution for emerging wearable devices. However, fiber supercapacitors often exhibit low energy storage capacity and poor rate capability due to their small volume, low specific volumetric capacitance, and poor electrode electrical conductivity. Here we demonstrate a novel hydrothermally assembled core-sheath fiber comprised of a graphite fiber core and a MoS2 nanosheet intercalated holey graphene oxide (HGO) sheath as electrodes for fiber supercapacitors. HGO and MoS2 nanosheets self-assemble around the graphite fiber core in a space-confined reactor during the hydrothermal synthesis. HGO nanosheets supply abundance channels for electrolyte ion transfer, MoS2 nanosheets provide large pseudocapacitance, and graphite fibers serve as faster electron transfer highways. The mass loading of MoS2 is easily tunable. The optimized composite fiber with 34.9 wt% MoS2 delivers a high volumetric capacitance 421 F cm−3 at the CV scan rate of 5 mV s−1 and the capacitance retention of 51.0% when the scan rate increases from 2 to 100 mV s−1. The core-sheath fiber enables fast reversible redox kinetics, and its surface capacitive energy storage contributes ∼75–80% of its total energy storage. The assembled solid-state fiber supercapacitor delivers a high device volumetric capacitance of 94 F cm−3 at 0.1 A cm−3 and an energy density of 8.2 mWh cm−3 at the power density of 40 mW cm−3, outperforming many recently reported fiber supercapacitors. The core-sheath fiber electrode design based on HGO, MoS2 and graphite fiber cores provides an efficient platform for designing various novel fiber electrodes for potential electrochemical applications.

Physical Interpretations of Electrochemical Impedance Spectroscopy of Redox Active Electrodes for Electrical Energy Storage

This study aims to provide physical interpretations of electrochemical impedance spectroscopy (EIS) measurements for redox active electrodes in a three-electrode configuration. To do so, a physicochemical transport model was used accounting for (i) reversible redox reactions at the electrode/electrolyte interface, (ii) charge transport in the electrode, (iii) ion intercalation into the pseudocapacitive electrode, (iv) electric double layer formation, and (v) ion electrodiffusion in binary and symmetric electrolytes. Typical Nyquist plots generated by EIS of redox active electrodes were reproduced numerically for a wide range of electrode electrical conductivity, electrolyte thickness, redox reaction rate constant, and bias potential. The electrode, bulk electrolyte, charge transfer, and mass transfer resistances could be unequivocally identified from the Nyquist plots. The electrode and bulk electrolyte resistances were independent of the bias potential, while the sum of the charge and mass transfer resis...

Preliminary investigation of electrical conductivity of monolithic biochar

Monolithic biochar is explored as electrode material in supercapacitor – a fast-charging, long-lasting energy storage device. Electrical conductivity of electrode is critical to supercapacitor's performance. Traditionally, biochar is used as a solid fuel for combustion where electrical conductivity is largely irrelevant and ignored. This work explores electrical conductivity of monolithic biochar and elucidates its dependence on micro and macro structures of biochar. Electrical conductivity of biochar was found to be highly dependent on its degree of carbonization. Bulk conductivity of biochar can increase by over six orders of magnitudes when its carbon content changes from 86.8 to 93.7 wt%. Transmission electronic microscope and x-ray diffraction analyses revealed the presence of graphite nanocrystals (∼3 nm) and the growth of biochar crystallinity after heat treatment at 950 °C. The highest skeletal conductivity of carbon was 343.2 S/m, found in a heat-treated sugar maple biochar with 96.2 wt% of carbon. It is higher than that of graphite single crystal in direction perpendicular to graphene plane (333.3 S/m). Moreover, it was observed conductivity of monolithic biochar increased with compressive loading and dropped to the pre-compression level when the loading was released - a new phenomenon termed “elastic behavior of electrical conductivity of biochar”.

Simulations and Interpretation of Three-Electrode Cyclic Voltammograms of Pseudocapacitive Electrodes

This study aims to provide physical interpretation of cyclic voltammograms obtained from pseudocapacitive electrodes using three-electrode systems. It presents numerical simulations based on a recent continuum model able to reproduce experimental CV curves obtained with different Nb2O5-based electrodes and LiClO4 in propylene carbonate as electrolyte. First, the respective contributions of faradaic and electric double layer charge storage mechanisms were clearly identified along with the associated faradaic and capacitive regimes. This was further illustrated by comparing CV curves for pseudocapacitive (Nb2O5) and EDLC (carbon) electrodes. Transition from the faradaic to the capacitive regime was caused by Li+ starvation at the electrode/electrolyte interface and the formation of ClO4− electric double layer. Moreover, the effects of electrode crystallinity on CV curves were reproduced and interpreted in terms of enhanced transport properties for lithium intercalation and electrode electrical conductivity. Finally, the electrode thickness featured an optimum corresponding to a compromise between accommodating large amounts of intercalated lithium and minimizing the potential drop across the electrode to drive faradaic reactions.

Review of Energy and Power of Supercapacitor Using Carbon Electrodes from Fibers of Oil Palm Fruit Bunches

Energy and power capability of a supercapacitor is important because of its function to provide backup power or pulse current in electronic/electric products or systems. The choice of its electrode materials, typically such as carbon, metal oxide or conducting polymer determines the mechanism of its energy storage process. This short review focuses on the supercapacitors using porous carbon electrode prepared, respectively, from fibers of oil palm empty fruit bunches. The specific energy and specific power of these supercapacitors were analyzed to observe their trend of change with respect to the electrode preparation parameters affecting the porosity, structure, surface chemistry and electrical conductivity of electrodes, and thence influence the energy and power capability of a supercapacitor. This review found that the trend of change in specific energy and specific power was not in favor of the expectation that both the specific energy and specific power should be in increasing trend with a significant progress.

Self-assembly of monodisperse starburst carbon spheres into hierarchically organized nanostructured supercapacitor electrodes.

We report a three-dimensional (3D) porous carbon electrode containing both nanoscale and microscale porosity, which has been hierarchically organized to provide efficient ion and electron transport. The electrode organization is provided via the colloidal self-assembly of monodisperse starburst carbon spheres (MSCSs). The periodic close-packing of the MSCSs provides continuous pores inside the 3D structure that facilitate ion and electron transport (electrode electrical conductivity ∼0.35 S m(-1)), and the internal meso- and micropores of the MSCS provide a good specific capacitance. The capacitance of the 3D-ordered porous MSCS electrode is ∼58 F g(-1) at 0.58 A g(-1), 48% larger than that of disordered MSCS electrode at the same rate. At 1 A g(-1) the capacitance of the ordered electrode is 57 F g(-1) (95% of the 0.24 A g(-1) value), which is 64% greater than the capacitance of the disordered electrode at the same rate. The ordered electrode preserves 95% of its initial capacitance after 4000 charging/discharging cycles.

An experimental work on using conductive powder-filled polymer composite cast material as tool electrode in EDM

This paper introduces the composite tool electrodes made of electrical conductive powder-filled polyester resin matrix material, providing promise for the electrical discharge machining (EDM) process. The dendrite-shaped copper powder, graphite powder, and their mixture were used as conductive fillers. Six different types of composite electrodes, namely, plain copper-polyester, pressed copper-polyester, furnaced copper-polyester, plain copper-graphite-polyester, pressed copper-graphite-polyester, and furnaced copper-graphite-polyester were prepared. It is found experimentally that increasing v f improved workpiece material removal rate, tool wear rate, relative wear, and electrical conductivity of electrodes. The pressed copper-polyester electrodes were found to be promising in the ED finishing of workpieces at low machining current settings. The practical applicability of the proposed composite electrodes in the industry was also illustrated.

Simulations of Cyclic Voltammetry for Electric Double Layers in Asymmetric Electrolytes: A Generalized Modified Poisson–Nernst–Planck Model

This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |zi| of either ion species. By contrast, the ion diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τCV and the “RC time scale” τRC corresponding to the characteristic time of ions’ electrodiffusion. For τRC ≪ τCV, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τRC ≫ τCV, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.

Effect of composition, sonication and pressure on the rate capability of 5 V-LiNi0.5Mn1.5O4 composite cathodes

Positive composite electrodes having LiNi0.5Mn1.5O4 spinel as active material, a blend of graphite and carbon black for increasing the electrode electrical conductivity and either polyvinyldenefluoride (PVDF) or a blend of PVDF with a small amount of Teflon® (1wt%) for building up the electrode. They have been processed by tape casting on an aluminum foil as current collector using the doctor blade technique. Additionally, the component blends were either sonicated or not, and the processed electrodes were compacted or not under subsequent cold pressing. Composites electrodes with high weight, up to 17mg/cm2, were prepared and studied as positive electrodes for lithium-ion batteries. The addition of Teflon® and the application of the sonication treatment lead to uniform electrodes that are well-adhered to the aluminum foil. Both parameters contribute to improve the capacity drained at high rates (5C). Additional compaction of the electrode/aluminum assemblies remarkably enhances the electrode rate capabilities. At 5C rate, remarkable capacity retentions between 80% and 90% are found for electrodes with weights in the range 3–17mg/cm2, having Teflon® in their formulation, prepared after sonication of their component blends and compacted under 2tonnes/cm2.