Peak Value Of Current Density Research Articles

Electrocatalytic performance of Shape-Controlled synthesized PdNi-rGO nano Cube on sodium borohydride and methanol electrooxidation

In recent years, increasing climate change, environmental pollution and water problems have increased the need for sustainable and environmentally friendly solutions in energy production. In this context, renewable energy sources, especially fuel cells, have become an important focus. In this study, the synthesis and characterization of the shape-controlled synthesized PdNi-rGO Cube electrocatalyst was carried out. X-ray diffraction (XRD), scanning electron microscopy with energy dispersive x-ray (SEM-EDX), and transmission electron microscope (TEM) characterization experiments were performed to examine the shape of the particles. TEM analysis revealed the formation of nanostructures with a size of 19.18 nm in the cubic structure of the PdNi-rGO. Furthermore, cyclic voltammetry (CV) measurements evaluated the usability of this electrocatalyst in the electrooxidation of sodium borohydride (NaBH4), and methanol (CH3OH). In this context, the anodic peak current density values were 77.34 mA/cm2 and 13.47 mA/cm2, for electrooxidation of sodium borohydride (NaBH4), and methanol (CH3OH), respectively. This study demonstrates that PdNi-rGO cube contains shape-controlled nanostructure, and these structures can play an important role in future renewable energy sources. It can also be considered an important step forward in the development of nanomaterial-based electrocatalysts capable of efficient energy conversion.

Calcium-, magnesium-, and yttrium-doped lithium nickel phosphate nanomaterials as high-performance catalysts for electrochemical water oxidation reaction

Abstract Electrochemical water oxidation reaction (WOR) lies among the most forthcoming approaches toward eco-conscious manufacturing of green hydrogen owing to its environmental favors and high energy density values. Its vast commoditization is restricted by high-efficiency and inexpensive catalysts that are extensively under constant research. Herein, calcium, magnesium, and yttrium doped lithium nickel phosphate olivines (LiNi1−x M x PO, LNMP; x = 0.1–0.9; M = Ca2+, Mg2+, and Y3+) were synthesized via non-aqueous sol-gel method and explored for catalytic WOR. Lithium nickel phosphates (LNP) and compositions were characterized via Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray diffraction techniques for the structural and morphological analyses. Glassy carbon electrode altered with the LNMPs when studied in a standard redox system of 5 mM KMnO4, displayed that yttrium doped LNP, i.e. LNYP-3 exhibits the highest active surface area (0.0050 cm2) displaying the lowest average crystallite size (D avg) i.e. ∼7 nm. Electrocatalytic behavior monitored in KOH showed that LNMP-2 offers the highest rate constant “k o,” value, i.e. 3.9 10−2 cm s−1 and the largest diffusion coefficient “D o,” i.e. 5.2 × 10−5 cm2 s−1. Kinetic and thermodynamic parameters demonstrated the facilitated electron transfer and electrocatalytic properties of proposed nanomaterials. Water oxidation peak current density values were indicative of the robust catalysis and facilitated water oxidation process besides lowering the Faradic onset potential signifying the transformation of less LNP into more conducive LNMP toward water oxidation.

Nano‐Nickel Doped Carbon Xerogel: Synthesis, Characterization and Catalytic Performance towards Ethanol Fuel Electro‐oxidation

AbstractIn this work, the synergism between the nano nickel particles and its carbon xerogel support, CX, together with their graphite substrate, G, leads to an efficient Nickel/CX/G electrode for electrocatalysis of ethanol oxidation reaction, EOR. The preparation conditions are optimized. The optimum electrode is made of 6 % weight of Ni doped in CX matrix and drop‐casted on a graphite surface, Ni‐6/CX/G. The catalyst structure and morphology are investigated using XRD, SEM, TEM and FTIR techniques. The electrochemical activity towards EOR is tested in 1 M NaOH+1 M Ethanol solutions by cyclic voltammetry combined with a rotating ring disk electrode. The optimum electrode shows an oxidation peak current density value of 5925 and considerable stability. This electrode may serve as a good candidate for the anode in the Direct Alkaline Ethanol Fuel Cell, DAEFC.

Optimizing Sustainable Energy Generation in Ethanol Fuel Cells: An Exploration of Carrageenan with TiO2 Nanoparticles and Ni/CeO2 Composites.

Based on the search for new biodegradable materials that are low cost and easy to synthesize by environmentally friendly methods, we report the use of carrageenan membranes (mixture of κ and λ carrageenans) with different concentrations of titanium dioxide nanoparticles (TiO2 NPs) and Ni/CeO2 (10 wt % Ni) for the fabrication of a novel fuel cell electrode for the oxidation of ethanol. Each membrane was characterized to determine its physicochemical properties using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. Using impedance spectroscopy (IS), a maximum value of 2.08 × 10-4 S/cm in ionic conductivity was found for the carrageenan nanocomposite with a concentration of 5 wt % TiO2 NPs (CR5%). Due to its high conductivity values, the CR5% membrane was mixed with Ni/CeO2 to prepare the working electrode for cyclic voltammetry measurements. Using a solution of 1 M ethanol and 1 M KOH, the oxidation of ethanol over CR5% + Ni/CeO2 resulted in peak current density values at forward and reverse scan voltages of 9.52 and 12.22 mA/cm2, respectively. From our results, the CR5% + Ni/CeO2 membrane proves to be more efficient in the oxidation of ethanol compared with commercially available Nafion membranes containing Ni/CeO2.

Mathematical characterization of performance and durability for the WO3 – Nb2O5 electrochromic thin films using finite experimental data

A comparison is made among the peak current density values of 1000 cycles of experimental chronoamperometry for WO3-Nb2O5 films with the simulated values. Quadratic and linear regression models are developed by using MATLAB standard function ‘fitlm’ to get least MSE and ‘predict’ method to extrapolate the current density values. Initial 400, 500, and 600 experimental cycles are used as starting references for predictions. Predicted model having −0.09 percent change with the experimental curve is followed to predict 10,000 cyclic values with −4.73 % difference. Binding energy values for W6+ (35.9, 38.05 eV), W5+ (36.8, 34.65 eV) and Nb5+ (210.35, 207.55 eV) are measured.

Enhanced methanol electrooxidation by electroactivated Pd/Ni(OH)2/N-rGO catalyst

Direct methanol fuel cells, in which electrocatalytic oxidation of methanol takes place, are one of the most promising technologies for facilitating the shift to renewable energy sources. However, they still suffer from high-catalyst-prices, as well as sluggish kinetics of methanol oxidation reaction (MOR). Therefore, herein, palladium/Nickel(II) hydroxide/nitrogen doped reduced graphene oxide (Pd/Ni(OH)2/N-rGO) hybrid was fabricated via facile two-step solution method and utilized as electrocatalyst for MOR. The in-situ electrochemical activation pre-treatment was proposed to engineer a highly active electrocatalyst. The Pd/Ni(OH)2/N-rGO, which had distinctive structural features along with robust synergistic effects, outperformed the commercial Pd electrocatalyst in terms of catalytic activity towards MOR, with elevated anodic peak current density values. The in-situ electrochemical activation pre-treatment lead to 3.3, 3.0, and 2.0-fold increase in activity of Pd/Ni(OH)2/N-rGO, Pd/N-rGO, and Pd/C, respectively. This research lays the door for a unique technique to manufacture high-performance, low-cost electrocatalysts that might be used in fuel cell technology instead of existing Pd electrocatalysts.

Ferroelectric-relaxor crossover induce large electrocaloric effect with ultrawide temperature span in NaNbO3-based lead-free ceramics

In this study, a large electrocaloric effect (ECE) of 0.49 K with an ultrawide temperature span of 80 °C ranging from −15 to 65 °C (0.49 K ± 10%) was reported in the 0.94(0.80NaNbO3–0.20BaTiO3)–0.06Bi0.5Na0.5TiO3 composition. The incorporation of Bi0.5Na0.5TiO3 (BNT) into the NaNbO3–BaTiO3 matrix induced a ferroelectric-to-relaxor (FR) phase transition, accompanied by polar P4 mm evolving to the nonpolar Pm3¯m phase and an increase in the relaxor degree. The inflexions in the peak current density value and Raman spectra indicated a successive downward-shift of FR temperature with the increasing BNT content, which established a continuous modulation of temperature corresponding to the peak ECE in this system. The obtained high ECE performance was believed to originate from an enhanced diffuse phase transition character and coexistence of P4 mm and Pm3¯m phases. This work may provide a guideline to designing high-efficiency solid-state cooling devices that are applied at mutable ambient temperature.

Effect of Acid Treatment on Electrocatalytic Performance of PtNi Catalyst

In this paper, we describe the synthesis of the AC-PtNi/G catalysts with graphene as the carrier, via the alcohol reduction and the sulfuric acid treatment. The prepared catalysts were microscopically characterized by X-ray diffractometry(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), electron spectroscopy(EDAX), and transmission electron micros-copy(TEM). We tested the electrochemical performance of the prepared catalysts using an electrochemical workstation and in situ infrared spectroscopy(FTIR). The results showed that the acid-treated AC-PtNi/G catalysts had a more uniform dispersion and with the increased of treatment time, the particle size of the catalyst became smaller. And the electrocatalytic performance of the AC-PtNi/G-48h catalyst treated with sulfuric acid for 48 h was significantly better than that of the untreated PtNi/G catalyst. Its electrochemically active surface area was 76.63 m2/g, and the peak current density value for catalytic oxidation of ethanol was 1218.83 A/g, which was 10 times that of ordinary commercial Pt/C catalyst. The steady-state current density value of 1100 s was 358.77 A/g, and it has excellent anti-CO toxicity performance. It was determined that a sulfuric acid treatment controlled catalyst particle size and increased the electrocatalytic activity of the catalytic oxidation of ethanol.

Remediation of lead (II)-contaminated soil using electrokinetics assisted by permeable reactive barrier with different filling materials

Removal of lead (II) (Pb2+) from contaminated soil was investigated using a new-type switchable-array-electrode electrokinetics assisted by permeable reactive barrier (SAE/EK-PRB). The soil pH after treatments with SAE/EK-PRB ranged from 3.5 to 4.8, and the peak values of current density was highest with 3.01 mA/cm2 at voltage gradient 2.5 V/cm. Both voltage gradient and moisture content promoted the removal of Pb2+. Moisture content 35% and 2.5 V/cm were considered as the optional operating conditions. Different PRB filling materials including zeolite, fly ash, active carbon alone and the combination of fly ash and graphene oxide were, therefore, investigated under the optional operating conditions. The highest removal reached 92.6% with the combination of fly ash and graphene oxide. Pb2+ forms in the soil with different PRB filling materials showed the percentages of weak bindings, such as exchangeable and carbonate forms decreased. However, strong binding, residual form increased largely, indicating the SAE/EK-PRB could effectively reduce the environmental risk of Pb2+ to a great extent. Fly ash and the combination of zeolite and fly ash as PRB filling materials demonstrated to be highly promising for the effective EK remediation of Pb2+-contaminated soil, taking the economic and environmental principles and remediation efficiency into consideration.

Effect of dry-electrode-based transcranial direct current stimulation on chronic low back pain and low back muscle activities: A double-blind sham-controlled study.

Dry-electrode-based transcranial direct current stimulation is a new type of non-invasive brain stimulation system which relieves chronic low back pain and improves related muscle movement, in a way that overcomes the drawback of conventional systems. To investigate the effectiveness of dry-electrode-based transcranial direct current stimulation in relieving chronic low back pain and altering pain-related low back muscles movement, by using pain assessment tool and surface electromyographic topography. We conducted a prospective, double-blind, randomized, sham-controlled study. 60 patients with non-specific chronic low back pain were randomly and evenly allocated into tDCS and sham groups. Each group accepted a single 20-minute stimulation at 2 mA on the primary motor cortex. Numeric rating scale for pain intensity assessment and root-mean-square difference parameter from surface electromyographic topography were measured before and after stimulation. The current direction in brain using finite element method was simulated to verify the current distribution under dry stimulation electrode. After stimulation, the pain intensity in the tDCS group significantly decreased, while it did not show evident change in the sham group. However, change of root-mean-square difference parameters between tDCS and sham groups showed no significant difference. Simulation results based on finite element method showed most of current focused on primary motor cortex while peak value of current density was 0.225 A/m2. Dry-electrode-based transcranial direct current stimulation can lower pain perception in patients with chronic low back pain. The analgesic mechanism can affect the top-down modulation pathway of pain.

Effect of electrode-electrolyte spatial mismatch on transcranial direct current stimulation: a finite element modeling study

Objective. Despite the encouraging pilot results of transcranial direct current stimulation (tDCS) revealing its effectiveness in neuromodulation, there are also studies reporting inconsistent outcomes. Apart from previously studied factors, such as the differences in head model structures, anodal displacements, electrode shape and size, and connector position, the hypothesis that the inevitable spatial mismatch between the electrolyte buffer and electrode might shape current flow in the cerebral cortex was tested in this work, and our results potentially explain some of the reported inconsistent outcomes. Approach. A finite element head model was built using cylinder electrodes with an arbitrary diameter of 2 cm. Current flow induced by different spatial mismatch types, degrees, and directions was simulated for three montages targeting the left motor cortex. Voxel-level current density differences and Jaccard index values of different percentiles for each mismatched configuration were calculated and compared throughout the cerebral cortex to determine the effect of electrode-electrolyte geometric mismatch. Main results. Spatial mismatch between the electrolyte buffer and electrode affected the current density distribution in the cerebral cortex to different extents, depending on the position of the return electrode and mismatch type, degree, and direction. Single cortical voxel current-density variance induced by the 50% excess or insufficient mismatch was as high as 14.44% or 38.04%, respectively. Moreover, the distribution of variance changed directionally with the mismatch orientation. Compared with the insufficient mismatch and single-directional mismatch, the excessive and symmetrical mismatch caused a less obvious effect on the current density distribution of tDCS. Specifically, the symmetrical excess electrolyte caused around 2%–4% current density changes for all the montages, with different degrees and directions of mismatch. When the target position was fixed at C3, maximum sensitivity to the electrolyte-electrode mismatch was achieved with Iz as the return electrode, compared with the other two choices. Further, more than 20% voxels with >90% percentile of the peak current density values would shift position if >30% insufficient geometric mismatch occurred for montage C3-Iz. Significance. Our findings suggest that special attention is required regarding the spatial matching of the electrolyte buffer to the electrode during tDCS to avoid unexpected large changes in current distribution.

In situ fuel phosphorylation facilitates the complete oxidation of glycerol in direct biomass cells

It is about a method to build direct biomass cells enabling complete fuel oxidation. Heated at a temperature from 40 °C to 90 °C, the fuel (glycerol) will be esterified in a solution of phosphoric acid to form monophosphate. A fuel cell fed with thus partly phosphorylated glycerol come with open circuit voltages varying from 0.65 to 0.83 V. The current densities are close to the values of a fuel cell run in a solution of NaOH, but 10 times higher than that of a cell with a neutral electrolyte (e.g. Na2SO4). Under optimized conditions, peak values of current density and power density are obtained at about 20 mA cm−2 and 2.2 mW cm−2 respectively. Thereafter a series of oxidized C1–C3 intermediates are detected in the discharged solutions. More importantly several cycles of fuel refeeding do not lead to any accumulation of glycerol or the discharging intermediates. This means in situ phosphorylation can successfully activate the fuel and facilitate its’ complete oxidation. Though discharging performance needs to be further improved, this partly phosphorylation method can be simple and effective to increase fuel utilization percentages in direct saccharide cells.

Influence of Parasitic Effects in Negative Differential Resistance Characteristics of Resonant Tunneling

A resonant tunneling electronic circuit (RTEC) with high and multiple peak-to-valley current density ratios (PVCDRs) exhibited in the negative differential resistance (NDR) curve has been proposed in this research. The PVCDR values in simulating research and experimental research of double PVCDR RTEC were respectively reached as high as 1.79 and 22 in average, which were obtained using the designed single PVCDR RTECs structure. Also, the peak current density (PCD) values of the last NDR in the double PVCDR RTEC structure in the simulation and experiment were respectively 1.85 A and 42 µA. Triple NDR characteristics also had been obtained with the PCD values reaching as high as 2.9 A and 46 µA, respectively, in simulating and experimental researches. The PVCDR values of triple NDR characteristic were respectively 1.5 and 4.6 in the simulation and experiment.

Silicon Tunnel Junctions Produced by Ion Implantation and Diffusion Processes for Tandem Solar Cells

This work reports on the fabrication of silicon tunnel junctions that can be used in silicon-based bottom cells for tandem solar cells. The tunnel junction was formed on n-type monocrystalline silicon wafers using the following two different processes: 1) a thermal diffusion of boron followed by an arsenic ion implantation; and 2) successive implantation steps of boron and arsenic ions. For both the processes, a rapid thermal annealing step was used to activate the dopants and cure the defects generated by the ion implantation. The activated dopant distribution across the tunnel junction was determined by electrochemical capacitancevoltage (ECV) measurements. The quality of the device was assessed from the peak-to-valley ratio and peak current density of its currentvoltage characteristics, as well as the resistivity. As a significant result, a peak current density value and a peak-to-valley ratio of approximately 50 A/cm2 and 1.7, respectively, were obtained for two consecutive implantations of boron and arsenic, followed by thermal annealing at 925C for 30 min. A very narrow depletion zone of 3.9nm was calculated from the ECV dopant concentrations measurements under full depletion approximation. Finally, solar cells fabricated using this optimized process resulted in a conversion efficiency of 10.1 against 12 obtained from the reference monocrystalline solar cell.

Exploring the Nickel–Graphene Nanocomposite Coatings for Superior Corrosion Resistance: Manipulating the Effect of Deposition Current Density on its Morphology, Mechanical Properties, and Erosion‐Corrosion Performance

The use of graphene‐based composite as anti‐corrosion and protective coatings for metallic materials is still a provocative topic worthy of debate. Nickel–graphene nanocomposite coatings have been successfully fabricated onto the mild steel by electrochemical co‐deposition technique. This research demonstrates the properties of nickel–graphene composite coatings influenced by different electrodeposition current densities. The effect of deposition current density on the; surface morphologies, composition, microstructures, grain sizes, mechanical, and electrochemical properties of the composite coatings are executed. The coarseness of deposited coatings increases with the increasing of deposition current density. The carbon content in the composite coatings increases first and then decreases by further increasing of current density. The improved mechanical properties and superior anti‐corrosion performance of composite coatings are obtained at the peak value of current density of 9 A dm−2. The incorporation of graphene sheets into nickel metal matrix lead to enhance the micro hardness, surface roughness, and adhesion strength of produced composite coatings. Furthermore, the presence of graphene in composite coating exhibits the reduced grain sizes and the enhanced erosion–corrosion resistance properties.

Room temperature synthesis of polyvinyl alcohol stabilized palladium nanoparticles: Solvent effect on shape and electro-catalytic activity

Palladium nanoparticles have been synthesized at room temperature, 25±.5°C by the reduction of K2PdCl4 using biocompatible polymer polyvinyl alcohol (PVA) as reducing and stabilizing agent in water and aqueous dimethyl formamide (DMF) media with varying composition of DMF. The effect of variation of composition of aqueous DMF on growth, morphology and size of palladium nanocrystals is explained. Different aqueous DMF mixtures furnish palladium nanoparticles of different shapes like triangular plates, cuboids, hexagon with different average edge length between (3–30 nm) indicating preferential interaction and blocking of DMF to some specific planes of nanocrystals leading to various shapes. The synthesized nanoparticles have been characterized by different spectroscopic, microscopic and electro-analytical studies like cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The increase in electro-catalytic activity is found to decrease with the increased size of the embedded crystallites deposited on the support constituting the electrodes and hence on the precursor medium. The same order of the studied electrodes is found from mole normalized peak current density values (Amol−1Pd) in CV, transition time in CP and steady current density values in CA, on increasing the content of DMF in the aqueous DMF solvent system as expected. The outcomes are explained on the basis of the crystallite size, morphology of the surface, unequal development of certain planes and purity of the products as guided by the rate of nucleation and growth of the particles formed in different media.

Effect of DC pulsed-current on deformation behavior of magnesium alloy thin sheets

A uniaxial tensile test was developed to investigate material deformation behavior under DC pulsed current load. Duty cycle was kept low to provide wide gap between peak current density and average current density. With average current density preserved at low value, the Joule heating effect can be minimized thus keeping temperature low. Tensile tests were carried out by changing peak current density value while keeping temperature near 40 ˚C. That approach can further distinguish effect of Joule Heating. In this research, it was observed that the effect of peak current density was not present.

Influence of Temperature on the Oxygen Electroreduction Activity at Micro-Mesoporous Carbon Support

Influence of temperature on the kinetics of oxygen electroreduction on molybdenum carbide derived carbon based catalysts has been analyzed in O2 saturated 0.1M KOH solution using rotating disc electrode and cyclic voltammetry methods. The calculated kinetic current density value (|jkin| = 62.6 A m−2) at the half-wave potential (−0.05 V vs. Hg|HgO|0.1M KOH) of platinum nanoparticles modified catalyst was maximal at 60°C. Two different linear areas in the Tafel-like plot have been observed for unmodified and Pt nanoparticles modified catalysts within the studied temperature range from 10 to 80°C. The calculated experimental apparent activation energy values for the oxygen reduction were within a range from 19 to 27 kJ mol−1 for Pt nanoparticles modified carbon catalyst within potential range from 0.05 to −0.07 V vs. Hg|HgO|0.1M KOH. The oxygen reduction peak current density values decrease with increasing the temperature from 10 to 80°C.

Ni Nano-particle Encapsulated in Hollow Carbon Sphere Electrocatalyst in Polymer Electrolyte Membrane Water Electrolyzer

The present study evaluates the synthesis by solvo-thermal method and electrocatalytic activity of nickel nano-particles encapsulated in hollow carbon sphere, in hydrogen and oxygen evolution reaction in PEM water electrolyzer. The XRD patterns have ascertained the formation of nickel metal with different planes in face centered cubic (fcc) and hexagonal closed pack (hcp) form. SEM and TEM images have confirmed the nickel nano-particles with diameter of 10–50nm inside the 0.2μm sized hollow carbon spheres. The BET surface area values gradually decreased with greater encapsulation of nickel; although the electrochemical active surface area (ECSA) values have been calculated as quite higher. It confirms the well dispersion of nickel in the materials and induces their electrocatalytic performance through the active surface sites. The cyclic voltammetric studies have evaluated hydrogen desorption peaks as five times more intense in nickel encapsulated materials, in comparison to the pure hollow carbon spheres. The anodic peak current density value has reached the highest level of 1.9Acm−2 for HCSNi10, which gradually decreases with lesser amount of nickel in the electrocatalysts. These electrocatalysts have been proved electrochemically stable during their usage for 48h long duration under potentiostatic condition.

Dual-functional Pt-on-Pd supported on reduced graphene oxide hybrids: Peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic

In this study, a facile hydrothermal method was developed to synthesize Pt-on-Pd supported on reduced graphene oxide (Pt-on-Pd/RGO) hybrids. Because of the synergistic effect between Pt-on-Pd and RGO, the obtained Pt-on-Pd/RGO had superior peroxidase-mimic activities in H2O2 reduction and TMB oxidation. The reaction medium was optimized and a sensing approach for H2O2 was developed with a linear range from 0.98 to 130.7μM of H2O2. In addition, the characteristic of electrocatalytic oxidation of methanol was investigated. The peak current density value, jf, for the Pt-on-Pd/RGO hybrid (328mAmg−1Pt) was about 1.85 fold higher than that of commercial Pt black (177mAmg−1Pt) and, also, more durable electrocatalytic activity could be obtained. For the first time, the dual-functional Pt-on-Pd/RGO with peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic was reported.