Hasil untuk "Industrial electrochemistry"

Raminta Šakickaitė, Zita Sukackienė, Virginija Kepenienė et al.

In this study, ternary NiFeP coatings were fabricated on a copper substrate using a simple, fast, and cost-effective electroless deposition method. The coatings were named Ni₈₅Fe₄P₁₂, Ni₈₀Fe₈P₁₂, and Ni₇₅Fe₁₂P₁₂, indicating 4, 8, and 12 at % of Fe, respectively. The surface morphology and composition of the coatings were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The activity of the prepared coatings was evaluated using the water-splitting reaction to determine the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1 M KOH electrolyte solution. Electrochemical measurements were carried out in a temperature range from 25 °C to 55 °C. The HER and OER current density values increased by up to 2.58 and 2.13 times, respectively, with temperature increase compared to the result at 25 °C. All three coatings demonstrated activity in both reactions. Ni₈₅Fe₄P₁₂ exhibited the highest catalytic efficiency in the HER, with the overpotential of 340 mV at 10 mAcm⁻² and a Tafel slope of 61 mVdec⁻¹. In the OER, the efficiency of the NiFeP catalysts correlated with their Fe content. The overpotential was 412 mV for Ni₈₀Fe₈P₁₂ and 432 mV for Ni₇₅Fe₁₂P₁₂ at 10 mAcm⁻² with Tafel slopes of 96 and 91 mVdec⁻¹, respectively. This study underscores the critical influence of Fe content on the catalytic efficiency of NiFeP coatings, with reduced Fe content enhancing HER and increased Fe content benefits OER.

Kye Hak Ko, Kum Hyok Ri, Song Chol Jong et al.

A novel view of the electrocatalysis of free chlorine on hydrogen oxidation was proposed by cyclic voltammetry (CV) in seawater solutions. Since seawater has good pH buffering from its composition (bicarbonate, carbonate, borate, etc.), there is no need for the addition of any supporting electrolyte during voltammetric analysis. In CV experiment using a Pt disk electrode, the peak of hydrogen oxidation reaction (HOR) was formed at about −0.8 V during the reverse scan and its height has correlated with increasing contents of free chlorine present in seawater solution. All experimental results showed that free chlorine exhibited clear electrocatalysis on HOR. It gives the possibility of the determination of free chlorine using its electrocatalysis on HOR. Our attempt to quantify free chlorine by electrocatalysis of free chlorine on HOR is thus a new perspective compared to many studies that have been conducted on direct detection of free chlorine using its own electrochemical properties. In a new electroanalytical method of free chlorine using the Pt disk electrode, the corresponding calibration curve exhibited a linear response in the content range from 0.02 to 0.4 mg L−1 with a correlation coefficient of 0.998. The limit of detection (LOD) calculated from S/N = 3 was 0.012 mg L−1 and the relative standard deviation (RSD) obtained was 4.4 %.

Tim Steeger, Raphael L. Streng, Anatoliy Senyshyn et al.

In recent years, Prussian blue analogs (PBAs) have gained significant attention due to their broad applicability. The synthesis routines of this material class have been shown to allow for great tunability by varying the corresponding parameters. The control of crystal phase, defect, and water content, as well as electrochemical properties, have been studied extensively for the state‐of‐the‐art coprecipitation method. In turn, electrochemical deposition, which is particularly suited for thin‐film production, remains mainly underexplored. This study investigates the effects of synthesis temperature, scan rate, precursor concentration, and supporting electrolyte pH on nickel hexacyanoferrate (NiHCF) films electrodeposited onto a high surface area carbon‐based substrate via cyclic voltammetry. Electrochemical analysis and morphological characterization reveal that higher deposition temperatures increase cation‐specific capacity, influence NiHCF coverage, and promote larger, more crystalline structures. Scan rate, precursor concentration, and pH variations further demonstrate the correlation between deposition parameters, crystallite size, and NiHCF structure. These findings highlight the tunability of electrodeposited PBAs for tailored electrochemical performance and morphology.

Dr. Anas El Attar, Badr Bouljoihel, Prof. Amine Ezzahi et al.

Abstract Herein, a new and simple strategy based on electrochemical cascade reactions was used to prepare copper/poly(para‐phenylenediamine). The catalysts were prepared by a facile one‐pot synthesis via an electrochemical method in a solution containing monomer and copper in a suitable concentration using potentiostatic or galvanostatic mode. Using galvanostatic mode leads to the formation of nanodendritic shape of copper hydroxide‐copper oxide in contrast with potentiostatic mode which leads to a spherical form. The response toward ethanol oxidation was greatly affected by the morphology of the obtained nanocomposite. Indeed, the current density obtained when using potentiostatic mode is about 26.55 mA cm−2 at 1.05 V vs Ag/AgCl. This performance is about 2.4 times higher than of the electrocatalyst prepared by galvanostatic mode (11.09 mA cm−2 at 0.85 V). The durability and long‐term stability of the obtained electrocatalysts were investigated using chronoamperometry and cyclic voltammetry. The decrease in current density is about 19 % and 49 % for electrocatalysts prepared by galvanostatic and potentiostatic mode respectively, after 700 scans. Finally, ex–situ FTIR spectroscopy was conducted in order to understand the reaction mechanism of ethanol oxidation in alkaline medium. It demonstrates that Cu(OH)2−Cu2O@PpPD can perform the complete oxidation of ethanol molecules, leading to the formation of CO2 molecule as the final product. This study highlighted a new simple and facile approach for synthesizing electrocatalysts based on Cu(OH)2−Cu2O@PpPD for alcohol oxidation applications.

Jian Gao, Mengxin Zhou, Xinyao Wang et al.

The oxygen reduction reaction (ORR) is of great importance for clean energy storage and conversion techniques such as fuel cells and metal–air batteries (MABs). However, the ORR is kinetically sluggish, and expensive noble metal catalysts are required. The high price and limited preservation of noble metal catalysts has largely hindered the wide application of clean power sources such as fuel cells and MABs. Therefore, it is important to prepare non-expensive metal catalysts (NPMC) to cut the price of the fuel cells and MABs for wide application. Here, we report the preparation of a Co₃O₄ carried on the N-doped carbon (Co/N-C) as the ORR NPMC with a facile Pharaoh’s Snakes reaction. The gas generated during the reaction is able to fabricate the porous structure of the resultant carbon doped with heteroatoms such as Co and N. The catalyst provides a high electrocatalytic activity towards ORR via the 4-e pathway with an onset and half-wave potential of 0.98 and 0.79 V (vs. RHE), respectively, in an electrolyte of 0.1 M KOH. The onset and half-wave potentials are close to those of the commercial Pt/C. This work demonstrates the promising potential of an ancient technology for preparing NPMCs toward the ORR.

Sanaz Momeni Boroujeni, Alexander Fill, Alexander Ridder et al.

Lithium metal anodes have again attracted widespread attention due to the continuously growing demand of cells with higher energy density. However, the lithium deposition mechanism and the affecting process of influencing factors, such as temperature, cycling current density, and electrolyte composition are not fully understood and require further investigation. In this article, the behavior of lithium metal anode at different temperatures (25, 40, and 60 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C), lithium salts, electrolyte concentrations (1 and 2 M), and the applied cell current (equivalent to 0.5 C, 1 C, and 2 C). is investigated. Two different salts were evaluated: lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesul-fonyl)imide (LiTFSI). The cells at a medium temperature (40 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C) show the highest Coulombic efficiency (CE). However, shorter cycle life is observed compared to the experiments at room temperature (25 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C). Regardless of electrolyte type and C-rate, the higher temperature of 60 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C provides the worst Coulombic efficiency and cycle life among those at the examined temperatures. A higher C-rate has a positive effect on the stability over the cycle life of the lithium cells. The best performance in terms of long cycle life and relatively good Coulombic efficiency is achieved by fast charging the cell with high concentration LiFSI in 1,2-dimethoxyethane (DME) electrolyte at a temperature of 25 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mo>∘</mo></msup></semantics></math></inline-formula>C. The cell has an average Coulombic efficiency of 0.987 over 223 cycles. In addition to galvanostatic experiments, Electrochemical Impedance Spectroscopy (EIS) measurements were performed to study the evolution of the interface under different conditions during cycling.

Robert Franke-Lang, Julia Kowal

Zinc-air batteries could be a key technology for higher energy densities of electrochemical energy storage systems. Many questions remain unanswered, however, and new methods for analyses and quantifications are needed. In this study, the distribution of relaxation times (DRT) based on ridge regression was applied to the impedance data of primary zinc-air batteries in a temperature range of 253 K and 313 K and at different State-of-Charges for the first time. Furthermore, the problem of the regularization parameter on real impedance spectroscopic measurements was addressed and a method was presented using the reconstruction of impedance data from the DRT as a quality criterion. The DRT was able to identify a so far undiscussed process and thus explain why some equivalent circuit models may fail.

Mustafa Aghazadeh, Mohammad Ghannadi Maragheh, Parviz Norouzi

Cu2+ doped iron oxide nanoparticles (Cu-IONPs) are prepared via a one-step facile electrodeposition procedure. In this procedure, Cu-IONPs are electro-deposited in a two-electrode set up from an additive-free aqueous solution of mixed Fe(NO3)3, FeCl2 and CuCl2 salts. The applied deposition parameters were current density of 10 mA cm-2, bath temperature of 25 25oC and deposition time of 30 min. The structural and morphological characterizations through X-ray diffraction (XRD), field emission electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) confirmed that the fabricated Cu-IONPs sample is composed of Cu2+ doped magnetite phase with particles with average size of 20nm. Magnetic studies by VSM showed that the deposited Cu-IONPs provide proper super-paramagnetic characters of saturation magnetization(Ms=54.47 emu g–1), remanent magnetization (Mr) (Mr=0.41 emu g–1) and coercivity (HCi=10.53 G). The obtained electrochemical data indicated that Cu-IONPs are enable to exhibit specific capacitance as high as 189.6 F g-1 at a discharging current of 2 Ag-1, and 88.8% capacity retention after 2000 GCD cycling. Based on the obtained results, our developed electrosynthesis method is proposed as a facile route for the synthesis of high performance Cu-IONPs.

Hansong Li, Shuxing Fu, Shen Niu et al.

Electrochemical mill-grinding (ECMG) is a new method of compound machining inspired by numerical-control milling. A simple rodlike grinding wheel that rotates at high speed is used as the cathode and processes the workpiece along a set trajectory. Electrochemical milling and grinding are both at play in ECMG, making it possible to machine large amounts of material from the workpiece while benefitting from excellent machining flexibility. In this paper, to machine GH4169 alloy highly efficiently, four types of rodlike grinding wheel are designed, all with a diameter of 10.2 mm, and the machining flow field is simulated using ANSYS software. The maximum feed rate of each grinding wheel is measured under different values of voltage and electrolyte pressure, and a groove-machining experiment is performed in which a maximum feed rate of 2.3 mm/min and material removal rate of 25.883 mg/s are achieved for a cutting depth of 10 mm. The machining accuracy and surface quality of the grooves are then compared and analysed.

Rajeev Jain, Alka Verma

A simple one step electroanalytical method has been developed for the first time for the quantification of antioxidant piperine at glassy carbon based sensor. Piperine is primary bioactive component of pepper which has gained a great deal of attention from researchers all over the world due to its wide range of potential biological applications as an antioxidant and anti-carcinogenic agent. In the present study electrochemical behavior of piperine was investigated using square wave voltammetry. The reaction kinetics was studied and experimental conditions were optimized. The voltammetric studies of piperine at glassy carbon electrode exhibited a well defined cathodic peak for its reduction in Britton-Robinson buffer at pH 7.36. Under optimized experimental condition the square wave reduction peak current was linear over concentration range 8 to 48 μg/mL (R2=0.995) with limit of detection (LOD) and limit of quantification of 2.4 μg/mL and 8.1μg/mL respectively. Developed method was successfully employed for the analysis of piperine in real samples.

Wenbin Tu, Yulin Cheng, Tingyan Zhan et al.

W-containing ceramic coatings were fabricated on AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) in an aluminate-based electrolyte with the addition of sodium tungstate (Na2WO4·2H2O). The addition of Na2WO4·2H2O not only increased the growth rate and surface roughness of the coatings but also improved the corrosion resistance of the PEO coating. The relationship between the corrosion resistance of the PEO coating and the concentration of Na2WO4·2H2O was studied, and the coating obtained in 10 g l-1 Na2WO4·2H2O showed the best corrosion resistance. Ce-based sealing followed by Al(H2PO4)3 sealing treatment was further carried out to improve the corrosion resistance of the coatings. It was found that the number and size of pores and micro-cracks decreased after sealing. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements indicated that the corrosion resistance of the PEO coatings was effectively improved by the two-step sealing method.

O.A. Farghaly, H.M. Al–Saidi, A.H. Naggar et al.

Ten metal ions viz, Fe(III), Cr(III), La(II), Sn(II), Co(II), Ba(II), Pd(II), Ti(II), Sr(II) and Zr(IV), were selected to elucidate their interaction with nalidixic acid (NA) using potentiometric and conductometric methods. The ligand ionization and the complexes stability constants have been obtained at 25±1.0 °C and 0.01 M ionic strength of NaCl in 25 % (v/v) aqueous–ethanol solution. Complexes of 1:1, 1:2 and/or 1:3 metals to ligand ratios were formed depending on the nature of the ligand or metal ions. As well as, the stoichiometry of complexes confirmed by the conductometric method. Also simple, precise, rapid and low–cost potentiometric and conductometric methods for NA determination and tablets are proposed. NA present in tablets containing known quantity of drug was potentiometrically titrated by 0.1 M of NaOH using a combined glass pH electrode. The detection limit was 0.19 mg L–1. The calibration graph was found to be linear in the range of 0.23–2.55 mg L–1. The correlation coefficient (r) was calculated to be 0.9952. The standard deviation (SD) was < 1.0. No interferences were observed in the presence of common components of the tablets. The percentage recoveries of NA in tablet dosage formulations by potentiometric and conductometric methods were (95.8–98.68) %, with standard deviations (SD) were within (0.18–0.4) (n=5).

Lingna Sun, Xianwen Yi, Chuan Shi et al.

A Li-rich Li[Li0.2Ni0.2Mn0.6]O2 cathode material coated with polyaniline (PANI) was prepared by a chemical in situ polymerization method. PANI is evenly coated on the surface of particles of the Li-rich material Li[Li0.2Ni0.2Mn0.6]O2 to form a good electrical conductive layer. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). When the PANI coating content was 6%, the Li-rich material exhibited a regular morphology and optimal electrochemical properties. The initial specific discharge capacity of the Li-rich material Li[Li0.2Ni0.2Mn0.6]O2/PANI was 262.0 mAh g-1 at 0.1 C, and that after 50 cycles was 243.7 mAh g-1, representing a capacity retention of 93% after 50 cycles.

Karla Carneiro de Siqueira Leite, Lívia M.F.C. Torres, Luane Ferreira Garcia et al.

The coumarins are an important class of phytochemicals with wide range of biological activities. The 7-hydroxy-6-methoxycoumarin, scopoletin is a biomarker widespread in plant kingdom, especially in the phytotherapic and nutraceutical ones. A considerable number of patents and scientific papers concerning its amazing pharmacological properties highlights the relevance of scopoletin. How your benzo-α-pyrone skeleton, resembling the flavonoid antioxidants, the electrochemical characterization of scopoletin can be a useful tool to understand the behavior between chemical and biological properties. Therefore, the aim of this work was to develop the electrochemical characterization of scopoletin at glassy carbon electrode, in a wide range of electrolyte conditions by means of cyclic, differential pulse and square wave voltammetry. Thus, it was found that akin to what would be expected for phenolic compounds, the 7-hydroxy group undergoes electrochemical oxidation at Ep1a ~0.7 V, meanwhile it leads to different oxidation products that showed to be oxidized at lower potentials. An oxidation mechanism was proposed, considering the results herein obtained.

Tamer Awad Ali, Gehad G. Mohamed, Ahmed R. Othman

New chemically modified carbon paste (CPEs) and screen-printed electrodes (SPEs) were fabricated incorborating copper oxide nanoparticles (CuO NPs) as a neutral ionophore and explored as Cu(II) selective electrodes. The electrodes were found to display Nernstian response over Cu(II) concentration of 5.3×10-7 to 1×10-2 and 6.1×10-8 to 1×10-2 mol L-1. The detection limits were found to be 5.3×10-7 and 6.1×10-8 mol L-1 for modified carbon paste (MCPEs; electrodes I and II) and screen-printed electrodes (MSPEs; electrodes III and IV), respectively. The MCPEs with dibutylphthalate (DBP) (electrode I) and tricresylphosphate (TCP) (electrode II) as plasticizers were found to have slope values of 29.65±0.30 and 28.99±0.60 mV decade-1, respectively. Also, the MSPEs with DBP (electrode III) and TCP (electrode IV) plasticizers showed Nernstian slopes of 30.01±0.20 and 29.35±0.40 mV decade-1, respectively. The electrodes have fast response time (8, 10, 5 and 7s for electrodes I, II, III and IV, respectively) and good selectivity with respect to different interfering ions. The fabricated electrodes were satisfactory applied to determine Cu(II) ion in pure solutions and different real spiked water samples using the proposed potentiometric method. The results obtained applying MCPEs and MSPEs agree well with the inductively coupled plasma atomic emission spectrometry (ICP-AES).

Kai Wang, Liwei Li, Tiezhu Zhang

The Ni (OH)2 particles are synthesized by repeated immersion method. The as-prepared particles are Ni (OH)2, which are well dispersed and have a fish-like shape. The electrochemical tests show that the particles have relatively high capacitance and excellent capacitive retention. The good structure and excellent performance suggest its promising application in supercapacitor.

Binbin Zhang, Yuan Zhou, Xiang Li et al.

FTIR (Fourier transformed infrared) spectra have been collected and analyzed for solutions of lithium tetrafluoroborate in propylene carbonate (PC). It has been shown that the carbonyl stretch, symmetric ring deformation stretch and ring deformation stretch bands for PC is very sensitive to the interaction between Li+ and the solvent molecule. Their half-peak breadth increases and bands split with the addition of LiBF4, indicating that a strong interaction exists between Li+ and PC molecule mainly through the oxygen group of C=O and ring position of PC.

Luciana S. Sanches, Claudia E.B. Marino, Lucia H. Mascaro

This paper reports on the study of electrodeposition films of Fe-Ni-W in sodium citrate solution at pH 5.0. Behavior alloys were obtained by cyclic voltammetry at different ion concentration ratios and films were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was concluded from the results of XPS that, during induced co-deposition of the species Fe (II), Ni (II) and W (VI), film growth consisted of a mixture of oxides of W (IV) and (V) doped with Fe and Ni (0), with these coatings analyzed by XPS.

Ali Babaei, David J. Garrett, Alison J. Downard

A novel composite film based on platinum nanoparticles (PtNPs), multi-walled carbon nanotubes (MWCNTs), room temperature ionic liquid (RTIL) and Nafion, is an effective matrix to immobilize myoglobin (Mb). Platinum nanoparticles were deposited on MWCNTs and characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. Direct electrochemistry and electrocatalysis of Mb were studied in detail using differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Using CA, the mediator-free biosensor response was linear with hydrogen peroxide (H2O2) concentration in the range of 0.5 to 210 μM with a detection limit of 0.1 μM.

Ilwhan Oh, Joohong Kye, Seongpil Hwang

The growth kinetics of a self-assembled monolayer (SAM) in solution was measured in situ in real time electrochemistry using microelectrode. The steady-state current produced by the oxidation of ferrocene in the presence of a microelectrode was recorded as a function of time. Introduction of 11-mercaptoundecanoic acid (MUA) into the electrochemical cell produced a decrease in the steady-state current related to formation of an insulating MUA SAM. The current decrease permitted monitoring of the SAM coverage formation over time. The time constants derived from fitting the time-dependent current to the rearrange-limited Langmuir model agreed well with previously reported results determined using other techniques, demonstrating that our simple method can reliably characterize SAM adsorption kinetics.