Hasil untuk "Industrial electrochemistry"

Muhammad Saleem Akhtar, Zaeem Ur Rehman, Witold Chromiński et al.

Transition metal sulfides have drawn a lot of interest in the field of electrochemical energy storage. However, their performance is hampered due to the stacking faults during the electrode fabrication. In this study, we report the Zn-doped Ni3S2 vertically grown 2-dimensional nanostructures on the conductive nickel foam by a one-step, rapid, energy-efficient, and cost-effective microwave-assisted method. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM) analyses confirmed the morphological and phase composition as initially identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical investigations substantiated the boosted performance of the electrode, an impressive specific capacitance value of 1984 F g−1 and 5.95 F cm−2 at a discharge current of 3 mA cm−2. Later on, this electrode, when tested in a Swagelok cell as a positive electrode and graphene nano pellets as a negative electrode, achieved a maximum energy density of 45.5 Whkg−1 and 910 Wkg−1 power at a discharge current rate of 1 A g−1. The pseudocapacitive characteristics of this binder-free nanostructured electrode, driven by reversible redox reactions, highlight their potential for high-performance energy storage applications.

Soumyadeep Sur, Nikhil Vekariya, Shikhar Krishn Jha et al.

High entropy materials have garnered substantial attention in the field of materials science due to its tunable properties in various structural and functional applications. This work demonstrates for the first time a facile synthesis of high-entropy spinel oxide (HESO) for natural sunlight-driven photocatalytic dye degradation. The oxide catalyst with a nominal composition (CoCrFeMnNi)3O4 was prepared by a modified sol-gel method followed by a heat treatment at 950 °C. The synthesized powder was characterized for its composition, morphology, and photocatalytic activity. The X-ray diffraction and the X-ray photoelectron spectroscopy analysis confirmed the formation of (CoCrFeMnNi)3O4 with high compositional purity. Methylene Blue dye was chosen for gauging the photocatalytic activity of the prepared material subjected to sunlight irradiation. The catalyst showed a rapid decomposition rate with greater than 95 % degradation efficiency in 100 min. It was found that the prepared high entropy catalyst can degrade the dye under varying reaction conditions, and the spent catalyst can quickly be recovered using an external magnetic field. Also, the most probable reaction mechanism and kinetic model for photocatalysis have been investigated.

Dr. Maryam Nazari, Prof. Soheila Kashanian, Dr. Fatemeh Parnianchi et al.

Abstract Electrochemical sensors and biosensors are today important analytical and monitoring tools in various fields, from agriculture and the food industry to environmental and biomedical/pharmaceutical applications. In particular, the integration of nanotechnology with electrochemical sensors and biosensors to develop a new generation of sensor platforms has made enormous progress in recent years. The outstanding properties of one‐dimensional (1D) nanofibers (NFs), such as high porosity, superior mechanical properties and high specific surface area have made them attractive electrocatalysts, support materials for the immobilization of biomolecules as well as mimetic materials for sensing and biosensing applications. Moreover, the possibility of fabricating multifunctional composites based on NFs increases (bio)sensing capabilities through synergistic effects and additive properties. This review describes the progress made over the last decade in the use of multifunctional NFs‐based composites as modified electrodes for the sensing of various analytes in biomedical, food, and wastewater treatment applications. The aim of this review is to provide a comprehensive overview and a guide for researchers from different disciplines to fabricate and improve their selective NFs‐based (bio)sensor platforms for the detection of desired analytes or multi‐analytes.

Yapci Remedios‐Díaz, Stefan Delgado, Dr. Juan Carlos Calderón et al.

Abstract In this work, catalytic performance of MoS2 supported on Mo2TiC2 and Ti3C2 MXenes towards the oxygen reduction reaction (ORR) was studied. These materials were synthesised through an etching route of MAX phases as precursors of MXenes, followed by a hydrothermal treatment to coat them with MoS2. This procedure generated MoS2 nanospheres covering the MXenes, which were verified by SEM‐EDX mapping, Raman spectroscopy and XPS. Activity of these materials towards ORR was studied by RRDE, comparing its performance with that of individual MoS2 and MXenes. As main features, it was demonstrated that production of HOO− occurring on the composites decreases in comparison with individual materials. Long‐term stability tests performed in O2‐saturated electrolyte showed a drop in the activity of the materials due to the increase in the production of HOO−, although no morphological or compositional changes were observed. Despite this result, the improvement of the catalytic properties of the individual materials means that these composites can be considered as candidates to be used as supports of active non‐noble metal nanoparticles in the cathodes of anion exchange membrane fuel cells (AEMFCs).

Siyabonga Patrick Mbokazi, Thabo Matthews, Makhaokane Paulina Chabalala et al.

Abstract Due to their low cost, accessibility of resources, and improved stability and durability, carbon‐based nanomaterials have attracted significant attention as cathode materials for oxygen reduction reactions. These materials also exhibit intrinsic physical and electrochemical features. However, their potential for use in fuel cells is constrained by low ORR activity and slow kinetics. Carbon nanomaterials can be functionalized and doped with heteroatoms to change their morphologies and generate a large number of oxygen reduction active sites to lessen the problems. Doping the carbon lattice with heteroatoms like N, S, and P and functionalizing the carbon structure with −OCH3, −F, −COO−, −O− are two of these modifications that can change specific properties of the carbon nanomaterials like expanding interlayer distance, producing a large number of active sites, and enhancing oxygen reduction activity. When compared to pristine carbon‐based nanomaterials, these doped and functionalized carbon nanomaterials, including their composites, exhibit accelerated rate performance, outstanding stability, and higher methanol tolerance. This article summarizes the most recent developments in heteroatom‐doped and functionalized carbon‐based nanomaterials, covering different synthesis approaches, characterization methods, electrochemical performance, and oxygen reduction reaction mechanisms. As cathode materials for fuel cell technologies, the significance of heteroatom co‐doping and transition metal heteroatom co‐doping is also underlined.

Jia Shen, Yating Zhu, Fengmei Zhou et al.

Abstract Pharmaceuticals and personal care products (PPCPs) are currently drawing significant attention due to their environmental impact. Electro‐Fenton, one of the advanced oxidation processes (AOPs), is an efficient and comprehensive technology to degrade all kinds of organic pollutants, but the degradation efficiency relies on cathode material. In this work, phosphorus‐doped porous carbon material coated graphite felt (P‐GF) was prepared by adopting phytic acid as a phosphorus source through high temperature solid‐state method. The microstructure and the elements composition of this fabricated material were investigated by SEM, BET and XPS. With phosphorus doping and plenty of carbon porous structures, the hydrophilicity and infiltrating property of the P‐GF had been greatly improved. The prepared P‐GF material enhanced the electrochemical reduction of O2 and could significantly enhance the yield of H2O2. It was used as a cathode to degrade pollutants under a constant potential, and methylparaben (MePa) was chosen as a research model for optimizing the experimental conditions and analyzing the possible degradation pathway. The P‐GF cathode achieved an excellent ability of degrading nearly 100 % of methylparaben within 3 h. The simultaneous removal ability of the P‐GF to four parabens was impressed. Additionally, the P‐GF material exhibited outstanding reusability.

M. Sepúlveda, J.G. Castaño, F. Echeverría et al.

The effect of alloying sputter-deposited Ti with 2 at.% of Au on the growth of anodic nanotubes was studied in monoethylene glycol electrolyte containing 1.0 mol dm−3 of water and 0.1 mol dm−3 of ammonium fluoride. The classic shape of nanotubes modified with quasi-spherical clusters of Au48-198 was obtained on Ti-Au (2 at.%). The results were compared to the formation of a barrier-type anodic film which suggested that gold located at the alloy/anodic film interface is enriched as a consequence of the preferential oxidation of titanium during the prior anodizing period and transported to the cell boundary region of the nanotubular film in the form of quasi-spherical clusters of Au48-198. A consequence of the inclusion of Au48-198 in the structure of the nanotubes was a reduction in the rate of nanotubular film growth due to the generation of oxygen catalysed on the clusters. A further increase in gold content up to 8 at.% in the alloy resulted in the formation of sponge-like or nanoporous anodic layers, with the structure depending on electrolyte composition.

Haidi Tang, Zongzi Jin, Yusen Wu et al.

Nanofiber-structured La2NiO4+δ (LNO) and LaNi0.6Fe0.4O3-δ (LNF) cathodes, which were fabricated by an electrospinning technique, were used for proton-conducting solid oxide fuel cells (H-SOFCs) for the first time, aiming to develop high-performance cobalt-free cathodes for H-SOFCs. High porosity and large specific surface area of LNO, LNF nanofiber-structured cathodes were beneficial for the cathode reactions, resulting in an encouraging peak power density of 508 mWcm−2 and 551 mWcm−2 for LNO and LNF cathode cell at 700 °C, respectively. The nanofiber-structured cathodes showed a higher fuel cell performance and lower polarization resistance compared with that of the cell using corresponding powder cathode, suggesting the construction of nanofiber-structured cathode provided an alternative and promising route to prepare high performance cathodes for H-SOFCs. Keywords: Proton conductor, Cobalt-free cathode, Nanofiber, Solid oxide fuel cells

Yanru Fan, Bingxu Feng, Yu Huang et al.

In this paper, the interface between two immiscible electrolyte solutions (ITIES) is adopted as the bionic interface model to investigate the interfacial electron transfer (ET) process of levodopa by using thin-layer cyclic voltammetry. Three zinc porphyrins with a systematic variation in structure are used as the reactants in the organic phase for the supply of varied overall driving forces at the ITIES. The consecutive two-step ET reactions between levodopa and three zinc porphyrins with the corresponding ET rate constants are evaluated precisely. The relationship between the interfacial ET rate constants and the overall driving force are also studied. It is found that the ET kinetics of the bimolecular reactions at the ITIES obeys the Marcus theory in a wide potential region. The results of this work will assist in our understanding of the interfacial electron-transfer process of levodopa in vivo.

Jingyi Xu

Chalcogenide nanostructures and nanocomposites as semiconductors have attracted intense attentions in various potential applications such as hydrogen production owing to their remarkable photoelectrochemical activity. In this study, ZnS-CdS nanocomposite with cubic ZnS and hexagonal CdS was synthesized with a simple wet chemical method. As can be seen from SEM and TEM images, CdS was formed on the outer layer of ZnS NPs. The hydrogen production rate of ZnS-CdS nanocomposite was much higher than that of ZnS NPs, indicating the remarkable enhancement of hydrogen production activity of photocatalyst with the addition of CdS. The hydrogen production rate increased more than 4 times after the deposition of Ru on the surface of ZnS-CdS. In addition, the as-prepared ZnS-CdS nancomposite demonstrated an excellent stability over 50 h.

M.S. Mohy Eldin, M.H. Abd Elmageed, A.M. Omer et al.

A novel sulfonated cellulose acetate (SCA) membranes synthesized for the first time as a proton exchange membrane for direct membrane fuel cells (DMFCs). Cellulose acetate was activated using epichlorohydrin (ECH) followed by doping the activated membranes in sodium sulfite solution later on. The chemical structure and surface properties of SCA membranes confirmed by Infrared spectrophotometric analysis (FTIR). Morphological characterization was examined using scanning electron microscopy (SEM).The thermal stability of the prepared membranes tested by the thermogravimetric analysis (TGA). Results indicated that SCA membranes were thermally stable up to 375.72oC. Interestingly, investigating essential characters required for polyelectrolyte membrane for fuel cell application show that the ion exchange capacity (IEC) estimated in the range of 0.369– 0.996meq/g compared to 0.9 meq/g for Nafion®117. Furthermore, long membrane lifetime under oxidative conditions (Fenton's reagent), high mechanical properties (49.25N), good dimensional stability, low water and methanol uptake. In addition to, lower methanol permeability (1.729*1017- cm2/S) compared to (1.14*109-cm2/S) for Nafion®117. These results make the low-cost SCA membranes a promising polyelectrolyte for direct methanol fuel cell application.

Junping Zhang, Zheng Wei, Aihua Zhang et al.

Aristolochic acids (1 and 2), a component in medicinal plants, have been reported as the cause of end-stage renal failure. For the identification and quantity determination of aristolochic acid a and 2 (AA-1 and AA-2) in Radix Aucklandiae, a liquid chromatography with electrochemical detection system was constructed in this paper. Both of the chromatographic peak heights for AA-1 and AA-2 at the detection potential of -0.8 V were found to be related linearly with the concentrations ranging from 10 ng/mL to 50 μg/mL. The limit of detection (S/N = 3) of AA-1 and AA-2 are 3.7 and 3.4 ng/mL, respectively.

Nataliya N. Yazvinskaya, Nikolay E. Galushkin, Dmitriy N. Galushkin et al.

In this research, there were obtained and analyzed experimental facts contradicting to the classical mechanism of the thermal runaway in nickel-cadmium batteries. It was shown that all the obtained experimental facts are in exact accordance to the new mechanism of thermal runaway consisting in the colligation of the thermal runaway with a powerful exothermic reaction initiation of the atomic hydrogen recombination.

Youqun Chu, Chongzhong Liu, Haiming Ren et al.

The mixed acids with different ratio of H2SO4 to CH3SO3H were prepared, and their application in the vanadium redox flow battery (VRFB) as supporting electrolytes had been examined. It was found the solubility and stability of vanadium ions can be significantly enhanced by the increasing of CH3SO3H content in the mixed acid system. The electrochemical behaviors of VO2+/VO2+ couple in different mixed acids were further studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the electrochemical activities, including the reversibility of electrode reaction, the reaction resistance for VO2+/VO2+ couple were closely related to the CH3SO3H content in the mixed acid system, and reached the best value in the solution using 2.75 mol/L H2SO4+0.25 mol/L CH3SO3H mixed acid as supporting electrolyte. The VRFB with the optimized mixed acid electrolyte exhibits higher energy efficiency and the similar current efficiency compared with those of H2SO4 system.

Fahamsyah H. Latief, El-Sayed M. Sherif, Koji Kakehi

In the present study, the role of aluminide coating on oxidation resistance of Ni-based single crystal superalloy was studied at 900 °C. The oxidation kinetics curves obey the parabolic law in both conditions. However, the significant difference was found after 100 h oxidation in both conditions. The coated specimens showed a better oxidation resistance than the uncoated ones. This is due to the phase transformation occurred from θ-Al2O3 to α-Al2O3 in the coated specimens with increasing oxidation time but not in the uncoated ones. The production of more α-Al2O3 during oxidation is expected since α-Al2O3 acts as a protective layer against oxidation due to its stability at high temperatures. It could be also recognized from the surface morphology of the oxidized coated specimen after 500 h oxidation.

Mengke Jia, Jiaolong Wang, Mingshu Shi et al.

The self-assembled nanofilms of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4- dithiolmon (AF17N) and 6-N,N-diallylamino-1,3,5-triazine-2,4-dithiol monosodium (DAN) were successfully fabricated on copper alloy surface. Surface wettability and coverage of the nanofilms were investigated by contact angle, surface free energy and cyclic voltammetry. Anticorrosion ability and surface morphology of the nanofilms were studied by potentiodynamic polarization, saline immersion test and scanning electron microscopy. The results show that the contact angle of copper surface modified by cured AF17N self-assembled film is up to 124.1° with the lowest surface free energy of 9.653 mJ/m2. Cyclic voltammetry reveals that the cured AF17N and DAN nanofilms are more homogeneous compared with uncured samples. Also, potentiodynamic polarization and saline immersion test demonstrate that the cured AF17N self-assembled film has better anticorrosion ability, which plays a significant role in metal protection and leads a further improvement in corrosion resistance.

Zéhira Hamoudi, My Ali El Khakani, Mohamed Mohamedi

The pulsed laser deposition has been used to synthesize Pt nanostructured films onto carbon paper substrate. In summary, we have examined the change occurring in structural characteristics of Pt thin films grown in a He background gas and in vacuum. The electrochemical studies showed that Pt deposited under 5 Torr of He background pressure displayed the highest electroactive surface area, and the highest current mass activity of methanol electro-oxidation. The reason for such enhanced electrocatalytic activity is ascribed to the high roughness of Pt5T surface, which offers more active sites. From an application point of view, this study demonstrates that using similar amount of Pt, the enhancement of the electrocatalytic activity can be achieved by tuning the surface roughness of the Pt rather than increasing its loading.

Qiang Yin, Linlin Wang, Maocheng Sun

Using carbon nanotubes(CNTs) as a toner, a novel, rapid and inexpensive spectrometric determination method for copper was developed in this work. Several factors affecting the absorbance of the coloration system, such as pH, kind of CNTs, concentration and addition order of reagents were investigated and optimized. The nature of the coloration system was also investigated. Comparative experiments prove that the absorption was increased by 74.1% due to the additing of CNTs into the coloration system. The calibration graph was linear in the range of 10-1100ng mL−1 and the limit of quantification (10s) was 5.8ng mL.

Mohammad Reza Ganjali, Mohammad Reza Moghaddam, Morteza Hosseini et al.

Based on our previous studies which indicated a strong interaction between 8-amino-N-(2-hydroxybenzylidene) naphthyl amine (ANA) with La(III) ions, ANA was used as a sensing material in a nano-composite based carbon paste electrode. The electrodes were made based on a nano-composite including multi-walled carbon nanotube (MWCNT), graphite, and room temperature ionic liquid (RTIL), 1-n-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF4. The best results were obtained for the nano-composite sensor with electrode composition of 5% MWCNT, 10% ANA, 15% RTIL, and 70% graphite powder. The proposed sensor shows a Nernstian response (19.8±0.3 mV decade-1) in the range of 1.0×10-6-1.0×10-2 M with detection limit of 8.0×10-7 M. The response of the sensor is independent of pH in the range of 4.0-9.0. The nano-composite based La(III) sensor displayed good selectivity, response time, and lifetime.

Sang Hern Kim, Yong Il Kim, Jeong Ho Park et al.

Composite electrodes consisting of Mn-Co oxide and high electrical conductive carbon nanofibers(vapor grown carbon nanofiber, VGCF)(CoMnO2/VGCF) were prepared by thermally decomposing manganese and cobalt nitrates directly onto the pore of a porous nickel foam substrate as a current collector to form manganese and cobalt oxides, and their supercapacitive properties were investigated using cyclic voltammetry in 1M KOH aqueous solution. The CoMnO2/VGCF electrodes exhibited high specific capacitance value of 630 F/g at 5 mV/s and excellent capacitance retention of 95% after 104 cycles.