Electrochemical Products Research Articles

Preparation of Ti-based Yb-doped SnO2–RuO2 electrode and electrochemical oxidation treatment of coking wastewater

In this study, the Ti/SnO2–RuO2 electrodes with different Yb contents were prepared by sol–gel method and thermal decomposition method, and the surface morphology and crystal structure of the electrodes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD), the electrochemical properties of the electrodes were tested by linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The electrochemical oxidation device was constructed with Yb-doped Ti/SnO2–RuO2 electrode as the anode and titanium plate as the cathode, and the electrochemical oxidation effect and product changes of the anode on coking wastewater were investigated. The results show that the surface of the electrode is flat with high crystallinity of SnO2 and RuO2 crystals at 1.5% Yb doping, and the LSV and CV curves indicate that the Yb doping of 1.5% increases the oxygen precipitation potential and electrocatalytic oxidation activity of the electrode. When the electrode with Yb doping of 1.5% is the anode with current density of 10 mA/cm2 electrochemical oxidation time of 30 min, the electrode can remove chemical oxygen demand (COD) up to 85.06%, total organic carbon (TOC) up to 60.59% and UV254 from 1.594 to 0.507 for coking wastewater. Gas chromatography (GC–MS), UV–vis and three-dimensional fluorescence results of coking wastewater before and after treatment show that large toxic substances in coking wastewater are degraded to low toxic organic substances, and most soluble organic substances are degraded and transformed. This study provides the possibility of basic research for the engineering practice of electrochemical oxidation for the treatment of coking wastewater.

A novel SERS substrate with high reusability for sensitive detection of miRNA 21

Electrochemistry combining with Surface Enhanced Raman Spectroscopy (EC-SERS) is a hot area which can achieve real-time analysis of the electrochemical product. In this work, a high-performance reusable Raman substrate was fabricated via electrochemical reduction for miRNA 21 assay. In this strategy, 2′-hydroxymethyl-3, 4-thylenedioxythiophene (EDOT-OH) was electropolymerized to form PEDOT-OH (Red), which acted as a part of SERS substrate and a Raman probe at the same time. The Raman intensity of PEDOT-OH was different between the reduction (Red) and oxidation state (Ox). When it is oxidized, the signal of the PEDOT-OH (Ox) on the electrode surface can be restored by applying a reduction voltage. In view of this feature, a Raman enhanced substrate displaying signal changes is constructed and the constructed Raman substrate can be recycled quickly and efficiently. Combining with double-amplification strategy, the SERS platform can detect miRNA 21 from 100 fM to 1 μM. The Raman substrate can be reused at least 15 times and solves the current problems of poor reusability and troublesome restoration of present reusable Raman substrate. As a result, it indicates that the reusable Raman substrate with high performance and non-destructive property will broaden the application of EC-SERS and SERS analysis.

Electrochemical simulation of metabolic reduction and conjugation reactions of unsymmetrical bisacridine antitumor agents, C-2028 and C-2053

Electrochemistry (EC) coupled with analysis techniques such as liquid chromatography (LC) and mass spectrometry (MS) has been developed as a powerful tool for drug metabolism simulation. The application of EC in metabolic studies is particularly favourable due to the low matrix contribution compared to in vitro or in vivo biological models. In this paper, the EC(/LC)/MS system was applied to simulate phase I metabolism of the representative two unsymmetrical bisacridines (UAs), named C-2028 and C-2053, which contain nitroaromatic group susceptible to reductive transformations. UAs are a novel potent class of antitumor agents of extraordinary structures that may be useful in the treatment of difficult for therapy human solid tumors such as breast, colon, prostate, and pancreatic tumors. It is considered that the biological action of these compounds may be due to the redox properties of the nitroaromatic group. At first, the relevant conditions for the electrochemical conversion and product identification process, including the electrode potential range, electrolyte composition, and working electrode material, were optimized with the application of 1-nitroacridine as a model compound. Electrochemical simulation of C-2028 and C-2053 reductive metabolism resulted in the generation of six and five products, respectively. The formation of hydroxylamine m/z [M+H-14]+, amine m/z [M+H-30]+, and novel N-oxide m/z [M+H-18]+ species from UAs was demonstrated. Furthermore, both studied compounds were shown to be stable, retaining their dimeric forms, during electrochemical experiments. The electrochemical method also indicated the susceptibility of C-2028 to phase II metabolic reactions. The respective glutathione and dithiothreitol adducts of C-2028 were identified as ions at m/z 873 and m/z 720. In conclusion, the electrochemical reductive transformations of antitumor UAs allowed for the synthesis of new reactive intermediate forms permitting the study of their interactions with biologically crucial molecules.

The effect of chemical species on the electrochemical reactions and corrosion product layer of carbon steel in CO2 aqueous environment: A review

AbstractThis study summarizes the chemical effects that can occur during the corrosion process of carbon steel in a CO2‐saturated aqueous environment. Particularly, it focuses more on the results that small chemical contaminations in the environment have on the corrosion process. Underground waters present complex chemistry with several different dissolved ions (chlorides, carbonates) even in high concentrations that impact substantially the corrosion rates of these materials. Moreover, gas impurities present in the gas mixture, such as oxygen in carbon capture and storage applications, constitute a supplementary form of significant contamination in the CO2‐saturated aqueous environment. In particular, the effect on both electrochemical reactions and corrosion product layer is examined for several chemical species that are commonly present either in the gas mixture or in underground waters.

Electrochemical deposition induced continuum damage-healing framework for the cementitious composite

The electrochemical deposition method is a promising approach to repair the deteriorated concrete in the aqueous environment. In this paper, a continuum damage-healing framework is presented for the electrochemical deposition method based on the multi-field coupling growth process of the electrochemical deposition products. The ion transportation and the electrode reactions are characterized by employing the Nernst-Planck equation and the current conservation equation. The level set method is adopted to capture the growth of the deposition products. Based on the deposition process, a new empirical healing law is presented, with which a new continuum damage-healing framework is presented for electrochemical deposition method. Numerical examples are conducted by applying the presented framework to the damaged cementitious composite under the tensile loadings. The presented framework is compared with the classic continuum damage-healing theory and the experimental data. The results show that the presented models can describe the electrochemical deposition method induced damage-healing for the cementitious composite. Furthermore, the effects of the healing time, the solution concentration and the external voltage on the damage-healing behaviors are investigated based on our proposed framework.

Al2O3 microparticles immobilized on glassy‑carbon electrode as catalytic sites for the electrochemical oxidation and high detectability of naproxen: Experimental and simulation insights

This work demonstrates that Al2O3 microparticles immobilized on a glassy‑carbon electrode (GCE) anticipate the electrochemical oxidation of naproxen in 150 mV and increases its oxidation current, resulting in a highly sensitive sensor. Considering their non-conducting nature, we suggest that Al2O3 microparticles act as adsorption sites that alter the electrochemical oxidation pathway of naproxen by adsorbing its intermediate(s) and facilitating the electron transfer at the GCE surface. Interestingly, the voltammetric results obtained for ibuprofen (presents similar chemical structure and electrochemical oxidation mechanism) indicated the same facilitated electron transfer that suggests that the interaction between naproxen (or ibuprofen) with Al2O3 microparticles occurs via the carboxylic group, which is removed after the first electron transfer according to the proposed mechanism. Molecular dynamics simulations showed stronger interaction of naproxen than ibuprofen with alumina sites which may explain the respective facilitated electron transfer. Moreover, a stronger interaction of a major electrochemical oxidation product of naproxen with alumina was confirmed by simulation and explains the electrode fouling occurred when more positive potentials (+1.4 V instead of +1.0 V vs. Ag/AgCl/KClsat) were applied for the naproxen amperometric detection. The alumina-modified GCE surface presented a detection limit of 12 nmol L−1 with a linear range between 50 and 500 nmol L−1 for naproxen determination (Edet = +1.0 V). These sensing characteristics are superior in comparison with electrodes modified with carbon nanotubes and their composites. Hence, a simpler protocol for electrode modification using a non-conducting material can provide a highly sensitive sensor for naproxen due to its catalytic properties facilitating the electron transfer between naproxen (or ibuprofen) and GCE.

A study of the structure and morphology of the graphite electrochemical exfoliation products

The paper presents a generalized analysis of the results of scanning electron microscopy, energy dispersive spectroscopy, and TG/DSC analysis of electrochemical exfoliation products from two types of initial graphite raw materials at different process temperatures in solutions of potassium hydroxide (KOH) and sulfuric acid (H2SO4). It is shown that an increase in the concentration of an alkaline electrolyte in the range from 0.1 to 1.0 molL–1 promotes the intensification of the process of separation and splitting of graphite into fragments. In the case of the formation of large fragments, the product contains a significant amount of intercalated potassium ions, which are not removed when the material is washed off. The products of electrochemical exfoliation of the spent electrocontact graphite material demonstrate structural heterogeneity, contain a significant amount of functional groups and impurities of the amorphous phase. Thermogravimetric curves have several sections of sample weight reduction. After heating these materials in an inert atmosphere to 900 °C, the total weight loss reaches 66 %. From a thermally expanded graphite foil, samples of nanographites, extremely homogeneous in chemical composition, with increased thermal stability and a minimum number of surface defects were obtained. The total weight loss of the samples when heated in an inert atmosphere to 900 °C does not exceed 17 %. It was shown that the replacement of an alkaline electrolyte with a sulfuric acid solution leads to an increase in the number of defects in the product.

Comparative life cycle assessment of electrochemical upgrading of CO2 to fuels and feedstocks

Comparative life cycle assessment on electrochemical CO2 reduction products, as compared to thermochemical CO2 reduction and incumbent processes.

Electrochemical product engineering towards sustainable recovery and manufacturing of critical metals

This review presents an overview of electrochemical product engineering towards critical metal recovery and manufacturing, looking at process optimization and product innovation aspects.

Hierarchical Microchannel Carbons Derived from Biological Phloem Tissues as High-Performance Anode for Lithium-Ion Batteries

With the upgrading of consumption, the existing carbon-based anode materials are facing the major challenges of high preparation cost and low initial Coulomb efficiency. The fast-growing and developed sieve tube network is an inspiration to transform cattail phloem tissue (CPT) into a high-performance carbon-based anode for lithium-ion battery. In this study, porous carbon materials from CPT with abundant microchannel and nanochannel were prepared by a top-down strategy combined with an indispensable passivation process. The sidewall and end of the sieve tube are fully covered by a large number of pore structures and various supporting cells, thus ensuring the stiffness and tensile strength of phloem tissue. And benefiting from the neoteric hierarchical porous structure without Li⁺ trapping sites, the cells with CPT anode showed high electrochemical performance. For the passivated CPT electrode, the reversible capacity increased to 321.6 mAh/g, and the initial Coulomb efficiency was 1.47 times higher than that of the passivated CPT electrode. The CPT exhibits excellent rate performance under high current, which indicates that the abundant pore structure on the surface of the sieve tube is an effective measure to improve ion diffusion. Besides, the generation mechanism of high-performance CPT is analyzed through microstructure characterization. The improvement of electrochemical performance of CPT in this work has provided a clear strategy for the application of resource-rich natural biomass to electrochemical products.

Prenatal exposure and transplacental transfer of perfluoroalkyl substance isomers in participants from the upper and lower reaches of the Yangtze River.

Data on gestational exposure characteristics and transplacental transfer are quite limited for perfluoroalkyl substance (PFAS) isomers, especially those from large-scale comparative studies. To fill this gap, we examined isomers of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in matched maternal and cord serum from Mianyang and Hangzhou, which are located in the upper and lower reaches of the Yangtze River, China, respectively. These data were compared with those from our previous study on Wuhan in the middle reach. The average ΣPFAS concentration increased from upstream to downstream (Mianyang (4.44ng/mL)<Wuhan (9.88ng/mL)<Hangzhou (19.72ng/mL)) and may be related to the per capita consumption expenditure of each city. The ln-transformed PFAS concentrations showed significant differences between Mianyang and Hangzhou after adjusting confounding factors (p<0.05). The percentages of linear PFOS and PFOA in maternal and cord serum from these cities all exceeded those in electrochemical fluorination products. The isomer profiles of PFASs in maternal and cord serum might be greatly influenced by local production processes of PFASs and residents' dietary habits. The transplacental transfer efficiencies decreased significantly with increasing concentrations in maternal serum for ΣPFAS, ΣPFOS, ΣPFOA, ΣPFHxS, n-PFOS, iso-PFOS, 4m-PFOS, 1m-PFOS, n-PFOA, n-PFHxS, and br-PFHxS (Spearman rank correlation coefficients (r)=0.373-0.687, p<0.01). These findings support an understanding of the regional characteristics in maternal exposure to PFASs along the Yangtze River, isomeric profiles of PFASs in these regions, and the transplacental transfer processes of PFAS isomers.

The effects of power ultrasound (24 kHz) on the electrochemical reduction of CO2 on polycrystalline copper electrodes

The electrochemical CO2 reduction reaction (CO2RR) on polycrystalline copper (Cu) electrode was performed in a CO2-saturated 0.10 M Na2CO3 aqueous solution at 278 K in the absence and presence of low-frequency high-power ultrasound (f = 24 kHz, PT ~ 1.23 kW/dm3) in a specially and well-characterized sonoelectrochemical reactor. It was found that in the presence of ultrasound, the cathodic current (Ic) for CO2 reduction increased significantly when compared to that in the absence of ultrasound (silent conditions). It was observed that ultrasound increased the faradaic efficiency of carbon monoxide (CO), methane (CH4) and ethylene (C2H4) formation and decreased the faradaic efficiency of molecular hydrogen (H2). Under ultrasonication, a ca. 40% increase in faradaic efficiency was obtained for methane formation through the CO2RR. In addition, and interestingly, water-soluble CO2 reduction products such as formic acid and ethanol were found under ultrasonic conditions whereas under silent conditions, these expected electrochemical CO2RR products were absent. It was also found that power ultrasound increases the formation of smaller hydrocarbons through the CO2RR and may initiate new chemical reaction pathways through the sonolytic di-hydrogen splitting yielding other products, and simultaneously reducing the overall molecular hydrogen gas formation.

The Use of Some Non-conventional Methods in Chemistry of Bicyclohomofarnesenic Methyl Esters

The present paper reports the results of microwave irradiation assisted method for the preparation of bicyclohomofarnesenic methyl esters versus classical Stoll and Hinder method. Moreover, the chemical transformations of bicyclohomofarnesenic methyl esters via anodic electrooxidation and dye-sensitized photooxidation were performed. A new method for the preparation of methyl 7-oxo-13,14,15,16-tetranorlabd-6,8(8)-dien-12-oate and the mechanism of electrochemical products formation are presented. The structure of all synthesized compounds was fully confirmed by spectral methods.

Synthesis of High-Quality Graphene Oxide Made By a Novel One-Step Electrochemical Exfoliation of Natural Graphite Flakes Based on a 3D-Printed Reactor

Since its discovery in 2004, Graphene has been widely study for different applications, noticeable for electrochemical energy devices, due to its excellent properties as a barrier material, electrical conductivity or high surface area. However, it is still an expensive material since it cannot be produced in a large scale. Graphene based materials such as Graphene oxide (GO) or Reduced Graphene Oxide (rGO) also present similar properties than Graphene and can be produce in a more economical way [1]. However, traditional method to produce GO, Hummer’s method, which base on chemical exfoliation of graphite, is a long and tedious process which requires the use of strong oxidants and hazardous chemicals leading environmental pollution that cannot be repaired [2,3]. Recently, electrochemical exfoliation of graphite to produce GO has attracted more and more attention due its environmental protection, low price, easy process and high efficiency [4-7]. Since natural graphite is mostly in the form of flakes and its tiny size is not conducive to its direct use in electrochemical exfoliation, currently, electrochemical exfoliation is mostly made of graphite foil, graphite rod and other graphite processed products. These materials are obtained by using processes such as chemical, thermodynamic, and mechanical compression, leading in physical or chemical changes that alter their original properties or structure. There are also some attempts to use natural graphite flakes for electrochemical exfoliation [8,9]. However, this makes electrochemical exfoliation require more voltage, longer time and less yield. In this work, we present novel design reactor to perform electrochemical exfoliation using natural graphite flakes as raw materials. By using ammonium sulphate as electrolyte, electrochemical exfoliation of natural graphite flakes can be done at low voltage with short time. This achievement also enables the comparison of electrochemical exfoliation products with different raw materials (graphite foil and natural graphite flakes) at the same exfoliation voltage and the same exfoliation time. We explored the properties of the product by raman spectroscopy, ultraviolet–visible spectroscopy (UV-VIS), fourier-transform Infrared Spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), four-probe method and contact angle measurement. We have found that by combining natural graphite flakes with the reactor, the product obtained is significantly different from the exfoliated product based on graphite foil, achieving better oxidation, better dispersion in deionized water, more defects and greater yield. In addition, the special structure of the reactor allows the exfoliation time to be controlled, and we also compare the products obtained at different exfoliation times. The Exfoliated Graphene Oxide (EGO) obtained it has been used as a filler material in proton exchange membranes for hydrogen fuel cells as well as a support material for electrocalyst to enhance the kinetics for the reactions which take place in these fuel cells.

Mechanistic Understanding and Rapid Electrochemical Reduction of Silica for Lithium-Ion Battery Anodes

The use of silica as an active material within a lithium-ion battery requires a pre-treatment. The electrochemical reduction between silica and lithium is partially irreversible and is postulated to produce silicon as a reaction product. The silicon formed can reversibly react with lithium to produce stable capacities, higher than current graphite materials. However, both the electrochemical reduction pathway and the electrochemical reduction products are unknown, thereby hampering the design, optimisation and use of such systems. Here we uncover the pathway for the electrochemical reduction and, for the first time, identify elemental silicon as a product of the reduction. We discovered new methods for studying the electrochemical reduction reaction – they are based on monitoring and analysing the capacity increase and the current flow as the material is reduced. Our results conclusively show that silica must be reduced to introduce reversible capacity and that this reduction reaction time can be greatly reduced using a constant load discharge at elevated temperature. Characterisation with total scattering X-ray pair distribution function shows the reduction products are amorphous in nature and confirmed why previous diffraction characterisation attempts were unsuccessful. Our results can help better understand the electrochemical reduction of any silica material. We anticipate these results can be used as a starting point for the development of a scaled-up synthesis route for in-situ reduced silica anodes and their incorporation into lithium-ion full cells.

Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Summary Production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250°C is demonstrated. The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer. Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electrooxidation. Cells were operated at 250°C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode. A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 m o l H 2 / g c a t h .

Electrochemical Ring Expansion to Synthesize Medium-Sized Lactams Through C–C Bond Cleavage

Medium-sized nitrogen heterocycles are prevalent motifs in many kinds of bioactive molecules and natural products. Owing to the unfavorable enthalpic and entropic barriers during the transition sta...

Polydopamine modified ultrathin hydroxyapatite nanosheets for anti-corrosion reinforcement in polymeric coatings

It is known that two-dimensional nanosheets such as graphene, hexagonal boron nitride and layered double hydroxide can provide organic coatings with enhanced anticorrosion performance due to the high aspect ratio and excellent barrier property. As a kind of biocompatible material, the corrosion resistance of hydroxyapatite (HAp) in the biological body leads to its wide application. In this work, ultrathin HAp nanosheets were noncovalently functionalized by situ self-polymerization of dopamine chemistry with an aim to improve their compatibility and dispersibility in epoxy matrix. Electrochemical impedance spectroscopy (EIS) illustrated composited coating exhibited a higher value of impedance at low frequency compared to pure epoxy coating after 50 days of immersion in 3.5 wt% NaCl solution. Local electrochemical impedance spectroscopy (LEIS), spray tests and corrosion products characterization were also carried out to evidence that the modified HAp nanosheets could significantly improve the anti-corrosion performance of epoxy coatings via the enhanced barrier property and corrosion inhibiting effect of polydopamine, which is expected to be widely applied as nano-reinforcing fillers in the anticorrosion field.

Insights into the Electrochemical Reduction Products and Processes in Silica Anodes for Next‐Generation Lithium‐Ion Batteries

AbstractThe use of silica as a lithium‐ion battery anode material requires a pretreatment step to induce electrochemical activity. The partially reversible electrochemical reduction reaction between silica and lithium has been postulated to produce silicon, which can subsequently reversibly react with lithium, providing stable capacities higher than graphite materials. Up to now, the electrochemical reduction pathway and the nature of the products were unknown, thereby hampering the design, optimization, and wider uptake of silica‐based anodes. Here, the electrochemical reduction pathway is uncovered and, for the first time, elemental silicon is identified as a reduction product. These insights, gleaned from analysis of the current response and capacity increase during reduction, conclusively demonstrated that silica must be reduced to introduce reversible capacity and the highest capacities of 600 mAh g−1 are achieved by using a constant load discharge at elevated temperature. Characterization via total scattering X‐ray pair distribution function analysis reveal the reduction products are amorphous in nature, highlighting the need for local structural methods to uncover vital information often inaccessible by traditional diffraction. These insights contribute toward understanding the electrochemical reduction of silica and can inform the development of pretreatment processes to enable their incorporation into next‐generation lithium‐ion batteries.

New Methodology for the Identification of Metabolites of Saccharides and Cyclitols by Off-Line EC-MALDI-TOF-MS.

A combination of electrochemistry (EC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (off-line EC-MALDI-TOF-MS) was applied for determination of the studied biologically active compounds (D-glucose, D-fructose, D-galactose, D-pinitol, L-chiro-inositol, and myo-inositol) and their possible electrochemical metabolites. In this work, boron-doped diamond electrode (BDD) was used as a working electrode. MALDI-TOF-MS experiments were carried out (both in positive and negative ion modes and using two matrices) to identify the structures of electrochemical products. This was one of the first applications of the EC system for the generation of electrochemical products produced from saccharides and cyclitols. Moreover, exploratory data analysis approaches (correlation networks, hierarchical cluster analysis, weighted plots) were used in order to present differences/similarities between the obtained spectra, regarding the class of analyzed compounds, ionization modes, and used matrices. This work presents the investigation and comparison of fragmentation patterns of sugars, cyclitols, and their respective products generated through the electrochemistry (EC) process.