Aqueous Alkaline Research Articles

A general separator modification tactic enables long-term stable cycling of small organic molecule electrodes in aqueous alkaline batteries

Rechargeable aqueous alkaline batteries based on small organic molecule anodes are a promising solution for large-scale energy storage due to their environmental friendliness and high energy efficiency. However, its development is limited by the poor cycling stability caused by the shuttling of soluble organic molecules between electrodes. Here, we propose a cell separator modified by metal organic framework (MOF) grown on the surface of graphene oxide (GO) to inhibit the shuttling of small organic molecules. It is demonstrated that the MOF@GO modified separator acts as an ion sieve in aqueous alkaline cells to effectively hold up small organic molecules without affecting the movement of metal ions. With the protection of the MOF@GO separator, soluble small molecules such as indanthrone (IDT) exhibit an amazing stability in alkaline electrolytes (a high reversible capacity of 137.0 mA h g−1 and a good capacity retention of 95.8% after 1000 cycles at 1 A g−1). It is the first report that employs carbonyl-containing small molecules as the electrodes for stable rechargeable aqueous alkaline batteries. Additionally, this strategy is also proved available to enhance the capacity and cycling stability of other active conjugated small molecules, such as PTCDI and 6CN-DQPZ, which will pave the way for the use of small organic molecules in aqueous alkaline batteries.

A novel method for the remediation of o‐ and p‐aminophenol from industrial wastewater by hexacyanoferrate (III) ions using Ir‐complex catalyst

AbstractIn this manuscript o‐ and p‐aminophenols model environmental pollutants are being remedied by catalytic oxidation process. A kinetic‐spectrophotometric technique was used to study the remediation of o‐ and p‐aminophenol by hexacyanoferrate (III) ions as an oxidant and synthesized Ir‐DTPy complex as a catalyst in aqueous alkaline medium. The optimum pH for these experiments was 9.0 and 11.0 for o‐ and p‐aminophenol respectively at the constant temperature 25°C. It has been studied how variations in the concentration of the catalyst (Ir‐DTPy), the hexacyanoferrate (III) ions, and substrate affect the rate of the reaction. At four different temperatures, ranging from 25 to 40°C, the change in reaction rate has been analyzed with thermodynamic variables like free energy of activation, enthalpy, frequency factor, and activation energy. FTIR, UV‐Vis, and ESI‐MS spectroscopic analytical methods have been used to identify the oxidized products. 2‐aminophenoxazin‐3‐one and NN'‐bis‐(p‐hydroxyphenyl)‐2‐hydroxy‐5‐amino‐1, 4‐benzoquinone di‐imine are the main products of oxidation of o‐and p‐aminophenol, respectively. Therefore, this technique for removing o‐ and p‐aminophenol from contaminated water resources is very effective and environmentally safe.

A kinetic and mechanistic investigation of oxidation of D-Mannitol by Diperiodatocuprate (III) in an aqueous alkaline medium

A kinetic and mechanistic investigation of oxidation of D-Mannitol by Diperiodatocuprate (III) in an aqueous alkaline medium

Long-lifespan aqueous alkaline and acidic batteries enabled by redox conjugated covalent organic polymer anodes

Herein, we introduce a redox conjugated covalent organic polymer (p-HATN, HATN = hexaazatrinaphthylene) anode bearing HATN species for long-lifespan aqueous alkaline and acidic batteries. The p-HATN features intriguing superhydrophilicity and unique wide pH adaptability, while the conjugated network and amorphous cross-linked structure further endow p-HATN with improved electron transport, facile ion diffusion and superior acid-alkali tolerability. As a result, p-HATN exhibits fast surface-controlled redox activity and superior stability for K+ and H+ ions storage with remarkable capacity retentions in three-electrode cells (88% capacity retention in 13 M KOH over 30000 cycles; nearly 100% capacity retention in 0.5 M H2SO4 over 54000 cycles). Moreover, the assembled p-HATN//Ni(OH)2 cell with 13 M KOH and p-HATN//PbO2 cell with 0.5 M H2SO4 also achieve capacity retentions of 83% retention over 55000 cycles and 92% over 15000 cycles, respectively, outperforming most similar systems. This work sheds light on the rational design of advanced polymer anodes for long-lifespan alkaline and acidic batteries.

Pyridine Diphosphonate Ligand for Stabilization of Tetravalent Uranium and Neptunium in Aqueous Medium under Aerobic Conditions.

Though uranium is usually present in its +6 oxidation state (as uranyl ion) in aqueous solutions, its conversion to oxidation states such as +4 or +5 is a challenging task. Electrochemical reduction and axial oxo activation are the preferred methods to get stable unusual oxidation states of uranium in an aqueous medium. In previous studies, dicarboxylic acid has been used to stabilize UO2+ in aqueous alkaline solutions. In the present work, a diphosphonate ligand was chosen due to its higher complexing ability compared to that of the carboxylate ligands. Neptunium complexation studies with 2,6-pyridinediphosphonic acid (PyPOH) indicated the formation of different species at different pH values and the complexation facilitates disproportionation of NpO2+ to Np4+ and NpO22+ at pH 2. Hexavalent actinides form insoluble complexes in aqueous media at pH = 2, as confirmed by UO22+ complexation studies. The in situ complexation-driven precipitation resulted in conversion to pure Np4+ in aqueous media as the Np4+-PyPOH complex. A strong complexing ability of the PyPOH ligand toward the Np4+ ion is also seen for the stabilization of the electrochemically generated U4+ in aqueous medium under aerobic conditions. The U4+-PyPOH complex was found to be stable for 3 months. Raman, UV-vis, fluorescence, and cyclic voltametric studies along with density functional theory (DFT) calculations were done to get structural insights into the PyPOH complexes of actinides in different oxidation states.

Isolation of partial coupled processes of anodic oxidation of OH– ion on gold using a combination of a graph-kinetic analysis method and linear voltammetry data

The presence of several interconnected electrochemical processes occurring on the surface of an electrode, strictly speaking, does not allow the use of the principle of independent reactions. Often, partial reactions of a complex multi-stage electrochemical process are coupled both through common intermediates and through the competitive adsorption of electroactive species. The presence of conjugation leads either to a change in the potential at which the corresponding electrochemical process becomes possible or to a change in the rate of partial processes. The latter is called kinetic coupling. This does not allow the simple calculation of the rate of each partial reaction as the difference between the current density of the target and background processes. The method of kinetic diagrams can be used to establish the kinetic patterns ofsuch processes. This study shows that this method is applicable not only for the analysis of coupled electrochemical processes of various types, but can also be used in obtaining partial currents of the stages of a separate complex electrode reaction occurring in a background solution. As an example, options for the kinetic modelling of the total voltammogram of the anodic process on an Au electrode in an aqueous alkaline medium in the mode of linear potential change are considered. The stationary degrees of covering of the gold surface with various surface-active forms of oxygen are calculated depending on the electrode potential. It was established that the change in concentration of ОН- ions mainly affects the region of their adsorption potentials. A detailed analysis of stationary partial anodic processes in the Au|OH-,H2O system was carried out and the shape of the general stationary voltammogram was determined by calculation. The latter is in qualitative agreement with the experimental polarization dependence. It was shown that the type of calculated polarization dependence is determined by the degree of reversibility of individual stages and the rate of their occurrence. The performed analysis is necessary not only for the detailed scheme of the background anodic reaction on gold in an alkaline solution, but also for the ubsequent kinetic description of the electrooxidation process of organic substances on a gold electrode

Electrocatalytic reduction of furfural to furfuryl alcohol using carbon nanofibers supported zinc cobalt bimetallic oxide with surface-derived zinc vacancies in alkaline medium

Electrocatalytic hydrogenation (ECH) reduction provides an environment-friendly alternative to conventional method for the upgrade of furfural to furfuryl alcohol. At present, exploring superior catalysts with high activity and selectivity, figuring out the reduction mechanism in aqueous alkaline environment are urgent. In this work, zinc cobalt bimetallic oxide (ZnMn2O4) with surface-derived Zn2+ vacancies supported by carbon nanofibers (d-ZnMn2O4-C) was fabricated. The d-ZnMn2O4-C exhibited excellent performance in electrocatalytic reduction of furfural, high furfuryl alcohol yield (49461.1 ± 228 µmol g−1) and Faradaic efficiency (95.5 ± 0.5 %) was obtained. In-depth research suggested that carbon nanofiber may strongly promoted the production of adsorbed hydrogen (Hads), and Zn2+ vacancies may significantly lowered the energy barrier of furfural reduction to furfuryl alcohol, the synergistic effect between carbon nanofiber and d-ZnMn2O4 probably facilitated the reaction between Hads and furfuryl alcohol radical, thereby promoting the formation of furfuryl alcohol. Furthermore, the reaction mechanism was clarified by inhibitor coating and isotope experiments, the results of which revealed that the conversion of furfural to furfuryl alcohol on d-ZnMn2O4-C followed both ECH and direct electroreduction mechanism.

Ultrasonic treatment duration: A nuanced parameter in synthesis affecting structural properties and ORR performance of KOH-activated carbon

In this study, we investigate the effects of the duration of ultrasonic treatment during the impregnation process of a carbon precursor with an aqueous alkaline solution on the structural and electrochemical properties of KOH-activated carbon materials. Our findings using polyacrylonitrile (PAN)-derived carbon materials reveal that extended ultrasonic treatment leads to a more consistent distribution of the activating agent, promoting more uniform surface activation. This leads to notable shifts in the material's structure and surface chemistry, thereby influencing its functionality as an electrode material in supercapacitors and its electrocatalytic activity in the oxygen reduction reaction (ORR). Our results indicate a 6 % difference in the specific surface area and an 8 wt% rise in oxygen content when comparing samples without ultrasonic treatment to those treated for 10 min. Moreover, the specific capacitance increases from 133.9 to 163.5 F g−1, and the ORR activity ascends from 1.88 to 2.23 mA cm−2. This research highlights the potential of ultrasonic treatment duration as a variable to fine-tune the structure and properties of porous carbon materials, emphasizing its scientific and technological significance in the production of stable porous carbon materials.

Three-dimensional NiCoS nanotubes@NiCo-LDH nanosheets core-shell heterostructure for high-rate capability alkaline zinc-based batteries.

Aqueous alkaline zinc-based batteries (AAZBs) are promising for large-scale applications due to their high working voltage, safety, and low cost. However, the further development of AAZBs has been significantly hindered by the low electronic conductivity and poor cycling stability of traditional nickel/cobalt-based cathode materials. In this work, a binder-free electrode was successfully designed by electrodepositing NiCo-LDH nanosheets on NiCoS nanotube arrays that were grown on nickel foam (NiCoS@NiCo-LDH). The unique three-dimensional core-shell heterostructures not only enhance electrical conductivity but also offer abundant active sites and rapid ion/electron transport channels, thereby improving its electrochemical performance. The as-fabricated NiCoS@NiCo-LDH electrode delivers a capacity of 312 mA h g-1 (0.624 mA h cm-2) at 2 mA cm-2 and exhibits high rate capability with 90% capacity retention at 10 mA cm-2. Additionally, the assembled NiCoS@NiCo-LDH//Zn battery exhibits a high energy density of 435.3 W h kg-1 at a power density of 4.1 kW kg-1 and maintains 95.9% of its capacity after 3000 cycles at a current density of 20 mA cm-2.

Potassium energy storage behavior of nickel–zinc co-doped Prussian blue analogs formed by a chelating-agent-assisted route and its application in a K+-proton hybrid-ion aqueous alkaline battery

Ni3Zn1HCF synthesized through chelating agent assisted route and an aqueous potassium/proton hybrid ions battery was proposed.

Low-temperature ionothermal polymerization of phenazine-based small molecules towards ultrastable and high-capacity anodes of aqueous alkaline sodium-ion batteries

A simple and green molten salt method was proposed for the dehydrogenation polymerization of electron-deficient phenazine-based small-molecule compounds, which effectively enhanced their capacity and cycle stability in aqueous sodium-ion batteries.

Aqueous alkaline phosphate facilitates the non-exchangeable deuteration of peptides and proteins.

The incorporation of deuterium into peptides and proteins holds broad applications across various fields, such as drug development and structural characterization. Nevertheless, current methods for peptide/protein deuteration often target exchangeable labile sites or require harsh conditions for stable modification. In this study, we present a late-stage approach utilizing an alkaline phosphate solution to achieve deuteration of non-exchangeable backbone sites of peptides and proteins. The specific deuteration regions are identified through ultraviolet photodissociation (UVPD) and mass spectrometry analysis. This deuteration strategy demonstrates site and structure selectivity, with a notable affinity for labeling the α-helix regions of myoglobin. The deuterium method is particularly suitable for peptides and proteins that remain stable under high pH conditions.

An aqueous alkaline zinc-sulfur flow battery.

We demonstrate a rechargeable aqueous alkaline zinc-sulfur flow battery that comprises environmental materials zinc and sulfur as negative and positive active species. Meanwhile, a nickel-based electrode is also obtained by a two-step process to decrease the polarization of the sulfur redox reaction, thus greatly improving the voltage efficiency of the system from 32% to 78% at 10 mA cm-2.

Manganese dissolution in alkaline medium with and without concurrent oxygen evolution in LiMn2O4

Manganese oxides such as LiMn2O4 exhibit two distinct Mn dissolution processes; one independent of oxygen evolution and the other associated with it. Less Mn4+ before the onset of the OER lowers the Mn dissolution rate.

Elucidation of Degradation Behavior of Nitrazepam, a Benzodiazepine Drug, under Basic Conditions: Study on Degradability of Drugs in Stomach (IV).

This study investigates the stability of nitrazepam (NZP), a benzodiazepine drug, under basic conditions, since alkaline putrefactive amines and ammonia are produced once bodies are left to decompose for a long period postmortem after a murder involving NZP or an accidental overdose of NZP. The degradation of NZP in an aqueous alkaline solution was investigated by LC/photodiode array detector (PDA) where the NZP degradation product was isolated and purified by solid-phase extraction using Oasis® MCX, and its chemical structure was determined by LC/time-of-flight (TOF)-MS, NMR spectroscopy, and single-crystal X-ray crystallography. The results revealed that NZP was immediately degraded under basic conditions with 2-amino-5-nitrobenzophenone being an intermediate which further degraded to provide 2-hydroxy-5-nitrobenzophenone as the final degradation product. These results are expected to be useful in clinical chemistry and forensic science, such as the detection of drugs during postmortem examination and suspected addiction.

Electrochemical performance of permanganate as an active material for catholyte in aqueous alkaline flow batteries

Fe–Mn flow batteries using Fe(BIS–TRIS) and MnO4-based electrolytes improve voltage and energy efficiencies, proving MnO4 as an effective alternative to ferrocyanide.

Breaking the diffusion coefficient limitation of bismuth oxide anodes for aqueous alkaline batteries with ultra-high rate capability

In this study, the double-high hierarchical porous amorphous Bi2O3 anode material (HPAM Bi2O3) is firstly synthesized by ion exchange strategy via employing Bi-BTC nanorod as the precursor.

Isolation and determination of phenolic acids in rowanberry fruits (Sorbus L.) by gas chromatography

Species of the genus Sorbus L. (rowan) are woody plants growing in the Northern Hemisphere; they are of interest as decorative, food and medicinal plants. Rowan fruits contain a unique complex of macro- and microelements, as well as biologically active substances, including phenolic compounds. Complexity of the composition of plant samples requires the development of highly selective and sensitive methods for determining the content of organic components of different classes. A method for determining phenolic acids in rowan fruits is proposed. The method is based on two-stage chemical modification of the acids, and involves preparing methyl esters under acidic methanolysis conditions, liquid extraction with toluene, intermediate re-extraction into an aqueous alkaline solution, subsequent silylation with N, O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and gas chromatographic determination of the obtained derivatives using a flame ionization or mass spectrometric detector. Conditions for extraction of phenolic acids from rowan fruits were studied according to the following parameters: type of extractant, sample to the extractant mass ratio, and duration of extraction (mechanical stirring). The stage of gas chromatographic determination of obtained phenolic acid derivatives was optimized, and their chromatographic characteristics established. The possibility of achieving practically complete separation of aliphatic acids and other accompanying components of a non-acidic nature from phenolic compounds in the course of sample preparation was demonstrated; which significantly increased both the selectivity and sensitivity of the determination of analytes. The range of determined content of phenolic acids (4-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-3-methoxy-benzoic acid, 4-hydroxycinnamic acid, 4-hydroxy-3-methoxy-cinnamic acid) in rowan fruits was 0.005–0.5 mg/g, the limit of detection was 0.001–0.002 mg/g, the relative error was 10–15%, the sample weight was 0.5 g, the total duration of the analysis was 4 hours.

Label-Free Detection of Unbound Bilirubin and Nitrophenol Explosives in Water by a Mechanosynthesized Dual Functional Zinc Complex: Recognition of Picric Acid in Various Common Organic Media.

High levels of unconjugated bilirubin (UB) in serum lead to asymptomatic and neonatal jaundice and brain dysfunctions. Herein, we have reported the detection of UB at as low as 1 μM in an aqueous alkaline medium using a Zn(II) complex. The specificity of the complex has been validated by the HPLC in the concentration window 6-90 μM, which is rare. The sensory response of the probe at physiological pH against nitro explosives developed it as an instant-acting fluorosensor for picric acid (PA) and 2,4-dinitrophenol (2,4-DNP). Spectroscopic titration provided a binding constant of 4×105 M-1 with PA. The naked eye detection was found to be 15 μM. The solid-state photoluminescent nature of the complex enabled it for PA sensing in the solid phase. Interestingly, the probe remained fluorescent in various volatile and non-volatile organic solvents. As a result, it can also detect PA and 2,4-DNP in a wide range of common organic media. NMR studies revealed the coordination of PA, 2,4-DNP, and UB to the Zn(II) center of the probe, which is responsible for the observed quenching of the probe with the analytes.

Evaluation of the efficiency of coconut dust extract as a corrosion inhibitor for steel reinforcement in concrete by mass spectrometry

Ethanol extraction was employed to isolate a range of compounds from waste products derived from coconut fiber production (coconut dust) in Ben Tre, Vietnam. Phytochemical screening confirmed the presence of flavonoids, tannins, polyphenols, saponins, alkaloids, flobatannins, and anthraquinones among the extracted substances. FT-IR spectroscopy analysis supported the identification of oxygen and nitrogen atoms within functional groups (e.g., O–H, N–H, C–O) and aromatic rings, characteristic of typical corrosion inhibitors. Mass spectrometry investigations indicated that when St3 steel was exposed to an alkaline solution lacking chlorides, a passive film composed of FeOOH formed on the surface. However, upon the addition of NaCl at a concentration of 1.00 mol/dm3, FeCl, FeCl2Cl–, and FeCl3Cl– compounds were detected across the analyzed surface, while peaks corresponding to FeOO– were absent. Remarkably, areas with the highest concentration of particles corresponded to regions exhibiting visible corrosion damage under magnification. The addition of 2.00 g/dm3 of coconut dust extract to the chloride solution prevents the formation of Fe and Cl compounds on the steel surface. Consequently, only peaks characteristic of FeOO– and organic fragments containing oxygen atoms from the extract were observed. Based on these results, it can be assumed that coconut dust extract has the potential to inhibit local (pitting) corrosion of low-carbon steel (St3) when exposed to aqueous alkaline solutions simulating concrete pore liquid containing chlorides. The addition of 2.00 g/dm3 of the extract has been shown to prevent pitting formation at a chloride concentration of 1.00 mol/dm3. Conversely, in the absence of the extract, visible local corrosion damage was observed upon magnification. These findings provide a basis for further exploration of the protective properties of coconut dust extract as an environment-friendly corrosion inhibitor for mild steel in concrete environments containing chlorides.