Ammonia In Aqueous Media Research Articles

Metal Alloy‐Functionalized 3D‐Printed Electrodes for Nitrate‐to‐Ammonia Conversion in Zinc‐Nitrate Batteries

AbstractElectrocatalytic nitrate reduction is a promising approach to remove harmful nitrate and produce ammonia in aqueous media. Here, we demonstrate how 3D printed polymer electrodes can be electroless plated with a bimetallic NiCu alloy film suitable for sustained nitrate‐to‐ammonia reduction. Characterization by powder X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning/transmission electron microscopy and energy‐dispersive X‐ray spectroscopy indicate that the electrode has a two‐layer structure consisting of polymer/ coating layer of metal alloys. The composite electrode shows high‐performance in the nitrate‐to‐ammonia electroreduction, giving NH3 Faradaic efficiencies of up to 83 % and NH3 yield rates up to 860 μg/(h cm2) at −0.38 V vs. RHE. We show that the electrode can easily be integrated into a Zn‐nitrate battery, giving a power density of 3.8 mW cm−2 with continuous NH3 production. The system combines three productive outputs, that is removal of nitrate pollutants, synthesis of valuable ammonia and generation of “green” electricity.

Supervised AI and Deep Neural Networks to Evaluate High-Entropy Alloys as Reduction Catalysts in Aqueous Environments.

Competitive surface adsorption energies on catalytic surfaces constitute a fundamental aspect of modeling electrochemical reactions in aqueous environments. The conventional approach to this task relies on applying density functional theory, albeit with computationally intensive demands, particularly when dealing with intricate surfaces. In this study, we present a methodological exposition of quantifying competitive relationships within complex systems. Our methodology leverages quantum-mechanical-guided deep neural networks, deployed in the investigation of quinary high-entropy alloys composed of Mo-Cr-Mn-Fe-Co-Ni-Cu-Zn. These alloys are under examination as prospective electrocatalysts, facilitating the electrochemical synthesis of ammonia in aqueous media. Even in the most favorable scenario for nitrogen fixation identified in this study, at the transition from O and OH coverage to surface hydrogenation, the probability of N2 coverage remains low. This underscores the fact that catalyst optimization alone is insufficient for achieving efficient nitrogen reduction. In particular, these insights illuminate that system consideration with oxygen- and hydrogen-repelling approaches or high-pressure solutions would be necessary for improved nitrogen reduction within an aqueous environment.

Selective sensing of free ammonia in aqueous medium by uniformly distributed silver nanoparticles composite of poly(meta-aminophenol)

The purpose of this communication is to develop a nanocomposite of poly(meta-aminophenol)/silver for chemiresistive sensing of free ammonia selectively in aqueous medium. Uniformly distributed silver nanoparticles was formed within the poly(meta-aminophenol) matrix by thermal reduction of silver mono-positive complexes with the functional groups of polymer. The silver loading within the poly(meta-aminophenol) matrix was optimized with respect to size and dispersion of the nanoparticles. The surface morphology and the interfacial interaction between the components of the prepared nanocomposite were characterized by various standard characterization techniques. The highest average DC-conductivity of the nanocomposite with ∼5 % silver loading with an average diameter of 50 nm ranging from 10 to 80 nm was achieved as 1.3 × 10−4 S cm−1 without using any other dopant. This poly(meta-aminophenol)/silver nanocomposite was found to have chemiresistive type sensing response towards ammonia in aqueous medium. The poly(meta-aminophenol)/silver nanocomposite film was responded significantly towards free ammonia in water with response time of 15–20 s, recovery time of 2.5–3 min and limit of detection or quantification of 5 mM. The selectivity of the ammonia sensing by the nanocomposite was also confirmed over ammonium sulfate, ammonium chloride, sodium nitrate and urea in aqueous medium.

Quinazoli-4-one ionic liquid as a fluorescent sensor for NH3 detection: Interaction with ctDNA, theoretical investigation and live cell bioimaging

A novel quinazoli-4-one based ionic liquid, 1-(3-aminopropyl)-3-methyl-4-oxo-3,4-dihydroquinazolin-1-ium bromide (QIL) for fluorometric determination of dissolved ammonia has been successfully synthesized and characterized by spectroscopic techniques such as 1H and 13C NMR, FTIR and HRMS spectrometry. In the proposed method, QIL is converted to a fluorescent derivative by the reaction with ammonia in aqueous medium. The excitation and emission wavelengths were 250 and 436 nm, respectively. Remarkably with the reaction time of >1 s, the binding constant and detection limit was found to be 6.43 × 108 M−1 and 0.73 × 10−8 M, respectively. QIL is found to be highly selective as no interference is observed from various cations, anions, organic molecules and amino acids. The sensing mechanism was further validated by the density functional theory studies. The fluorophore exhibited great sensing property in 3.0–14.0 pH range, hence, it can be employed in diverse matrices. In addition, the fluoro-sensor is highly reversible and reusable in the presence of ctDNA molecule. Moreover, a live-cell imaging study of QIL in Drosophila larval gut tissue has also been carried out to investigate the cell permeability of QIL and its efficiency for selective detection of NH3 in cellular micro environment. To show practical applicability of the fluoro-sensor, test strip kit has been constructed. A detailed comparison table has been shown to evaluate the efficiency of this method.

First GC/MS identification of aqueous ammonia: utilization of ethenesulfonyl fluoride as a selective and rapid derivatization reagent of ammonia in aqueous media.

Identification as well as quantification of ammonia are required in some analytical fields including forensic science. For this purpose, gas chromatography/mass spectrometry (GC/MS) analysis is one of the most suitable techniques. Although ammonia needs to be derivatized for GC/MS analysis, conventional derivatization reagents require anhydrous conditions because they are highly reactive with water. Here, we investigated ethenesulfonyl fluoride (ESF) as a selective reagent for ammonia derivatization in aqueous media to develop a rapid identification method for ammonia in aqueous media. The Michael addition reaction of ammonia with ESF rapidly produced a tri-ESF derivative suitable for GC/MS analysis. We optimized the derivatization reaction conditions and extraction solvent. With the optimized protocol, the detection limit for aqueous ammonia was 0.05 μg mL-1. The calibration curve showed good linearity (R2 = 0.9998) in the range of 0.10-100.0 μg mL-1, and the accuracy (% bias) and the precision (% relative standard deviation) for concentrations of 0.10, 0.25, 10.0, and 75.0 μg mL-1 were within ± 10% (intra- and inter-day). The proposed ESF-based method could quantify ammonia in samples containing interfering nucleophilic substances. This method was successfully applied to ammonia-containing commercial products.

Revealing Ammonia Quantification Minefield in Photo/Electrocatalysis.

Photo/electrocatalytic ammonia synthesis has recently developed fast while the ammonia yields over state-of-the-art photo/electrocatalysts are still very moderate. Such low concentration of synthesized NH3 brings about a challenge to the reliable quantification of the product in photo/electrocatalysis. Notably, we found that the quantitative detection of ammonia concentration below 0.2 ppm is error-prone, which is likely the case happening in the majority of photo/electrocatalytic NH3 synthesis, thus arising concerns about the rationality and accuracy for low-concentration ammonia quantification in these processes. Herein, we discuss the methodology used and analyze the reliability of various detection methods for the detection of trace ammonia in aqueous media. The challenges facing the detection of low concentration of ammonia in photo/electrocatalysis can be overcome by integration with multiple detection methods. According to the data presented, we also propose an effective criterion for precise quantification of ammonia, avoiding the unreasonable comparisons in photo/electrocatalytic ammonia synthesis.

Revealing Ammonia Quantification Minefield in Photo/Electrocatalysis

AbstractPhoto/electrocatalytic ammonia synthesis has recently developed fast while the ammonia yields over state‐of‐the‐art photo/electrocatalysts are still very moderate. Such low concentration of synthesized NH3 brings about a challenge to the reliable quantification of the product in photo/electrocatalysis. Notably, we found that the quantitative detection of ammonia concentration below 0.2 ppm is error‐prone, which is likely the case happening in the majority of photo/electrocatalytic NH3 synthesis, thus arising concerns about the rationality and accuracy for low‐concentration ammonia quantification in these processes. Herein, we discuss the methodology used and analyze the reliability of various detection methods for the detection of trace ammonia in aqueous media. The challenges facing the detection of low concentration of ammonia in photo/electrocatalysis can be overcome by integration with multiple detection methods. According to the data presented, we also propose an effective criterion for precise quantification of ammonia, avoiding the unreasonable comparisons in photo/electrocatalytic ammonia synthesis.

Urea-Urease Reaction in Controlling Properties of Supramolecular Hydrogels: Pros and Cons.

Supramolecular hydrogels are useful in many areas such as cell culturing, catalysis, sensing, tissue engineering, drug delivery, environmental remediation and optoelectronics. The gels need specific properties for each application. The properties arise from a fibrous network that forms the matrix. A common method to prepare hydrogels is to use a pH change. Most methods result in a sudden pH jump and often lead to gels that are hard to reproduce and control. The urease‐urea reaction can be used to control hydrogel properties by a uniform and controlled pH increase as well as to set up pH cycles. The reaction involves hydrolysis of urea by urease and production of ammonia which increases the pH. The rate of ammonia production can be controlled which can be used to prepare gels with differing properties. Herein, we show how the urease‐urea reaction can be used for the construction of next generation functional materials.

Density-Dependent Carrier Recombination in MoS2 Quantum Dots and Its Implications for Luminescence Sensing of Ammonium Hydroxide

Zero-dimensional molybdenum disulfide (MoS2) quantum dots (QDs) have attracted remarkable interest due to their peculiar properties such as the quantum-confinement effect and high surface area. Exploring recombination dynamics in MoS2 QDs is not only expected to gain a deeper insight into their fundamental physics, it is also important for potential applications in optoelectronics and energy-conversion technology. This study synthesized p-type MoS2 QDs doped with diethylenetriamine (DETA) using pulsed laser ablation method. A hole concentration as high as 2.08 × 1012 cm–2 has been demonstrated by gate-dependent conductance measurements. A 110-fold enhancement of photoluminescence in the p-type MoS2 QDs has been found after the introduction of DETA, and the dependence of the radiative and nonradiative recombination of MoS2 QDs on carrier densities were studied. As the carrier density was increased, a decrease of the radiative lifetime was found, which is similar to the behavior of the radiative lifetime in monolayer MoS2. The Shockley-Read-Hall (SRH) and Auger recombination dominates the nonradiative recombination at low and high carrier densities, respectively. The SRH lifetime of MoS2 QDs increases with the increased carrier density, suggesting that the recombination mechanism at the low carrier density is dominated by the SRH recombination. This study found that as the carrier densities exceeded 0.53 × 1012 cm–2, the Auger recombination was responsible for the reduction of PL. Furthermore, MoS2 QDs was used as a fluorescent sensor for the detection of ammonium hydroxide (NH4OH). The PL intensity of MoS2 QDs demonstrates a gradual decrease with increasing NH4OH concentration. By investigating the time-resolved PL (TRPL), the mechanism that leads to the decrease of PL in MoS2 QDs is addressed. This investigation is expected to demonstrate a promising development of an effective and low-cost MoS2 QDs-based fluorescent sensor with superior sensitivity for the rapid detection of ammonia in aqueous media.

Simple and cost-effective sonochemical preparation of ternary NZnO–Mn2O3@rGO nanohybrid: a potential electrode material for supercapacitor and ammonia sensing

The present work deals with a simple and cost-effective sonochemical assisted synthesis of binary transition metal oxide (BTMOs) (NZnO–Mn2O3) and NZnO–Mn2O3@rGO ternary nanohybrid using a imidazole derivative as an organic precursor aimed at the application in supercapacitor and sensing of ammonia in aqueous medium. Morphological analysis using various physicochemical techniques, like FESEM, TEM, XRD, and BET, revealed surface enriched property (high surface area and porous nature) with uniform decoration of binary metal oxides (NZnO–Mn2O3) over reduced graphene oxide (rGO). Formation and synergistic interaction of nanohybrid materials were confirmed from FTIR and Raman analysis. Electrochemical measurements showed maximum capacitance performance via cyclic voltammetry (CV) achieved by ternary nanohybrid NZnO–Mn2O3@rGO (252.77 Fg−1 at scan rate 50 mV s−1) which is in good agreement with the charging–discharging (GCD) and electrochemical impedance spectroscopy (EIS) analysis. Further, the ternary nanohybrid material exhibited good sensing of ammonia in aqueous medium as indicated by continuous amperometric reponse with a lowest sensitivity of 0.47 ppm.

Development of microporous cellulose-based smart xerogel reversible sensor via freeze drying for naked-eye detection of ammonia gas

Microporous cellulose xerogel can be defined as low density biomaterial that can be employed for a variety of promising applications of different fields. The characteristics of xerogel are a consequence of their microstructure. An easy-to-use and reversible solid-state colorimetric sensor for ammonia gas was developed by embedding a bromocresol purple (BCP) pH-sensory chromophore into the environmental friendly carboxymethyl cellulose as bio-based polymer (CMC) matrix. The bromocresol purple was immobilized into cross-linked carboxymethyl cellulose (CMC-BCP) xerogel followed by freeze-drying to introduce a microporous network of regenerated cellulose host in which bromocresol purple chromophore was immobilized to function as a spectroscopic probe guest. Identification of ammonia gas occurred via proton shift from the hydroxyl group of the BCP dye to ammonia nitrogen. Both qualitative and quantitative activities were determined. The architectures of the prepared cellulose xerogel at different degree of substitutions (DS) was investigated using Fourier-transform infrared spectroscopy (FTIR) and scan electron microscopy (SEM), which displayed a high porosity and pores diameter in the range of 10–50 μm. The resultant CMC-BCP displayed high sensitivity for gaseous ammonia. Moreover, excellent reversibility and short detection time were also monitored. The vapochromic xerogel provided an instant color alteration signal from yellow to purple when exposed to ammonia gas or an ammonium hydroxide aqueous environment as monitored by the absorption maxima, color coordinates and color strength. The visual color change of CMC-BCP xerogel was observed to alter in the order from yellow, orange, red to purple in proportional with raising the ammonia concentration in an aqueous environment. Moreover, the CMC-BCP xerogel displayed rapid response time, concentration detection limit as low as 9.0 × 10−2 ppb for ammonia in aqueous media, and very good reversibility.

Activated Alumina Granules with nanoscale porosity for water defluoridation

Highly porous alumina granules have been processed by virtue of modified sol–gel method. Activated alumina (AA) granules were obtained through hydrolysis of aluminum nitrate controlled by ammonia in aqueous media and granules were formed in ammonia–paraffin oil bath. The prepared granules were found to be consisting of high porosity amorphous γ- alumina particles which were characterized by XRD, SEM, TEM, FT-IR and Brunauer–Emmett–Teller (BET) techniques. The material prepared via this method were found to be composed of nano-particles with an average grain size of 30 nm and a large BET surface area 447 m2/g which is very high compared with commercial alumina available in the market. The fluoride removal capacity of prepared granules with variation of fluoride dose has also been studied by employing AA in domestic candle type filters. It also shows better regeneration and reusability after ten cycles of usage. Fluoride removal from aqueous solution in continuous mode depends on adsorbent doses and initial concentration of fluoride.

Photocatalytic N2 conversion to ammonia using efficient nanostructured solar-energy-materials in aqueous media: A novel hydrogenation strategy and basic understanding of the phenomenon

To reduce carbon dioxide emission and supply the nitrogen demand of living organisms, it is crucial to employ a green, solar-based strategy to produce ammonia in aqueous media under ambient conditions, via N2 reaction with transiently photogenerated H-atoms upon appropriate semiconductor materials. In this paper, by using a facile precipitation/calcination route, we synthesized some Fe2O3 and TiO2-based uniform nanoparticles and applied them in a water photosplitting setup to photosynthesize ammonia. The maximum yield was obtained for Fe2O3 and was interpreted in terms of its ability to temporarily store hydrogen atoms, adsorb nitrogen molecules, and harvest more photons in the visible region. Based on photocatalytic reduction of protons to H-atoms and stepwise hydrogenation of N≡N molecules on the photocatalyst surface, a reaction pathway was proposed. During this N2-photofixation process, the generation of hydrazine by-product was also predicted and confirmed by empirical evidence. Moreover, the role of hole-scavenger additive was discussed in detail from physicochemical standpoint.

Electroreduction of N2 to Ammonia at Ambient Conditions on Mononitrides of Zr, Nb, Cr, and V: A DFT Guide for Experiments

A rapid and facile reduction of nitrogen to achieve sustainable and energy-efficient production of ammonia is critical to its use as a hydrogen storage medium, chemical feedstock, and especially for manufacturing inorganic fertilizers. For a decentralization of catalytic ammonia production, small-scale N2 reduction devices are required that are equipped with the most stable, selective, and active catalysts that operate at low temperature and ambient pressure. Here, we report the development of new and cost-efficient catalysts, transition metal nitrides, which enable electrochemical reduction of molecular nitrogen to ammonia in aqueous media at ambient conditions with only a low applied bias. The most promising catalysts are VN, ZrN, NbN, and CrN, which are identified among a range of transition metal nitride surfaces through a comprehensive density functional theory based analysis. All four nitrides are found to be more active toward nitrogen reduction than toward the competing hydrogen evolution reaction...

Spectrophotometric determination of ammonia using ninhydrin assay and kinetic studies

A spectrophotometric method for the determination of ammonia in aqueous media was investigated. This newly developed method for the reaction of ammonia with ninhydrin found to be simple, accurate and precise. A deep red color product was formed in the presence of sodium hydroxide at wavelength of 508 nm. The effects of variables such as temperature, time, acidity and reagents concentration have been evaluated to select the appropriate conditions for this reaction. Beer's law is obeyed; the calibration curve is linear over the range of 2×10 -4 -1.4×10 -3 M of ammonia with regression coefficient ( r 2 ) of 0.994 (n = 7). The calculated molar absorptivity and Sandell's sensitivity values are 1.069×10 3 L/mol.cm and 0.015 μg/cm 2 , respectively. The limits of detection (LOD) and quantification (LOQ) are calculated to be 1.2×10 -5 and 3.6×10 -5 M, respectively. The intra-day accuracy expressed as relative error was less than 0.5% with precision (RSD) ranging from 0.49 to 1.55%. The inter-day accuracy ranged (RSD) from 0.49 to 1.90 % with a relative error was less than 1.50 %. The stoichiometry of this reaction was determined to be of 1:2 between ammonia and ninhydrin with first order reaction.

Dinitrogen reduction on a polypyrrole coated Pt electrode under high-pressure conditions: electrochemical impedance spectroscopy studies

The electrochemical impedance spectroscopy (EIS) responses of a polypyrrole (PPy)-coated platinum electrode were investigated during N$_{2}$-reduction to ammonia in aqueous medium. Kinetic parameters such as film resistance, pore resistance, and double layer capacitance were analyzed as a function of applied potential and polymer film thickness. The relation between kinetic parameters was discussed by combining electrolysis results. It was found that the optimum film thickness of polypyrrole was 0.73 $\mu $m and optimum potential for ammonia synthesis was -0.150 V under 60 bar N$_{2}$-pressure. The impedance responses under these conditions presented the lowest pore resistance value of ca. 2 $\Omega $ cm$^{2}$. The electrolyte resistance was also 2 $\Omega $ cm$^{2}$ and the film resistance was ca. 5 $\Omega $ cm$^{2}$. Tafel slopes calculated from the Tafel curve and EIS-Tafel diagram gave corresponding results: 0.121 V dec$^{-1}$ and 0.128 V dec$^{-1}$, respectively; $\alpha $-transfer coefficient of 0.49 and an exchange current density with a value of 3.17 10$^{-3}$ A cm$^{-2}$ were characteristic for H$_{ad}$ formation in acidic aqueous medium.

Carboxymethylguargum-silver nanocomposite: green synthesis, characterization and an optical sensor for ammonia detection

This work describes the preparation of new carboxymethyl guar gum-silver nanocomposite (CMGG/Ag NC) by green synthesis method. For this carboxymethyl guar gum was used as a reducing agent as well as stabilizer. The silver nanoparticles obtained were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis spectroscopy, Fourier transform infrared (FTIR) and energy dispersive x-ray analysis (EDX). The average size of the silver nanoparticles was found of ∼6 nm. Thus, the obtained CMGG/AgNPs NC was examined for optical sensing property for detection of ammonia in aqueous medium. The response time and the detection limit of ammonia in aqueous solution were detected at room temperature. It was concluded that in the future, at this room temperature optical ammonia sensor may be used for medical diagnosis and clinically for detecting low ammonia level (up to 1 ppm) in biological samples for various biomedical applications.

MnO2/graphene oxide: a highly active catalyst for amide synthesis from alcohols and ammonia in aqueous media

Rod-like MnO2 uniformly attached on both side of GO sheets (MnO2/GO) is an efficient heterogeneous catalyst for the synthesis of primary amides from primary alcohols and ammonia as well as from aldehydes or nitriles. Water is the best solvent for these reactions, analytically pure crystals of product could be isolated by simply cooling in ice and this catalyst has excellent recyclability.

Low overpotential reduction of dinitrogen to ammonia in aqueous media

Abstract The molecular nitrogen fixation to ammonia is one of the most important processes in chemistry. In this connection, our aim was to realize an electrochemical reaction under extremely mild conditions in an aqueous media for the first time. The reduction of dinitrogen was achieved on a polypyrrole electrode in aqueous 0.1 M Li2SO4/0.03 M H+ solution at 60 bar N2-pressure. The reaction product was only ammonia and the ammonia formation efficiency depends strongly on the applied pressure, temperature, electrode potential, supporting electrolyte, film thickness of polymer electrode, as well as on the amount of proton source added to the electrolyte medium. The maximum yield of NH3 was 53 μM obtained at −0.165 VNHE after 5 h of electrolysis.

Electrocatalytic reduction of nitric oxide by water-soluble manganese porphyrins

Manganese porphyrins electrochemically catalyze the reduction of nitric oxide to hydroxylamine and ammonia in aqueous media. The reactions occurs via an ECE pathway. Demetallation and porphine ring reduction are the main factors of deactivation.