NH4Cl Aqueous Solution Research Articles

Aqueous hybrid iron-ion battery capacitors with ultra-long cycle life

With the over-exploitation of lithium resources, there is a tendency to find a new metal-ion energy storage device to replace lithium-ion batteries. In recent years, Fe-ion energy storage devices are acknowledged for their low cost, abundant resources, and safe characteristics, but their full potential has yet to be widely explored. Herein, we propose a new hybrid iron-ion battery capacitor (H-IIBC) energy storage device. The H-IIBC device prepared with nano flower-like activated carbon (FAC) as the cathode material, high-purity iron sheet as the anode material, and 1 M FeSO4 + NH4Cl aqueous solution as the electrolyte. After atomic molecular dynamics simulations and ex situ characterization analysis, ion adsorption/desorption occurs on the surface of the FAC cathode during the charging/discharging process, accompanied by the redox of iron ions. The stripping/deposition of iron occurs at the high-purity iron anode. With the charging/discharging process, the reaction at the anode favors the interconversion between Fe2+ and Fe3+ which requires less energy, thus ensuring that the high purity iron will not be depleted. Thus, the specific capacitance of prepared H-IIBC could reach 644 mF g−1 (399 mF cm−2) at a current density of 1 mA cm−2 in the voltage window of 0–1 V and shows ultra-high cycling stability at 3,000 cycles test. This economical, long-life and safe H-IIBC is expected to realize great potential in the field of energy storage in the near future.

Effect of Hydrogen on Corrosion Behavior of 321 Stainless Steel in NH4Cl Solution.

For a hydrogenation heat exchanger operating under severe working conditions such as high temperature, high pressure and a hydrogen environment, perforation accidents caused by NH4Cl corrosion occur frequently. However, few reports on the effect of hydrogen on the corrosion behavior of metal materials in NH4Cl aqueous solution have been published. In this paper, X-ray photoelectron spectroscopy (XPS), electrochemical dynamic potential polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky (M-S) curves and scanning electron microscopy (SEM) were used to study the effect of electrochemical hydrogen charging (EHC) on the corrosion behavior of 321 stainless steel in an NH4Cl solution environment. The results show that: (1) hydrogen can change the structure and chemical composition of 321 stainless steel passive film and promote the conversion of metal oxide to hydroxide. At the same time, it can reduce the stability of the passive film. (2) Hydrogen can increase the thermodynamic and kinetic tendency of corrosion reaction and cooperate with Cl− to promote the occurrence of pitting corrosion.

Iron-Catalyzed Cross-Electrophile Coupling of Inert C–O Bonds with Alkyl Bromides

Iron-Catalyzed Cross-Electrophile Coupling of Inert C–O Bonds with Alkyl Bromides

Recovery and Reuse of Spent ITO Targets through Electrochemical Techniques

Indium is a strategically scarce metal with excellent conductivity and light transmittance that is widely used to prepare ITO targets. In this work, an electrolysis method was exploited to recover and reuse spent ITO (s-ITO) targets to provide a novel way to recycle valuable resources. The electrochemical behaviors of indium tin oxide were studied first by cyclic voltammetry in CaCl2 at 850 °C. A reduction peak corresponding to the simultaneous reduction of indium tin oxide was found at −0.5 V vs Pt. Then, indium-tin alloy was recovered by electrolysis of s-ITO particles in CaCl2 at −2.8 V and 850 °C. The mass ratio of In and Sn in the alloy obtained by electrolysis is almost the same as that in the initial s-ITO before electrolysis. In addition, oxide composite powders were obtained by electrolysis of the alloy in NH4Cl aqueous solution, which can be used to synthesize ITO targets. The particle size of the composite powders was between 20 nm and 60 nm, and the distribution of each element was uniform.

Treatment of ammonia-embodied wastewater by a transition-metal-based photochemical catalysis strategy

Inspired by the self-purification process and a low nitrogen content of the ocean, and the fact that the driving-force behind ecological cycle is solar irradiation, a novel photochemical strategy was designed to spontaneously remove inorganic ammonia nitrogen from wastewater with solar irradiation. This strategy is based on the principles of green chemistry and energy efficiency, and meanwhile the prevention from the introduction of accompanying pollution. In our strategy, a photo-Fe (or Mn)–O2 system was built to remove ammonia-nitrogen from its aqueous solution. The results show that with full band solar irradiation at a range of 10–30 mW cm−2, in weak alkaline condition, more than 90% of ammonia-nitrogen can be effectively removed from NH4Cl aqueous solution by the new strategy, with a residual concentration as low as 2 mg L−1. Mn(III) was proved to be a better catalyst than Fe(III). The catalytic mechanism of N-removal is the generation of •OH during the process of the photoreduction of transition metal hydroxides. DFT theory had been applied to help explaining the mechanism. Different from general knowledge, in our strategy, an alkaline environment, where the generation rate of radicals was relatively slow and comparable to oxidation rate of transition metal ions, can guarantee the stability and persistency of the catalytic reaction. No NOx was produced in this strategy. This new strategy provides a new possibility of cost-efficient and environmental-friendly wastewater treatment, and has certain meaning of understanding how self-purification works in nature.

Local structure of NH4Cl solution and its correlation with osmotic coefficient by molecular dynamics simulation and Raman spectroscopy

The NH4Cl aqueous solution ranging from 1.00 wt.% to 22.00 wt.% have been studied by molecular dynamic simulation, Raman spectroscopy and polarized Raman spectroscopy. Radial distribution function (RDF), diffusion property, structure of hydrogen bond network, excess Raman spectroscopy and non-coincidence effect (NCE) were obtained. The contact ion pairs of cation and anion appeared in NH4Cl solution of 15.00 wt.%, leading to fundamental changes in hydrogen bonds and the hydrated shell. The evolution of hydrogen bond with mass fraction in solution was described. The osmotic coefficient of NH4Cl aqueous solution was obtained by thermodynamic calculation, and its linear relationship with double donor single acceptor hydrogen bond (DDA-OH) was preliminarily summarized. Moreover, the experimental results are in good agreement with the simulation results.

Morphological control of carbon-supported Pt-based nanoparticles via one-step synthesis

The morphology of Pt-based nanoparticles supported on carbon is controlled to enhance the oxygen reduction reaction (ORR) catalytic performance. Herein a simple one-step method without a polymer surfactant is demonstrated to synthesize Pt-Cu nanoclusters, Pt-Cu nanospheres, and Cu-doped Pt nanoplates. Metal precursors are reduced by sodium tetrahydroborate in a NaCl or NH4Cl aqueous solution containing carbon supports, and nanoparticles are directly deposited on carbon. Cl− ions generated from NaCl or NH4Cl delay the reduction of metal ions when O2 is dissolved in the synthesis solution, leading to larger particles. In addition, NH4+ ions guide the growth direction of Pt to form a plate-like morphology that exposes the {111} facets. However, stable amine complex lowers the Cu content in the nanoplates. Nanoclusters and nanospheres are obtained in the absence of Cl−/O2 and NH4+, respectively. Half-cell measurements are performed in acidic media to evaluate the electrochemical properties. Cu-doped Pt nanoplates exhibit a 3.67-times higher ORR catalytic activity than the commercial Pt catalysts thanks to the synergistic effect with a small amount of Cu and selective exposure of the {111} facets. The result suggests that transition metals in Pt-based electrocatalysts may be unnecessary to form intermetallic alloyed crystals for the enhanced ORR performance.

Charge-Transfer-to-Solvent Reaction in a Hydrophobic Tetrabutylammonium Iodide Molecular Layer in Aqueous Solution.

We present ultrafast photoelectron spectroscopy of the charge-transfer-to-solvent reaction in a segregated TBAI (tetrabutylammonium iodide) molecular layer in aqueous solution. The reaction times and electron binding energies of transient species vary with TBAI concentration from a very low value of 1 × 10-3 mol L-1, which is in contrast to NaI solution exhibiting no concentration (0.01-1.0 mol L-1) dependence. The result from soft X-ray N(1s) spectroscopy indicates that the photoelectron intensity in TBAI aqueous solution is about 70 times enhanced as compared to that in NH4Cl aqueous solution for an identical salt concentration, and TBA+ drags I- to the surface region. At high TBAI concentrations, electrons released from I- are trapped and held in the TBAI molecular layer owing to electrostatic attraction by TBA+.

CO2 sequestration by pH-swing mineral carbonation based on HCl/NH4OH system using iron-rich lizardite 1T

In pH-swing mineral carbonation, several acid/base systems has been investigated. Currently the main acid/base systems employed are HCl/NaOH and NH4HSO4/NH4OH. However, the use of a HCl/NH4OH system was not yet elucidated. This study proposes to evaluate the feasibility of a pH-swing mineral carbonation based on HCl/NH4OH system at atmospheric pressure and moderate temperatures using mining waste from asbestos production from Goiás State, Brazil (S-GO) for two conditions (i.e. stoichiometric conditions (T2E) and acid excess (T2)). Results indicated that the Fe3+ content in S-GO acted as a catalyst, due to FeCl3 hydrolysis in aqueous solutions. Thus, high Mg and Fe extraction efficiency (95 ± 2%), were achieved in the leaching stage for both conditions. The S1 solid residue was mainly SiO2 with 90 ± 1% purity content. In the purification stage 91.7 ± 1.9% of Fet were removed, however, a loss of Mg of 13.6 ± 2.3% was also detected. On the carbonation stage, high purity hydromagnesite was formed in T2E; this stage had a 85% efficiency, thus, 36.7% of CO2 was fixed. On T2, excess H2O and CO2 promoted dypingite formation and reduced hydromagnesite formation. After carbonation, the formation of crystals was observed in the NH4Cl aqueous solution at 25 °C, indicating NH4Cl supersaturation. The results of mass balance indicate that 4 ton of mineral waste will be employed for each ton of captured CO2, as well as 2.6 ton of HCl, and 4.5 ton of NH4OH. However, 1.7 ton of SiO2, 0.55 ton of iron oxides, and 2.7 ton of hydromagnesite could be produced.

In-situ preparation of iron(III) hexacyanoferrate nano-layer on polyacrylonitrile membranes for cesium adsorption from aqueous solutions

Ion-exchange adsorption is an effective method for separating cesium and rubidium from other alkaline metal ions in aqueous solutions. Herein, we developed a novel and facile method for in-situ preparation of Prussian blue (PB) nano-layer on porous polyacrylonitrile (PAN) membranes by heterogeneous nucleation in potassium ferrocyanide solution and then growth in FeCl3 solution, or potassium ferrocyanide solution as single precursor. The effects of reactant concentrations and reaction time on the PB layer, the static adsorption, dynamic adsorption, desorption and reuse of PB membranes were investigated. The results showed that the maximum adsorption capacity of PB nano-layer for cesium attains 0.714mmolg−1 (25°C), and the ideal selectivity factor of Cs+ vs. Li+, K+, and Na+ is found to be 41.76, 35.50, and 23.67 respectively. Compared with the PB powder, the immobilized PB on membrane surface does not deteriorate in the adsorption performance. NH4Cl aqueous solution exhibits excellent eluting effect, and the membrane can be reused for 5 times without apparent deterioration, indicating practical perspective in adsorption of cesium and rubidium from aqueous solutions.

Investigation of the Solidification Behavior of NH4Cl Aqueous Solution Based on a Volume-Averaged Method

Based on solidification theory and a volume-averaged multiphase solidification model, the solidification process of NH4Cl-70 pct H2O was numerically simulated and experimentally verified. Although researchers have investigated the solidification process of NH4Cl-70 pct H2O, most existing studies have been focused on analysis of a single phenomenon, such as the formation of channel segregation, convection types, and the formation of grains. Based on prior studies, by combining numerical simulation and experimental investigation, all phenomena of the entire computational domain of the solidification process of an NH4Cl aqueous solution were comprehensively investigated for the first time in this study. In particular, the sedimentation of equiaxed grains in the ingot and the induced convection were reproduced. In addition, the formation mechanism of segregation was studied in depth. The calculation demonstrated that the equiaxed grains settled from the wall of the mold and gradually aggregated at the bottom of the mold; when the volume fraction reached a critical value, the columnar grains stopped growing, thus completing the columnar-to-equiaxed transition (CET). Because of solute partitioning, negative segregation occurred at the bottom region of the ingot concentrated with grains, whereas a wide range of positive segregation occurred in the unsolidified, upper part of the ingot. Experimental investigation indicated that the predicted results of the sedimentation of the equiaxed grains in the ingot and the convection types agreed well with the experimental results, thus revealing that the sedimentation of solid phase and convection in the solidification process are the key factors responsible for macrosegregation.

Surface texture of pulse-magnetron-sputtered ZnO:Al films by using a diluted NH4Cl aqueous solution

This paper mainly addresses the effects of the NH4Cl concentration and etching time on the surface texture of -oriented ZnO:Al films deposited by using direct-current pulse-magnetron reactive sputtering. A mechanism for the etching of the ZnO:Al films by NH4Cl is also proposed. The best surface texture was observed the same as it was etched for 15 min by using a 3.0 wt.% NH4Cl solution. The average reflectivity at wavelengths from 300 nm to 800 nm was sharply reduced to 4.607%. The etching with NH4Cl is closely related to the preferential orientation rather than the usual preferential orientation. The increased number of defects around the boundary is responsible for the surface texture and the blueshift of the absorption edge of the films.

Synthesis of Zeolite NaA from Low Grade (High Impurities) Indonesian Natural Zeolite

The zeolite NaA has been successfully synthesized from the low grade natural zeolite with high impurities. The synthesis method was started by mixing natural zeolite powder with NH4Cl aqueous solution in the reactor as pretreatment. The use of pretreatment was to reduce the impurities contents in the zeolite. The process was followed by alkaline fusion hydrothermal treatment to modify the framework structure of natural zeolite and reduce the SiO2/Al2O3 ratio. Finally, the synthesized zeolite was calcined at 600 °C for 2 h. The final zeolite product was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the morphology of the zeolite NaA was cubic shape as observed by SEM analysis and the synthesized zeolite NaA with pretreatment gave less impurity than without pretreatment.

Optimization of ZnO:Al based back reflectors for applications in thin film flexible solar cells

Back reflectors based on Aluminum and Molybdenum as the reflecting materials and ZnO:Al as the transparent conductive oxide, were deposited at low temperature on polyethylene naphthalate by magnetron sputtering. The optimization of the layer thickness of the constituent materials and the final texture of the structure was performed in order to achieve structures with appropriate properties to be applied to amorphous silicon solar cells. In this sense, average total reflectance values of 71% in the wavelength range of 400–800 nm were obtained for the layer stack of 80 nm-thick ZnO:Al layer on 235 nm-thick Aluminum deposited directly on the flexible substrate. However, this structure showed a poor adherence onto the substrate. This issue was improved using a thin Molybdenum layer between the metal and the substrate, maintaining similar optical properties. On the other hand, textured back reflectors were obtained etching the transparent conductive oxide with NH4Cl aqueous solution. After the etching process, the highest enhancement was achieved for the sample that used an Mo/Al bilayer as reflective metal. In this case, a roughness of around 29 nm and a haze factor of 25% at 600 nm were achieved.

Development of two-step etching approach for aluminium doped zinc oxide using a combination of standard HCl and NH4Cl etch steps

An etching method for ZnO:Al films deposited by radio-frequency sputtering is presented. The method is developed to achieve appropriate surface morphology for efficient light scattering. This etching method consists of a first step where the sample is dipped in standard diluted HCl (0.5wt.%) for 40s (the “standard Jülich” etch process) and a subsequent step where a NH4Cl aqueous solution with concentrations ranging from 2 to 20wt.% is used. The introduction of the second step leads to a slight modification of the surface feature shape and an increase in the surface roughness of up to around 37% in relation with that obtained using only the first step. High haze values are also obtained, reaching up to 93% at 550nm and strong light scattering into angles above 50° at 632nm. On the other hand, the resistivity of the textured films remains low enough for cell application, being ranged from 6 to 13Ω/sqr depending on the NH4Cl concentration used. Finally, in order to assess the role of the features obtained on the surface as effective light trapping, the textured films are applied as front contact in silicon thin film solar cells.

Texture optimization process of ZnO:Al thin films using NH4Cl aqueous solution for applications as antireflective coating in thin film solar cells

ZnO:Al thin films varying the thickness from 80 to 110nm were deposited on polished float zone <100> Si wafers by radio frequency magnetron sputtering at 100°C. To texturize these surfaces with the aim of being used as antireflective coating, a wet etching process based on NH4Cl was applied. Taking into account that the layer thickness was small, the control of the etch parameters such as etchant concentration and etching time was evaluated as a function of the textured film properties. An appropriate control of the etching rate to adjust the final thickness to the 80nm required for the application was realized. Using NH4Cl concentrations of 10wt.% and short times of up to 25s, an increase of the film roughness up to a factor of 5.6 of the as-deposited films was achieved. These optimized textured films showed weighted reflectance values below 15% and considerable better electrical properties than the as-deposited 80nm-thick ZnO:Al films.

Electrochemical Stabilization of Prussian Blue Films in NH4Cl Aqueous Medium

Derivative voltabsommetric scans in near-UV/visible-NIR electromagnetic range together with nano-electrogravimetric measurements during the stabilization process of Prussian Blue in NH4Cl aqueous solution yields information about the localization of the into the crystalline structure of this material. It is proposed that the ammonium ion is placed into the vacancies of the framework that affect to the motional resistance. The simultaneous measure of current, mass, motional resistance, and near-UV-vi-N IR spectra allows to explain the differences observed between the Prussian Blue films placed in a solution of NH4Cl salt regarding the behaviour showed in KCl aqueous solution.

Etching process optimization using NH4Cl aqueous solution to texture ZnO:Al films for efficient light trapping in flexible thin film solar cells

0.5μm-thick aluminum-doped zinc oxide (ZnO:Al) films were deposited at 100°C on polyethylene terephthalate substrates by Radio Frequency magnetron sputtering. The as-deposited films were compact and dense, showing grain sizes of 32.0±6.4nm and resistivities of (8.5±0.7)×10−4Ωcm. The average transmittance in the visible wavelength range of the structure ZnO:Al/PET was around 77%. The capability of a novel two-step chemical etching using diluted NH4Cl aqueous solution to achieve efficient textured surfaces for light trapping was analyzed. The results indicated that both the aqueous solution and the etching method resulted appropriated to obtain etched surfaces with a surface roughness of 32±5nm, haze factors at 500nm of 9% and light scattering at angles up to 50°. To validate all these results, a commercially ITO coated PET substrate was used for comparison.

Comparable study on the effect of diluted NH 4Cl solution on the postdeposition surface texture of as-deposited aluminum-doped zinc oxide films by direct current pulse and direct current reactive magnetron sputtering

Effect of 5.0% diluted NH 4Cl aqueous solution was comparably investigated on the postdeposition surface texture of the as-deposited smooth aluminum-doped zinc oxide (AZO) films by direct current pulse reactive magnetron sputtering (DCP-sputtering) and direct current reactive magnetron sputtering (DC-sputtering). The as-deposited AZO films by DCP-sputtering showed an effective surface texture for light trapping upon the etching of 5.0% diluted NH 4Cl solution, while the as-deposited AZO films by DC-sputtering demonstrated an obscure surface texture upon the same etching treatment. The different result might be attributable to a big difference in film strain and film compactness. The formation of interstitial Zn, interstitial Al and grain boundary is the key to realize effective surface texture for the as-deposited AZO films.

Site-Selective Growth of Highly Oriented ZnO Rod Arrays on Patterned Functionalized Si Substrates from Aqueous Solution

Site-selective deposition of highly oriented ZnO rod arrays was successfully achieved in an aqueous solution of zinc nitrate and hexamethyltetramine (C6H12N4) at low temperature. A patterned self-assembled monolayers (SAMs) surface was used as the template. ZnO nanorods were selectively deposited on the -CH3 terminated SAMs but were hindered on the OH-covered regions due to the preferential binding of C6H12N4−H+ complex with -OH endgroups. Continuous stirring during the reaction played a role in improving the crystal orientation and crystalline quality of ZnO nanorods. A little NH4Cl aqueous solution had a positive effect to increase the nucleation density of ZnO crystals, and thus enhance their order degree. These results provide a one-step process to fabricate micropatterns of thin films from a harmless substance at ordinary temperature and atmospheric pressure.