Ammonium Iodide Research Articles

Review on mixed cation effect in gel polymer electrolytes for quasi solid-state dye-sensitized solar cells

This paper reviews the efforts made to enhance the power conversion efficiencies of dye-sensitized solar cells (DSCs) by employing binary and ternary iodides in gel polymer electrolytes. Reported studies about mixed cation effects in quasi-solid-state electrolytes have been investigated using polyacrylonitrile (PAN), polyvinylidene fluoride, polyvinyl alcohol, polyethylene oxide, polymethylmethacrylate, and phthaloylchitosan as host polymers, with PAN being the most commonly employed. Ionic conductivities, their dependence on the composition of iodide salts, and the nature of counterion have been studied by preparing many different sets of gel polymer electrolytes. DSCs that were fabricated and characterized using different gel polymer electrolytes containing binary salt combinations showed efficiency enhancements. The general trend of open-circuit voltage (Voc) is to increase with an increasing radius of counterion, while short-circuit current density (Jsc) tends to be enhanced with reducing the size of the counterion in the cell. This behavior has been confirmed by studying single salt systems based on alkali metal iodides as well as quaternary ammonium iodides. The studies emphasized a significant enhancement of cell performance for binary cationic systems with respect to their single cation counterparts. In conclusion, the efficiency of the DSCs can be improved by employing a mixed cationic system with high and low charge densities.

Structural, Impedance and Electrochemical Characteristics of Electrical Double Layer Capacitor Devices Based on Chitosan: Dextran Biopolymer Blend Electrolytes.

This report presents the preparation and characterizations of solid biopolymer blend electrolyte films of chitosan as cationic polysaccharide and anionic dextran (CS: Dextran) doped with ammonium iodide (NH4I) to be utilized as electrolyte and electrode separator in electrical double-layer capacitor (EDLC) devices. FTIR and XRD techniques were used to study the structural behavior of the films. From the FTIR band analysis, shifting and broadening of the bands were observed with increasing salt concentration. The XRD analysis indicates amorphousness of the blended electrolyte samples whereby the peaks underwent broadening. The analysis of the impedance spectra emphasized that incorporation of 40 wt.% of NH4I salt into polymer electrolyte exhibited a relatively high conductivity (5.16 × 10−3 S/cm). The transference number measurement (TNM) confirmed that ion (tion = 0.928) is the main charge carriers in the conduction process. The linear sweep voltammetry (LSV) revealed the extent of durability of the relatively high conducting film which was 1.8 V. The mechanism of charge storage within the fabricated EDLC has been explained to be fully capacitive behavior with no redox peaks appearance in the cyclic voltammogram (CV). From this findings, four important parameters of the EDLC; specific capacitance, equivalent series resistance, energy density and power density were calculated as 67.5 F/g, 160 ohm, 7.59 Wh/kg and 520.8 W/kg, respectively.

High-Performance Perovskite Light-Emitting Diodes with Surface Passivation of CsPbBrxI3–x Nanocrystals via Antisolvent-Triggered Ion-Exchange

Inorganic lead halide perovskite nanocrystals (PeNCs) have intensively drawn the attention as efficient light emitting materials for optoelectronic applications due to fine optoelectronic properties with high photoluminescence quantum yield and easily tunable saturated emission color. However, the low stability of the red-emitting PeNCs have become an obstacle because of the uncontrollable iodine substitution from the PeNCs owing weak Pb-I bonding. In this work, we have demonstrated a ligand-mediated post-treatment (LMPT) method using halide ion-pair ligand, tridodecylmethyl ammonium iodide (TrDAI), for the air stable and high-quality red-emitting PeNCs. Through the LMPT method, the optoelectronic properties of red-emitting PeNCs are dramatically improved resulting in the PLQY of 88.7% at 637 ± 2 nm emission with increased carrier lifetime from 20.77 ns to 31.52 ns. We achieve highly efficient red perovskite light-emitting diodes exhibiting a maximum current efficiency of 7.69 cd A-1 and an external quantum efficiency of 6.36% at 637 ± 2 nm electroluminescence emission with a sharp full-width at half maximum of 31 nm.

Electrochemical synthesis of ion exchange polymers: Comparison between hydroxide and proton conductors

We report the electrochemical synthesis of proton- and hydroxide-conducting ionomers. Sulfonated poly(phenyl ether) with various degree of functionalization was synthesized starting from a precursor isomer mixture or from pure ortho- or para-hydroxybenzenesulfonic acid. The ionic conductivity can be related to the different ion exchange capacity of the ionomers. Two hydroxide-conducting ionomers were prepared from (N-allyl-N-benzyl-N,N-dimethyl)ammonium iodide (ABDMA) or N-(p-vinylbenzyl)-N,N,N-trimethylammonium chloride (VBTMA). The ionic conductivity of VBTMA polymer is two orders of magnitude higher than that of ABDMA. This result can be explained by the different structure of the two polymers, which changes the ion mobility drastically. The electrochemical synthesis of ionomers is a promising research field, where many advances can be made by clever choice of highly functionalized precursor monomers with appropriate positions of the ionic groups.

Electrochemical Characteristics of Glycerolized PEO-Based Polymer Electrolytes.

In this article, poly(ethylene oxide)-based polymer electrolyte films doped with ammonium iodide (NH4I) and plasticized with glycerol were provided by a solution casting method. In the unplasticized system, the maximum ionic conductivity of S cm−1 was achieved by the electrolyte comprised of 70 wt. % PEO:30 wt. % NH4I. The conductivity was further enhanced up to S cm−1) for the plasticized system when 10 wt. % glycerol was added to the highest conducting unplasticized one at ambient temperature. The films were characterized by various techniques to evaluate their electrochemical performance. The results of impedance spectroscopy revealed that bulk resistance (Rb) considerably decreased for the highest plasticized polymer electrolyte. The dielectric properties and electric modulus parameters were studied in detail. The LSV analysis verified that the plasticized system can be used in energy storage devices with electrochemical stability up to 1.09 V and the TNM data elucidated that the ions were the main charge carrier. The values of the ion transference number (tion) and electron transfer number (tel) were calculated. The nonappearance of any redox peaks in the cyclic voltammograms indicated that the chemical reaction had not occurred at the electrode/electrolyte interface.

Polyvinylpyrrolidone with ammonium iodide and plasticizer ethylene carbonate solid polymer electrolyte for supercapacitor application

The present work deals a new polymer electrolyte, that is, polyvinylpyrrolidone doped with salt ammonium iodide and plasticizer ethylene carbonate (EC) prepared via solution casting technique for supercapacitor application. Electrochemical impedance spectroscopy was carried out using CH instrument electrochemical work station which shows enhancement in conductivity ( σ) value by doping EC. Polarized optical microscopy confirms the reduction of crystallinity in the polymer electrolyte which established a good relation with our conductivity data. Fourier transform spectroscopy proves the composite nature of plasticized polymer electrolyte. X-Ray diffraction shows the decrease in the crystallinity in polymer matrix after incorporation with the plasticizer. A laboratory-scale electrical double-layer capacitor has been fabricated using graphene oxide electrode and maximum conducting polymer electrolyte which shows reasonable performance.

Experimental Study on Pool Boiling Heat Transfer of Perfluoroalkyl Surfactant Solutions

In this work, pool boiling heat transfer of three kinds of aqueous perfluoroalkyl surfactant solutions were investigated experimentally. Specifically, applied surfactants were Perfluoroalkyl Quaternary Ammonium Iodide (PQAI), Perfluoroalkyl Phosphate (PPA) and Perfluoroalkyl Polyether (PPE) in the concentration range of 5-400 ppm. It is found the perfluoroalkyl surfactants have outstanding effect on reducing the surface tension of based fluid. The surface tension of water could be reduced by ~50 mN/m as the tiny addition. Boiling curve and bubble behavior were measured under the heat flux of 10-80 W/cm2. The results show that the bubble behavior of surfactant solutions is influenced by their absorption and amphiphilic characteristics. It can be seen that the perfluoroalkyl solutions could effectively enhance heat transfer performance and the enhancement is more obvious as increasing concentration. Moreover, aqueous surfactant solutions have the higher heat transfer coefficient (HTC) at the lower heat flux. PQAI solution has the biggest enhancement at the heat flux of 10 W/cm2 when the concentration is kept as 300 ppm, which reduces the superheat of heating surface by 49.3% and HTC increases by 109% than the deionized water.

N-Methyl-N,N-bis(Silatranylmethyl)amine: Structure and reactivity

Trimethylsilylacetonitrile Me3SiCH2CN and N-methyl-N,N-bis(silatranylmethyl)amine hygrohalogenide were obtained by the interaction of N-methyl-N,N-bis(silatranylmethyl)amine MeN[CH2Si(OCH2CH2)3N]21 with MeCN/Me3SiX (X = Cl, I). The key stage of this reaction is the formation of the intermolecular complexes between amine 1 and Me3SiX. The alkylation of amine 1 by ICH2SiX3 (SiX3 = SiMe3, Si(OMe)3 and Si(OCH2CH2)3N) give rise to the generation of the corresponding ammonium salts {(X3SiCH2)MeN[CH2Si(OCH2CH2)3N]2}+I-. The molecular structures of N-methyl-N,N-bis(silatranylmethyl)amine (1), N-methyl-N-[(trimethylsilyl)methyl]-N,N-bis(silatranylmethyl)ammonium iodide (4) and N-methyl-N-N,N-tris(silatranylmethyl)ammonium iodide (6) were determined by single-crystal X-ray diffraction. Compound 1 exists as mix of the conformers 1A (values lN→Si are equal 2.212 Å and 2.274 Å), 1B (values of lN→Si are equal 2.252 Å and 2.272 Å) and 1C (values lN→Si are equal 2.273 Å and 2.291 Å). The length of dative bond N→Si of molecules 1A-1C is longer than in molecules 4 and 6 (Δl lie between 0.105 Å and 0.199 Å), but length of Si–CH2 bond is shorter on 0.001–0.034 Å.

Triazine-based Organic Polymer-catalysed Conversion of Epoxide to Cyclic Carbonate under Ambient CO2 Pressure.

In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO2 pressure (1.02 atm) using a balloon setup. The triazine containing polymer (CYA-ANIS) was prepared from cyanuric chloride (CYA-Cl) and o-dianisidine (ANIS) in anhydrous DMF as solvent by refluxing under the N2 gas environment. The presence of triazine and amine functional groups in the polymer results in the adsorption of CO2 up to 7 cc/g at 273 K. This inspired us to utilize the polymer for the conversion of a series of functionalised epoxides into their corresponding cyclic carbonates in the presence of tetrabutyl ammonium iodide (TBAI) as co-catalyst. The product has wide range of applications like solvent in lithium ion battery, precursor for polycarbonate, etc. The catalyst was efficient for the conversion of different mono and di-epoxides into their corresponding cyclic carbonates under atmospheric pressure in the presence of TBAI as co-catalyst. The study indicates that epoxide attached with electron withdrawing groups (like, CH2 Cl, glycidyl ether, etc.) displayed better conversion compared to simple alkane chain attached epoxides. This is mainly due to the stabilization of electron rich intermediates produced during the reaction (e. g. epoxide ring opening or CO2 incorporation into the halo-alkoxide anion). This catalyst mixture was capable to maintain its reactivity up to five cycles without losing its activity. Post catalytic characterization clearly supports the heterogeneous and recyclable nature of the catalyst.

Structural, Morphological, Electrical and Electrochemical Properties of PVA: CS-Based Proton-Conducting Polymer Blend Electrolytes.

Polymer blend electrolytes based on poly(vinyl alcohol):chitosan (PVA:CS) incorporated with various quantities of ammonium iodide were prepared and characterized using a range of electrochemical, structural and microscopic techniques. In the structural analysis, X-ray diffraction (XRD) was used to confirm the buildup of the amorphous phase. To reveal the effect of dopant addition on structural changes, field-emission scanning electron microscope (FESEM) was used. The protrusions of salt aggregates with large quantity were seen at the surface of the formed films at 50 wt.% of the added salt. The nature of the relationship between conductivity and dielectric properties was shown using electrochemical impedance spectroscopy (EIS). The EIS spectra were fitted with electrical equivalent circuits (EECs). It was observed that both dielectric constant and dielectric loss were high in the low-frequency region. For all samples, loss tangent and electric modulus plots were analyzed to become familiar with the relaxation behavior. Linear sweep voltammetry (LSV) and transference number measurement (TNM) were recorded. A relatively high cut-off potential for the polymer electrolyte was obtained at 1.33 V and both values of the transference number for ion (tion) and electronic (telec) showed the ion dominant as charge carrier species. The TNM and LSV measurements indicate the suitability of the samples for energy storage application if their conductivity can be more enhanced.

Perovskites fabricated on textured silicon surfaces for tandem solar cells

The silicon surface texture significantly affects the current density and efficiency of perovskite/silicon tandem solar cells. However, only a few studies have explored fabricating perovskite on textured silicon and the effect of texture on perovskite films because of the limitations of solution processes. Here we produce conformal perovskite on textured silicon with a dry two-step conversion process that incorporates lead oxide sputtering and direct contact with methyl ammonium iodide. To separately analyze the influence of each texture structure on perovskite films, patterned texture, high-resolution photoluminescence (μ-PL), and light beam-induced current (μ-LBIC), 3D mapping is used. This work elucidates conformal perovskite on textured surfaces and shows the effects of textured silicon on the perovskite layers with high-resolution 3D mapping. This approach can potentially be applied to any type of layer on any type of substrate.

Ab initio studies on ammonium iodine under high pressure**Project supported by the National Natural Science Foundation of China (Grant Nos. 11574109, 51632002, 51572108, 91745203, and 11574112), the National Key Research and Development Program of China (Grant Nos. 2016YFB0201204 and 2018YFA0305900), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT 15R23), and the National Fund

Ammonium iodine (NH4I) as an important member of hydrogen-rich compounds has attracted a great deal of attention owing to its interesting structural changes triggered by the relative orientations of adjacent ammonium ions. Previous studies of ammonium iodide have remained in the low pressure range experimentally, which we first extended to so high pressure (250 GPa). We have investigated the structures of ammonium iodine under high pressure through ab initio evolutionary algorithm and total energy calculations based on density functional theory. The static enthalpy calculations show that phase V is stable until 85 GPa where a new phase Ibam is identified. Calculations of phonon spectra show that the Ibam phase is stable between 85 GPa and 101 GPa and the Cm phase is stable up to 130 GPa. In addition, ammonium iodine dissociates into NH3, H2, and I2 at 74 GPa. Subsequently, we analyzed phonon spectra and electronic band structures, finding that phonon softening is not the reason of dissociation and NH4I is always a semiconductor within the pressure range.

Self‐Crystallized Multifunctional 2D Perovskite for Efficient and Stable Perovskite Solar Cells

AbstractRecently, perovskite solar cells (PSC) with high power‐conversion efficiency (PCE) and long‐term stability have been achieved by employing 2D perovskite layers on 3D perovskite light absorbers. However, in‐depth studies on the material and the interface between the two perovskite layers are still required to understand the role of the 2D perovskite in PSCs. Self‐crystallization of 2D perovskite is successfully induced by deposition of benzyl ammonium iodide (BnAI) on top of a 3D perovskite light absorber. The self‐crystallized 2D perovskite can perform a multifunctional role in facilitating hole transfer, owing to its random crystalline orientation and passivating traps in the 3D perovskite. The use of the multifunctional 2D perovskite (M2P) leads to improvement in PCE and long‐term stability of PSCs both with and without organic hole transporting material (HTM), 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) compared to the devices without the M2P.

Fabrication and optimization of nanocube mixed halide perovskite films for solar cell application

In this article, we report the tailoring of nanostructured mixed halide perovskite MAPb(I1-xBrx)3 films with tunable band gap fabricated by anion exchange reaction. In this process, we used PbBr2 and methyl ammonium iodide (MAI) in order to fabricate mixed halide perovskite films. We have observed an uncommon shape transformation from nanocube-hollow tetraoids-nanocubes/plate. The underlying mechanism of shape transformation was discussed based on experimental results. The driving force for such shape transformation is combined effect of anion exchange reaction between I− and Br− at the solid/liquid interface of PbBr2 and MAI, and mechanical driving force exerted by the spin coating process. The shape transformation is highly reproducible, verified by two step process, dipping as well as spinning process. The best performing device using the nanostructured perovskite films in a device architecture FTO/TiO2/MAPb(I1-xBrx)3/Spiri-OMeTAD/Au shows a current density (Jsc,) of 23.58 mA/cm2, open circuit voltage (Voc) of 0.891 V and fill factor (FF) of 0.608, with a power conversion efficiency (η) of 12.79% in forward sweep. In reverse sweep, the device shows the Jsc (mA/cm2), Voc (V), FF, and η (%) are 23.852, 0.891, 0.716 and 15.237, respectively.

Improved performance and stability of hole-conductor-free mesoporous perovskite solar cell with new amino-acid iodide cations

Carbon-based and hole-transporting-material-free perovskite solar cells (PSCs) are a promising alternative structure for low-cost applicable method to their manufacturing. However, in this technology, the presence of 5-ammonium valeric acid iodide (5-AVAI) as co-cation to the commonly used MAPbI3 perovskite is necessary which promotes the crystal nucleation and growth within TiO2/ZrO2 mesoscopic oxide scaffold, while affects the contact of perovskite with hydrophobic carbon electrodes. Herein, we present the use of alternative and very low-cost amino acids with comparable and even better performance in some cases of as-used 5-AVAI. On that purpose, two common amino acids of dl-leucine and dl-alanine are used for the synthesis of their iodide derivatives also performed as co-cation with methyl ammonium iodide into the MAPbI3. The structural, optical, and electrical characteristics of the PSCs prepared with newly presented amino acids are examined in comparison with those obtained for (5-AVA)xMA1–xPbI3 perovskite as a reference. In the case of dl-leucine iodide-based perovskite, enhanced stability and performance over 5-AVAI was monitored to their PSCs for over 120 days referring to unsealed devices under 60% relative humidity.

Polyvinylpyrrolidone with ammonium iodide and 1-hexyl-3-methylimidazolium iodide ionic liquid-doped solid polymer electrolyte for efficient dye sensitized solar cell

Polymer electrolytes were prepared by doping polyvinylpyrrolidone and ammonium iodide ion with an ionic liquid (IL) 1-hexyl-3-methylimidazolium iodide. Polymer electrolytes were prepared by solution cast technique. Ionic conductivity was improved by the addition of IL which is studied using complex impedance spectroscopy by evaluating ionic conductivity. Using maximum electrical conductivity film, laboratory-scale dye-sensitized solar cell has been fabricated which shows stable performance.

Protonic EDLC cell based on chitosan (CS): methylcellulose (MC) solid polymer blend electrolytes

In this work, preparation and application of solid polymer blend electrolytes (SPBEs) based on chitosan: methylcellulose (CS:MC) incorporated with various amounts of ammonium iodide (NH4I) salt are described. Solution cast technique was adapted for the preparation of the SPBE films. Structural investigation and extent of interaction of the NH4I salt with the CS:MC film surface were conducted through X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy measurements. Electrical DC conductivity of the prepared samples was studied by electrochemical impedance spectroscopy. It is confirmed through transference number (TNM) analysis that ions are the dominant charge carrier in the polymer electrolyte system, in which the ionic (tion) and electron (tel) transference numbers were found to be 0.934 and 0.036, respectively. Through the use of linear sweep voltammetry (LSV), the CS:MC:NH4I system is found to experience electrolyte degradation at 2.1 V. The polymer blend electrolyte sample with highest DC conductivity property was also used as separator in electrical double-layer capacitor (EDLC) cell. Two identical activated carbon electrodes were used to sandwich the electrolyte film. Cyclic voltammetry (CV) was used to show the capacitive behavior of the fabricated EDLC cell, in which no redox peaks were observed. The EDLC was examined for 100 cycles at current density of 0.2 mA/cm2. The values of specific capacitance and equivalent series resistance were determined to be 1.76 F/g, and 650 to 1050 Ω, respectively.

Effect of ohmic-drop on electrochemical performance of EDLC fabricated from PVA:dextran:NH4I based polymer blend electrolytes

Proton conducting solid polymer blend electrolytes based on poly(vinyl alcohol)(PVA):dextran that were doped with different quantities of ammonium iodide (NH4I) were prepared. The X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) study were carried out to examine the compatibility of NH4I withPVA:dextran polymers. FTIR spectroscopy assessment was used to establish the presence of a complex formation between the PVA:dextran and added salt through the modification and reduction in the intensity of FTIR bands relevant to the functional groups. The field emission scanning electron microscopy (FESEM) examination was used to assess the channels for proton transport. Electrical impedance spectroscopy (EIS) was used to analyse the samples conductivity behaviour. The sample with 20 wt.% of added salt has shown a high DC conductivity which can be employed in electrochemical devices such as EDLC. It is also demonstrated by the transference number (TNM) and linear sweep voltammetry (LSV) that it is appropriate to use the largest conducting sample for electrochemical device. There was electrochemical stability of the electrolyte sample with voltage sweeping linearly to 1.3 V. It is shown by the outcome of cyclic voltammetry (CV) plot that charge storage at the site of electrode-electrolyte is non-Faradiac. A high drop voltage (Vd=IR) is implied by the usual galvanostatic charge-discharge. The equivalent series resistance (Res) increases as a result of the increase in Vd all the way through the charge-discharge cycle. Specific capacitance (Csp) is nearly constant from the foremost cycle to the 100th cycle, with average of 4.2 F/g.

Copper- and DMF-mediated switchable oxidative C-H cyanation and formylation of imidazo[1,2-a]pyridines using ammonium iodide.

The cyanation and formylation of imidazo[1,2-a]pyridines were developed under copper-mediated oxidative conditions using ammonium iodide and DMF as a nontoxic combined cyano-group source and DMF as a formylation reagent. Mechanistic studies indicate that the cyanation of imidazo[1,2-a]pyridines proceeds through a two-step sequence: initial iodination and then cyanation. The cyanation has a broad substrate scope and high functional group tolerance, and can be safely conducted on a gram scale. A novel copper-mediated formylation using the widely available DMF as the formylation reagent and environmentally friendly molecular oxygen as the oxidant has also been developed. This protocol also provided a convenient approach for the synthesis of clinically used saripidem.

Base-promoted aerobic oxidative synthesis of fused 1,3,5-triazines under metal-free conditions

An efficient base-promoted aerobic oxidation procedure for the synthesis of fused 1,3,5-triazines from 2-aminobenzimidazoles, aromatic aldehydes, and ammonium iodide under metal-free conditions has been developed.