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The selection of an appropriate solvent is essential for achieving high yields and selectivity in chemical reactions. The chemical and physical parameters of organic solvents have been classified into several groups, and solvents can be compared with each other with respect to these properties. The acceptor number (AN), donor number (DN) and polarity (ETN) have been widely accepted and used for theoretically and quantitatively evaluating the properties of organic solvents. In a similar manner, the AN, DN and ETN of room temperature ionic liquids (RTILs) have been estimated from spectral changes in solvatochromic compounds. In this paper, the AN and ETN of eight types of imidazolium-based RTILs were estimated from the relationship between the AN and ETN values and the first redox potential obtained from the voltammograms of polyoxometalates (POMs) in various organic solvents. The obtained parameters were compared with those estimated by spectrophotometric methods reported previously by several groups. This new method for estimating the AN and ETN of RTILs using the voltammetric behaviour of POMs with low charge density and high symmetry could provide the other path to obtain more reliable AN and ETN of RTILs.

The solution-mediated behavior of lithium-sulfur (Li-S) batteries presents a wide range of opportunity for evaluating and improving the performance at practical lean-electrolyte conditions. Here, we introduce methyl trifluoroacetate (CH(3)TFA) as an additive to the Li-S electrolyte to evaluate the joint effects of two distinct strategies: high donor number solvents/salts and organosulfur-mediated discharge. CH(3)TFA is shown to react with lithium polysulfides in-situ to form lithium trifluoroacetate (LiTFA) and dimethyl polysulfides. We find that both the methyl group and trifluoroacetate anion considerably enhance Li-S discharge behavior over the course of cycling, though they have distinctly beneficial effects. The TFA anion impacts solution coordination behavior, improving polarization and discharge kinetics during cycling. Meanwhile, the derivatization to dimethyl polysulfides improves the solubility of intermediate species, enhancing overall utilization under lean-electrolyte conditions. CH(3)TFA thus represents a new class of additives for Li-S batteries, enabling an in-situ systematic molecular engineering of intermediate species for improved performance.

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process., A low defect halide perovskite film can be fabricated using trimethyl phosphate (TMP). TMP directly forms perovskite without intermediate phase due to weak Lewis basicity. The TMP‐based film reduces hysteresis in current‐voltage curve of perovskite solar cell. The TMP‐based device exhibits better performance (>20%) than other solvent‐based ones.

Summary Quinone-based sodium-ion batteries (SIBs) are highly desirable electrochemical devices with high capacity and low cost but suffer from poor cycle life and low practical energy because of quinone dissolution in aprotic electrolyte. Herein, we report a facile strategy of using ionic liquid (IL) to tackle the dissolution of quinone electrodes. The inhibitory effect of ILs on quinone dissolution correlates with their polarity, donor number, and interaction energy, as revealed by combined density functional theory and spectroscopy studies. Particularly, in N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([PY13][TFSI]) electrolyte with weak donor ability and large polarity, calix[4]quinone cathode exhibits high capacity (>400 mAh g−1) and superior capacity retention (∼99.7% at 130 mA g−1 for 300 cycles), significantly outperforming that in ether-based electrolyte. Moreover, the remarkable cyclability and considerable rate capability of 5,7,12,14-pentacenetetrone in [PY13][TFSI] render it a promising sodium-storage material. This work would promote the development of high-performance SIBs with quinone electrodes and IL electrolyte.

Uncontrolled growth of insulating lithium sulfide leads to passivation of sulfur cathodes, which limits high sulfur utilization in lithium-sulfur batteries. Sulfur utilization can be augmented in electrolytes based on solvents with high Gutmann Donor Number; however, violent lithium metal corrosion is a drawback. Here we report that particulate lithium sulfide growth can be achieved using a salt anion with a high donor number, such as bromide or triflate. The use of bromide leads to ~95 % sulfur utilization by suppressing electrode passivation. More importantly, the electrolytes with high-donor-number salt anions are notably compatible with lithium metal electrodes. The approach enables a high sulfur-loaded cell with areal capacity higher than 4 mA h cm−2 and high sulfur utilization ( > 90 %). This work offers a simple but practical strategy to modulate lithium sulfide growth, while conserving stability for high-performance lithium-sulfur batteries., The development of new electrolyte systems is needed to optimize performance in lithium-sulfur batteries. Here the authors employ anions with high donor numbers in electrolytes to prevent passivation of the cathode surface, thereby improving sulfur utilization and energy density in a lithium-sulfur cell.

Aqueous Zn batteries are promising energy storage devices for large-scale energy-storage due to low cost and high energy density. However, their lifespan is limited by the water decomposition and Zn dendrite growth. Here, we suppress water reduction and Zn dendrite growth in dilute aqueous electrolyte by adding dimethyl sulfoxide (DMSO) into ZnCl2-H2O, in which DMSO replaces the H2O in Zn2+ solvation sheath due to a higher Gutmann donor number (29.8) of DMSO than that (18) of H2O. The preferential solvation of DMSO with Zn2+ and strong H2O-DMSO interaction inhibit the decomposition of solvated H2O. In addition, the decomposition of solvated DMSO forms Zn12(SO4)3Cl3(OH)15·5H2O, ZnSO3, and ZnS enriched-solid electrolyte interphase (SEI) preventing Zn dendrite and further suppressing water decomposition. The ZnCl2-H2O-DMSO electrolyte enables Zn anodes in Zn||Ti half-cell to achieve a high average Coulombic efficiency of 99.5% for 400 cycles (400 h), and the Zn||MnO2 full cell with a low capacity ratio of Zn:MnO2 at 2:1 to deliver a high energy density of 212 Wh/kg (based on both cathode and anode) and maitain 95.3% of the capacity over 500 cycles at 8 C.

A comprehensive study regarding the effect of different solvent vapours on organolead halide perovskite properties is lacking. In the present work, the impact of exposing CH3NH3PbI3 films to the vapours of commonly available solvents has been studied. The interaction with perovskite has been correlated to solvent properties like dielectric constant, molecular dipole moment, Gutmann donor number and boiling point. Changes in the crystallinity, phase, optical absorption, morphologies at both nanometer and micrometer scale, functional groups and structures were studied using X-ray diffraction, UV-visible absorption, FE-SEM, FTIR and Raman spectroscopies. Among the aprotic solvents DMSO and DMF vapours deteriorate the crystallinity, phase, and optical, morphological and structural properties of the perovskite films in a very short time, but due to the difference in solvent property values acetone affects the perovskite properties differently. Polar protic 2-propanol and water vapours moderately affect the perovskite properties. However 2-propanol can solvate the organic cation CH3NH3+ more efficiently as compared to water and a considerable difference was found in the film properties especially the morphology at the nanoscale. Nonpolar chlorobenzene vapour minutely affects the perovskite morphology but toluene was found to enhance perovskite crystallinity. Solvent properties can be effectively used to interpret the coordination ability of a solvent. The present study can be immensely useful in understanding the effects of different solvent vapours and also their use for post-deposition processing (like solvent vapour annealing) to improve their properties.

In this work, the textural parameters of graphene oxide (GO) and graphite (Gr) samples were determined. The non-local density functional theory (NLDFT) and quenched solid density functional theory (QSDFT) kernels were used to evaluate the pore size distribution (PSD) by modeling the pores as slit, cylinder and slit-cylinder. The PSD results were compared with the immersion enthalpies obtained using molecules with different kinetic diameter (between 0.272 nm and 1.50 nm). Determination of immersion enthalpy showed to track PSD for GO and graphite (Gr), which was used as a comparison solid. Additionally, the functional groups of Gr and GO were determined by the Boehm method. Donor number (DN) Gutmann was used as criteria to establish the relationship between the immersion enthalpy and the parameter of the probe molecules. It was found that according to the Gutmann DN the immersion enthalpy presented different values that were a function of the chemical groups of the materials. Finally, the experimental and modeling results were critically discussed.

Glycol ethers, or glymes, have been recognized as good candidates as solvents for lithium-air batteries because they exhibit relatively good stability in the presence of superoxide radicals. Diglyme (bis(2-methoxy-ethyl)ether), in spite of its low donor number, has been found to promote the solution mechanism for the formation of Li2O2 during the discharge reaction, leading to large deposits, that is, high capacities. It has been suggested that lithium salt association in these types of solvents could be responsible for this behavior. Thus, the knowledge of the speciation and transport behavior of lithium salts in these types of solvents is relevant for the optimization of the lithium-air battery performance. In this work, a comprehensive study of lithium trifluoromethanesulfonate (LiTf) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1,2-di-methoxyethane (DME) and diglyme, over a wide range of concentrations, have been performed. Consistent ion pairs and triplet ions formation constants have been obtained by resorting to well-known equations that describe the concentration dependence of the molar conductivities in highly associated electrolytes, and we found that the system LiTf/DME would be the best to promote bulky Li2O2 deposits. Unexpected differences are observed for the association constants of LiTf and, to a lesser extent, for LiTFSI, in DME and diglyme, whose dielectric constants are similar. Molecular dynamics (MD) simulations allowed us to rationalize these differences in terms of the competing interactions of the O-sites of the ethers and the SOx groups of the corresponding anions with Li+ ion. The limiting Li+ diffusivity derived from the fractional Walden rule agrees quite well with those obtained from MD simulations, when solvent viscosity is conveniently rescaled. Fil: Horwitz, Gabriela. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Factorovich, Matias Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Rodriguez, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina Fil: Laria, Daniel Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Corti, Horacio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Solvent basicity is recognized as playing a major role in solvation and is included, through empirical basicity parameters, in linear free energy relationships that account for the effects of changes in solvent on chemical reactions. It is reasonable to postulate that the basicity of a solvent molecule reflects some combination of its molecular properties. In the present study, density functional calculations using the B3LYP functional, and Hartree–Fock calculations have been used to calculate the partial atomic charges (using the Hirshfeld and CM5 models), orbital energies, polarizabilities, dipole moments and quadrupolar amplitudes for over one hundred molecules for which there are experimental values for two basicity parameters, Kamlet and Taft’s hydrogen bond acceptor strength, β, and Gutmann’s donor number, DN, a measure of Lewis basicity. Regression of the experimental β and DN values against molecular descriptors reflecting the above molecular properties yields a remarkably consistent picture. For both parameters the values for alcohols and amines lie systematically off of the regression lines through the remaining compounds, which include alkanes, aromatics, halogenated alkanes and aromatics, esters, carbonates, carboxylic acids, ketones, ethers, nitriles, phosphates, sulfides and sulfates. Independent of the calculation method or method of estimating the partial atomic charges, both experimental β and DN are essentially determined by two molecular properties: the charge on the most negative atom of the molecule and the molecular orbital from which charge donation would occur. The regression results using any of the fours sets of descriptors (reflecting the two calculation methods and two methods of charge estimation) are remarkably similar for β and DN supporting the view that these are measures of the same “basicity”.

A novel methodology is reported on the use of internally referenced diffusion-ordered spectroscopy (IR-DOSY) in divulging the solution structure of lithium-ion battery electrolytes. Toluene was utilized as the internal reference for 1H-DOSY analysis due to its exceptionally low donor number and reasonable solubility in various electrolytes. With the introduction of the internal reference, the solvent coordination ratio of different species in the electrolytes can be easily determined by 1H-DOSY or 7Li-DOSY. This new technique was applied to different carbonate electrolytes, and the results were consistent with a Fourier transform infrared (FTIR) analysis. Compared to conventional vibrational spectroscopy, this IR-DOSY technique avoids the complicated deconvolution of the spectrum and allows determination of the solvent coordination ratio of different species in electrolyte systems with two or more organic solvents.

The development of the rechargeable Li–O2 battery (LOB) has encountered several bottlenecks till date. One of the biggest challenges is to lower the oxidation potential of Li2O2, which is the insulating and insoluble discharge product. A possible solution to this problem is to use high acceptor number (AN) or donor number (DN) solvents to increase the solubility of Li2O2, so that the dissolved Li2O2 can diffuse to the cathode surface and get oxidized at a relatively low potential. Herein, we explored the efficiency and side-reactions in the LOB charge process with different Li2O2 soluble electrolytes. The relationship between the solubility of Li2O2 and charging rate was analyzed quantitatively with ultraviolet-visible (UV-Vis) spectroscopy and rotating disk electrode experiments. As a result, electrolytes with high AN usually have higher solubility for Li2O2 than electrolytes with high DN, and thus exhibit higher Li2O2 oxidation rates. Nevertheless, higher Li2O2 solubility in high AN electrolytes also induces more severe side reactions and easily passivates the electrode surface. The trade-off between charging reaction rate and electrolyte stability is a key issue to be considered when designing high performance LOB electrolytes.

The study of the influence of salts on the spectral data of solvatochromic probes in solution is often a subject of difficult interpretation due to the puzzling nature of the species involved (solute, solvent, and salt). This ternary system can be understood in a similar way to the studies of binary solvent mixtures in the presence of solvatochromic dyes. Recently, a preferential–solvation index (PSI) was introduced for the study of binary solvent mixtures. The index is calculated as a ratio of two areas from a typical experimental PS plot and is not based on any theoretical model nor fitting parameters of questionable meaning. In this paper, the PSI approach was defined and used to understand salt–dependent processes in electrolyte solutions. The PSI values were calculated for fifty examples of halochromism available in the literature involving six solvatochromic probes. It was applied to systems comprising different solvents, salts, and probes, where one of these three variables was systematically varied. The values of PSI for the systems were compared with solvent (Reichardt’s ET (30) and Gutmann’s donor number) and cation (Klopman’s softness character and ionic radii) parameters. The observed trends shed light on probe–salt and solute–solvent interactions in solution, allowing a deeper understanding of halochromic and other salt–dependent systems.

Solution-processed hybrid organic–inorganic perovskites (HOIPs) from organoammonium halide and lead halide precursors form efficacious active layers for photovoltaics, light-emitting diodes, and flexible electronics. Though solvent–solute coordination plays a critical role in HOIP crystallization, the influence of solvent choice on such interactions is poorly understood. We demonstrate Gutmann’s donor number, DN, as a parameter that indicates the coordinating ability of the processing solvent with the Pb2+ center of the lead halide precursor. Low DN solvents interact weakly with the Pb2+ center, favoring instead complexation between Pb2+ and iodide and subsequent crystallization of perovskite. High DN solvents coordinate more strongly with the Pb2+ center, which in turn inhibits iodide coordination and stalls perovskite crystallization. Varying the concentration of high-DN additives in precursor solutions tunes the strength of lead–solvent interactions, allowing finer control over the crystallization and ...

The conditions under which alizarin, purpurin, carminc acid, quinalizarin and alizarin red S in the solution of several organic solvents can be electrochemically transformed are analysed. The electrochemical activity of these molecules with quinone and phenolic moieties is relatively easy detected by cyclic voltammetry. Numerous electro-reduction/oxidation processes without and with added acid or base are observed. The number, the current intensity and the peak potential of the charge transfer processes are rationalized on the basis of the homogeneous dissociation equilibriums of the phenolic-OH groups. These equilibria are significantly altered by the medium. A supporting electrolyte unexpected and important effect on the electrochemical behaviour is observed. Alkaline cation of the supporting electrolyte promotes the changes in the electrochemical behaviour by coordinating with opposite charge species. A confusion published in the literature that the electro-reduction of the hydroxyquinones proceeds only through the formation of a radical-anion and a dianion is revealed. Solvent effect is explained by the stabilization of charge species, which is related to some solvent properties (Gutmann acceptor/donor number and dielectric constant). Solvents with strong acceptor properties favour the dissociation of the phenolic-OH groups. The dissociation equilibriums of phenolic-OH groups in each solvent are confirmed by UV-vis spectra of each dye in solution. Alizarin in DMA solvent with added base shows a particular electrochemical behaviour. For alizarin/DMF system a reaction mechanism is proposed, and alternative mechanisms are suggested for other dyes.

In the present work, the electrochemical oxidation of acid orange 7 (AO7) on a glassy carbon (GC) electrode has been investigated by cyclic voltammetry in different solvents: aqueous solvent (H2O), dimethyl sulfoxide (DMSO) and acetone (ACE), using sulfuric acid as a supporting electrolyte. The analysis of AO7 oxidation voltammograms in different solvents showed that the more donor numbers, the easier it becomes the oxidation of AO7. The experimental parameters show that the oxidation peak current of AO7 was linearly proportional to its concentration in a range from 0.04 mM to 0.2 mM. The limit of detection was estimated by gradually decreasing the concentration levels of AO7, and was found to be 6.6 μM.

High donor number (DN) solvents in Li-O2 batteries that dissolve superoxide intermediates in lithium peroxide (Li2 O2 ) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li-O2 batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)3 ) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)3 integrates with the superoxide intermediate, accelerating O2 reduction kinetics and reducing side reactions. During charge, V(acac)3 acts as a redox mediator that permits efficient oxidation of Li2 O2 . The cells with V(acac)3 exhibit low overpotential, high rate performance, and considerable cycle stability.

Nano-composite polymer gel electrolytes were synthesized by using polyethylene oxide (PEO), ammonium tetrafluoroborate (NH4BF4), fumed silica (SiO2), dimethylacetamide (DMA), ethylene carbonate (EC), and propylene carbonate (PC) and characterized by conductivity studies. The effect of donor number of solvent on ionic conductivity of polymer gel electrolytes has been studied. The mechanical strength of the gel electrolytes has been increased with the addition of nano-sized fumed silica along with an enhancement in conductivity. Maximum room temperature ionic conductivity of 2.63 × 10−3 and 2.92 × 10−3 S/cm has been observed for nano-composite gel electrolytes containing 0.1 and 0.5 wt% SiO2 in DMA+1 M NH4BF4+10 wt% PEO, respectively. Nano-composite polymer gel electrolytes having DMA have been found to be thermally and electrically stable over 0 to 90 °C temperature range. Also, the change in conductivity with the passage of time is very small, which may be desirable to make applicable for various smart devices.

We report an experimental study on the effect of solvents on the model SN Ar reaction between 1-chloro-2,4-dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf2 (-) , DCN(-) , SCN(-) , CF3 SO3 (-) , PF6 (-) , and FAP(-) with the series of cations 1-butyl-3-methyl-imidazolium ([BMIM](+) ), 1-ethyl-3-methyl-imidazolium ([EMIM](+) ), 1-butyl-2,3-dimethyl-imidazolium ([BM2 IM](+) ), and 1-butyl-1-methyl-pyrrolidinium ([BMPyr](+) ). The observed solvent effects can be attributed to an "anion effect". The anion effect appears related to the anion size (polarizability) and their hydrogen-bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.

The therrmodynamic parameters and equilibrium constant of displacement of dimethy sulfide by 3-carboaldehyde pyridine as N-donor ligand in cis-[Pt(4-MeC6H4)2(SMe2)2] complex have been measured using UV vis spectroscopy in acetone, dichloromethane and benzene at various temperatures (T=15-20 °C) and compared with previous my reported about similar reaction. ΔHo (KJ.mol-1) of the mentioned reaction in acetone has been 7.158 while obtained less in dichloromethane (4.109 ) and more in benzene(9.96). The entropy of the reaction has been obtained 86.86 J.mol-1.K-1 in acetone , while calculated less in CH2Cl2 (73.29 J.mol-1.K-1) and more in last solvent (97.40 J.mol-1.K-1). Also, the Gibbs energy, ΔG (J.mol-1), of the reaction obtained -18738.79, -17741.55 and -19043.06 respectively, with the same order. In all three solvents, the values of enthalpy and entropy change have been positive and decreased as the donor number of the solvents decreased.

Understanding and controlling the kinetics of O2 reduction in the presence of Li(+)-containing aprotic solvents, to either Li(+)-O2(-) by one-electron reduction or Li2 O2 by two-electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li-O2 batteries. Standard potentials of O2 /Li(+)-O2(-) and O2/O2(-) were experimentally measured and computed using a mixed cluster-continuum model of ion solvation. Increasing combined solvation of Li(+) and O2(-) was found to lower the coupling of Li(+)-O2(-) and the difference between O2/Li(+)-O2(-) and O2/O2(-) potentials. The solvation energy of Li(+) trended with donor number (DN), and varied greater than that of O2 (-) ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li(+)-O2(-) solubility and DN. These results highlight the importance of the interplay between ion-solvent and ion-ion interactions for manipulating the energetics of intermediate species produced in aprotic metal-oxygen batteries.

The lithium-sulfur (Li-S) battery is one of the promising energy storage alternatives because of its high theoretical capacity and energy density. Factors governing the stability of polysulfide intermediates in Li-S batteries are complex and are strongly affected by the solvent used. Herein, the polysulfide reduction and the bond cleavage reactions are calculated in different solvent environments by the density functional theory (DFT) methods. We investigate the relationship between the donor numbers (DN) as well as the dielectric constants (ε) of the solvent system and the relative stability of different polysulfide intermediates. Our results show that the polysulfide reduction mechanism is dominated by its tendency to form the ion-pair with Li+ in different organic solvents.

The use of concentrated aprotic electrolytes in lithium batteries provides numerous potential applications, including the use of high-voltage cathodes and Li-metal anodes. In this paper, we aim at understanding the effect of salt concentration on the variation of the Li/Li+ Quasi-Reference Electrode (QRE) potential in Tetraglyme (TG)-based electrolytes. Comparing the obtained results to those achieved using Dimethyl sulfoxide DMSO-based electrolytes, we are now able to take a step forward and understand how the effect of solvent coordination and its donor number (DN) is attributed to the Li-QRE potential shift. Using a revised Nernst equation, the alteration of the Li redox potential with salt concentration was determined accurately. It is found that, in TG, the Li-QRE shift follows a different trend than in DMSO owing to the lower DN and expected shorter lifespan of the solvated cation complex., publishedVersion

To fabricate efficient MAPbI3 perovskites using the Lewis acid-base adduct approach, we used a Lewis base hexamethylphosphoramide (HMPA) having a high donor number (DN), and investigated the effect of high-DN HMPA treatment on the properties of planar MAPbI3-based solar cells. The main functions of the HMPA treatment were to passivate the perovskites by forming well-distributed PbI2 phases and to densify the perovskites by controlling the rate constants. The treatment with Lewis base HMPA by one-step spin coating and subsequent solvent washing promoted the formation of pinhole-free perovskite films by increasing the coordination ability of HMPA with Pb2+ adducts and controlling the nucleation and growth rates of the perovskites. In addition, treatment with various concentrations of HMPA led to the formation of a residual PbI2 phase that acted as a passivation layer, even though stoichiometric quantities of precursors were used. Through a series of advanced electron microscopy studies, the exact three-dimensional locations of the PbI2 passivation layers were determined. Furthermore, by calculating the decreased active trap concentrations and carrier densities, we verified the passivation effect of remnant PbI2. Importantly, we achieved the best power conversion efficiency of 17.09% by the controlled addition of Lewis base HMPA, thus demonstrating a much improved performance than that obtained without HMPA treatment (15.73%).

Factors influencing the sign and size of effective surface (zeta) potential in suspensions of very low dielectric constants are evaluated. For non-aqueous suspensions it was found that Gutmann's donor number ( DN = negative Lewis type molar acid-base adduct formation enthalpy) was successfully related to zeta potential changes, similarly as pH is optimal for aqueous suspensions. Negative molar proton dissociation enthalpy (Brϕnsted type HD number), negative hydrogen bond enthalpy ( HB number), logarithmic hydrogen bond equilibrium constant (molar Gibbs free energy), standard reduction potential of solvated protons ( E o ( H L + / H 2 )), electrolytic dissociation potential of water ( E o ( H 2 O / H 2 , O 2 )) and electron exchange Fermi potentials could equally well be related to zeta potential changes. All these properties were linearly dependent on each other. Correlations to products of Gutmann's DN and AN numbers and other relevant properties such as polar, hydrogen bond and acid-base contributions to solubility parameters and to surface tensions were found to be less successful particularly when very polar liquids were encountered. Commonly used DLVO models for repulsive interaction energy between pair of particles in aqueous electrolyte suspensions have been simplified when dealing with low-polar, non-polar and apolar suspensions. When evaluating factors contributing to attractive and repulsive interaction energies, it is found that in order for the models to be relevant the extension of diffuse charging has to be much larger than the distance to repulsive barrier ensuring suspension stability. At this limit and at high surface potentials, the repulsive energy grows exceptionally large being in the range of lattice energy of each solid. The models fail when surface potential is low and the extension of diffuse charging is much smaller than the distance to repulsive barrier. Then interaction energies are reasonable. The investigated (Au, SiO 2 , Glass, TiO 2 , Al 2 O 3 , CaCO 3 , MgO) suspensions fall between these limits. The attractive energy is small but significant as compared to repulsive energy. All energies were larger than the estimated lower limit for stable suspensions.

Zinc contaminants have been identified as suspects leading to nozzle deposit formation and copper contaminants quickly reduce the oxidation stability of diesel fuel. Ionic liquids (ILs) are commonly referred to as ‘designer solvents’ due to the great degree of fine-tuning of physical and chemical properties afforded by modification of the constituent cation and anion. The tunable properties of the IL ions allows the ‘design’ to meet the requirements for a particular application, making ILs an ideal potential candidate for the extraction of trace (ppb to ppm) amounts of zinc and copper heavy metals from diesel fuel. We report for the first time that ILs can extract up to 99.3% of zinc at a zinc concentration of just 2 mg kg−1 and copper can be extracted up to 99.7% at copper concentration of just 1 mg kg−1 from a model diesel fuel. Factors affecting the extent of extraction were investigated via correlation with experimental descriptors. 23Na NMR was used in the determination of donor number (DN) and Kamlet–Taft parameters were gathered for each IL providing information of possible hydrogen-bond acidity/basicity (α/β), and dipolarity/polarizability effects (π*). In addition, the non-random two liquid (NRTL) model was applied to determine τ parameters for each of the ILs. We determined that the extraction is controlled strongly by the hydrogen bond basicity of the IL which is directly related to the ability of the anion of the IL to complex Zn2+ and Cu2+ thus removing it from the fuel. DN, τ parameters and β, in addition to density and viscosity values, provide further information on the extraction mechanisms and predict performance, informing chemical design of ILs that are ideal for fuel purification.