Br Anions Research Articles

Influence of anion variation and cation modification on the packing of tetraazamacrocyclic Au(III) complexes

Abstract The work presents the analysis of the packings of crystal structures of unsaturated tetraazamacrocyclic gold(III) complexes with different anions ([Au(С14H22N4)]X (X = Br (I), ReO4 (II), BPh4 (III), AuBr2 (IV)) and with modified (halogenated [Au(С14Н20N4Y2)]ClO4 (Y = Cl (V), Br (VI), protonated [Au(С14H23N4)](ClO4)2 (VII), [Au(С14H24N4)](H3O)(ClO4)4 (VIII) cations. Crystal-chemical regularities and features of the packings depend on the composition and structure of cations, as well as on the nature and geometry of counter-anions. In the packings of the complexes I–VII whose ligands contain one or two iminate six-membered rings, the 3D supramolecular architecture of the crystal lattice is determined and stabilized by an extensive network of secondary non-covalent intermolecular interactions (non-classical H-bonds C–H…A (A = π, Br, Cl, O, Au) and contacts Au⋯Au (O, N, π); O⋯Cl (Br, N). In the iminate complexes with nonlinear inorganic anions Br−, ClO4−, ReO4−, the main structure-forming role belongs to the cations which are interconnected by non-classical H-bonds C–H…π. The halogenation of iminate rings of the cation and the protonation of one of the rings do not cause profound changes in the packing. In the structures of the complexes with a bulky organic anion BPh4– (III) and with a coordinatively unsaturated linear anion AuBr2− (IV), the decisive role belongs to the anions which prevent the association of cations by forming H-bonds and contacts with them. The linear acceptor-active anion AuBr2− has the greatest influence on the packing of diiminate macrocyclic gold(III) complexes by providing the parquet packing of the structure. The 1D crystal structure of the diprotonated diimine complex VIII is stabilized by classical H-bonds Ow–H...O of the oxonium ion and by the contacts of the central atom of the macrocyclic cation Au⋯O.

Adsorption of Surface Active Ionic Liquids on Different Rock Types under High Salinity Conditions

A new class of surface active ionic liquids (SAIL) have been reported to be a greener alternative to the conventional surfactants in enhanced oil recovery (EOR). These SAILs work efficiently under harsh salinity conditions encountered in the reservoir thereby recovering more additional oil during the tertiary oil recovery process. Adsorption mechanism of SAILs on different rock surface is however, not yet reported in the literature. This article highlights adsorption mechanism of three cationic SAILs having different headgroups, viz., imidazolium, pyridinium, pyrrolidinium, on different rock surfaces (crushed natural carbonate rock and crushed sandstone rock). All the SAILs studied here however had the same tail length and same anion (Br−) attached to it. XRD and XPS characterization techniques reveal that the crushed natural carbonate rock contains a substantial amount of silica, thus rendering it a slight negative charge. Static adsorption tests show that the retention efficiency on the natural carbonate type of rock for all the SAILs was lower than the conventional cationic surfactant, CTAB. The adsorption data obtained thereby was examined using four different adsorption isotherm models (Langmuir, Freundlich, Redlich-Peterson, and Sips). Results suggest that Sips adsorption isotherm model can satisfactorily estimate the adsorption of all the surface active agents on the natural carbonate rock. Factors like mineralogical composition of rock surface, presence of divalents, temperature, and structure of surfactants strongly affect the amount of surfactant adsorbed on reservoir rock. In order to evaluate the simultaneous effect all these factors as well as their interdependence on the retention capability of the three SAILs, a design of experiments approach has been employed further in this study. Statistical analysis of the data obtained after performing the full factorial experiments reveal that at high salinity, imidazoluim based SAIL show minimal adsorption on crushed natural carbonate rock at higher temperature. In general, at a given ionic strength, with increasing temperature as the amount of divalent in the aqueous solution increases, the amount of SAIL adsorbed on both the rock types decreases. Electrostatic attraction is the basic mechanism in governing adsorption of SAILs on the two types of rock surfaces. Results presented in this work can be used for EOR schemes.

Computation-Guided Exploration for New-Chemistry Solid Electrolyte with Fast Ion Conduction and Good Electrochemical Stability

A key challenge in enabling all-solid-state Li-ion batteries is the development of solid electrolyte materials with high Li ionic conductivity and good electrochemical stability.Current research efforts on solid-state Li-ion conductors focus mostly on oxides and sulfides. Unfortunately, oxide and sulfide chemistries have an undesirable trade-off between ionic conductivity and stability. New solid-state chemistries that can exhibit a low activation energy, good stability, and other desirable properties are a promising research direction for new solid electrolytes in solid-state batteries. Using ab initio computation, we systematically explored new anion chemistries beyond oxides and sulfides, such as nitrides and halides. Our computation found nitride anion chemistry exhibits unique stability against Li metal, which is either thermodynamically intrinsic or a result of stable passivation. Many nitrides materials can serve as promising lithium metal protection materials to achieve long-term stability. In addition, our first principles computation study confirmed that chlorides and bromides exhibit fast Li-ion conduction, wide electrochemical stability, and good cathode interface compatibility. We found Cl and Br anion chemistries can achieve fast Li-ion conduction in a variety of anion sublattices, and do not require the rare bcc anion lattice as in current fast ion-conducting sulfides or the concerted migration mechanism in current fast-conducting oxides. Further, we found chlorides and bromides generally exhibit wide electrochemical windows, poor electronic conductivity, and good cathode interface compatibility, and thus hold desirable conducting and stability properties for SE applications. Our presentation highlight nitrides, chlorides and bromides as highly promising alternative chemistries for solid electrolytes in solid-state batteries.

Dendrite-Free Epitaxial Growth of Lithium for Efficient Charging of Li–O2 Batteries with Improved Cycle Life

Realization of rechargeable Li-metal batteries with high energy density is hindered by uneven Li deposition leading to dendrite formation during repeated cycles. Uncontrolled dendrite growth induces internal short-circuits which limit the cell lifetime and generate ohmic heat leading to catastrophic failure when a volatile electrolyte is used. Several strategies have been conceived by the researchers to suppress dendritic growth and delay the premature death of the cell. These efforts include using electrolyte additives to form a porous ion-conducting solid electrolyte interphase (SEI) layer on metal preventing further reaction,1 implementing solid electrolytes with optimum mechanical properties,2 designing a Li matrix,3 reducing local space charge on the Li surface,4 and so on. Although considerable improvements have been achieved from these earlier studies, microscopically smooth Li surface covered with thin and uniform SEI layers is yet to be realized. Alternatively, here we show an unprecedented dendrite-free epitaxial electrodeposition of Li in the presence of LiBr–LiNO3/glyme ether electrolyte under O2 atmosphere. Stripping and plating of Li metal was investigated by using a symmetrical Li│Li cell and it has been found that in 1 M LiNO3+0.05 M LiBr/tetraglyme electrolyte the plating of Li metal shows dendrite-free epitaxial growth up to a thickness of >20 μm which is clearly observed by the scanning electron microscopic (SEM) images and electron backscatter diffraction (EBSD) signal in Figure 1. The epitaxial growth of Li metal seems to be benefited from the synergistic effect of the anions Br− and NO3 − forming a thin and homogeneous Li2O–rich solid electrolyte interphase (SEI) layer which is formed during the very first discharge (stripping) process, where the corrosive nature of Br− removes the original thick passivation layer on Li surface which is then again oxidized (passivated) by the NO3 − to prevent further reactions with the electrolyte. Because of this, the SEI layer remains thin and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process. Similar epitaxial growths of Li have been observed for both symmetrical Li│Li cell and Li–O2 full cell resulting in a much improved performance with longer cycle life.5,6 However, in contrast, LiNO3 alone or other lithium salts, such as Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium trifluoromethanesulfonate (LiTf), do not exhibit any epitaxial Li deposition. This demonstrates the bi-functional activity of the dual anion electrolyte LiNO3–LiBr towards dendrite-free epitaxial growth of Li. The role of deposition rate, effect of electrolyte solvent and a detailed mechanism of epitaxial growth will be discussed in the presentation.

A Revised Structure Model for the UCl6 Structure Type, Novel Modifications of UCl6 and UBr5 , and a Comment on the Modifications of Protactinium Pentabromides.

The redetermination of the crystal structure of trigonal UCl6 , which is the eponym for the UCl6 structure type, showed that certain atomic coordinates had been incorrectly reported. This led to noticeably different U-Cl distances within the octahedral UCl6 molecule (2.41 and 2.51 Å). Within the revised structure model presented here, which is based on single crystal data as well as quantum chemical calculations, all U-Cl distances are essentially equal within standard uncertainty (2.431(5), 2.437(5), and 2.439(6) Å). This room temperature modification, called rt-UCl6 , crystallizes in the trigonal space group P m1, No. 164, hP21, with a=10.907(2), c=5.9883(12) Å, V=616.9(2) Å3 , Z=3 at T=253 K. A new low-temperature (lt) modification of UCl6 is also presented that was obtained by cooling a single crystal of rt-UCl6. The phase change occurs between 150 and 175 K. lt-UCl6 crystallizes isotypic to a low-temperature modification of SF6 in the monoclinic crystal system, space group C2/m, No. 12, mS42, with a=17.847(4), b=10.8347(18), c=6.2670(17) Å, β=96.68(2)°, V=1203.6(5) Å3 , Z=6 at 100 K. The Cl anions form a close-packed structure corresponding to the α-Sm type with uranium atoms in the octahedral voids. During the synthesis of UBr5 a new modification was obtained that crystallizes in the triclinic crystal system, space group P , No. 2, aP36, with a=10.4021(6), b=11.1620(6), c=12.2942(7) Å, α=68.3340(10)°, β=69.6410(10)° and γ=89.5290(10)°, V=1231.84(12) Å3 , Z=3 at T=100 K. In this structure the UBr5 units are dimerized to U2 Br10 molecules. The Br anions also form a close-packed structure of the α-Sm type with adjacent uranium atoms in the octahedral voids. Comparisons of the crystal structures of the compounds MX5 (M=Pa, U; X=Cl, Br) show that the crystal structure of monoclinic α-PaBr5 is probably not correct.

From Large to Small Polarons in Lead, Tin, and Mixed Lead-Tin Halide Perovskites.

The origin of the long carrier lifetime in lead halide perovskites is still under debate, and, among different hypotheses, the formation of large polarons preventing the recombination of charge couples is one of the most fascinating. Using state-of-the art ab initio calculations, we report a systematic study of the polaron formation process in metal halide perovskites, focusing on the influence of the chemical composition of the perovskite on the polaron properties. We examine variations in A-site cations (FA, MA, Cs, and Cs-MA), B-site cations (Pb, Sn, and Pb-Sn), and X-site anions (Br, I). Our study confirms that stronger structural distortions occur for Cs than for MA and FA, with the effect of different A-site cations being almost additive. For the same A cation, bromide features stronger distortions than iodide perovskites. The pure Sn phase has an almost double polaron stabilization energy compared with the pure Pb phase. Surprisingly, the trend of polaron stabilization energy is nonmonotonic in mixed Sn-Pb perovskites, with a maximum for small Sn percentages. Polaron formation is found to be promoted by bond asymmetry, ranging from small to large polarons in mixed Sn-Pb perovskites depending on the relative Sn percentage.

DFT study of fructose dehydration to 5-hydroxymethylfurfural catalyzed by imidazolium-based ionic liquid

Abstract DFT calculations have been performed to gain insight into the mechanism of production 5-hydroxymethylfurfural (HMF) from fructose catalyzed by a representative imidazolium-based ionic liquid (IL), 1-butyl-3-methyl-imidazolium bromide ([BMIM]Br). The overall barrier of the catalytic conversion is found to be 41.5 kcal/mol, which is in contrast to 75.6 kcal/mol located in previous literature. Different from the mechanism proposed in the literature, which Br anion of IL interacts with the hydroxyl group of the substrate via H-bonding to induce the dehydration process, while cation of IL acts as a spectator, the present calculations emphasize the collaboration of cation and anion of IL.

Dibromidobis(3-bromobenzyl-κC)(4,7-diphenyl-1,10-phenanthroline-κ2 N,N′)tin(IV)

In the title compound, [SnBr2(C7H6Br)2(C24H16N2)], the Sn atom is coordinated to a 4,7-diphenyl-1,10-phenanthroline, two 3-bromobenzyl and two bromide ligands, leading to a six-coordinate C2Br2N2 donor set. The bromobenzyl ligands are trans to each other, while the Br anions are in a cis arrangement. One of the two 3-bromobenzyl ligands is disordered over two similar conformations, with occupancies of 0.7078 (18) and 0.2922 (18). In the crystal, molecules are linked into centrosymmetric dimers by Br...Br halogen bonds [3.5972 (12) Å], which are linked into a supramolecular layer in the ac plane by weak intermolecular C—H...Br interactions.

An Interplay Role between Ammonium and Halide Anions as Additives in Perovskite CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>

Methylammonium lead trihalide perovskites have emerged as attractive materials for solar cell applications. The major eminence of this materials can be crystallized via various solution methods to produce the solid state of thin films. However, the crystallinity of perovskite depends on the composition of perovskites. Here, we study NH4Cl and NH4Br as precursor additives for improving crystallinity of perovskites. Perovskite was synthesized by mixing precursor solutions of CH3NH3I and Pb(Ac)2with or without additives NH4Cl and NH4Br using the one-step spin-coating method. By characterizing the thin films using XRD, SEM and UV-Vis spectrophotometer, we found anion Cl and Br performed an important role toward crystallinity, morphology, and optical absorption of perovskites, respectively. Meanwhile, ammonium has assisted to facile remove the residual DMSO solvent confirmed by FTIR. These results shed light on using ammonium halides as potentially dual side additives in the synthesis of perovskites.

Insights into the Structure of Halide-Rich Hydrochloric and Hydrobromic Acid: A Structural and Quantum-Chemical Investigation of the [H6X4O2]2− (X = Cl, Br) Anions

The previously unknown dianions [H6Cl4O2]2− and [H6Br4O2]2− were prepared as their bis(triphenyl-λ5-phosphanylidene)ammonium ([Ph3PNPPh3]+ ≡ [PNP]+) salts from [PNP]+ halides and aqueous hydrochloric or hydrobromic acid, respectively. The crystal structures of the two salts [PNP]2[H6Cl4O2] and [PNP]2[H6Br4O2] are reported. The unprecedented dianions [H6Cl4O2]2− and [H6Br4O2]2−, which represent a section of the structure of halide-rich hydrochloric or hydrobromic acid, are discussed. Quantum-chemical calculations support the findings. The crystal structure of [PNP][HBr2], a rare example for a crystallographically determined hydrogen dibromide structure, is presented as well. The dianions [H6Cl4O2]2− and [H6Br4O2]2− were prepared as their [PNP]+ salts and structurally characterized.

Ferroelastic phase transition in Cu6PS5Br1-xClx mixed crystals

ABSTRACTCu6PS5Br1-xClx mixed crystals were grown by chemical vapour transport. Optical absorption edge and optical polarization measurements were performed in the temperature range 77–320 K. The influence of anionic Br→Cl substitution on the phase transitions in Cu6PS5Br1-xClx mixed crystals is studied. Compositional dependence of the ferroelastic phase transition temperature for Cu6PS5Br1-xClx mixed crystals is obtained. The variation of optical parameters at ferroelastic phase transition is analyzed.

Radiation-induced debromonation of 1,2-dibromotetrafluoroethane (Halon2402) in alcohols followed by Br2•− formation – A pulse radiolysis study

Pulse radiolysis technique was used to investigate early stages of radiation-induced reactions in alcohols (methanol and 2-propanol) containing a halogenated compound, Halon2402, and it was found that repetition of irradiation leads to accumulation of a transient species having absorption around 360 nm, which is attributed to dibromine radical anion (Br2•−). The alcohols containing bromide anion (Br−) were also investigated because it is reported debromonation occurs during the radiation-induced degradation, revealing that at first Br− is oxidized into bromine atom (Br•) by alkoxy radicals of the solvent alcohols, and then, Br2•− is formed by its reaction with another Br−. Since not only Br− but also acid (H+) is produced during the degradation, influence of acid was also investigated, showing that acid is essential in the oxidation of Br− into Br• in the alcohols. In addition, deuteration of the solvent alcohols resulted in significant increase in the amount of Br2•− production, implying it is alkoxy radicals of the solvent alcohols that oxidize Br− into Br•. Difference in the Br− oxidation between methanol and 2-propanol was also discussed in relevance to difference in redox potentials of the transient species.

Manganese N-Heterocyclic Carbene Pincers for the Electrocatalytic Reduction of Carbon Dioxide

We report the synthesis, characterization, and catalytic CO2 reduction activity of two LMn(CO)3Br complexes with carbene-pyridine-carbene pincer ligands, [MnCNCMe]Br 1 and [MnCNCBn]Br (Bn = benzyl) 2. X-ray crystallography reveals an octahedral coordination environment with an outer sphere Br anion for 1. Catalyst 2 performs the reduction of CO2 to CO at 100 mV more positive potential with similar current densities as 1. We hypothesize the bulkier benzyl arms on the pincer hinder formation of a dimer. They also alter the wingtip electronics, enabling operation at a lower overpotential. We use normal pulse voltammetry and diffusion ordered spectroscopy to quantify a 1e– reduction per manganese center at the catalytic onset. We now show turnover even in the absence of added protons..

Imidazolium-based ionic liquids with inorganic anions in the extraction of salidroside and tyrosol from Rhodiola: The role of cations and anions on the extraction mechanism

The role of cations and anions of imidazolium ionic liquid-based microwave-assisted extraction system for salidroside and tyrosol of Rhodiola was investigated. To evaluate eight kinds of imidazolium-based ionic liquid with different cations and anions on molecule level, the geometries of related IL molecules and target extracts were optimized by density functional theory at the B3LYP/6-311++G(d, p) level. Electrostatic potential (ESP) distributions of these molecules above are identified in the water modeled by the polarizable continuum model. The theoretical and experimental analysis shows there is some correlation between the characteristic values of ESP distribution and extraction yield. The more similar the ESP distribution of ILs are to salidroside and tyrosol, the higher the extraction yields are. Wider variability of ESP is beneficial to extraction. The main role of cations is interaction with extract molecules by its positive ESP regions. So the cations influence the solubility of extracts by the molecular interaction. Unlike the cations, the types of anions can affect the structure of the cell wall. The ILs with Br anion have greater ability to dissolve cellulose and break the cell wall, which made the target components within the cell could effectively dissolve. Due to the differing function of cations and anions of ILs, the ionic liquid-based MAE could provide higher extraction yields and take much shorter extraction time than conventional organic solvents.

A balance of redox and ligand-exchange processes in the reaction of H2[OsCl6] with thiourea: Isolation and characterization of a novel osmium complex [(NH2)2CSSC(NH2)2]2[OsIVCl6]Cl2·3H2O

A novel complex with the stoichiometry [(NH2)2CSSC(NH2)2]2[OsIVCl6]Cl2·3H2O (1) is isolated as a product of the reaction of H2[OsCl6] with thiourea in concentrated HCl under deliberately optimized conditions favoring a partial thiourea oxidation to α,α′-dithiobisformamidinium dication but preserving hexachloroosmate [OsCl6]2- anions. A bromide analogue [(NH2)2CSSC(NH2)2]2[OsIVBr6]Br2·3H2O 2 is afforded by a similar reaction. A counter synthesis of 1 is accomplished via the direct ion-exchange reaction between H2[OsCl6] and [S2C2(NH2)4]Cl2. Crystal structures of 1 and 2 are unambiguously established by synchrotron radiation-based single-crystal X-ray diffraction at 100 K. The two compounds are isostructural and are crystallized in the orthorhombic space group Cmcm, Z = 4. Unit cell parameters are for 1:a = 11.279(2) Å, b = 13.611(3) Å, c = 16.731(3) Å; for 2: a = 11.695(2) Å, b = 14.005(3) Å, c = 17.015(3) Å. The osmium atoms in [OsX6]2− (X = Cl or Br) anions adopt slightly distorted octahedral coordination. The α,α′-dithiobisformamidinium cations are paired into rings via the NH…Cl− hydrogen bonds. The rings are further linked into a spatial network by H-bonds with water molecules and S…Cl nonvalence interactions.

Self-Assembly of an Anion-Binding Cryptand for the Selective Encapsulation, Sequestration, and Precipitation of Phosphate from Aqueous Systems.

The self-assembled trimetallic species [L2 Cu3 ]6+ contains a cavity that acts as a host to many different anions. By using X-ray crystallography, ESI-MS, and UV/Vis spectroscopy we show that these anions are encapsulated both in the solid state and aqueous systems. Upon encapsulation, the anions Br- , I- , CO32- , SiF62- , IO63- , VO43- , WO42- , CrO42- , SO42- , AsO43- , and PO43- are all precipitated from aqueous solution and can be removed by filtration. Furthermore, the cavity can be tuned to be selective to either phosphate or sulfate anions by variation of the pH. Phosphate anions can be removed from water, even in the presence of other common anions, reducing the concentration from 1000 to <0.1 ppm and recovering approximately 99 % of the phosphate anions.

Self‐Assembly of an Anion‐Binding Cryptand for the Selective Encapsulation, Sequestration, and Precipitation of Phosphate from Aqueous Systems

AbstractThe self‐assembled trimetallic species [L2Cu3]6+ contains a cavity that acts as a host to many different anions. By using X‐ray crystallography, ESI‐MS, and UV/Vis spectroscopy we show that these anions are encapsulated both in the solid state and aqueous systems. Upon encapsulation, the anions Br−, I−, CO32−, SiF62−, IO63−, VO43−, WO42−, CrO42−, SO42−, AsO43−, and PO43− are all precipitated from aqueous solution and can be removed by filtration. Furthermore, the cavity can be tuned to be selective to either phosphate or sulfate anions by variation of the pH. Phosphate anions can be removed from water, even in the presence of other common anions, reducing the concentration from 1000 to &lt;0.1 ppm and recovering approximately 99 % of the phosphate anions.

The Impact of Bromide-based Ionic Liquids on Alkaline Water Electrolysis

As global energy demands are rapidly increasing, the development of a sustainable energy system is of fundamental importance in the near term. A strong possibility has been pointed as the “hydrogen economy”, consisting in using hydrogen (H2) as an energy vector. Hydrogen attractiveness arises from the fact that it may be burned to produce heat or reacted with air in a fuel cell to produce electricity. This could be a solution to global energy problems, while minimizing the environmental impact (1). An attractive technology for the production of H2 is water electrolysis, which is not dependent on fossil hydrocarbon sources and originates no carbon emissions. Moreover, it allows the production of very pure H2, being able to rely exclusively on renewable primary energy sources. However, the relatively limited overall energy efficiency of industrial water electrolysis cells still hinders its wide application. Industrial water electrolyzers typically employ nickel (Ni) or other metal-based electrodes, operating in 6 to 9 M potassium (or sodium) hydroxide electrolyte in the 60 - 80 ºC temperature range. The hydrogen evolution reaction (HER) and the ohmic drop in the bath are closely related to the low energy efficiency. Additional technical issues are the low stability and corrosion of the electrode materials and other cell resistances associated with the electrolyzer under operating conditions (2). The efficient removal of H2 bubbles from the solution is also a challenge. Room temperature ionic liquids (RTILs) are salts composed of organic cations and organic or inorganic anions at (or near) room temperature. They are characterized by a wide range of fluidity, high ionic conductivity, excellent thermal and chemical stability, as well as high heat capacity and cohesive energy density (2,3). They may be used in replacement of aqueous electrolytes or in mixture with conventional ones and, therefore, are interesting candidates for application in water electrolyzers. RTILs with several imidazolium-based cations have been studied for water electrolysis, originating electrolytes with unique properties in terms of electrical conductance, chemical and electrochemical stability, and leading to beneficial effects on the HER using different electrode materials (4). Increased currents were also reported, as well as a significant decrease of the overall impedance in the RTILs-added solutions (5). The enhancement of the HER was related to surface pre-adsorption of the RTIL additives, stabilizing the intermediate hydrogen atoms and modifying adsorption and charge transfer processes at the metal-electrolyte interface (5). In the present work, bromide-based RTILs are studied as electrolyte additives for water electrolysis in alkaline media. Several ionic liquids are investigated, such as 1-butyl-3-ethylimidazolium bromide (beim Br), 1,3-dibutylimidazolium bromide (bbim Br), 1-butyl-3-hexylimidazolium bromide (bhim Br), 1-butyl-3-octylimidazolium bromide (boim Br) and 1,3-diethylimidazolium bromide (eeim Br), which are composed by the same anion (Br-) and different imidazolium-based cations. The effect of the bromide anion and its combined effect with the different cations when used as electrolyte additives for water electrolysis, particularly on the HER kinetics, were previously unknown. The electrolysis performance after addition of small amounts of these ionic liquids to the KOH electrolyte is herein investigated and compared with that of IL-free KOH electrolyte. Electrochemical techniques such as linear scan voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) were used. Measurements were performed in the 25 - 80 ºC temperature range, using a Pt foil electrode in 8 M KOH electrolyte, with and without the addition of the bromide-based RTILs. The additives beneficial or detrimental effects on the HER are reported and discussed considering the RTILs composition, namely the effect of the bromide anion and the effect of each of the studied cations on the electrode processes. The reported results may contribute to the enhancement of the performance of industrial alkaline water electrolyzers. D.M.F. Santos, B. Šljukić, C.A.C. Sequeira, D. Macciò, A. Saccone and J.L. Figueiredo, Energy, 50, 486 (2013).C. Lagrost, D. Carrié, M. Vaultier and P. Hapiot, J. Phys. Chem. A, 107, 745 (2003).M. Opallo and A. Lesniewski, J. Electroanal. Chem. 656, 2 (2011).R.F. de Souza, J.C. Padilha, R.S. Gonçalves, M. O. de Souza and J. Rault-Berthelot, J. Power Sources, 164, 792 (2007).L. Amaral, D.S.P. Cardoso, B. Šljukić, D.M.F. Santos and C.A.C. Sequeira, J. Electrochem. Soc. 164 (4) F427 (2017).

Stabilizing Lead-Free All-Inorganic Tin Halide Perovskites by Ion Exchange.

Because of its thermal stability, lead-free composition, and nearly ideal optical and electronic properties, the orthorhombic CsSnI3 perovskite is considered promising as a light absorber for lead-free all-inorganic perovskite solar cells. However, the susceptibility of this three-dimensional perovskite toward oxidation in air has limited the development of solar cells based on this material. Here, we report the findings of a computational study which identifies promising RbyCs1–ySn(BrxI1–x)3 perovskites for solar cell applications, prepared by substituting cations (Rb for Cs) and anions (Br for I) in CsSnI3. We show the evolution of the material electronic structure as well as its thermal and structural stabilities upon gradual substitution. Importantly, we demonstrate how the unwanted yellow phase can be suppressed by substituting Br for I in CsSn(BrxI1–x)3 with x ≥ 1/3. We predict that substitution of Rb for Cs results in a highly homogeneous solid solution and therefore an improved film quality and applicability in solar cell devices.

Crosslinked Polymer Ionic Liquid/Ionic Liquid Blends Prepared by Photopolymerization as Solid-State Electrolytes in Supercapacitors.

A photopolymerization method is used to prepare a mixture of polymer ionic liquid (PIL) and ionic liquid (IL). This mixture is used as a solid-state electrolyte in carbon nanoparticle (CNP)-based symmetric supercapacitors. The solid electrolyte is a binary mixture of a PIL and its corresponding IL. The PIL matrix is a cross-linked polyelectrolyte with an imidazole salt cation coupled with two anions of Br− in PIL-M-(Br) and TFSI− in PIL-M-(TFSI), respectively. The corresponding ionic liquids have imidazolium salt cation coupled with two anions of Br− and TFSI−, respectively. This study investigates the electrochemical characteristics of PILs and their corresponding IL mixtures used as a solid electrolyte in supercapacitors. Results show that a specific capacitance, maximum power density and energy density of 87 and 58 F·g−1, 40 and 48 kW·kg−1, and 107 and 59.9 Wh·kg−1 were achieved in supercapacitors based on (PIL-M-(Br)) and (PIL-M-(TFSI)) solid electrolytes, respectively.