SrPtIn,Sr2Pt3In4, and Ca2Au3In4 – Alkaline Earth Compounds with Complex Three-Dimensional [PtIn], [Pt3In4], and [Au3In4] Polyanions

Single phase SrPtIn, Sr₂Pt₃In₄ and Ca₂Au₃In₄ were prepared by high-frequency melting of the elements in water-cooled glassy carbon crucibles. X-ray diffraction of powders and single crystals yielded Pnma, oP12, a = 758.57(9) pm, b = 451.52(6) pm, c = 846.0(2) pm, wR2 = 0.0937, 467 F² values, 20 variables for SrPtIn, P62m, hP36, a = 1465.9(2) pm, c = 448.24(6) pm, wR2 = 0.0722, 1059 F² values, 44 variables for Sr₂Pt₃In₄ and Pnma, oP36, a = 1463.6(4) pm, b = 443.23(9) pm, c = 1272.3(2) pm, wR2 = 0.0694, 1344 F² values, 56 variables for Ca₂Au₃In₄. SrPtIn adopts the TiNiSi type structure. The indium atoms have a distorted tetrahedral platinum coordination. These InPt_4/4 tetrahedra are edge- and corner-shared, forming a three-dimensional [PtIn] polyanion in which the strontium atoms are embedded. Sr₂Pt₃In₄ crystallizes with the Hf₂Co₄P₃ type structure with the more electronegative platinum atoms occupying the phosphorus sites while the indium atoms are located on the cobalt positions. Ca₂Au₃In₄ is a new site occupancy variant of the YCo₅P₃ type. Gold atoms occupy the phosphorus sites and indium the cobalt sites, but one cobalt site is occupied by calcium atoms leading to the composition Ca₂Au₃In₄. Common geometrical motifs of both structures are condensed, platinum(gold)-centered trigonal prisms formed by the alkaline earth and indium atoms. The platinum (gold) and indium atoms form complex three-dimensional [Pt₃In₄] and [Au₃In₄] polyanions, respectively. The alkaline earth cations are located in distorted hexagonal tubes.     

Gd3Pt4In12 and Tb3Pt4In12 — New Ternary Indides with Condensed Distorted [PtIn6] Trigonal Prisms

The ternary indium compounds Gd₃Pt₄In₁₂ and Tb₃Pt₄In₁₂ were synthesized from an indium flux. Arc‐melted precursor alloys with the starting compositions ∼GdPtIn₄ and ∼TbPtIn₄ were annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. Both compounds were investigated by X‐ray powder diffraction: a = 990.5(1), c = 1529.5(3) pm for Gd₃Pt₄In₁₂ and a = 988.65(9), c = 1524.0(1) pm for Tb₃Pt₄In₁₂. The structure of the gadolinium compound was solved and refined from single crystal X‐ray data: P3¯m1, wR2 = 0.0470, 1469 F² values and 62 variable parameters. Both crystallographically different platinum sites have a slightly distorted trigonal prismatic indium coordination. These [PtIn₆] prisms are condensed via common edges and corners forming a complex three‐dimensional [Pt₁₂In₃₂] network. The gadolinium, In1 and In7 atoms fill cavities within this polyanion. Tb₃Pt₄In₁₂ is isotypic with the gadolinium compound.     

Structural investigations and luminescence of In2Ge2O7 and In2Si2O7

The crystal structures of the ordinary pressure forms of indium digermanate In₂Ge₂O₇ and disilicate In₂Si₂O₇ have been studied from X-ray powder diffraction data by Rietveld refinement. They are closely related to that of the thortveitite which crystallizes in the monoclinic system with the space group C2/m and Z = 2. They show luminescence properties below 160 K and 200 K respectively. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent indium oxides.     

Gas Sensing Properties of In2O3and Au-doped In2O3Films for Detecting Carbon Monoxide in Air

Catalytic and sensing properties of several metal oxides in the reaction of CO oxidation and in the sensor detection of CO in air have been studied and compared to each other. Indium oxide has been found to be the most sensitive and possessing a relatively low catalytic activity in the oxidation of CO. Possible reasons for the high activity of the indium oxide sensor matrix are discussed. The promoting effect of Au and Pd doping of In₂O₃in the detection of CO in air has been studied, and a mechanism explaining the enhanced sensor response of Au-doped In₂O₃has been proposed. A change in humidity has no significant effect on the sensor response of Au-doped In₂O₃in the detection of CO in air.     

Gas-Sensing Properties of Doped In2O3 Films as Sensors for NO2 in Air

A number of sensing systems based on indium oxide doped with various metal oxides (In₂O₃ · WO₃, In₂O₃ · ZnO, In₂O₃ · RuO₂, In₂O₃ · Gd₂O₃, and In₂O₃ · Sm₂O₃) in amounts of no more than 3–5 mol % and also Au · In₂O₃ films were studied as sensors for detecting NO₂ in air. The working temperature of sensors was 250°C (except for In₂O₃ · RuO₂, for which T = 150–190°C). In₂O₃ · WO₃-based sensors reach a high sensitivity especially at a concentration of NO₂ in air higher than 10 ppm (the relative sensor conductivity changes by 2.5 orders of magnitude). However, a shortcoming of this system is an increased response time (7–9 min) as compared to the other studied systems, for which the response time does not exceed 15–20 s. In₂O₃ · Gd₂O₃ and In₂O₃ · Sm₂O₃ films exhibit the best sensing properties in sensitivity, selectivity, and stability. Various NO₂ species adsorbed on the surface of dispersed indium oxide were detected by Fourier-transform IR spectroscopy. The mechanism of changing the conductivity of In₂O₃ · Gd₂O₃ films upon detecting NO₂ in air is discussed.     

Gallium‐Indium Ordering in the Complex [Ni2Ga3In] Network of GdNi2Ga3In

Polycrystalline samples of the isotypic quaternary compounds RENi₂Ga₃In (RE = Y, Gd – Tm) were obtained by arc‐melting of the elements. Crystals of the gadolinium compound were found by slow cooling of an arc‐melted button of the initial composition “GdNiGa₃In”. All samples were characterized by powder X‐ray diffraction. The structure of GdNi₂Ga_2.89In_1.11 was refined from single‐crystal X‐ray diffractometer data: new type, Pnma, a = 2426.38(7), b = 418.17(2), c = 927.27(3) pm, wR₂ = 0.0430, 1610 F² values and 88 variables. Two of the six crystallographically independent gallium sites show a small degree of Ga/In mixing. The nickel atoms show tricapped trigonal prismatic coordination by gadolinium, gallium, and indium. Together, the nickel, gallium, and indium atoms build up a complex three‐dimensional [Ni₂Ga₃In]^δ– network, which leaves cages for the gadolinium atoms. The indium atoms form zigzag chains with In–In distances of 337 pm. The crystal chemical similarities of the polyhedral packing in the GdNi₂Ga₃In and La₄Pd₁₀In₂₁ structures are discussed.     

Kinetics of precipitation and growth of thin indium(III) sulfide films

Thin films of indium(III) sulfide have been prepared by chemical precipitation from aqueous solutions containing indium(III) nitrate, thioacetamide, tartaric acid, and hydroxylamine hydrochloride at 333–368 K. Kinetics of In₂S₃ precipitation and the films growth under conditions of spontaneous formation of the solid phase in the solution has been studied. Formal rate law of indium(III) sulfide formation accounting for the partial orders of In₂S₃ precipitation with respect to the system components and the process activation energy has been derived. The effects of the reaction mixture composition, temperature, and the synthesis duration of In2S3 films growth have been studied.     

Indiumwolframat,In2(WO4)3 – ein In3+ leitender Festkörperelektrolyt

Indium Tungstate, In₂(WO₄)₃ – an In³⁺ Conducting Solid Electrolyte Polycrystalline In₂(WO₄)₃ has been electrochemically characterized and unambiguously identified as an In³⁺ conducting solid electrolyte. By heating, indium tungstate undergoes a phase transition between 250 °C and 260 °C transforming from a monoclinic to an orthorhombic phase for which the conduction properties have been determined. The adopted crystal structure in this high temperature region corresponds to the Sc₂(WO₄)₃ type structure. The electrical conductivity was investigated by impedance spectroscopy in the temperature range 300–700 °C and amounts to about 3.7 · 10^–5 Scm^–1 at 600 °C with a corresponding activation energy of 59.5 kJ/mol. Polarization measurements indicated an exclusive current transport by ionic charge carriers with a transference number of about 0.99. In dc electrolysis experiments, the trivalent In³⁺ cations were undoubtedly identified as mobile species. A current transport by oxide anions was not observed.     

Electrosynthesis of a Defective Indium Selenide with 3D Structure on a Substrate for Tunable CO2 Electroreduction to Syngas

Syngas (CO/H₂) is a feedstock for the production of a variety of valuable chemicals and liquid fuels, and CO₂ electrochemical reduction to syngas is very promising. However, the production of syngas with high efficiency is difficult. Herein, we show that defective indium selenide synthesized by an electrosynthesis method on carbon paper (γ‐In₂Se₃/CP) is an extremely efficient electrocatalyst for this reaction. CO and H₂ were the only products and the CO/H₂ ratio could be tuned in a wide range by changing the applied potential or the composition of the electrolyte. In particular, using nanoflower‐like γ‐In₂Se₃/CP (F‐γ‐In₂Se₃/CP) as the electrode, the current density could be as high as 90.1 mA cm^?2 at a CO/H₂ ratio of 1:1. In addition, the Faradaic efficiency of CO could reach 96.5 % with a current density of 55.3 mA cm^?2 at a very low overpotential of 220 mV. The outstanding electrocatalytic performance of F‐γ‐In₂Se₃/CP can be attributed to its defect‐rich 3D structure and good contact with the CP substrate.     

Synthesis of substitutional solid solutions in Na2O-P2O5-In2O3-M 2 III O3 (MIII = Cr, Fe, and Mn) systems

Solid solutions based on Na₇(InP₂O₇)₄PO₄ and Na₃In₂(PO₄)₃, where chromium, iron, and manganese substitute for indium, have been prepared. When chromium and iron substitute for indium in Na₇(InP₂O₇)₄PO₄, a continuous solid solution series exists. When manganese substitutes for indium, it enters the compound in the oxidation state +3. The substitution of chromium for indium in Na₃In₂(PO₄)₃ occurs within the range from 0.11 to 0.74 (mol/mol), and that of iron for indium, from 0.09 to 0.62 (mol/mol). When manganese substitutes for indium, it enters the structure of the crystalline phase in insignificant amounts as a two-charged cation.     

Electrical properties of In2O3

Conductivity data for In₂O₃ both from literature and from new measurements are critically compared. They are correlated with atmospheric conditions and temperature. The conductivity data and structural considerations lead to the conclusion that non-stoichiometric In₂O₃ is an n-type semiconductor. Interstitial indium ions are probably the predominant defects.     

Hydrothermal synthesis of [C6H16N2][In2Se3(Se2)]: A new one-dimensional indium selenide

A new organically templated indium selenide, [C₆H₁₆N₂][In₂Se₃(Se₂)], has been prepared hydrothermally from the reaction of indium, selenium and trans-1,4-diaminocyclohexane in water at 170 °C. This material was characterised by single-crystal and powder X-ray diffraction, thermogravimetric analysis, UV-vis diffuse reflectance spectroscopy, FT-IR and elemental analysis. The compound crystallises in the monoclinic space group C2/c (a=12.0221(16) Å, b=11.2498(15) Å, c=12.8470(17) Å, β=110.514(6)°). The crystal structure of [C₆H₁₆N₂][In₂Se₃(Se₂)] contains anionic chains of stoichiometry [In₂Se₃(Se₂)]²⁻, which are aligned parallel to the [1 0 1] direction, and separated by diprotonated trans-1,4-diaminocyclohexane cations. The [In₂Se₃(Se₂)]²⁻ chains, which consist of alternating four-membered [In₂Se₂] and five-membered [In₂Se₃] rings, contain perselenide (Se₂)²⁻ units. UV-vis diffuse reflectance spectroscopy indicates that [C₆H₁₆N₂][In₂Se₃(Se₂)] has a band gap of 2.23(1) eV.     

Das Indiumsesquichlorid,In2Cl3: ein pseudobinäres,gemischtvalentes Indium(I)-hexachloroindat(III)

Indium Sesquichloride, In₂Cl₃: a Pseudobinary, Mixed-valence Indium(I) Hexachloroindate(III) Colorless In₂Cl₃, obtained by reduction of InCl₃ with metallic In, according to In[In^IIICl₆] a pseudobinary, mixed-valence indium(I) hexachloroindate(III), crystallizes orthorhombic (Pnma, Z = 32) with a = 1261.4(3), b = 2523.8(5), c = 1456.2(2) pm (Guinier-Simon data), V_m(In₂Cl₃) = 87.3 cm³ × mol^?1. In^III occupies octahedral holes separated from each other (d?(In^III? Cl) = 251 pm). Coordination numbers of 7 to 11 are observed for In^I (d?(In^I? Cl) = 329–359 pm). In₂Cl₃ is isotypic with α-Tl₂Cl₃.     

New Indium‐Rich Compounds EuRhIn2 and EuRh2In8

EuRhIn₂ and EuRh₂In₈ were obtained by reacting the elements in sealed tantalum tubes in a high‐frequency furnace in a water‐cooled quartz glass sample chamber. Both indides were investigated by X‐ray powder and single crystal techniques: Cmcm, oC16, a = 432.2(1), b = 1058.8(1), c = 805.5(2) pm, wR2 = 0.0393, 471 F ² values, 16 variables for EuRhIn₂ and Pbam, oP44, a = 1611.8(2), b = 1381.7(2), c = 436.44(6) pm, wR2 = 0.0515, 1592 F ² values, 70 variables for EuRh₂In₈. EuRhIn₂ adopts the MgCuAl₂ type structure and may be considered as a rhodium filled variant of the binary Zintl phase EuIn₂. The indium substructure is homeotypic to the lonsdaleite type. Within the three‐dimensional [RhIn₂] polyanion the strongest bonding interactions occur for the Rh–In contacts followed by In–In. EuRh₂In₈ is the first indide with CaCo₂Al₈ type structure. The rhodium atoms have a trigonal prismatic indium coordination and the indium atoms form distorted indium centered InIn₈ cubes and InIn₁₀ pentagonal prisms with In–In distances ranging from 288 to 348 pm. Again, the rhodium and indium atoms together build a complex three‐dimensional [Rh₂In₈] polyanion in which the europium atoms are located within distorted pentagonal channels. Chemical bonding in EuRhIn₂ and EuRh₂In₈ is briefly discussed.     

In-situ Synthesis of the Thinnest In2Se3/In2S3/In2Se3 Sandwich-Like Heterojunction for Photoelectrocatalytic Water Splitting

The efficient utilization of solar energy for photoelectrocatalytic (PEC) water splitting is a feasible solution for developing clean energy and alleviating environmental issues. However, as the core of PEC technology, the existing photoanode catalysts have disadvantages such as poor photoelectrocatalytic conversion efficiency, low conductivity of photogenerated carriers, and instability. Here, we report the ultrathin two-dimensional sandwich-like (SW) heterojunction of In₂Se₃/In₂S₃/In₂Se₃ (SW In₂S₃@In₂Se₃) for the first time for PEC water splitting. Our findings identify the efficient separation of electrons and holes by constructing SW In₂S₃@In₂Se₃ heterojunction. The in situ synthesis of ultrathin nanosheet arrays by using surface substitution of Se atom to epitaxially grow cell In₂Se₃ maximizes the contact area of heterogeneous interface and accelerates the transmission of charge carrier. Benefitting from the unique structure and composition characteristic, SW In₂S₃@In₂Se₃ displays excellent performance in PEC water splitting. The photocurrent density of SW In₂S₃@In₂Se₃ reaches 8.43 mA cm⁻² at 1.23 V_RHE. Compared with In₂S₃, the SW In₂S₃@In₂Se₃ photoanode has nearly 12 times higher PEC performance, which represents the best performance among the In₂S₃-based photoanode heterojunction reported so far. The evolution rate of O₂ reaches 78.8 μmol cm⁻² h⁻¹, and the photocurrent has no apparent variety within 24 h.     

The mono-, sesqui-, and dibromides of indium: InBr,In2Br3, and InBr2

Of the four reduced indium bromides, InBr, In₂Br₃, InBr₂, and In₄Br₇, synthesis, crystal growth and structure determination of the first three is reported. InBr (orthorhombic), Cmcm, Z = 4, a = 446.6(1), b = 1236.8(2), c = 473.9(1) pm, V_m = 39.42(1) cm³ mol^?1) crystallizes with the TlI-type structure. In₂Br₃ (orthorhombic, Pnma, Z = 16, a = 1300.6(5), b = 1649.8(5), c = 1289.7(9) pm, V_m = 104.16(9) cm³ mol ^?1), isotypic with Ga₂Br₃, is according to In₂[In₂Br₆] a mixed-valence In^I–In^II-bromid with eclipsed [In₂Br₆]^2? groups with d(In–In) = 268.8 and 271.6 pm, respectively. InBr₂(?In[InBr₄]) is a mixed-valence In^I? In^III bromide with the GaCl₂-type structure (orthorhombic, Pnna, Z = 8, a = 798.6(2), b = 1038.5(2), c = 1042.5(5) pm, V_m = 65.09(4) cm³ mol^?1).     

Enhanced photocurrent generations in RuL2(NCS)2/di-(3-aminopropyl)-viologen self-assembled on In2O3 nanorods

A Ru(2,2′-bipyridine-4,4′-dicarboxylic acid)₂(NCS)₂ [RuL₂(NCS)₂]/di-(3-aminopropyl)-viologen (DAPV)/In₂O₃ nanorod system was prepared and applied for photocurrent generation with its maximum surface area . The In₂O₃ nanorods were prepared using the chemical-bath-deposition method. The various surface morphology of In₂O₃ were obtained by adding different amounts of 0.1 M HCl solution to the indium-containing solution. The DAPV and RuL₂(NCS)₂ were easily self-assembled on the indium-oxide surface. The energy levels of RuL₂(NCS)₂, DAPV, In₂O₃, and tin-doped indium oxide (ITO) were well arranged, and the system forms an efficient acceptor-sensitizer. The photocurrent measurement of the systems showed excellent photocurrent of 50 nA/cm² under the air mass (AM) 1.5 condition (100 mW/cm²), which was increased by a factor of ten compared to ones without indium-oxide layers.     

Propane dehydrogenation over extra-framework In(i) in chabazite zeolites

Indium on silica, alumina and zeolite chabazite (CHA), with a range of In/Al ratios and Si/Al ratios, have been investigated to understand the effect of the support on indium speciation and its corresponding influence on propane dehydrogenation (PDH). It is found that In₂O₃ is formed on the external surface of the zeolite crystal after the addition of In(NO₃)₃ to H-CHA by incipient wetness impregnation and calcination. Upon reduction in H₂ gas (550 °C), indium displaces the proton in Brønsted acid sites (BASs), forming extra-framework In⁺ species (In-CHA). A stoichiometric ratio of 1.5 of formed H₂O to consumed H₂ during H₂ pulsed reduction experiments confirms the indium oxidation state of +1. The reduced indium is different from the indium species observed on samples of 10In/SiO₂, 10In/Al₂O₃ (i.e., 10 wt% indium) and bulk In₂O₃, in which In₂O₃ was reduced to In(0), as determined from the X-ray diffraction patterns of the product, H₂ temperature-programmed reduction (H₂-TPR) profiles, pulse reactor investigations and in situ transmission FTIR spectroscopy. The BASs in H-CHA facilitate the formation and stabilization of In⁺ cations in extra-framework positions, and prevent the deep reduction of In₂O₃ to In(0). In⁺ cations in the CHA zeolite can be oxidized with O₂ to form indium oxide species and can be reduced again with H₂ quantitatively. At comparable conversion, In-CHA shows better stability and C₃H₆ selectivity (∼85%) than In₂O₃, 10In/SiO₂ and 10In/Al₂O₃, consistent with a low C₃H₈ dehydrogenation activation energy (94.3 kJ mol⁻¹) and high C₃H₈ cracking activation energy (206 kJ mol⁻¹) in the In-CHA catalyst. A high Si/Al ratio in CHA seems beneficial for PDH by decreasing the fraction of CHA cages containing multiple In⁺ cations. Other small-pore zeolite-stabilized metal cation sites could form highly stable and selective catalysts for this and facilitate other alkane dehydrogenation reactions.

Indium-containing chabazite zeolites show better stability and C₃H₆ selectivity for propane dehydrogenation than In₂O₃, In/SiO₂ and In/Al₂O₃. Extra-framework In⁺ is identified as the stable active site upon reduction of an impregnated sample.     

Structure and Magnetic Properties of Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26

New indides Ce₃Ge_0.66In_4.34 and Ce₁₁Ge_4.74In_5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La₃GeIn₄ type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F² values, 17 variables for Ce₃Ge_0.66In_4.34 and I4/mmm, Sm₁₁Ge₄In₆ type (ordered version of the Ho₁₁Ge₁₀ type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F² values, 41 variables for Ce₁₁Ge_4.74In_5.26. The Ce₃Ge_0.66In_4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce₁₁Ge_4.74In_5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce³⁺ ions. The compound Ce₃GeIn₄ remains paramagnetic down to 1.72 K, whereas Ce₁₁Ge₄In₆ orders ferromagnetically at T_C = 7.5 K.     

Single‐microemulsion‐based Hydrothermal Approach to In(OH)3 and In2O3 Nanocubes

Well‐defined indium hydroxide [In(OH)₃] nanocubes have been successfully prepared through a facile single‐microemulsion‐mediated hydrothermal process at a relatively low temperature. Calcination of the In(OH)₃ precursor at 400°C in a furnace yielded In₂O₃ crystals with the same morphology. X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), and transmission electron microscopy (TEM) were used to characterize the samples. The effects of reaction parameters on the formation of nanostructures were also discussed, and the nucleation, aggregation and anisotropic growth mechanism was proposed. Room temperature photoluminescence (PL) spectra as well as the ultraviolet‐visible (UV‐vis) absorbance spectra were carried out on the In₂O₃ crystals to investigate their optical properties.