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Supramolecular frameworks have been widely synthesized for ion transport applications. However, conventional approaches of constructing ion transport pathways in supramolecular frameworks typically require complex processes and display poor scalability, high cost, and limited sustainability. Here, we report the scalable and cost-effective synthesis of an ion-conducting (e.g., Na + ) cellulose-derived supramolecule (Na-CS) that features a three-dimensional, hierarchical, and crystalline structure composed of massively aligned, one-dimensional, and ångström-scale open channels. Using wood-based Na-CS as a model material, we achieve high ionic conductivities (e.g., 0.23 S/cm in 20 wt% NaOH at 25 °C) even with a highly dense microstructure, in stark contrast to conventional membranes that typically rely on large pores (e.g., submicrometers to a few micrometers) to obtain comparable ionic conductivities. This synthesis approach can be universally applied to a variety of cellulose materials beyond wood, including cotton textiles, fibers, paper, and ink, which suggests excellent potential for a number of applications such as ion-conductive membranes, ionic cables, and ionotronic devices.

An overarching challenge of the electrochemical carbon dioxide reduction reaction (eCO2RR) is finding an earth-abundant, highly active catalyst that selectively produces hydrocarbons at relatively low overpotentials. Here, we report the eCO2RR performance of two-dimensional transition metal carbide class of materials. Our results indicate a maximum methane (CH4) current density of −421.63 mA/cm2 and a CH4 faradic efficiency of 82.7% ± 2% for di-tungsten carbide (W2C) nanoflakes in a hybrid electrolyte of 3 M potassium hydroxide and 2 M choline-chloride. Powered by a triple junction photovoltaic cell, we demonstrate a flow electrolyzer that uses humidified CO2 to produce CH4 in a 700-h process under one sun illumination with a CO2RR energy efficiency of about 62.3% and a solar-to-fuel efficiency of 20.7%. Density functional theory calculations reveal that dissociation of water, chemisorption of CO2 and cleavage of the C-O bond—the most energy consuming elementary steps in other catalysts such as copper—become nearly spontaneous at the W2C surface. This results in instantaneous formation of adsorbed CO—an important reaction intermediate—and an unlimited source of protons near the tungsten surface sites that are the main reasons for the observed superior activity, selectivity, and small potential., It is of high interests to develop new catalysts for selective CO2 electroreduction. Here the authors investigate two-dimensional transition metal carbides for CO2 to methane conversion with superior activity, selectivity and low overpotentials.

We have investigated the doping-induced local structural and electronic effects in the recently developed low band gap room temperature ferroelectric Mn-Nb co-doped BaTiO3. Experimental and theoretical Raman spectroscopies are utilized to quantify the Ti off-centering, identified to be the intrinsic origin of ferroelectricity in these systems. Mn and Nb exhibit contrasting doping behaviors that have remarkable effects on BaTiO3 functionality. Jahn-Teller distorted Mn3+ is primarily associated with lowering of the bulk band gap, while charge-compensating Nb5+ off-centers within the O-6 octahedra, creating a polar mode that stabilizes the ferroelectric ground state. The charge neutral aliovalent Mn3+-Nb5+ pair effectively couples to the inherent ferroelectric instability of the BaTiO3 lattice, restoring some spontaneous polarization lost by doping Mn3+ (d(4)) ions at Ti4+ (d(0)) sites.

The practical electrosynthesis of hydrogen peroxide (H

As a new class of lithium rich cathodes, disordered rock-salt cathodes have been of primary interest, because of their ability to deliver a promisingly high capacity up to 300 mA h/g. Nevertheless, some fundamental issues are yet to be fully understood and a comprehensive mastering of their solid-state chemistry, kinetics and thermal stability is required. Here, we select a high capacity cation-disordered positive electrode- Li1.2Ni0.4Nb0.4O2 as a model compound to study intrinsic reaction mechanism, including charge compensation mechanism, kinetics, thermal stability, and structural evolution. By combining soft and hard X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) with operando and ex-situ differential scanning calorimetry (DSC), galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and X-ray diffraction (XRD), we present holistic information on disordered rock-salt cathode. This work provides beneficial insights into designing and tailoring new positive electrodes with disordered rock-salt structure.

Double perovskite oxides with d8-d3 electronic configurations are expected to be ferromagnetic from the Goodenough-Kanamori rules, such as ferromagnetic La2NiMnO6. In search of new ferromagnetic insulators, double perovskite Ba2NiIrO6 was successfully synthesized by high-pressure and high-temperature methods (8 GPa and 1573 K). Ba2NiIrO6 crystallizes in a cubic double perovskite structure (space group: Fm3m), with an ordered arrangement of NiO6 and IrO6 octahedra. X-ray absorption near-edge spectroscopy confirms the nominal Ni(II) and Ir(VI) valence states. Ba2NiIrO6 displays an antiferromagnetic order at 51 K. The positive Weiss temperature, however, indicates that ferromagnetic interactions are dominant. Isothermal magnetization curves at low temperatures support a field-induced spin-flop transition.

The sequestration of metal ions into the crystal structure of minerals is common in nature. To date, the incorporation of technetium(IV) into iron minerals has been studied predominantly for systems under carefully controlled anaerobic conditions. Mechanisms of the transformation of iron phases leading to incorporation of technetium(IV) under aerobic conditions remain poorly understood. Here we investigate granular metallic iron for reductive sequestration of technetium(VII) at elevated concentrations under ambient conditions. We report the retarded transformation of ferrihydrite to magnetite in the presence of technetium. We observe that quantitative reduction of pertechnetate with a fraction of technetium(IV) structurally incorporated into non-stoichiometric magnetite benefits from concomitant zero valent iron oxidative transformation. An in-depth profile of iron oxide reveals clusters of the incorporated technetium(IV), which account for 32% of the total retained technetium estimated via X-ray absorption and X-ray photoelectron spectroscopies. This corresponds to 1.86 wt.% technetium in magnetite, providing the experimental evidence to theoretical postulations on thermodynamically stable technetium(IV) being incorporated into magnetite under spontaneous aerobic redox conditions. For the geological disposal of radionuclides through immobilization within minerals, naturally aerobic conditions need to be considered. Here the authors report a quantitative reduction of Tc7+ and partial structural incorporation of Tc4+ into in situ formed nonstochiometric magnetite under ambient conditions.

Solar conversion of carbon dioxide (CO2) into hydrocarbon fuels offers a promising approach to fulfill the world’s ever-increasing energy demands in a sustainable way. However, a highly active cata...

As an important class of inorganic compounds that exhibit a variety of physical, chemical, and electrochemical properties, ABO3±δ perovskites are generally known as active electrocatalysts for the anodic oxygen evolution reaction (OER). However, the inferior performance for the cathodic hydrogen evolution reaction (HER) limits their wide potential in constructing stable oxide-based alkaline electrolyzers for hydrogen production. Here, we show that the efficient decoration of perovskite oxide (K0.469La0.531)TiO3 (KLTO) via surface ion exchange with Ru cations and nucleation growth of Ti-doped RuO2 (TRO) nanoparticles could form a composite oxide-type electrocatalyst. It enables fast water dissociation with excellent HER activity in alkaline solution, superior to other oxide electrocatalysts and commercial Pt/C. Theoretical and experimental studies imply that the co-existence of surface TRO nanoparticles and the Ru-doped KLTO (RKLTO) substrate synergistically enhances the alkaline hydrogen evolution kinetics. Ti doping into the RuO2 lattice could significantly reduce the barrier of water dissociation to facilitate the Volmer process. The surface doping of Ru in the KLTO substrate could regulate and optimize the hydrogen adsorption free energy. The present strategy represents a new concept for designing oxide-based electrocatalysts related to devices for energy conversion and storage.

The detailed structure of ZnO doped with 5 at.% (metal) of the large aliovalent Eu3+-ions was investigated using EXAFS to describe the local Eu and Zn coordination. The microstructure, crystalline phases, contents and ZnO unit-cell parameters for the ZnO:5%Eu sponges synthesised at 200 to 900 oC were obtained by XRD, SEM, and TEM analysis. XRD showed peaks solely of h-ZnO for the 600 oC sample, while heating at 700 oC and higher caused phase separation into h-ZnO:Eu and c-Eu2O3. XRD showed a close to zero increase in ZnO unit cell-volume of ca. 0.4 vol%, compared to un-doped ZnO for the non-phase separated, clean oxide made at 600 oC. The Zn EXAFS data showed an almost intact local ZnO structure. The Eu EXAFS showed an unusually low coordination number (CN) of ca. 5 for the 200-600 oC samples, while the CN increased for higher temperatures, in concert with the formation of c-Eu2O3. 23 DFT-generated theoretical ZnO structures containing Eu-clusters built from 1 to 4 Eu3+-Zn2+-vacancy- Eu3+ pairs were compared with the experimental data. The lowest formation energies and ZnO unit-cell volume increase versus un-doped ZnO (0.6-0.7 vol%), were obtained when combining two or four Eu3+-Zn2+-vacancy- Eu3+ pairs into Eu4 and Eu8 clusters showing an average Eu CN of ca. 5. These theoretically determined lowest energy structures were all in good agreement with the experimental results obtained by EXAFS and XRD. Photoluminescence excitation and emission spectra performed on the ZnO:5at%Eu sponges obtained at various temperatures, showed strong quenching of the characteristic Eu3+ transitions for samples obtained at 600 and 800 °C, most likely due to changes in the ZnO defect states, which are crucial for Eu3+ excitation, and due to self-quenching upon Eu clustering and c- Eu2O3 phase separation. Thus, the optical data further supported Eu clustering found by EXAFS, DFT and XRD techniques, corroborating structure-property relationships in these materials. Overall, as far as we can find, the findings reported herein point to a doping structure very different from those previously proposed in the literature. It demonstrates that the semiconductor ZnO can host molecular-sized clusters of metal-oxides, very dissimilar to ZnO.

Nanocrystalline ZnO sponges doped with 5 mol% EuO1.5 are obtained by heating metal–salt complex based precursor pastes at 200–900 °C for 3 min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu2O3 takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu-doping and an average Eu3+ ion coordination number of ≈5.2. Comparisons of 23 density functional theory-generated structures having differently sized Eu-oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2–5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu3+ excitation, while c-Eu2O3 phase separation results in loss of the characteristic Eu3+ photoluminescence. The formation of molecule-like Eu-oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

Strongly correlated electrons in layered perovskite structures have been the birthplace of high-temperature superconductivity, spin liquid, and quantum criticality. Specifically, the cuprate materials with layered structures made of corner sharing square planar CuO$_4$ units have been intensely studied due to their Mott insulating grounds state which leads to high-temperature superconductivity upon doping. Identifying new compounds with similar lattice and electronic structures has become a challenge in solid state chemistry. Here, we report the hydrothermal crystal growth of a new copper tellurite sulfate Cu$_3$(TeO$_4$)(SO$_4$)$\cdot$H$_2$O, a promising alternative to layered perovskites. The orthorhombic phase (space group $Pnma$) is made of corrugated layers of corner-sharing CuO$_4$ square-planar units that are edge-shared with TeO$_4$ units. The layers are linked by slabs of corner-sharing CuO$_4$ and SO$_4$. Using both the bond valence sum analysis and magnetization data, we find purely Cu$^{2+}$ ions within the layers, but a mixed valence of Cu$^{2+}$/Cu${^+}$ between the layers. Cu$_3$(TeO$_4$)(SO$_4$)$\cdot$H$_2$O undergoes an antiferromagnetic transition at $T_N$=67 K marked by a peak in the magnetic susceptibility. Upon further cooling, a spin-canting transition occurs at $T^{\star}$=12 K evidenced by a kink in the heat capacity. The spin-canting transition is explained based on a $J_1$-$J_2$ model of magnetic interactions, which is consistent with the slightly different in-plane super-exchange paths. We present Cu$_3$(TeO$_4$)(SO$_4$)$\cdot$H$_2$O as a promising platform for the future doping and strain experiments that could tune the Mott insulating ground state into superconducting or spin liquid states., 29 pages

Strongly correlated electrons in layered perovskite structures have been the birthplace of high-temperature superconductivity, spin liquids, and quantum criticality. Specifically, the cuprate materials with layered structures made of corner-sharing square-planar CuO

Perovskite based catalysts have recently been investigated as replacements for traditional solid oxide fuel cell (SOFC) anode materials to tolerate carbon containing fuels in these devices and resi...

Polycrystalline samples of Cs1.17In0.81Cl3 were prepared by annealing a mixture of CsCl, InCl, and InCl3, stoichiometric for the targeted CsInCl3. Synchrotron powder X-ray diffraction refinement and chemical analysis by energy dispersive X-ray indicated that Cs1.17In0.81Cl3, a tetragonal distorted perovskite derivative (I4/m), is the thermodynamically stable product. The refined unit cell parameters and space group were confirmed by electron diffraction. In the tetragonal structure, In+ and In3+ are located in four different crystallographic sites, consistent with their corresponding bond lengths. In1, In2, and In3 are octahedrally coordinated, whereas In4 is at the center of a pentagonal bipyramid of Cl because of the noncooperative octahedral tilting of In4Cl6. The charged-ordered In+ and In3+ were also confirmed by X-ray absorption and Raman spectroscopy. Cs1.17In0.81Cl3 is the first example of an inorganic halide double perovskite derivative with charged-ordered In+ and In3+. Band structure and optical conductivity calculations were carried out with both generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ) approach; the GGA calculations estimated the band gap and optical band gap to be 2.27 eV and 2.4 eV, respectively. The large and indirect band gap suggests that Cs1.17In0.81Cl3 is not a good candidate for photovoltaic application.

In this study, the long-term cycle behavior of nano-LiCoO2 cathodes over 500 cycles at high rates is investigated. Furthermore, the postmortem analysis of the cycled nano-LiCoO2 cathodes using a combination of X-ray absorption spectroscopy and X-ray diffraction is also conducted to shed light on the capacity decay mechanisms. It is found that crystalline nano-LiCoO2 after 500 charge/discharge cycles at 10C becomes amorphous, exhibits Co2+ species rather than the expected Co3+ at the fully lithiated condition, has longer Co–O bond length than that of pristine nano-LiCoO2 and micro-LiCoO2, and exhibits 53% specific capacity loss over 500 cycles at 10C. In addition, slow Li-ion intercalation and deintercalation at the electrode/electrolyte interface are found to be the rate-limiting step for nano-LiCoO2 during discharge and charge, respectively. Thus, to achieve the high-rate capability of LiCoO2, not only LiCoO2 particle sizes should be reduced to nanoscales but also the Li-ion intercalation and deintercala...

Reversible cycling of MnO2 cathodes remains a challenge in alkaline rechargeable battery development. In prior work, we have developed new platelet shaped MnO2 nanoparticles with stable performance...

Double perovskite oxides with d

X-ray absorption spectroscopy experiments are the primary scientific focus of the MRCAT bending magnet beamline, 10-BM of the Advanced Photon Source at Argonne National Laboratory. This technique is used for ex situ and in situ structural characterization of materials, many of which are non-crystalline. An intense X-ray beam is often required for these experiments. This beamline presently operates using a detuned double crystal monochromator system without any focusing. Typically, samples are illuminated by a 0.5 x 0.5 mm2 monochromatic beam with a photon flux in the range of 2 - 9 x 108 photons/s (in the 5 - 33 keV range). In this study, several alternate focusing schemes to capture a large portion of the bending magnet beam are compared. It is shown that, in principle, one can obtain an increase over two orders of magnitude in photon flux. These beamline schemes are outlined comparing them for photon flux, energy resolution, cost, and complexity in design and operation.

A new porous activated carbon (AC) material with very high specific surface area (3193 m2 g&minus, 1) was prepared by the carbonization of a colloidal silica-templated melamine&ndash, formaldehyde (MF) polymer composite followed by KOH-activation. Several electrical double-layer capacitor (EDLC) cells were fabricated using this AC as the electrode material. A number of organic solvent-based electrolyte formulations were examined to optimize the EDLC performance. Both high specific discharge capacitance of 130.5 F g&minus, 1 and energy density 47.9 Wh kg&minus, 1 were achieved for the initial cycling. The long-term cycling performance was also measured.

The main drawbacks of today's state-of-the-art lithium-air (Li-air) batteries are their low energy efficiency and limited cycle life due to the lack of earth-abundant cathode catalysts that can drive both oxygen reduction and evolution reactions (ORR and OER) at high rates at thermodynamic potentials. Here, inexpensive trimolybdenum phosphide (Mo

We report on the electronic structure of doped $\mathrm{LaFe}{\mathrm{O}}_{3}$ at the crossover from an insulating-to-metallic phase transition. Comprehensive x-ray spectroscopic methodologies are used to understand core and valence electronic structure as well as crystal structure distortions associated with the electronic transition. Despite the antiferromagnetic (AFM) ordering at room temperature, we show direct evidence of itinerant carriers at the Fermi level revealed by resonant photoemission spectroscopy (RPES) at the Mo ${L}_{3}$ edge. RPES data taken at the Fe ${L}_{3}$ edge show spectral weight near the valence band edge and significant hybridization with O $2p$ states required for AFM ordering. Resonant inelastic x-ray scattering spectra taken across Fe ${L}_{2,3}$ edges show electron correlation effects ($U$) driven by Coulomb interactions of $d$ electrons as well as broad charge-transfer excitations for $x\ensuremath{\ge}0.2$ where the compound crosses over to a metallic state. Site substitution of Fe by Mo ions in the Fe-${\mathrm{O}}_{6}$ octahedra enhances the separation of the two Fe-O bonds and Fe-O-Fe bonding angles relative to the orthorhombic $\mathrm{LaFe}{\mathrm{O}}_{3}$, but no considerable distortions are present to the overall structure. Mo ions appear to be homogeneously doped, with average valency of both metal sites monotonically decreasing with increasing Mo concentration. This insulator-to-metal phase transition with AFM stability is primarily understood through intermediate interaction strengths between correlation ($U$) and bandwidth ($W$) at the Fe site, where an estimation of this ratio is given. These results highlight the important role of extrinsic carriers in stabilizing a unique phase transition that can guide future efforts in antiferromagnetic-metal spintronics.

Lithium-sulfur (Li–S) batteries have promise to deliver energy density two to three times higher than that of currently used lithium-ion batteries. The commercialization of Li–S batteries is primarily hindered due to the polysulfide shuttle (PSS) effect, which not only leads to the loss of active materials from the cathode, but also causes serious irreversible reactions between the polysulfide intermediates and the lithium metal anode, resulting in low coulombic efficiency, high self-discharge and short cycle life. In this paper, we report the design and synthesis of a new graphitic carbon nitride-coated dual core–shell structured sulfur cathode (S@HCS@g-C3N4) to address these issues, leading to superior capacity retention properties in Li–S cells. This structural design allows confinement of polysulfide intermediates within a dual-core electrically conductive structure consisting of a hollow mesoporous carbon sphere (HCS) core, and a peripheral graphitic carbon nitride (g-C3N4) layer, which is known to suppress the PSS effect by enhanced chemical interactions with polysulfide intermediates. Indeed, the S@HCS@g-C3N4 cathode displayed excellent electrochemical performance in terms of high initial specific capacity (1446 mA h g−1 at 0.2C) and very good long-term cycling performance (capacity decay rate of 0.049% per cycle after 500 cycles at 1C).

The emerging need for high-performance lithium&ndash, sulfur batteries has motivated many researchers to investigate different designs. However, the polysulfide shuttle effect, which is the result of dissolution of many intermediate polysulfides in electrolyte, has still remained unsolved. In this study, we have designed a sulfur-filled dual core&ndash, shell spindle-like nanorod structure coated with manganese oxide (S@HCNR@MnO2) to achieve a high-performance cathode for lithium&ndash, sulfur batteries. The cathode showed an initial discharge capacity of 1661 mA h g&minus, 1 with 80% retention of capacity over 70 cycles at a 0.2C rate. Furthermore, compared with the nanorods without any coating (S@HCNR), the MnO2-coated material displayed superior rate capability, cycling stability, and Coulombic efficiency. The synergistic effects of the nitrogen-doped hollow carbon host and the MnO2 second shell are responsible for the improved electrochemical performance of this nanostructure.

Fluorinated ethers have been used as a co-solvent in traditional ether-based electrolytes to suppress the polysulfide shuttle effect in lithium-sulfur batteries. In this work, five partially fluorinated ether compounds have been synthesized. The key properties, such as viscosity, ionic conductivity and polysulfide solubility of the electrolytes containing these co-solvents have been systematically studied. The electrolyte formulation showed best physical properties was tested in lithium-sulfur coin cells. The new fluoroether-based electrolytes displayed superior electrochemical performance compared to that of the traditional ether-based electrolytes.

We have investigated the local environment around Mn3+ and In3+ ions in YMn1- xIn xO3 chromophores to understand the origin of the intense blue color for small values of x in these solid solutions. While X-ray diffraction results provide an average description of the trigonal bipyramidal (TBP) units about Mn/In atoms with five oxygens surrounding the cation, the X-ray absorption near edge structure (XANES) as well as extended X-ray absorption fine structure (EXAFS) of these materials clearly suggest the presence of two different TBP environments, one of which is similar to MnO5 TBP in YMnO3. EXAFS in conjunction with first-principles calculations show that replacing larger In3+ ions by smaller Mn3+ ones additionally gives rise to another TBP strongly distorted along the axial direction, expanding one of the axial Mn-O bonds by ∼11%. The relative fraction of these two environments changes in close agreement with the global stoichiometry with the elongated TBP, therefore, being dominant in the regime of the low Mn content. This local structural difference is responsible for the intense, but relatively narrow, absorption feature in the red-yellow region of the absorption spectrum, and hence YMn1- xIn xO3 appears blue for small Mn dopings. This distortion is relatively less abundant in Mn-rich compositions, and therefore, such compositions appear black, controlled by the wide absorption feature of the trigonal bipyramid coordination with Mn-O bond lengths that are essentially the same as those in YMnO3, covering the entire visible range. The chromophore properties are, thus, governed by the ratio of these two MnO5 TBP environments, one with a characteristic optical absorption giving it a blue color and the other absorbing over the entire visible range.

A new polar and magnetic oxide, YCrWO6, was successfully synthesized and characterized. YCrWO6 crystallizes in polar orthorhombic space group Pna21 (no. 33) of edge-sharing dimers of CrO6 and WO6 octahedra, which are connected by corner-sharing to form a three-dimensional framework structure with Y3+ cations located in the channels. The structure of YCrWO6 is related to that of CaTa2O6; however, the ordering of Cr3+ and W6+ in the octahedral sites breaks the inversion symmetry of the parent CaTa2O6 structure. X-ray absorption near edge spectroscopy of YCrWO6 confirmed the oxidation state of Cr3+ and W6+. Temperature-dependent optical second harmonic generation measurements on YCrWO6 confirmed the noncentrosymmetric character and evidenced a noncentrosymmetric-to-centrosymmetric phase transition above 800 °C. Piezoresponse force microscopy measurements on YCrWO6 at room temperature show strong piezoelectric domains. Magnetic measurements of YCrWO6 indicate antiferromagnetic order at TN of ∼22 K with Weiss ...