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1. Mo ₃ S ₁₃ Chalcogel: A High‐Capacity Electrode for Conversion‐Based Li‐Ion Batteries

   https://doi.org/10.1002/cssc.202400084  

   Islam, Taohedul; Chandra Roy, Subrata; Bayat, Sahar; Adigo Weret, Misganaw; Hoffman, Justin M.; Rao, Keerthan R.; Sawicki, Conrad; Nie, Jing; Alam, Robiul; Oketola, Oluwaseun; et al (April 2024, ChemSusChem)

   Abstract Despite large theoretical energy densities, metal‐sulfide electrodes for energy storage systems face several limitations that impact the practical realization. Here, we present the solution‐processable, room temperature (RT) synthesis, local structures, and application of a sulfur‐rich Mo₃S₁₃chalcogel as a conversion‐based electrode for lithium‐sulfide batteries (LiSBs). The structure of the amorphous Mo₃S₁₃chalcogel is derived throughoperandoRaman spectroscopy, synchrotron X‐ray pair distribution function (PDF), X‐ray absorption near edge structure (XANES), and extended X‐ray absorption fine structure (EXAFS) analysis, along with ab initio molecular dynamics (AIMD) simulations. A key feature of the three‐dimensional (3D) network is the connection of Mo₃S₁₃units through S−S bonds. Li/Mo₃S₁₃half‐cells deliver initial capacity of 1013 mAh g⁻¹during the first discharge. After the activation cycles, the capacity stabilizes and maintains 312 mAh g⁻¹at a C/3 rate after 140 cycles, demonstrating sustained performance over subsequent cycling. Such high‐capacity and stability are attributed to the high density of (poly)sulfide bonds and the stable Mo−S coordination in Mo₃S₁₃chalcogel. These findings showcase the potential of Mo₃S₁₃chalcogels as metal‐sulfide electrode materials for LiSBs. 

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2. Local lattice distortions and dynamics in extremely overdoped superconducting YSr ₂ Cu _2.75 Mo _0.25 O _7.54

   https://doi.org/10.1073/pnas.1918704117  

   Conradson, Steven D.; Geballe, Theodore H.; Gauzzi, Andrea; Karppinen, Maarit; Jin, Changqing; Baldinozzi, Gianguido; Li, Wenmin; Cao, Lipeng; Gilioli, Edmondo; Jiang, Jack M.; et al (February 2020, Proceedings of the National Academy of Sciences)

   A common characteristic of many “overdoped” cuprates prepared with high-pressure oxygen isT_cvalues ≥ 50 K that often exceed that of optimally doped parent compounds, despite O stoichiometries that place the materials at the edge or outside of the conventional boundary between superconducting and normal Fermi liquid states. X-ray absorption fine-structure (XAFS) measurements at 52 K on samples of high-pressure oxygen (HPO) YSr₂Cu_2.75Mo_0.25O_7.54,T_c= 84 K show that the Mo is in the (VI) valence in an unusually undistorted octahedral geometry with predominantly Mo neighbors that is consistent with its assigned substitution for Cu in the chain sites of the structure. Perturbations of the Cu environments are minimal, although the Cu X-ray absorption near-edge structure (XANES) differs from that in other cuprates. The primary deviation from the crystal structure is therefore nanophase separation into Mo- and Cu-enriched domains. There are, however, indications that the dynamical attributes of the structure are altered relative to YBa₂Cu₃O₇, including a shift of the Cu-apical O two-site distribution from the chain to the plane Cu sites. Another effect that would influenceT_cis the possibility of multiple bands at the Fermi surface caused by the presence of the second phase and the lowering of the Fermi level. 

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3. Solving the structure of “single-atom” catalysts using machine learning – assisted XANES analysis

   https://doi.org/10.1039/D1CP05513E  

   Xiang, Shuting; Huang, Peipei; Li, Junying; Liu, Yang; Marcella, Nicholas; Routh, Prahlad K.; Li, Gonghu; Frenkel, Anatoly I. (February 2022, Physical Chemistry Chemical Physics)

   “Single-atom” catalysts (SACs) have demonstrated excellent activity and selectivity in challenging chemical transformations such as photocatalytic CO 2 reduction. For heterogeneous photocatalytic SAC systems, it is essential to obtain sufficient information of their structure at the atomic level in order to understand reaction mechanisms. In this work, a SAC was prepared by grafting a molecular cobalt catalyst on a light-absorbing carbon nitride surface. Due to the sensitivity of the X-ray absorption near edge structure (XANES) spectra to subtle variances in the Co SAC structure in reaction conditions, different machine learning (ML) methods, including principal component analysis, K-means clustering, and neural network (NN), were utilized for in situ Co XANES data analysis. As a result, we obtained quantitative structural information of the SAC nearest atomic environment, thereby extending the NN-XANES approach previously demonstrated for nanoparticles and size-selective clusters. 

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4. X-ray absorption spectroscopy insights on the structure anisotropy and charge transfer in Chevrel Phase chalcogenides

   https://doi.org/10.1039/d1cp04851a  

   Hyler, Forrest P.; Wuille Bille, Brian A.; Ortíz-Rodríguez, Jessica C.; Sanz-Matias, Ana; Roychoudhury, Subhayan; Perryman, Joseph T.; Patridge, Christopher J.; Singstock, Nicholas R.; Musgrave, Charles B.; Prendergast, David; et al (July 2022, Physical Chemistry Chemical Physics)

   The electronic structure and local coordination of binary (Mo 6 T 8 ) and ternary Chevrel Phases (M x Mo 6 T 8 ) are investigated for a range of metal intercalant and chalcogen compositions. We evaluate differences in the Mo L 3 -edge and K-edge X-ray absorption near edge structure across the suite of chalcogenides M x Mo 6 T 8 (M = Cu, Ni, x = 1–2, T = S, Se, Te), quantifying the effect of compositional and structural modification on electronic structure. Furthermore, we highlight the expansion, contraction, and anisotropy of Mo 6 clusters within these Chevrel Phase frameworks through extended X-ray absorption fine structure analysis. Our results show that metal-to-cluster charge transfer upon intercalation is dominated by the chalcogen acceptors, evidenced by significant changes in their respective X-ray absorption spectra in comparison to relatively unaffected Mo cations. These results explain the effects of metal intercalation on the electronic and local structure of Chevrel Phases across various chalcogen compositions, and aid in rationalizing electron distribution within the structure. 

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5. High pressure raman spectroscopy and X-ray diffraction of K2Ca(CO3)2 bütschliite: multiple pressure-induced phase transitions in a double carbonate

   https://doi.org/10.1007/s00269-023-01262-5  

   Zeff, G.; Kalkan, B.; Armstrong, K.; Kunz, M.; Williams, Q. (January 2024, Physics and Chemistry of Minerals)

   Abstract The crystal structure and bonding environment of K₂Ca(CO₃)₂bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus,$${K}_{0}=46.9$$ $K_0=46.9$GPa with an imposed value of$${K}_{0}^{\prime}= 4$$ $K_0^{\prime }=4$for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along thec-axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinicC2/mstructure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields$${V}_{0}=322.2$$ $V_0=322.2$ Å³$$,$$ $,$$${K}_{0}=24.8$$ $K_0=24.8$GPa and$${K}_{0}^{\prime}=4.0$$ $K_0^{\prime }=4.0$using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of theC2/mphase involves interlayer displacement and twisting of the [CO₃] units, and an increase in coordination number of the K⁺ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO₃] bonding environments within the structure. 

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