Journal of Solid State Chemistry最新文献

Rationally designing new materials is a crucial objective in modern solid-state chemistry, employing different synthetic strategies to vary a reaction's energetic aspects and, hence, effectively control its direction. In that context, and aided by density-functional-based enthalpy diagrams, we have developed a solid-state cyanamide metathetic method allowing to synthetically scan its activation energy profile, thus yielding milder reaction conditions and preventing potential product decomposition. This approach has led to the preparation of the ternary cyanamide LiSc(NCN)₂ via solid-state metathesis between Na₂NCN, ScCl₃ and LiCl, essentially by the existence of an intermediate, Li_xNa_1–xSc(NCN)₂, and the subsequent stepwise exchange of Na⁺ with Li⁺ ions. Both LiSc(NCN)₂ and the solid solution crystallize in an orthorhombic crystal structure with Pbcn symmetry, similar to the rest of the LiM(NCN)₂ cyanamide family with M = Al, In, Yb and Y. Structural analysis of the coordination environment around the NCN²⁻ group reveals a relaxation in the distortion of this unit and also an inversion of the cyanamide orientation as Na⁺ ions are progressively replaced with Li⁺, thus making the formation of the targeted compound highly favorable.

It is of great significance to study the nucleation mechanism of Si and P elements in the Fe₂Mo-Laves phase to control their precipitation and improve the strength of steel. Based on the first-principles calculations, the effects of Si and P elements on the stability of Fe₂Mo were studied. The addition of Si and P greatly increases the possibility of its formation in steel. When the Si and P concentrations are 37.5 %, the formation energy is the lowest. Si and P elements improve the stress deformation resistance and the stiffness of Laves phase, which makes Laves phase more stable in high-temperature environment. The addition of Si and P significantly improves the kinetic stability of Fe₂Mo, but the improvement effect of P is not as good as that of Si. This study provides theoretical guidance for controlling the precipitation of the Fe₂Mo-Laves phase in practical production.

In this paper, we investigate the effect of calcination on the properties of Cu₂FeSnS₄ (CFTS) prepared by solid-state reaction. As fabricated, the polycrystalline sample was crushed and the powders was calcined at different temperatures (T_C = 800, 900 and 1000 °C). A Rietveld analysis shows that the calcined powders have predominately the stannite phase with a nearly stoichiometric composition, with the presence of a small amount of SnS, supported by Raman scattering. Energy dispersive spectroscopy confirms the homogeneity of the CFTS materials. Moreover, the analysis of the surfaces of CFTS pellets using scanning electron microscopy showed a more compact and dense morphology as the calcination temperature increases, thus enhanced photosensitivity. From optical studies, we found that the bandgap energy decreases from 1.40 to 1.18 eV with increasing calcination temperature. Calcination can be a tool to engineer the optical band gap.

Li₂TiO₃:Mn⁴⁺ has been previously identified as a potential candidate to replace commercial red-emitting Eu²⁺-activated phosphors. Its luminescent efficiency is limited by the presence of defects and the sensitivity of Mn⁴⁺ to redox processes. A series of co-doped Li₂TiO₃: x Mg²⁺, 0.01 Mn⁴⁺ samples were prepared to gain insight on the effect of electron doping on the structure and photoluminescent properties, through characterization by powder X-ray diffraction, elemental analysis, and optical spectroscopy. As Mg²⁺ substitutes for Li⁺, the ordered arrangement of cations within the honeycomb layers in the parent structure (Li₂SnO₃-type, an ordered derivative of rocksalt) gradually transforms to a more disordered arrangement. The increased cation site disorder leads to less intense and broader emission peaks as well as lower quantum yields.

Metal sulfides have been expected huge practical potential for sodium-ion batteries (SIBs), which are mainly owing to their admirable merits of natural abundance, low price, and high theoretical capacity. However, the inferior electrical conductivity and enormous volume variation originating from sodiation/desodiaziton reactions usually result in unsatisfied rate and cycling properties. In this work, a coprecipitation with a following sulfurization method has been rationally designed to prepare the triphasic heterostructured hollow Zn–Sn–S nanoboxes encapsulated by N, S-codoped carbon (ZSS@NCS) as anodes for SIBs. The coexistence of triphasic ZSS heterostructures that consist of ZnS, SnS₂, and Sn₂S₃ effectively facilitates the fast Na ⁺ diffusion. The N, S-codoped carbon (NSC) derived from the polydopamine is coated outside of the ZSS heterostructures, which provides infinite affinity between ZSS and NSC that efficiently accelerates the electron transport and maintains the structural stability via the confinement effect. The synergistic effects of the heterostructured ZSS and NSC endow the ZSS@NSC anode with favorable sodium storage properties including decent discharge capacity (683.8 mAh g⁻¹ at 0.1 A g⁻¹), satisfying rate (232.6 mAh g⁻¹ at 10.0 A g⁻¹) and cycling properties (402.2 mAh g⁻¹ over 150 cycles).

Raman spectra of three NpO₂ samples and two samples produced from a modified direct denitration (MDD) process were collected. The spectral features of the NpO₂ samples were consistent and indicated only NpO₂. The spectra of the MDD samples indicated the presence of NpO₂ and an additional phase attributed to the neptunium binary oxide Np₂O₅. These Raman spectra are the first reported of Np₂O₅, and the proportions of these neptunium oxide phases varied within the samples, suggesting significant sample inhomogeneity. Peaks in the Raman spectra of Np₂O₅ at 569 and 782 cm⁻¹ were tentatively assigned to concerted, symmetric stretches of the neptunyl cations. Laser-induced heating of regions in the MDD samples that were rich in Np₂O₅ showed spectral features that indicated conversion to NpO₂.

Photocatalytic technology driven by sunlight is rapidly developing in response to energy shortage and environmental pollution. ABX₃ perovskite materials have gained widespread attention in photocatalysis due to their narrow band gap, high quantum efficiency, and high carrier mobility. The energy band structure plays a critical role in carrier generation, separation and redox processes in photocatalytic reactions. In this paper, we modulated the energy band structures of CsPbBr₃ and UiO-66 by changing the reaction parameters, and prepared CsPbBr₃/UiO-66 composites with different energy band structures to investigate photocatalytic activities. Our results showed that the degradation rate of (Methyl Orange) MO by CsPbBr₃/UiO-66 was significantly enhanced. The change in the CsPbBr₃ energy band structure did not significantly affect the photocatalytic activity of the composites. This work provides a new opportunity to improve the photocatalytic performance of perovskite-based composites using the energy band structure regulation strategy. Our findings may contribute to the design and development of highly efficient and stable perovskite-based photocatalysts for environmental remediation and energy conversion.

Excessive carbon dioxide (CO₂) emissions from flue gases intensify the greenhouse effect. Exploring porous adsorbents with high CO₂/N₂ selectivity is of great significance to reducing the CO₂ content in flue gases. Herein, we report a novel PtS-type metal-organic framework (MOFs), termed ZSTU-21, with narrow pore size and excellent CO₂/N₂ separation performance with dual open copper sites. At 298 K, ZSTU-21 exhibits a CO₂ uptake capacity of 62 cm³ g⁻¹ and a high selectivity of 105 for CO₂/N₂ (CO₂/N₂ = 15/85, v/v). Multicomponent adsorption breakthrough experiments further verified the superior performance of ZSTU-21 MOF in CO₂/N₂ separation. Moreover, the synthesis of ZSTU-21 MOF can be carried out under mild experimental conditions at room temperature, making the process simple and cost-effective, thus laying a solid foundation for its widespread application in CO₂/N₂ separation.

The growing demand for high-capacity and energy-dense lithium-ion batteries has driven the increase of nickel content in commercially available cathodes. However, during deep charging (delithiation), these Ni-rich cathodes experience a detrimental phase transformation and a sudden, significant decrease in lattice volume. This lattice collapse is considered the primary culprit behind the limitations in the cathode's electrochemical performance. Notably, the exact cause-and-effect relationship between the phase change and the collapse remains unclear. In the present study, the effect of the site of substitution on the performance of the LiNiO₂ cathode has been investigated by adopting tungsten as a dopant. To gain deeper insights into this connection within Ni-rich LiNiO₂, the contraction of the c-axis and the change in the a-axis during the delithiation have been investigated using ab initio density functional theory. Findings reveal that the free energy difference between the suspected phases in Ni-rich LiNiO2 is minimal at room temperature, facilitating the transition from the H2 to the H3 phase. This transition appears to be driven by the movement (gliding) of the NiO₂ layer towards the adjacent Li layer. The findings of the present study indicate that among two different configurations due to different sites of substitution, the WLNO-2 configuration suppresses H2 –H3 phase conversion to a greater extent by hindering the gliding of the NiO₂ layer toward the Li layer. Furthermore, a reduction in the collapse of the c-axis lattice during deep de-lithiation for the WLNO-2 configuration has been observed. This reduced collapse is primarily attributed to the altered charge distribution within oxygen atoms and the weakened screening effect from lithium ions.

In this study, a series of π-complexed CO adsorbents of xCu@MIL-101(Fe) were successfully prepared by hydrothermal and low-temperature reduction methods, which the objective was to overcoming the difficulties of stable and highly dispersed Cu⁺ loading. At the same time, the physical and chemical properties of the adsorbents were deeply analyzed using various characterization techniques, and the effects of different metal sites on CO adsorption were explored using molecular dynamics simulations. The results demonstrated that incorporating Cu⁺ augmented the adsorbent's thermal stability and enhanced the CO adsorption performance through competitive coordination. Notably, the CO adsorption reached a maximum of 2.66 mmol/g when the Cu loading reached 20 wt%. This study presents a novel approach for developing efficient, stable, and cost-effective Cu⁺ π-complexed CO adsorbents.