Mixed alkali-ion transport and storage in atomic-disordered honeycomb layered NaKNi2TeO6

Layered Na2Ti3O7-supported Ru catalyst for ambient CO2 methanation

The methanation of CO2 offers a practical solution for storing renewable energy and mitigating global climate risks. However, the primary challenge lies in achieving efficient CH4 production at lower temperatures. Here, we report a layered Na2Ti3O7-supported Ru catalyst as a stabilizer of low-valence Ru that enables CO2 activation at low temperatures. This catalyst leads to a CH4 production rate of 33.6 and 139.1 mmol gcat-1 h-1 at 140 and 180 °C, respectively, with a gas hourly space velocity of 24,000 mL g-1 h-1 at ambient pressure (1 bar), significantly surpassing state-of-the-art catalysts performance. Moreover, the catalyst demonstrates robustness to on-off intermittency and 220-hour long-term stability tests, indicating its reliability under challenging conditions. The catalyst is also successfully synthesized at the gram scale and on a 3D-printed metal self-catalytic reactor by a facile ion-exchange method, confirming its excellent scalability. This study marks a significant step forward in the design of catalysts for the low temperature CO2 hydrogenation.

Theoretical prediction and shape-controlled synthesis of two-dimensional semiconductive Ni3TeO6

Current progress in two-dimensional (2D) materials explorations leads to constant specie enrichments of possible advanced materials down to two dimensions. The metal chalcogenide-based 2D materials are promising grounds where many adjacent territories are waiting to be explored. Here, a stable monolayer Ni3TeO6 (NTO) structure was computationally predicted and its stacked 2D nanosheets experimentally synthesized. Theoretical design undergoes featuring coordination of metalloid chalcogen, slicing the bulk structure, geometrical optimizations and stability study. The predicted layered NTO structure is realized in nanometer-thick nanosheets via a one-pot shape-controlled hydrothermal synthesis. Compared to the bulk, the 2D NTO own a lowered bandgap energy, more sensitive wavelength selectivity and an emerging photocatalytic hydrogen evolution ability under visible light. Beside a new 2D NTO with the optoelectrical and photocatalytic merits, its existing polar space group, structural specification, and design route are hoped to benefit 2D semiconductor innovations both in species enrichment and future applications.

Lithium Manganese Sulfates as a New Class of Supercapattery Materials at Elevated Temperatures

To make supercapattery devices feasible, there is an urgent need to find electrode materials that exhibit a hybrid mechanism of energy storage. Herein, we provide a first report on the capability of lithium manganese sulfates to be used as supercapattery materials at elevated temperatures. Two compositions are studied: monoclinic Li₂Mn(SO₄)₂ and orthorhombic Li₂Mn₂(SO₄)₃, which are prepared by a freeze-drying method followed by heat treatment at 500 °C. The electrochemical performance of sulfate electrodes is evaluated in lithium-ion cells using two types of electrolytes: conventional carbonate-based electrolytes and ionic liquid IL ones. The electrochemical measurements are carried out in the temperature range of 20-60 °C. The stability of sulfate electrodes after cycling is monitored by in-situ Raman spectroscopy and ex-situ XRD and TEM analysis. It is found that sulfate salts store Li⁺ by a hybrid mechanism that depends on the kind of electrolyte used and the recording temperature. Li₂Mn(SO₄)₂ outperforms Li₂Mn₂(SO₄)₃ and displays excellent electrochemical properties at elevated temperatures: at 60 °C, the energy density reaches 280 Wh/kg at a power density of 11,000 W/kg. During cell cycling, there is a transformation of the Li-rich salt, Li₂Mn(SO₄)₂, into a defective Li-poor one, Li₂Mn₂(SO₄)₃, which appears to be responsible for the improved storage properties. The data reveals that Li₂Mn(SO₄)₂ is a prospective candidate for supercapacitor electrode materials at elevated temperatures.

Recent Progress on Honeycomb Layered Oxides as a Durable Cathode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb-layered-oxides (HLOs) manifest outstanding structural stability, high redox potential, and long-life electrochemistry. Here, recent progress on HLOs as well as Na₃ Ni₂ SbO₆ and Na₃ Ni₂ BiO₆ as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state-of-the-art sodium-ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure-property relationship, and inspire more interest in high output voltage, long lifespan sodium-ion batteries.

Dual-Ion Intercalation Chemistry Enabling Hybrid Metal-Ion Batteries

To outline the role of dual-ion intercalation chemistry to reach sustainable energy storage, the present Review aimed to compare two types of batteries: widely accepted dual-ion batteries based on cationic and anionic co-intercalation versus newly emerged hybrid metal-ion batteries using the co-intercalation of cations only. Among different charge carrier cations, the focus was on the materials able to co-intercalate monovalent ions (such Li⁺ and Na⁺ , Li⁺ and K⁺ , Na⁺ and K⁺ , etc.) or couples of mono- and multivalent ions (Li⁺ and Mg²⁺ , Na⁺ and Mg²⁺ , Na⁺ and Zn²⁺ , H⁺ and Zn²⁺ , etc.). Furthermore, the Review was directed on co-intercalation materials composed of environmentally benign and low-cost transition metals (e. g., Mn, Fe, etc.). The effect of the electrolyte on the co-intercalation properties was also discussed. The summarized knowledge on dual-ion energy storage could stimulate further research so that the hybrid metal-ion batteries become feasible in near future.

Revealing the Elusive Structure and Reactivity of Iron Boride α-FeB

Crystal structures can strongly deviate from bulk states when confined into nanodomains. These deviations may deeply affect properties and reactivity and then call for a close examination. In this work, we address the case where extended crystal defects spread through a whole solid and then yield an aperiodic structure and specific reactivity. We focus on iron boride, α-FeB, whose structure has not been elucidated yet, thus hindering the understanding of its properties. We synthesize the two known phases, α-FeB and β-FeB, in molten salts at 600 and 1100 °C, respectively. The experimental X-ray diffraction (XRD) data cannot be satisfactorily accounted for by a periodic crystal structure. We then model the compound as a stochastic assembly of layers of two structure types. Refinement of the powder XRD pattern by considering the explicit scattering interference of the different layers allows quantitative evaluation of the size of these domains and of the stacking faults between them. We, therefore, demonstrate that α-FeB is an intergrowth of nanometer-thick slabs of two structure types, β-FeB and CrB-type structures, in similar proportions. We finally discuss the implications of this novel structure on the reactivity of the material and its ability to perform insertion reactions by comparing the reactivities of α-FeB and β-FeB as reagents in the synthesis of a model layered material: Fe₂AlB₂. Using synchrotron-based in situ X-ray diffraction, we elucidate the mechanisms of the formation of Fe₂AlB₂. We highlight the higher reactivity of the intergrowth α-FeB in agreement with structural relationships.

Honeycomb-Layered Oxides With Silver Atom Bilayers and Emergence of Non-Abelian SU(2) Interactions

Honeycomb-layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next-generation energy storage applications. Herein, global honeycomb-layered oxide compositions, Ag2 M2 TeO6 (M = Ni , Mg , etc $M = \rm Ni, Mg, etc$ .) exhibiting Ag $\rm Ag$ atom bilayers with sub-valent states within Ag-rich crystalline domains of Ag6 M2 TeO6 and Ag $\rm Ag$ -deficient domains ofAg 2 - x Ni 2 TeO 6 ${\rm Ag}_{2 - x}\rm Ni_2TeO_6$ (0 < x < 2 $0 < x < 2$ ). The Ag $\rm Ag$ -rich material characterized by aberration-corrected transmission electron microscopy reveals local atomic structural disorders characterized by aperiodic stacking and incoherency in the bilayer arrangement of Ag $\rm Ag$ atoms. Meanwhile, the global material not only displays high ionic conductivity but also manifests oxygen-hole electrochemistry during silver-ion extraction. Within the Ag $\rm Ag$ -rich domains, the bilayered structure, argentophilic interactions therein and the expected Ag $\rm Ag$ sub-valent states (1 / 2 + , 2 / 3 + $1/2+, 2/3+$ , etc.) are theoretically understood via spontaneous symmetry breaking of SU(2)× U(1) gauge symmetry interactions amongst 3 degenerate mass-less chiral fermion states, justified by electron occupancy of silver4 d z 2 $4d_{z^2}$ and 5s orbitals on a bifurcated honeycomb lattice. This implies that bilayered frameworks have research applications that go beyond the confines of energy storage.

The effect of vacancy defects on the electromechanical properties of monolayer NiTe2 from first principles calculations

The electromechanical properties of monolayer 1-T NiTe₂ under charge actuation were investigated using first-principles density functional theory (DFT) calculations. Monolayer 1-T NiTe₂ in its pristine form has a work area density per cycle of up to 5.38 MJ m^-3 nm upon charge injection and it can generate a strain and a stress of 1.51% and 0.96 N m^-1, respectively. We found that defects in the form of vacancies can be exploited to modulate the electromechanical properties of this material. The presence of Ni-vacancies can further enhance the generated stress by 22.5%. On the other hand, with Te-vacancies, it is possible to improve the work area density per cycle by at least 145% and also to enhance the induced strain from 1.51% to 2.92%. The effect of charge polarity on the contraction and expansion of monolayer 1T-NiTe₂ was investigated. Due to its excellent environmental stability and good electromechanical properties, monolayer NiTe₂ is considered to be a promising electrode material for electroactive polymer (EAP) based actuators.

Cationic vacancies as defects in honeycomb lattices with modular symmetries

Layered materials tend to exhibit intriguing crystalline symmetries and topological characteristics based on their two dimensional (2D) geometries and defects. We consider the diffusion dynamics of positively charged ions (cations) localized in honeycomb lattices within layered materials when an external electric field, non-trivial topologies, curvatures and cationic vacancies are present. The unit (primitive) cell of the honeycomb lattice is characterized by two generators, [Formula: see text] of modular symmetries in the special linear group with integer entries, corresponding to discrete re-scaling and rotations respectively. Moreover, applying a 2D conformal metric in an idealized model, we can consistently treat cationic vacancies as topological defects in an emergent manifold. The framework can be utilized to elucidate the molecular dynamics of the cations in exemplar honeycomb layered frameworks and the role of quantum geometry and topological defects not only in the diffusion process such as prediction of conductance peaks during cationic (de-)intercalation process, but also pseudo-spin and pseudo-magnetic field degrees of freedom on the cationic honeycomb lattice responsible for bilayers.

Stacking Versatility in Alkali-Mixed Honeycomb Layered NaKNi2TeO6

The reaction between P2-type honeycomb layered oxides Na₂Ni₂TeO₆ and K₂Ni₂TeO₆ enables the formation of NaKNi₂TeO₆. The compound is characterized by X-ray diffraction and ²³Na solid-state nuclear magnetic resonance spectroscopy, and the structure is discussed through density functional theory calculations. In addition to the honeycomb Ni/Te cationic ordering, NaKNi₂TeO₆ exhibits a unique example of alternation of sodium and potassium layers instead of a random alkali-mixed occupancy. Stacking fault simulations underline the impact of the successive position of the Ni/Te honeycomb layers and validate the presence of multiple stacking sequences within the powder material, in proportions that evolve with the synthesis conditions. In a broader context, this work contributes to a better understanding of the alkali-mixed layered compounds.