Large Interlayer Distance Research Articles

Half-metallic behavior and anisotropy of two-dimensional MoSi2N4/ScSi2N4 heterojunction

Heterojunctions formed by stacking different two-dimensional monolayer materials typically have tunable electronic properties, which will greatly broaden the application prospects of 2D materials in electron devices. In this paper, the structures, electron properties, and anisotropy of MoSi2N4/ScSi2N4 heterojunctions formed by stacking MoSi2N4 monolayer with semiconductor properties and ScSi2N4 monolayer with half-metallic properties have been systematically studied. The results show that Type-Ⅰ configuration has the most stable structure in terms of total energy, binding energy, phonon spectrum and molecular dynamics among the three configurations formed by MoSi2N4/ScSi2N4 heterojunctions. The MoSi2N4/ScSi2N4 heterojunction has robust half-metallic behavior and tensile anisotropy at equilibrium. At the same time, MoSi2N4/ScSi2N4 heterojunction can still maintain stable ferromagnetic and half-metallic properties under large interlayer distance changes. Studies of magnetic anisotropy show that the direction of hard axis for MoSi2N4/ScSi2N4 heterojunction is perpendicular to the 2D layer plane. The tunable properties of MoSi2N4/ScSi2N4 heterojunction provides promising exploration for novel 2D materials.

Template-directed strategy synthesis of CoNi-layered double hydroxide nanosheet coated with polypyrrole for enhanced capacitive deionization

Recently, faradic material layered double hydroxide (LDH) has been widely used as an anode for capacitive desalination (CDI), due to its reversible ion insertion/deintercalation process and high anion storage capacity. Unfortunately, the issues of poor conductivity and self-stacking of LDH limit its application in the CDI. Herein, CoNi-LDH coated with polypyrrole (PPy) was meticulously designed and synthesized PPy@CoNi-LDH nanohybrids using ZIF-67 as the precursor by template-directed strategy and in-situ polymerization. The CoNi-LDH has large interlayer distance of 0.91 nm, which is beneficial for ion insertion. Introduced PPy conductive layer improved the interface transfer rate of charges and increased the ion storage capacity of composite. The experimental test results indicate that PPy@CoNi-LDH1:1 electrode has a higher specific capacitance of 223.1F g−1 and lower resistivity of 62.33 Ω·cm compared to CoNi-LDH electrode (35.2F g−1 and 3.39 × 104 Ω·cm). Obtained PPy@CoNi-LDH1:1 also has abundant mesoporous and excellent hydrophilicity, which can promote ions transfer. Meanwhile, the specific surface area of PPy@CoNi-LDH1:1 with the coating structure is 1.78 times that of CoNi-LDH, effectively suppressing the self-stacking of CoNi-LDH and exposing more active sites. When employed PPy@CoNi-LDH1:1 as an anode and the activated carbon as a cathode, the PPy@CoNi-LDH1:1//AC cell exhibited a high Cl− removal capacity (60.20 mg g−1), a swift Cl− removal rate (11.45 mg g−1 min−1) and good cycling stability (the retention rate is 89.67 % after 50 cycles) in NaCl solution of 500 mg L−1 and 1.4 V applied voltage. Additionally, the adsorption mechanism indicated that surface charge attraction, ligand exchange, and ion insertion jointly promote the Cl− removal. This study provides a feasible solution about successful design of high adsorption capacity anode materials for CDI.

Phase Engineering of Two-Dimensional WS2 Nanostructures for Superior Hybrid Supercapacitors

Two-dimensional (2D) tungsten sulfide (WS2) has recently emerged as a nontrivial material for electrochemical applications; however, the boundaries associated with its 1T (instability) and 2H (low electrical conductivity) phases limit its electrochemical parameters. In this work, this issue is addressed using an exclusive chemical approach to evolve a dual-phase 1T-2H WS2 heterostructure that combines two different 1T (trigonal) and 2H (hexagonal) phases directly on the current collector which demonstrated 2D transformable phase structure, large interlayer distance, and highly exposed edge active sites. A simple inert-atmosphere annealing approach under phosphorus vapors is designed to elicit a fractional phase conversion of WS2 from conventional 2H to the 1T phase, where phosphorus is accommodated in the WS2 interspace and lattice, resulting in interlayer expansion. Theoretical calculations confirmed that the 1T WS2 structure formed after phosphorus doping exhibits semimetallic feature with no band gap, thereby elucidating the high electrical conductivity. The presence of edge-enriched metallic phase and interlayer engineering of 1T-2H WS2 heterostructure validates the exceptional sodium (Na+) ion intercalation when tested in hybrid supercapacitor (HSCs) against Prussian blue analog (PBA) cathodes. As a result, the assembled HSC cell with a 1T-2H WS2 heterostructured anode and a CuFe-PBA cathode shows superior specific energy of 65.5 Wh kg-1 at a specific power of 784 W kg-1, and maintains 75% rate capability and 95.7%cycling stability over 10,000 cycles. This work paves a technique for engineering a simple phase transition of 2D materials and sheds light on the expansion of high-performance next-generation energy storage systems.

Bond-Engineered MoSe2 Nanosheets with Expanded Layers and an Enriched 1T Phase for Highly Efficient Na+ Storage.

MoSe2 has attracted significant interest for Na+ storage due to its large interlayer distance, favorable band gap structure, and satisfying theoretical specific capacity. Nevertheless, the poor conductivity and large volume stress/strain always lead to poor cycle stability and limited rate capability. Herein, the P-Se bond and phase engineering strategies are proposed to enhance the stability of MoSe2 with the assistance of carbon compositing. Systematical characterizations confirm that the presence of a strong P-Se bond can ensure the good structural stability and enlarge the layer distance of the MoSe2 anode. 1T phase-enriched composition endows excellent conductivity and thus fast Na+ transport kinetics. Additionally, the combination of carbon contributes to the improvement of electron conductivity, further enhancing the reversible Na+ storage and cyclic stability. Consequently, an ultrastable reversible specific capacity of 347.8 mAh g-1 with a high retention ratio of 99.1% can be maintained after 1000 cycles at 1 A g-1, which is superior to the previous reports of MoSe2 nanosheets. The presented strategy is ingenious, offering an effective guidance to designing advanced electrodes to be applied in rechargeable batteries with a long lifespan.

Insight into the configuration of hard-soft carbon composites for high performance sodium-ion batteries

Hard carbon materials are considered suitable anode materials for sodium-ion batteries due to their abundant defect sites and large interlayer distance, which are respectively beneficial to the adsorption/desorption and insertion/extraction behaviors of Na+ during the electrochemical process. However, the poor electrical conductivity resulting from the intrinsic short-range ordered structure in the carbon skeleton and limited active sites significantly hinders their electrochemical performance. Herein, hard and soft carbon composites with various configurations are developed using a layer-by-layer coating method with SiO2 nanospheres as templates. These composites, including the hard carbon coated soft carbon composite structure (SC@HC), soft carbon coated hard carbon composite structure (HC@SC), and uniformly mixed soft and hard carbon composites (HSC), are prepared through confined-carbonization under the outermost SiO2 layer. The resulting hollow nanospheres possess ultra-small diameters (approximately 50 nm), ultra-thin wall thicknesses (5-6 nm), and different hard/soft carbon layer arrangements. Evaluation of sodium storage properties showed that the combination of soft and hard carbon outperformed pure soft or hard carbon, with HC@SC configuration offering materials with larger interlayer spacing, higher defect concentration, and a more complete conductive network. This enhances sodium storage capacity (293 mAh g-1@1 A g-1) and rate performance (242 mAh g-1@5 A g-1). The findings of this study present a novel approach to designing soft and hard carbon composites for high-performance sodium-ion batteries.

Polyaniline modified exfoliated graphene aerogel as high-performance anion-capture electrode for hybrid capacitive deionization

The synergistic effect between polyaniline (PANI) and graphene nanosheets significantly enhances the monolithic capacitance and cycling stability, making it an attractive choice for use as an anode material in capacitive deionization (CDI). However, traditional preparation processes are usually complex and time-consuming. Herein, we proposed a simplified solid-phase strategy by using air-plasma technique to fabricate 3D puffy graphene aerogel supported PANI (PANI@PG) nanocomposites within 1 s. In this material, elongated dumbbell-shaped PANI particles with diameters of 30–60 nm were firmly anchored and highly dispersed on graphene sheets, meanwhile, the exfoliated graphene sheets with a large interlayer distance of 0.4 nm were well interconnected. It was demonstrated that as prepared PANI@PG is characteristic of 2–50 nm mesopores, which both ensures a sufficient exposure of PANI active sites to electrolyte and favors the Cl− diffusion-intercalation process. The freestanding PANI@PG electrode exhibited excellent figure-of-merits of the salt adsorption capacity (43.5 mg g−1), charge efficiency (88.6 %), and cycling stability (retention of 77.1 % after 40 cycles). This work paves a new way for constructing 3D conducting polymer/graphene nanocomposites with promising applications in CDI and beyond.

Exciton-Driven and Layer-Independent Linear and Nonlinear Optical Properties in NbOCl2.

We investigate the electronic structure and linear and nonlinear [second-harmonic generation (SHG)] spectra of the NbOCl2 monolayer, bilayer, and bulk by using a real-time first-principles approach based on many-body theory. First, the interlayer couplings between NbOCl2 layers are very weak, due to the relatively large interlayer distance, saturation of the p orbital of Cl atoms, and high degree of localization of charge density around the Nb atom for both the lowest conduction band and the highest valence band. Second, the quasiparticle gaps and exciton binding energy for the three systems show layer-dependent features and decrease with an increase in layer thickness. Most importantly, the linear and SHG spectra of the NbOCl2 monolayer, bilayer, and bulk are dominated by strong excitonic resonances and exhibit layer-independent features due to the weak interlayer couplings. Our findings demonstrate that excitonic effects should be included in studying the optical properties of not only two-dimensional materials but also layered bulk materials with weak interlayer couplings.

Hybrid bilayered vanadium oxide electrodes with large and tunable interlayer distances in lithium-ion batteries

The interlayer distances in layered electrode materials, influenced by the chemical composition of the confined interlayer regions, have a significant impact on their electrochemical performance. Chemical preintercalation of inorganic metal ions affects the interlayer spacing, yet expansion is limited by the hydrated ion radii. Herein, we demonstrate that using varying concentrations of decyltrimethylammonium (DTA+) and cetyltrimethylammonium (CTA+) cations in chemical preintercalation synthesis followed by hydrothermal treatment, the interlayer distance of hybrid bilayered vanadium oxides (BVOs) can be tuned between 11.1 Å and 35.6 Å. Our analyses reveal that these variations in interlayer spacing are due to different amounts of structural water and alkylammonium cations confined within the interlayer regions. Increased concentrations of alkylammonium cations not only expand the interlayer spacing but also induce local bending and disordering of the V-O bilayers. Electrochemical cycling of hybrid BVO electrodes in non-aqueous lithium-ion cells show that specific capacities decrease as interlayer regions expand, suggesting that the densely packed alkylammonium cations obstruct intercalation sites and hinder Li+ ion transport. Furthermore, we found that greater layer separation facilitates the dissolution of active material into the electrolyte, resulting in rapid capacity decay during extended cycling. This study emphasizes that layered electrode materials require both spacious interlayer regions as well as high structural and chemical stabilities, providing guidelines for structural engineering of organic–inorganic hybrids.

Poly(dicarbon monofluoride) (C2F)n bridges the neutron reflectivity gap

Graphites covalently intercalated with fluorine to form (C2F)n structural type compounds shows a dramatic increase of the interlayer distance up to by a factor of almost 3 to reach ∼9 Å. Such graphite fluoride compounds containing only carbon and fluorine offer the rare opportunity to bridge the so-called gap in the reflectivity of neutron reflectors. Slow neutron reflectors are of great interest in designing neutron sources as well as in fundamental and applied science; they require synthesizing high thermal and chemical compound stability graphite fluorides. In this work, a new strategy is proposed for synthesizing (C2F)n compounds in a well-controlled method. Our results show that the outcome (C2F)n has a covalent character with only sp3 hybridized carbon atoms. Moreover, C–F bonds in the fluorocarbon sheets and CF2 groups on the sheet edges lead to the desired stability and hydrophobic character. A dedicated home-made neutron diffractometer was built for measurements of double-differential neutron cross sections of crystals with specific large interlayer distances found in (C2F)n compounds. We demonstrate that the synthesized fluorine intercalated graphites developed effectively cover the gap in the reflectivity for the new generation of neutron reflectors.

Modulating the graphitic domains of hard carbons via tuning resin crosslinking degree to achieve high rate and stable sodium storage

Sodium-ion batteries (SIBs) are regarded as an outstanding alternative to lithium-ion batteries (LIBs) due to abundant sodium sources and their similar chemistry. As a most promising anode of SIBs, hard carbons (HCs) receive extensive attention because of their low potential and low cost, but their rational design for commercial SIBs is restricted by their variable and complicated microstructure, which is analogous to that of graphite in LIBs. Herein, a series of controllable HC materials derived from 3-aminophenol formaldehyde resin (AFR) were designed and fabricated. We discover that the optimized HC features expanded graphite regions, highly developed nanopores, and reduced defect content, contributing to the enhanced Na+ storage. This optimization is achieved by adjusting the resin crosslinking degree of the precursor. Specifically, a resin precursor with a higher crosslinking degree can produce HC with a larger interlayer distance, relatively higher crystallinity, and a lower specific surface area. Encouragingly, the as-optimized AFR-HC electrode manifests superior electrochemical performance in the aspect of high capacity (383 mAh·g-1 at 0.05 A·g-1), better rate capability (140 mAh·g-1 at 20 A·g-1), and high initial coulombic efficiency (82%) than other contrast samples. Moreover, the as-constructed full cell coupled with a Na3V2(PO4)3 cathode shows an energy density of 250 Wh·kg-1. Together with the simple synthesis, cost-efficiency of the precursors and superior electrochemical performance, AFR-HCs are promising for the commercial application.

Cobalt doped K-birnessite as ultrastable cathode for aqueous calcium-ion batteries

Aqueous Ca ion batteries (ACIBs) are one of the emerging energy-storage technologies due to their low costs and low polarization strength. Birnessite-MnO2 is one kind of promising cathode because of its large interlayer distance for facile Ca2+ ion intercalation and high theoretical specific capacity (241 mAh g−1), but the inferior cycling performance significantly limits its application in ACIBs. Herein, 2% Co-doped K-birnessite K0.11Co0.02Mn0.98O2·1.4H2O (CB-2) with superior structural stability is reported for the first time. The Co-doped K-birnessite exhibits enhanced conductivity and capacitance ability. Moreover, after Co doping, the Mn–O ionic bond is shortened and the banding energy is reduced, which effectively inhibits the Jahn-Taller effect and improves the thermodynamic stability. More interestingly, we find that Ca2+ can restrain the irreversible transition of birnessite from layered to spinel. CB-2 cathode delivers an excellent rate performance of 181.2 mAh g−1 at 200 mA g−1 and structural stability of 1000 cycles at 2 A g−1 with 90.4% capacity retention. Finally, a stable ACIB is constructed by using the CB-2 cathode and polyimide anode, which shows a decent specific capacity of 51.9 mAh g−1 at 200 mA g−1 and superior cycling stability. This demonstrates effective foreign metal ion doping for K-birnessite to achieve superior Ca2+ storage in aqueous batteries.

Synergistic Modulating Interlayer Space and Electron-Transfer of Covalent Organic Frameworks for Oxygen Reduction Reaction.

Covalent organic frameworks (COFs) are an ideal template to construct high-efficiency catalysts for oxygen reduction reaction (ORR) due to their predictable properties. However, the closely parallel-stacking manner and lacking intramolecular electron transfer ability of COFs limit atomic utilization efficiency and intrinsic activity. Herein, COFs are constructed with large interlayer distances and enhanced electronic transfer ability by side-chain functionalization. Long chains with electron-donating features not only enlarge interlayer distance, but also narrow the bandgap. The resulting DPPS-COF displays higher electrochemical surface areas to provide more exposed active sites, despite <1/10 surface areas. DPPS-COF exhibits excellent electrocatalytic ORR activity with half-wave potential of 0.85V, which is 30 and 60mV positive than those of Pt/C and DPP-COF, and is the record among the reported COFs. DPPS-COF is employed as cathode electrocatalyst for zinc-air battery with a maximum power density of 185.2mW cm-2, which is superior to Pt/C. Theoretical calculation further reveals that longer electronic-donating chains not only facilitate the formation of intermediate OOH* from O2, but also promote intermediates desorption , and thus leading to higher activity.

Hydrothermal synthesis of NiO nanoparticles decorated hierarchical MnO2 nanowire for supercapacitor electrode with improved electrochemical performance

In this work, MnO2/NiO nanocomposite electrode materials have been synthesized by a cost-effective hydrothermal method. The effect of the concentrations (0, 1, 3, 5, and 7 wt%) of NiO nanoparticles on the surface morphology, structural properties, and electrochemical performance of the nanocomposites was characterized by different characterization techniques. The scanning electron micrographs (SEM) reveal that the as-prepared NiO nanoparticles are well connected and stuck with the MnO2 nanowires. The transmission electron microscopy (TEM) analysis showed an increase in the interplanar spacing due to the incorporation of NiO nanoparticles. The different structural parameters of MnO2/NiO nanocomposites were also found to vary with the concentration of NiO. The MnO2/NiO nanocomposites provide an improved electrochemical performance together with a specific capacitance as high as 343 F/g at 1.25 A/g current density. The electrochemical spectroscopic analysis revealed a reduction in charge transfer resistance due to the introduction of NiO, indicating a rapid carrier transportation between the materials interface. The improved electrochemical performance of MnO2/NiO can be attributed to good interfacial interaction, a large interlayer distance, and low charge transfer resistance. The unique features of MnO2/NiO and the cost-effective hydrothermal method will open up a new route for the fabrication of a promising supercapacitor electrode.

Molecular Intercalation Enables Phase Transition of MoSe2 for Durable Na-Ion Storage.

1T-MoSe2 is recognized as a promising anode material for sodium-ion batteries, thanks to its excellent electrical conductivity and large interlayer distance. However, its inherent thermodynamic instability often presents unparalleled challenges in phase control and stabilization. Here, a molecular intercalation strategy is developed to synthesize thermally stable 1T-rich MoSe2, covalently bonded to an intercalated carbon layer (1TR/2H-MoSe2@C). Density functional theory calculations uncover that the introduced ethylene glycol molecules not only serve as electron donors, inducing a reorganization of Mo 4d orbitals, but also as sacrificial guest materials that generate a conductive carbon layer. Furthermore, the C─Se/C─O─Mo bonds encourage strong interfacial electronic coupling, and the carbon layer prevents the restacking of MoSe2, regulating the maximum 1T phase to an impressive 80.3%. Consequently, the 1TR/2H-MoSe2@C exhibits an extraordinary rate capacity of 326mAhg-1 at 5Ag-1 and maintains a long-term cycle stability up to 1500 cycles, with a capacity of 365mAhg-1 at 2Ag-1. Additionally, the full cell delivers an appealing energy output of 194Whkg-1 at 208Wkg-1, with a capacity retention of 87.3% over 200 cycles. These findings contribute valuable insights toward the development of innovative transition metal dichalcogenides for next-generation energy storage technologies.

Two-dimensional architecture of N,S-codoped nanocarbon composites embedding few-layer MoS2 for efficient lithium storage.

The exploration and advancement of highly efficient anode materials for lithium-ion batteries (LIBs) are critical to meet the growing demands of the energy storage market. In this study, we present an easily scalable synthesis method for the one-pot formation of few-layer MoS2 nanosheets on a N,S dual-doped carbon monolith with a two-dimensional (2D) architecture, termed MoS2/NSCS. Systematic electrochemical measurements demonstrate that MoS2/NSCS, when employed as the anode material in LIBs, exhibits a high capacity of 681 mA h g-1 at 0.2 A g-1 even after 110 cycles. The exceptional electrochemical performance of MoS2/NSCS can be attributed to its unique porous 2D architecture. The few-layer MoS2 sheets with a large interlayer distance reduce ion diffusion pathways and enhance ion mobility rates. Additionally, the N,S-doped porous carbon matrix not only preserves structural integrity but also facilitates electronic conductivity. These combined factors contribute to the reversible electrochemical activities observed in MoS2/NSCS, highlighting its potential as a promising anode material for high-performance LIBs.

Highly dispersed ultrasmall BiOCl nanoclusters on graphene sheets as high-performance anion-capture electrode for hybrid capacitive deionization

BiOCl nanomaterials, because of their unique layered structure and fascinating physicochemical properties, have attracted enormous attention as anode material for capacitive deionization (CDI) towards the relief of global freshwater scarcity. However, the synthesis of ultrasmall BiOCl nanoclusters remains a considerable challenge, while the effect of crystalline surfaces on the Cl− ion intercalation/deintercalation has not yet been explored so far. In this work, highly dispersed BiOCl nanoclusters with the predominant exposure of (110) and (101) planes on graphene sheets (BiOCl@G) are fabricated by nanoconfinement and air-plasma strategy. On one hand, the ultrasmall BiOCl nanoclusters with size of ∼3 nm significantly increased their atomic utilization and electrochemical active sites, whereas the preferred crystalline planes of (110) and (101) favored the Cl− intercalation/deintercalation process within BiOCl. On the other hand, the dominant mesopores, along with a large interlayer distance (∼0.4 nm) between exfoliated graphene sheets, ensured the fast ion transport-adsorption at BiOCl/solution interface. With these novel structural features, the BiOCl@G possesses excellent figure-of-merits in terms of the Cl−-adsorption capacity (109.8 mg g−1), adsorption rate (0.110 mg g−1 s−1), energy consumption, and CDI cycling stability. These results provide new fundamental insights for developing high performance BiOCl-graphene nanocomposites used in CDI desalination and beyond.

THE INFLUENCE OF THE SYNHTETIC WAY OF LAYERED-TYPE MANGANSESE DIOXIDE ON THE PROPERTIES OF CATHODE MATERIALS FOR AQUEOUS ZINC-ION BATTERIES

This research presents an analysis of physico-chemical, structural and electrochemical properties of cathode materials for aqueous zinc-ion batteries based on manganese dioxide with birnessite-type structure in dependence on the conditions of hydrothermal synthesis. The manganese oxides obtained are capable to the reversible zin ions intercalation into the crystal lattice because of large interlayer distances. They were considered two approaches of synthesis: a reaction between manganese sulfate and potassium permanganate at 160 °С (MnO2-I) and a hydrothermal treatment of potassium permanganate solution at 220 °С (MnO2-II). From the structural analysis it was shown that both methods allow obtaining the birnessite-type manganese dioxide. At the same time, electrochemical properties of cathodes obtained differ in the models of aqueous zinc-ion batteries. MnO2-II material demonstrate higher initial specific capacity (180 mAh∙g-1 at current density 0.3 A∙g-1) while its cyclic stability is on 40% lower than for MnO2-I material. This can be explained with higher surface area of the active material and lower crystallinity.

Inorganic salt-assisted hydrothermal synthesis of composite vanadium oxides for stabilization of aqueous zinc ion batteries with low current density cycling

Vanadium-based materials have been widely investigated as cathode materials for aqueous zinc-ion batteries because of their multiple valences, large interlayer spacing and open framework. However, their sluggish reaction kinetics, poor structural stability and cycling stability at low rates still limit their further development. At present, the improvement of vanadium-based materials mostly involves complex processes or expensive materials that are difficult to synthesize on a large scale. In this work, by introducing an inorganic salt (NH4)2HPO4 as an additive and adjusting the reaction temperature of hydrothermal synthesis, a composite vanadium oxide (NVO(210)-2P) with the coexistence of NH4V4O10 and V5O12·6H2O was successfully synthesized. Compared with the surfactant-assisted process, the inorganic salt-assisted hydrothermal synthesis has the advantages of being greener and more environmentally friendly. As a cathode material for aqueous zinc ion batteries, the obtained NVO(210)-2P shows excellent cycle stability at low current density (88.1 % retention over 250 cycles at 0.3 A/g and 80 % after 600 cycles at 0.5 A/g). The excellent electrochemical performance is attributed to the well-structured nanosheets synthesized using (NH4)2HPO4 as an additive. At the same time, the generated V5O12·6H2O provides a large interlayer distance, reduces the structural water molecules of electrostatic interaction and indirectly forms a heterogeneous layered structure with NH4V4O10, which reduces the distribution density of NH4+ and avoids irreversible deamination.

Frustrated magnetism of the spin-1 kagome antiferromagnet β-BaNi3(VO4)2(OH)2

We propose the newly synthesized β-BaNi3(VO4)2(OH)2 (space group: ) as a candidate for the spin-1 kagome Heisenberg antiferromagnet (KHA). The compound features a uniform kagome lattice of Ni2+ (S = 1) ions with a large interlayer distance. High-field measurements at low temperatures reveal a susceptibility local minimum at ∼9 T, resembling a 1/3 magnetization plateau as predicted by the pure S = 1 KHA model. Below ∼6 K, approximately 1% of the spins exhibit spin-glass order, which may be attributed to the nanocrystalline grain size of ∼50 nm. Despite the antiferromagnetic exchange coupling strength of ∼7 K, the majority of spins remain disordered down to ∼0.1 K as indicated by the observed power-law behaviors in magnetic specific heat . Our results demonstrate that the low-energy magnetic excitations in β-BaNi3(VO4)2(OH)2 are gapless, which contradicts the current theoretical expectations of the ideal model.

A handbook for graphitic carbon nitrides: revisiting the thermal synthesis and characterization towards experimental standardization

Graphitic carbon nitrides (g-C3N4s) have continued to attract attention as metal-free, low-cost semiconductor catalysts. Herein, a systematic synthesis and characterization of g-C3N4s prepared using four conventional precursors (urea (U), dicyandiamide (DCDA), semicarbazide hydrochloride (SC-HCl), and thiosemicarbazide (TSC)) and an unexplored one (thiosemicarbazide hydrochloride (TSC-HCl)) is presented. Equal synthesis conditions (e.g. heating and cooling rates, temperature, atmosphere, reactor type/volume etc) mitigated the experimental error, offering fair comparability for a library of g-C3N4s. The highest g-C3N4 amount per mole of the precursor was obtained for D-C3N4 (∼37.85 g), while the lowest was for S-C3N4 (∼0.78 g). HCl addition to TSC increased the g-C3N4 production yield (∼5-fold) and the oxygen content (T-C3N4 ∼ 3.17% versus TCl-C3N4 ∼ 3.80%); however, it had a negligible effect on the level of sulphur doping (T-C3N4 ∼ 0.52% versus TCl-C3N4 ∼ 0.45%). S-C3N4 was the darkest in color (reddish brown), and the band gap energies were S-C3N4(2.00 eV) < T-C3N4(2.74 eV) < TCl-C3N4(2.83 eV) ≤ D-C3N4(2.84 eV) < U-C3N4(2.97 eV). The experimentally derived conduction band position of S-C3N4(−0.01 eV) was closer to the Fermi energy level than the others, attributable to high oxygen atom doping (∼5.11%). S-C3N4 displayed the smallest crystallite size (∼3.599 nm by XRD) but the largest interlayer distance (∼0.3269 nm). Furthermore, BET surface areas were 138.52 (U-C3N4), 22.24 (D-C3N4), 18.63 (T-C3N4), 10.51 (TCl-C3N4), and 9.31 m2 g−1 (S-C3N4). For the first time, this comprehensive handbook gives a glimpse of a researcher planning g-C3N4-based research. It also introduces a novel oxygen-sulphur co-doped g-C3N4 (TCl-C3N4) as a new halogen-free catalyst with a relatively high production yield per mole of precursor (∼24.09 g).