Multidimensional Evolution of Carbon Structures Underpinned by Temperature-Induced Intermediate of Chloride for Sodium-Ion Batteries

Different dimensions of carbon materials with various features have captured numerous interests due to their applications on the tremendous fields. Restricted by the raw materials and devices, the controlling of their morphology is a major challenge. Utilizing the catalytic features of the intermediates from the low-cost salts and polymerization of 0D carbon quantum dots (CQDs), 0D CQDs are expected to self-assemble into 1/2/3D carbon structures with the assistance of temperature-induced intermediates (e.g., ZnO, Ni, and Cu) from the salts (ZnCl2, NiCl2, and CuCl). The formation mechanisms are illustrated as follows: 1) the "orient induction" to evoke "vine style" growth mechanism of ZnO; 2) the "dissolution-precipitation" of Ni; and 3) the "surface adsorption self-limited" of Cu. Subsequently, the degree of graphitization, interlayer distance, and special surface area are investigated in detail. 1D structure from 700 °C as anode displays a high Na-storage capacity of 301.2 mAh g-1 at 0.1 A g-1 after 200 cycles and 107 mAh g-1 at 5.0 A g-1 after 5000 cycles. Quantitative kinetics analysis confirms the fundamentals of the enhanced rate capacity and the potential region of Na-insertion/extraction. This elaborate work opens up an avenue toward the design of carbon with multidimensions and in-depth understanding of their sodium-storage features.

The Concept of "Noble, Heteroatom-Doped Carbons," Their Directed Synthesis by Electronic Band Control of Carbonization, and Applications in Catalysis and Energy Materials

Carbonization of organic compounds with a highest occupied molecular orbital (HOMO) level more positive than 1.3 V practically automatically results in highly sp² -conjugated, heteroatom-doped carbons. Due to the stability of the starting compounds, carbon bond formation is restricted to result in morphologies with a surprisingly high local order which as such are noble, i.e., they are hard to oxidize and combust. The work function of electrons in these systems is so positive that the systems usually accept electrons, i.e., they oxidize other matter rather than being oxidized. Such noble, heteroatom-doped carbons have been proven to be efficient, metal-free electrocatalysts, but can be also beneficially used in the manufacturing of carbon nanomaterials for energy applications or as highly active, non-innocent catalytic supports.

Beyond the Compositional Threshold of Nanoparticle-Based Materials

The design of inorganic nanoparticles relies strongly on the knowledge from solid-state chemistry not only for characterization techniques, but also and primarily for choosing the systems that will yield the desired properties. The range of inorganic solids reported and studied as nanoparticles is however strikingly narrow when compared to the solid-state chemistry portfolio of bulk materials. Efforts to enlarge the collection of inorganic particles are becoming increasingly important for three reasons. First, they can yield materials more performing than current ones for a range of fields including biomedicine, optics, catalysis, and energy. Second, looking outside the box of common compositions is a way to target original properties or to discover genuinely new behaviors. The third reason lies in the path followed to reach these novel nano-objects: exploration and setup of new synthetic approaches. Indeed, willingness to access original nanoparticles faces a synthetic challenge: how to reach nanoparticles of solids that originally belong to the realm of solid-state chemistry and its typical protocols at high temperature? To answer this question, alternative reaction pathways must be sought, which may in turn provide tracks for new, untargeted materials. The corresponding strategies require limiting particle growth by confinement at high temperatures or by decreasing the synthesis temperature. Both approaches, especially the latter, provide a nice playground to discover metastable solids never reported before. The aim of this Account is to raise attention to the topic of the design of new inorganic nanoparticles. To do so, we take the perspective of our own work in the field, by first describing synthetic challenges and how they are addressed by current protocols. We then use our achievements to highlight the possibilities offered by new nanomaterials and to introduce synthetic approaches that are not in the focus of recent literature but hold, in our opinion, great promise. We will span methods of low temperature "chimie douce" aqueous synthesis coupled to microwave heating, sol-gel chemistry and processing coupled to solid state reactions, and then molten salt synthesis. These protocols pave the way to metastable low valence oxyhydroxides, vanadates, perovskite oxides, boron carbon nitrides, and metal borides, all obtained at the nanoscale with structural and morphological features differing from "usual" nanomaterials. These nano-objects show original properties, from sensing, thermoelectricity, charge and spin transports, photoluminescence, and catalysis, which require advanced characterization of surface states. We then identify future trends of synthetic methodologies that will merit further attention in this burgeoning field, by emphasizing the importance of unveiling reaction mechanisms and coupling experiments with modeling.

Mesoporous Hollow Ge Microspheres Prepared via Molten-Salt Metallothermic Reaction for High-Performance Li-Storage Anode

Generally, Ge-based anodes are prepared by metallothermic reduction of GeO₂ with Mg at 650 °C. Herein, a molten-salt system is developed a low-temperature metallothermic reduction of GeO₂ to prepare nanostructured Ge based anode materials. Typically, mesoporous hollow Ge microspheres are prepared by reduction of GeO₂ with metallic Mg in molten ZnCl₂ (mp 292) at 350 °C. Monodispersed Ge particles are synthesized through reduction of GeO₂ with Mg in molten AlCl₃ (mp 192 °C) at 250 °C. The meso-porous Ge anode delivers the reversible capacity of 1291 mA h g^-1 at 0.2 C after 150 cycles with a retention of 97.3%, 1217 mA h g^-1 at 0.8 C after 400 cycles with a retention of 91.9%, and superior rate capability with a capacity of 673 mA h g^-1 even at 10 C. Then, the reaction mechanism and full-cell performance of as-prepared Ge anodes are studied systemically.

Multifunctional 3D K2Ti6O13 nanobelt-built architectures towards wastewater remediation: selective adsorption, photodegradation, mechanism insight and photoelectrochemical investigation

Efficient wastewater remediation was achieved via initial selective adsorption and subsequent photodegradation using multifunctional 3D K₂Ti₆O₁₃ NAs with promising photoelectrochemical application.

High-capacitance Ti3C2TxMXene obtained by etching submicron Ti3AlC2grains grown in molten salt

The capacitance of small-sized Ti₃C₂T_xMXene particulates is more than twice that of the large ones.

Growth of {100}-faceted NaFeTiO4 crystals with a tunable aspect ratio from a NaCl–Na2SO4 binary flux

The controlled growth of NaFeTiO₄ crystals with needle and planar bar shapes from a NaCl–Na₂SO₄ binary flux with different compositions.

Facile synthesis of high-surface-area nanoporous carbon from biomass resources and its application in supercapacitors

It is critical for nanoporous carbons to have a large surface area, and low cost and be readily available for challenging energy and environmental issues. The pursuit of all three characteristics, particularly large surface area, is a formidable challenge because traditional methods to produce porous carbon materials with a high surface area are complicated and expensive, frequently resulting in pollution (commonly from the activation process). Here we report a facile method to synthesize nanoporous carbon materials with a high surface area of up to 1234 m² g⁻¹ and an average pore diameter of 0.88 nm through a simple carbonization procedure with carefully selected carbon precursors (biomass material) and carbonization conditions. It is the high surface area that leads to a high capacitance (up to 213 F g⁻¹ at 0.1 A g⁻¹) and a stable cycle performance (6.6% loss over 12 000 cycles) as shown in a three-electrode cell. Furthermore, the high capacitance (107 F g⁻¹ at 0.1 A g⁻¹) can be obtained in a supercapacitor device. This facile approach may open a door for the preparation of high surface area porous carbons for energy storage.

High-surface-area nanoporous carbon is obtained by direct pyrolysis of biomass resources without an activation process. An electrochemical test shows high capacitance.

In Situ Wrapping Si Nanoparticles with 2D Carbon Nanosheets as High-Areal-Capacity Anode for Lithium-Ion Batteries

Silicon (Si) has aroused great interest as the most attractive anode candidate for energy-dense lithium-ion batteries (LIBs) in the past decade because of its significantly high capacity and low discharge potential. However, the large volume change during cycling impedes its practical application, which is more serious in the case of high mass loading. Designing Si anode with high mass loading and high areal capacity by a simple, scalable, and environmentally friendly method is still a big challenge. Herein, we report in situ one-pot synthesis of Si/C composite, where Si nanoparticles are wrapped by graphene-like 2D carbon nanosheets. After 500 cycles at 420 mA g^-1, the Si/C anode displays a gravimetric capacity of 881 mAh g^-1 with 86.4% capacity being retained. More specially, a high areal capacity of 3.13 mAh cm^-2 at 5.00 mg cm^-2 after 100 cycles is achieved. This study demonstrates a novel route for the preparation of the Si/C composite with high material utilization and may expand the possibility of future design Si-based anode with high areal capacity for high energy LIBs.

Hydroxylated graphene-based flexible carbon film with ultrahigh electrical and thermal conductivity

Graphene-based films are widely used in the electronics industry. Here, surface hydroxylated graphene sheets (HGS) have been synthesized from natural graphite (NG) by a rapid and efficient molten hydroxide-assisted exfoliation technique. This method enables preparation of aqueous dispersible graphene sheets with a high dispersed concentration (∼10.0 mg ml^-1) and an extraordinary production yield (∼100%). The HGS dispersion was processed into graphene flexible film (HGCF) through fast filtration, annealing treatment and mechanical compression. The HGS endows graphene flexible film with a high electrical conductivity of 11.5 × 10⁴ S m^-1 and a superior thermal conductivity of 1842 W m^-1 K^-1. Simultaneously, the superflexible HGCF could endure 3000 repeated cycles of bending or folding. As a result, this graphene flexible film is expected to be integrated into electronic packaging and high-power electronics applications.

Low-Dimensional Nitridosilicates Grown from Ca/Li Flux: Void Metal Ca8In2SiN4 and Semiconductor Ca3SiN3H

Reactions of indium and silicon with lithium nitride in Ca/Li flux produce two new nitridosilicates: Ca₈In₂SiN₄ (orthorhombic, Ibam; a = 12.904(1) Å, b = 9.688(1) Å, c = 10.899(1) Å, Z = 4) and Ca₃SiN₃H (monoclinic, C2/c; a = 5.236(1) Å, b = 10.461(3) Å, c = 16.389(4) Å, β = 91.182(4)°, Z = 8). Ca₈In₂SiN₄ features isolated [SiN₄]^8- units and indium dimers surrounded by calcium atoms. Ca₃SiN₃H features infinite chains of corner-sharing SiN₄ tetrahedra and distorted edge-sharing H@Ca₆ octahedra. Optical properties and band structure calculations indicate that Ca₈In₂SiN₄ is a void metal with calcium and indium states at the Fermi level and Ca₃SiN₃H is a semiconductor with a band gap of 3.1 eV.

Panoramic Synthesis as an Effective Materials Discovery Tool: The System Cs/Sn/P/Se as a Test Case

The common approach to the synthesis of a new material involves reactions held at high temperatures under certain conditions such as heating in a robust vessel in the dark for a period until it is judged to have concluded. Analysis of the vessel contents afterward provides knowledge of the final products only. Intermediates that may form during the reaction process remain unknown. This lack of awareness of transient intermediates represents lost opportunities for discovering materials or understanding how the final products form. Here we present new results using an emerging in situ monitoring approach that shows high potential in discovering new compounds. In situ synchrotron X-ray diffraction studies were conducted in the Cs/Sn/P/Se system. Powder mixtures of Cs₂Se₂, Sn, and PSe₂ were heated to 650 °C and then cooled to room temperature while acquiring consecutive in situ synchrotron diffraction patterns from the beginning to the end of the reaction process. The diffraction data was translated into the relationship of phases present versus temperature. Seven known crystalline phases were observed to form on warming in the experiment: Sn, Cs₂Se₃, Cs₄Se₁₆, Cs₂Se₅, Cs₂Sn₂Se₆, Cs₄P₂Se₉, and Cs₂P₂Se₈. Six unknown phases were also detected; using the in situ synchrotron data as a guide three of them were isolated and characterized ex situ. These are Cs₄Sn(P₂Se₆)₂, α-Cs₂SnP₂Se₆, and Cs₄(Sn₃Se₈)[Sn(P₂Se₆)]₂. Cs₄(Sn₃Se₈)[Sn(P₂Se₆)]₂ is a two-dimensional compound that behaves as an n-type doped semiconductor below 50 K and acts more like a semimetal at higher temperatures. Because all crystalline phases are revealed during the reaction, we call this approach "panoramic synthesis".

Rapid mass production of two-dimensional metal oxides and hydroxides via the molten salts method

Because of their exotic electronic properties and abundant active sites, two-dimensional (2D) materials have potential in various fields. Pursuing a general synthesis methodology of 2D materials and advancing it from the laboratory to industry is of great importance. This type of method should be low cost, rapid and highly efficient. Here, we report the high-yield synthesis of 2D metal oxides and hydroxides via a molten salts method. We obtained a high-yield of 2D ion-intercalated metal oxides and hydroxides, such as cation-intercalated manganese oxides (Na_0.55Mn₂O₄·1.5H₂O and K_0.27MnO₂·0.54H₂O), cation-intercalated tungsten oxides (Li₂WO₄ and Na₂W₄O₁₃), and anion-intercalated metal hydroxides (Zn₅(OH)₈(NO₃)₂·2H₂O and Cu₂(OH)₃NO₃), with a large lateral size and nanometre thickness in a short time. Using 2D Na₂W₄O₁₃ as an electrode, a high performance electrochemical supercapacitor is achieved. We anticipate that our method will enable new path to the high-yield synthesis of 2D materials for applications in energy-related fields and beyond.

Reactive Hypersaline Route: One-Pot Synthesis of Porous Photoactive Nanocomposites

Herein, porous photoactive nanocomposites are prepared by a simple one-pot synthesis approach using a salt and aqueous media. Within this reactive hypersaline route, the salt not only serves in the structuring of the composite but also becomes an integral active part of it. Here, the addition of sodium thiocyanate to a titania precursor guides, on the one hand, the formation of needle-shaped nanoparticles and, on the other hand, forms yellow compound isoperthiocyanic acid, which is homogeneously incorporated into the porous nanocomposite. Compared to a pure titania reference, this material reveals a 7-fold-increased photodegradation rate of Rhodamine B as a model compound. This reveals the reactive hypersaline route to be a promising and facile synthesis route toward photoactive porous materials.

Synthesis of Pt3Y and Other Early-Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent

Early-late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt₃Y-targeted as a prototypical example of an early-late intermetallic-has been synthesized as nanoparticles approximately 5-20 nm in diameter via a solution process and characterized by XRD, TEM, EDS, and XPS. The key development is the use of a molten borohydride (MEt₃BH, M = Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of the two metals are used. Accordingly, no organic ligands are necessary, as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by the synthesis of other intermetallic phases such as Pt₃Sc, Pt₃Lu, Pt₂Na, and Au₂Y.

K-ion and Na-ion storage performances of Co3O4-Fe2O3 nanoparticle-decorated super P carbon black prepared by a ball milling process

The hybridisation of Co₃O₄ and Fe₂O₃ nanoparticles dispersed in a super P carbon matrix is proposed as a favourable approach to improve the electrochemical performance (reversible capacity, cycling stability and rate capability) of the metal oxide electrodes in metal-ion batteries. Hybrid Co₃O₄-Fe₂O₃/C is prepared by a simple, cheap and easily scalable molten salt method combined with ball-milling and used in sodium-ion and potassium-ion batteries for the first time. The electrode exhibits excellent cycling stability and superior rate capability in sodium-ion cells with a capacity recovery of 440 mA h g^-1 (93% retention) after 180 long-term cycles at 50-1000 mA g^-1 and back to 50 mA g^-1. In contrast, Co₃O₄-Fe₂O₃, Co₃O₄ and Fe₂O₃ electrodes display unsatisfactory electrochemical performance. The hybrid Co₃O₄-Fe₂O₃/C is also reactive with potassium and capable of delivering a reversible capacity of 220 mA h g^-1 at 50 mA g^-1 which is comparable with the most reported anode materials for potassium-ion batteries. The obtained results broaden the range of transition metal oxide-based hybrids as potential anodes for K-ion and Na-ion batteries, and suggest that further studies of these materials with potassium and sodium are worthwhile.

Fast and scalable synthesis of strontium niobates with controlled stoichiometry

An ionic liquid/dextran blend is used to synthesise strontium niobates with exceptional control over stoichiometry.

Bottom-up engineering of thermoelectric nanomaterials and devices from solution-processed nanoparticle building blocks

Nanoparticle-based bottom-up engineered nanomaterials are extremely appealing for the direct solid-state conversion between heat and electricity.

Synthesis of BaTaO2N oxynitride from Ba-rich oxide precursor for construction of visible-light-driven Z-scheme overall water splitting

A novel synthesis of BaTaO₂N photocatalyst with low defect density is introduced for promotion of overall water splitting performance.

Chlorine-Induced In Situ Regulation to Synthesize Graphene Frameworks with Large Specific Area for Excellent Supercapacitor Performance

Three-dimensional (3D) graphene frameworks are usually limited by a complicated preparation process and a low specific surface area. This paper presents a facile suitable approach to effectively synthesize 3D graphene frameworks (GFs) with large specific surface area (up to 1018 m(2) g(-1)) through quick thermal decomposition from sodium chloroacetate, which are considerably larger than those of sodium acetate reported in our recent study. The chlorine element in sodium chloroacetate may possess a strong capability to induce in situ activation and regulate graphene formation during pyrolysis in one step. These GFs can be applied as excellent electrode materials for supercapacitors and can achieve an enhanced supercapacitor performance with a specific capacitance of 266 F g(-1) at a current density of 0.5 A g(-1).

Eutectic Syntheses of Graphitic Carbon with High Pyrazinic Nitrogen Content

Mixtures of phenols/ketones and urea show eutectic behavior upon gentle heating. These mixtures possess liquid-crystalline-like phases that can be processed. The architecture of phenol/ketone acts as structure-donating motif, while urea serves as melting-point reduction agent. Condensation at elevated temperatures results in nitrogen-containing carbons with remarkably high nitrogen content of mainly pyrazinic nature.

The flux growth of single-crystalline CoTiO3 polyhedral particles and improved visible-light photocatalytic activity of heterostructured CoTiO3/g-C3N4 composites

Novel CoTiO₃/g-C₃N₄ heterostructures with improved photocatalytic activity were successfully synthesized by a facile in situ growth route with the flux-grown CoTiO₃ polyhedral crystals serving as an efficient visible-light sensitizer.

A Novel Mesoporous Single-Crystal-Like Bi2WO6 with Enhanced Photocatalytic Activity for Pollutants Degradation and Oxygen Production

The porous single-crystal-like micro/nanomaterials exhibited splendid intrinsic performance in photocatalysts, dye-sensitized solar cells, gas sensors, lithium cells, and many other application fields. Here, a novel mesoporous single-crystal-like Bi2WO6 tetragonal architecture was first achieved in the mixed molten salt system. Its crystal construction mechanism originated from the oriented attachment of nanosheet units accompanied by Ostwald ripening process. Additionally, the synergistic effect of mixed alkali metal nitrates and electrostatic attraction caused by internal electric field in crystal played a pivotal role in oriented attachment process of nanosheet units. The obtained sample displayed superior photocatalytic activity of both organic dye degradation and O2 evolution from water under visible light. We gained an insight into this unique architecture's impact on the physical properties, light absorption, photoelectricity, and luminescent decay, etc., that significantly influenced photocatalytic activity.

Topochemical molten salt synthesis for functional perovskite compounds

A topochemical molten salt synthesis (TMSS) method, which is rapid and a modification of the molten salt synthesis method (MSS), to facilitate crystal growth with improved phase-purity and particle homogeneity, is one of the strategic approaches aimed at a controllable morphology synthesis. The TMSS method is an environmentally friendly and mild way to prepare pure and controllable perovskites, which are famous functional materials, used as piezoelectrics, catalysts, ferroelectrics, multiferroics, and negative thermal expansion compounds, at a moderate reaction temperature in a short soaking time. This report reviews various TMSS reactions and their applications in fulfilling the demand for the tunable morphology of perovskite materials, such as one dimensional, two dimensional and three dimensional perovskites in molten salts, which mainly include: piezoelectrics, photocatalysts, negative thermal expansion matters and other functional perovskites. The double and layered perovskites obtained by TMSS methods are also discussed. We believe that a comprehensive understanding of the TMSS method for functional perovskites will definitely promote the development of a clean, efficient and tunable production process for advanced functional materials.

Anatase titania synthesised at low temperature: recent breakthroughs

To overcome the limitations of conventional techniques that employ high-temperature calcinations to prepare nanosized anatase titania (TiO2), and thus find effective methods for low-temperature methods to synthesise nanosized TiO2 with high catalytic activity, has been one of the most challenging aspects in the photocatalyst field. In this article, the recent progress in low-temperature synthesis of nanosized anatase TiO2 is reviewed. The advances in this field are discussed in the light of the progress in the development of suitable synthetic methods. Particular emphasis is placed on the special conditions and demands to prepare uniform and stable anatase nanostructures at low temperature. The principles, reactions, synthesising procedures as well as the advantages and disadvantages of reported methods are presented. Furthermore, to overcome the intrinsic shortcomings of pure nanosized TiO2 as photocatalyst, that is, the rather low quantum efficiency and the incapability of utilising visible light, this review is also extended to the technologies of preparing TiO2 composites such as ion-doping, rare metal deposit and composite semiconductors. Finally the developing trends and the potential focus of future research in this field are prospected.

Schiff-base polymer derived nitrogen-rich microporous carbon spheres synthesized by molten-salt route for high-performance supercapacitors

A molten-salt route and Schiff-base chemistry are combined to prepare high-capacitive nitrogen-rich microporous carbon spheres. The simple and environmentally friendly synthetic route holds great potential for industrial application.

Flux-mediated crystal growth of metal oxides: synthetic tunability of particle morphologies, sizes, and surface features for photocatalysis research

Flux crystal growth of mixed-metal oxide photocatalysts with (A) rod- and (B) platelet-shaped morphologies grown under varied flux conditions.

Controlled nitridation of tantalum (oxy)nitride nanoparticles towards optimized metal-support interactions with gold nanocatalysts

Optimized metal-support interactions were achieved on ionothermally prepared tantalum (oxy)nitrides with controlled nitridation, and the as-formed Auδ⁻ species on TaON is efficient for nitrobenzene hydrogenation.

Molten salt assisted synthesis of black titania hexagonal nanosheets with tuneable phase composition and morphology

A facile high yield molten salt route to fabricate black titania hexagonal nanosheets under atmospheric pressure and low temperature.