Salt Melt Synthesis Research Articles

Tailored anion radii of molten-salts systems toward graphite regeneration with excellent energy-storage properties

Graphite, as the typical non-renewable resource, low-cost recycling of graphite from spent lithium-ion batteries (LIBs) enjoys great significance in economic growth and resources reusing. However, the traditional regenerated manners still suffer from the incomplete repairing, especially the inferior isotropy. Herein, assisted by salt melt synthesis (SMS), the effect recycling process to repair spent graphite is successfully developed. Tailored by the melting-boiling points and ionic strength of molten salts, the as-regenerated graphite performed different repaired properties, including interlayer distance, grain size, and crystallinity, leading to a difference in electrochemical performance. As Li-storage anodes, the as-optimized sample displayed an attractive lithium-storage capability of 352 mAh g−1 after 200 loops at 1.0 C. Even at 5.0 C, it could exhibit about 175 mAh g−1. Simultaneously, supported by of detailed kinetic analysis, the evolutionary properties of molten liquid phase could improve interlayer isotropy, thereby enhancing rate performance. Moreover, for repairing spent graphite, the cost of the proposed process is 745.74 $ t−1, and the recycling profit for regenerating graphite is approximately 7200 $ t−1. Given this, this work was expected to offer the effective repairing manners of spent graphite, meanwhile demonstrating the feasibility about the molten salt approach.

Salt-Melt Synthesis of Poly Heptazine Imides with Enhanced Optical Absorption for Photocatalytic Hydrogen Production.

Broadening the visible light absorption range and accelerating the separation and migration process of charge carriers are effective ways to improve photocatalytic quantum efficiencies. In this study, we show that poly heptazine imides with enhanced optical absorption and promoted charge carrier separation and migration could be obtained by means of a rational design of the band structures and crystallinity of polymeric carbon nitride. Copolymerization of urea with monomers such as 2-aminothiophene-3-carbonitrile would first generate amorphous melon with enhanced optical absorption, while further ionothermal treatment of melon in eutectic salts would increase the polymerization degree and create condensed poly heptazine imides as final products. Accordingly, the optimized poly heptazine imide presents an apparent quantum yield of 12 % at 420 nm for photocatalytic hydrogen production.

In2O3 sensing electrode prepared by salt melt method for impedancemetric-type NH3 sensor

Salt melt synthesis is a kind of inorganic material synthesis method developed in modern times, which has certain potential advantages and development prospects. The sensing electrode (SE) material In2O3 was synthesized by the salt melt method. The composition and morphology of the synthesized products under different conditions were studied in detail by combining XRD, SEM and TEM characterization. The results show that the salt melt method can facilely synthesize high-purity In2O3 powder at a lower temperature, and its morphology changes regularly with the change of reaction conditions. The effects of synthesis times and temperatures on the gas-sensing performance of In2O3 were discussed. The sensor based on In2O3 (380 °C − 30 min)-SE exhibited superior gas-sensing performance in the range of NH3 concentration of 50–500 ppm. The NH3 response characteristics exhibited little effect at different relative humidity (RH) and oxygen partial pressure conditions. In addition, the sensor exhibited good repeatability and selectivity.

Controlling of Ni-Based Composites in Salt Melt Synthesis with High Sodium-Ion Storage Performance.

Owing to its fascinating properties (such as high theoretical specific capacity and considerable conductivity), nickel sulfide (NiS) was investigated comprehensively as an anode material in sodium-ion batteries. However, they still suffered from volume expansion and sluggish kinetics, resulting in serious cycle capabilities. Herein, through controlling the kind of molten salts (Na2SO4, NaCl, and Na2CO3) in salt melt synthesis (SMS), a series of NiS with an N, S-codoped carbon layer was successfully prepared, accompanied with different morphologies and structures (earthworm-like belts and triangular and spherical particles). Tailored by the ionic strength and viscosity of molten salts, the as-prepared samples displayed different crystallization behaviors, bringing about a difference in electrochemical performance. As earthworm-like NiS@C was explored as an anode material for SIBs, an initial capacity of 712.5 mAh g-1 at 0.5 A g-1 could be obtained, and it still kept 527.4 mAh g-1 after 100 cycles. Even at 2.0 A g-1, a capacity of 508.6 mAh g-1 could be achieved. Meanwhile, with the assistance of detailed kinetic analysis, the rapid diffusion behaviors of Na+ and redox reaction mechanisms of as-fabricated samples were proven for the enhanced electrochemical properties. Given this, this work is expected to provide a method for designing the morphology and structure of metal sulfides, while shedding light on the orientation of fabricating advanced electrode materials for SIBs.

Enhanced capacitive deionization boosted by Co and N co-doping in carbon materials

In this study, cobalt, nitrogen co-doped porous carbon materials (Co-N/CN) as effective electrode materials were synthesized via salt melt synthesis method for capacitive desalination (CDI). The as-synthetized materials possess suitable micro/mesoporous cross-linking structure, more structure defect and multi-function groups. The systematic investigations demonstrated that Co, N codoping can promote the electrochemical performance and CDI performance. By comparison with the single N doped sample, the Co-N/CN samples achieve higher specific capacitance, lower ion/electron transport resistance and larger deionization capacity. Such superior capacitive desalination performance can be contributed to the synergistic effect of doped Co and N, such as the generation of Co-N sites. Additionally, the optimum Co-N/CN electrode displays an outstanding desalination capacity of 58.82 mg NaCl g−1 (71.4 mg Cl g−1 of anode) at 1.4 V in a NaCl concentration of 824 mg L−1 and great cycling stability with no obvious degradation in charge storage during 100 charge/discharge cycles. Therefore, we believe that Co-N/CN electrode has great potential for CDI practical applications.

One-Step Low-Temperature Molten Salt Synthesis of Two-Dimensional Si@SiOx@C Hybrids for High-Performance Lithium-Ion Batteries.

Various strategies have been developed to mitigate the huge volume expansion of a silicon-based anode during the process of (de)lithiation and accelerate the transport rate of the ions/electrons for lithium-ion batteries (LIBs). Here, we report a one-step synthetic route through a low-temperature eutectic molten salt (LiCl-KCl, 352 °C) to fabricate two-dimensional (2D) silicon-carbon hybrids (Si@SiOx@MpC), in which the silicon nanoparticles (SiNPs) with an ultrathin SiOx layer are fully encapsulated by graphene-like carbon nanosheets derived from a low-cost mesophase pitch. The combination of an amorphous graphene-like carbon conductive matrix and a SiOx protective layer strongly promotes the electrical conductivity, structure stability, and reaction kinetics of the SiNPs. Consequently, the optimized Si@SiOx@MpC-2 anode delivers large reversible capacity (1239 mAh g-1 at 1.0 A g-1), superior rate performance (762 mAh g-1 at 8 A g-1), and long cycle life over 600 cycles (degradation rate of only 0.063% every cycle). When coupled with a homemade nano-LiFePO4 cathode in a full cell, it exhibits a promising energy density of 193.5 Wh kg-1 and decent cycling stability for 200 cycles at 1C. The methodology driven by salt melt synthesis paves a low-cost way toward simple fabrication and manipulation of silicon-carbon materials in liquid media.

Salt melt synthesis of Chlorella-derived nitrogen-doped porous carbon with atomically dispersed CoN4 sites for efficient oxygen reduction reaction

Carbon-supported single-atom catalysts (C-SACs) demonstrate great potential in various key electrochemical reactions. Nevertheless, the development of facile and economical strategies is highly appealing yet challenging given that the commonly used pyrolysis method has strict requirements on the structure and composition of precursors. Here, we demonstrate for the first time a facile and low-cost pyrolysis strategy assisted by molten salts at high temperature for preparing porous C-SACs with well-dispersed Co-N4 sites directly from a Chlorella precursor. Based on the X-ray absorption fine structure results and aberration-corrected scanning transmission electron microscopy images, we show that single atom Co-N4 moieties are anchored on a carbon matrix. A porous structure with a large specific surface area (2907 m2 g−1) and atomically dispersed active sites of Co provide the as-prepared Co-N/C-SAC with excellent electrocatalytic activity and stability for the ORR. The electrochemical measurements show that the half-wave potential and limited current density of this material are 0.83 V vs. RHE and 5.5 mA cm−2, respectively, which are comparable to those of commercial Pt/C.

Salt melt synthesis of curved nitrogen-doped carbon nanostructures: ORR kinetics boost

Implementing metal-free electrocatalysts for the oxygen reduction reaction (ORR) and revealing crucial chemical or topographical parameters driving their activity are vital for the development of power cells. The carbon-based catalysts are very often synthesized through carbonization of biopolymers, in particular, those one containing nitrogen groups such as chitosan. Unfortunately, the resulting carbonaceous materials usually lack specific porosity and exhibit low catalytic activity.Here, we demonstrate that pyrolysis of chitosan in a ZnCl2 melt assisted by the presence of LiCl results not only in a highly porous activated carbon material with a specific surface area of 1317.97 m2/g and the total nitrogen content of 6.5%, but also induces unexpected curvature in the grown graphitic layers. This is the first work that shows curved graphene layers obtained from a biopolymer precursor by its pyrolytic decomposition in the melted salt media.On the other hand, a carbonaceous material obtained from chitosan but without the salts has very low specific surface area of 7.8 m2/g, possesses no specific structural features, and contains 4.7% of nitrogen.The electrochemical studies show, that the former material is highly active towards four-electron pathway of the ORR in terms of an onset potential (0.89 V vs RHE) and the turnover frequency (TOFmax = 0.095 e site−1 s−1).We attribute this high catalytic performance to the presence of the pyridinic and pyrrolic sites in the structure. The ORR kinetics is probably further promoted by curvature in the graphitic layers.

Determination of Crystal Structure of Graphitic Carbon Nitride: Ab Initio Evolutionary Search and Experimental Validation

Although graphitic carbon nitride (g-C3N4) is a promising photofunctional material, its structure is poorly understood. Here, we present a systematic study of stable crystal structures of g-C3N4 by ab initio evolutionary searching. It was discovered that off-plane distortion of heptazine units is a characteristic of the most stable structure, which explains a known discrepancy between the lattice parameters determined by X-ray diffraction (XRD) patterns and the planar structures modeled in previous studies. A phase transition from a metastable phase to the global minimum phase provides a reasonable explanation for the observed red shift in photoabsorption edges upon high-temperature annealing. The recently suggested salt-melt synthesis for g-C3N4 is subject to the contamination of hydrogen, chlorine, and lithium according to our detailed analysis of the crystal structures of C6N9H3-Li3Cl and C6N9H3-LiCl in comparison with the measured XRD patterns of these samples. Finally, a viable synthesis pathway for ...

Efficiency of Ni Nanoparticles Supported on Hierarchical Porous Nitrogen-Doped Carbon for Hydrogenolysis of Kraft Lignin in Flow and Batch Systems

Ni nanoparticles supported on nitrogen-doped carbon (NDC) prepared via salt-melt synthesis with a hierarchical porosity were successfully applied as the catalyst for the degradation of Kraft lignin. It is shown that Ni-NDC is more efficient when compared to Ni nanoparticles deposited on an N-free carbon support, prepared with similar porosity features (Ni–C) and to Ni nanoparticles deposited on a commercial carbon (Ni-Cref). The efficiency of these materials was compared for reactions performed both in batch and flow reactors, highlighting the effect of the reactor setup on the stability of the recovered catalysts.

Facile Preparation of Nitrogen-doped Porous Carbons via Salt Melt Synthesis with Efficient Catalytic Desulfurization Performance

Facile Preparation of Nitrogen-doped Porous Carbons via Salt Melt Synthesis with Efficient Catalytic Desulfurization Performance

Development of nano electrodes for cell/tissue stimulation

Event Abstract Back to Event Development of nano electrodes for cell/tissue stimulation Tobias Weigel1, Jihyoung Choi1, Tobias Schmitz1, Maren Jannasch1, Sabine Gätzner1 and Jan Hansmann1 1 University Hospital of Wuerzburg, Tissue Engineering & Regenerative Medicine, Germany Introduction: A central challenge of current tissue electrodes is a high energy consumption caused by inefficient electrical stimulation of the objective cells. Leakage currents, the distance between electrode and target cells as well as the encapsulation of the electrode through the foreign body reaction (FBR) are reasons for this. In our study, nano structured electrodes are developed to optimize the energy transfer at the interface between electrode and cell/tissue. Therefore, conductive electrospun scaffolds with different dimensions and structures are generated, to identify an ideal electrode interaction with cells and tissue. Materials and Methods: The conductive nano fibers were generated by electrospinning of a polyacrylonitrile (PAN) solution with different fiber orientations, diameters and pores. Through an oxidation step and subsequent carbonization, the PAN fibers were converted to carbon fibers. Additionally the nano fibers are nano structured with graphene or other carbonaceous materials by salt melt synthesis (SMS). The properties of the fibers were characterized by SEM and Raman, as well as the electrical conductivity and impedance. Biocompatibility and cell interaction was investigated with human fibroblasts. The electrical stimulation characteristics were tested with cardio muscle stripes in a myograph integrated organ bath. Results: The carbon nano fibers for the cell test exhibited a diameter of about 140, 290 and 530 nm. While the 140 nm fibers are completely disorientated, the other fibers showed a preferred orientation. The conductivity of the fibers was approximately 150 S/cm. Carbonaceous functionalized fibers showed a doubled conductivity and increased tear strength. Contact angle measurements, impedance spectroscopy and protein adsorption assays demonstrated interaction of the nano fibers with the cell culture medium. Cell culture studies using human fibroblasts could demonstrate varying reactions to the different fiber morphologies. Furthermore the generated electrodes were instituted to simulate the energy consumption with human cardio muscle stripes. First results showed a comparable or lower energy expenditure of the nano fibers electrodes compared to commercial electrodes. Discussion: The electrical and mechanical improvement of the carbon fibers is achieved by wrapping and interconnecting with carbonaceous materials. Tests with fibroblasts showed an increased ingrowth into the fiber matrix with higher pore diameter. Additionally released cytokines are measured to compare the different nano fiber structures. Keywords: nanofiber, electric, biomedical application, bioinerface Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Biocompatibility of nanobiomaterials Citation: Weigel T, Choi J, Schmitz T, Jannasch M, Gätzner S and Hansmann J (2016). Development of nano electrodes for cell/tissue stimulation. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02212 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Tobias Weigel Jihyoung Choi Tobias Schmitz Maren Jannasch Sabine Gätzner Jan Hansmann Google Tobias Weigel Jihyoung Choi Tobias Schmitz Maren Jannasch Sabine Gätzner Jan Hansmann Google Scholar Tobias Weigel Jihyoung Choi Tobias Schmitz Maren Jannasch Sabine Gätzner Jan Hansmann PubMed Tobias Weigel Jihyoung Choi Tobias Schmitz Maren Jannasch Sabine Gätzner Jan Hansmann Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Highly Porous Materials as Tunable Electrocatalysts for the Hydrogen and Oxygen Evolution Reaction

The facile preparation of highly porous, manganese doped, sponge‐like nickel materials by salt melt synthesis embedded into nitrogen doped carbon for electrocatalytic applications is shown. The incorporation of manganese into the porous structure enhances the nickel catalyst's activity for the hydrogen evolution reaction in alkaline solution. The best catalyst demonstrates low onset overpotential (0.15 V) for the hydrogen evolution reaction along with high current densities at higher potentials. In addition, the possibility to alter the electrocatalytic properties of the materials from the hydrogen to oxygen evolution reaction by simple surface oxidation is shown. The surface area increases up to 1200 m2g−1 after mild oxidation accompanied by the formation of nickel oxide on the surface. A detailed analysis shows a synergetic effect of the oxide formation and the material's surface area on the catalytic performance in the oxygen evolution reaction. In addition, the synthesis of cobalt doped sponge‐like nickel materials is also delineated, demonstrating the generality of the synthesis. The facile salt melt synthesis of such highly porous metal based materials opens new possibilities for the fabrication of diverse electrode nanostructures for electrochemical applications.

ChemInform Abstract: Salt Melt Synthesis of Ceramics, Semiconductors and Carbon Nanostructures

AbstractReview: 201 refs.

Salt melt synthesis of ceramics, semiconductors and carbon nanostructures

Materials synthesis in the liquid phase, or wet-chemical synthesis, utilizes a solution medium in which the target materials are generated from a series of chemical and physical transformations. Although this route is central in organic chemistry, for materials synthesis the low operational temperature range of the solvent (usually below 200 °C, in extreme 350 °C) is a serious restriction. Here, salt melt synthesis (SMS) which employs a molten inorganic salt as the medium emerges as an important complementary route to conventional liquid phase synthesis. Depending on the nature of the salt, the operational temperature ranges from near 100 °C to over 1000 °C, thus allowing the access to a broad range of inorganic crystalline materials and carbons. The recent progress in SMS of inorganic materials, including oxide ceramic powders, semiconductors and carbon nanostructures, is reviewed here. We will introduce in general the range of accessible materials by SMS from oxides to non-oxides, and discuss in detail based on selected examples the mechanisms of structural evolution and the influence of synthetic conditions for certain materials. In the later sections we also present the recent developments in SMS for the synthesis of organic solids: covalent frameworks and polymeric semiconductors. Throughout this review, special emphasis is placed on materials with nanostructures generated by SMS, and the possible modulation of materials structures at the nanoscale in the salt melt. The review is finalized with the summary of the current achievements and problems, and suggestions for potential future directions in SMS.