Search

A combination of ionothermal synthesis and hot-injection techniques leads to novel nanocarbons made from organic solvents. Controlled addition of commonly used organic solvents into a hot ZnCl2 melt gives rise to spherical, sheetlike, and branched nanofibrous carbon nanoparticles with surprisingly high carbon efficiency. When heteroatom-containing solvents were used, the doping levels reach up to 14 wt. % nitrogen and 13 wt. % sulfur. Materials with high surface areas and large pore volumes of solvent carbons as high as 1666 m2 g−1 and 2.80 cm3 g−1 in addition to CO2 adsorption capacities of 4.13 mmol g−1 at 273 K and 1 bar can be obtained. The new method works not only for pure carbon materials, but was also extended for the synthesis of carbon/inorganic nanocomposites. ZnS@C, Ni@C, and Co@C were successfully prepared with this straightforward procedure. The obtained Ni@C nanocomposites perform well in the electrocatalytic water oxidation, comparable with commercial noble-metal catalysts. [ABSTRACT FROM AUTHOR]

The production of functional nanostructured materials starting from cheap natural precursors using environmentally friendly processes is a highly attractive subject in material chemistry today. Recently, much attention has been focused on the use of plant biomass to produce functional carbonaceous materials, encompassing economic, environmental and social issues. Besides the classical route to produce activated carbons from agricultural side products, the hydrothermal carbonization (HTC) process shows clear advantages in that it can generate a variety of cheap and sustainable carbonaceous materials with attractive nanostructure and functionalization patterns for a wide range of applications. In this tutorial reviewwe present the latest developments in this traditional but recently invigorated technique. It will be shown that HTC does not only access carbonaceous materials under comparatively mild hydrothermal conditions, but also replaces the more technical and structurally well-defined charring by a controlled chemical process. It will be shown that this makes it possible to tailor the final structure with the tools of colloid and polymer science, leading to very different morphologies with miscellaneous applications, including modern carbon nanocomposites and hybrids. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) converts wet biomass into hydrochar and a process liquid, but aromatic compounds in the products have been reported as a roadblock for soil applications as they can inhibit germination, plant growth, and soil microbial activity. Here, we compared HTC and hydrothermal humification (HTH) of cow manure digestate while varying the initial alkaline content by adding KOH. HTH converted 37.5 wt% of the feedstock to artificial humic acids (A-HAs) found in both solid and liquid, twice that of HTC. HTH reduced phenolic and furanic aromatic compounds by over 70% in solids and 90% in liquids. The A-HAs in HTH resemble natural humic acids (N-HA), based on FTIR, UV–vis spectra, and CHN and XRD analysis. The HTH liquid possesses 60% higher total organic carbon (TOC) than HTC. Although one-third of TOC can be precipitated as A-HA, a high TOC concentration remains in the liquid, which is shown to be mainly organic acids. Therefore, we also evaluated the HTC and HTH liquids for anaerobic biomethane production, and found that compared to the original cow manure digestate, the HTH liquids increased methane yield by 110.3 to 158.6%, a significant enhancement relative to the 17.2% increase seen with HTC liquid. The strong reduction in organic acids during biogas production from HTH liquid indicates the potential for converting soluble byproducts into methane, while maintaining high A-HAs levels in the solid product. Highlights: Hydrothermal humification of the digestate feedstock created about 37.5 wt% artificial humic acids in both solid and liquid phases. Increasing the alkaline content of the reaction media significantly decreased the aromatic content in the process liquid while increasing the concentration of organic acids and sugars. There was little to no gas production observed in the HTH process at higher alkaline contents, indicating carbon preservation in the liquid and solid phases. Anaerobic processing of the hydrothermal humification (HTH) process liquid resulted in a 158.6% increase in methane production compared to the primary biomass. The organic acid concentrations decreased after the anaerobic fermentation, while the main HTH product, artificial humic acids, remained nearly unchanged. [ABSTRACT FROM AUTHOR]

The chemistry of humic substances (HSs) occurs hidden from our sight, but is of key importance to agriculture and the environment, and nowadays even to medicine and technology. HSs are nowadays not only natural, but extracted and engineered, and in the past 20 years such products have been widely used in soil improvement and environment governance. In this review, we collate and summarize the applications and working principles of such HSs in agriculture and environmental ecology, mainly to elaborate the multiple roles of this functional polymer along with physical chemical quantification. Then several of the latest synthesis technologies, including hydrothermal humification technology (HTH), hydrothermal carbonization technology (HTC) and hydrogen peroxide oxidation technology (HOT) are presented, which were introduced to prepare artificial humic substances (A-HSs). The availability of reproducible and tunable synthetic A-HSs is a new chemical tool, and effects such as solubilization of insoluble phosphorus minerals, recovery of phosphorus, improvement of soil fertility for crop growth and reduction of toxicity of typical pollutants, can now be analyzed in detail and quantified. As a result, we can provide an effective chemical technology for utilizing biomass side products ("biowaste") to generate A-HSs of different types, thus realizing improvement in agricultural production and control of environmental pollution by the macro-synthesis of A-HSs-. [ABSTRACT FROM AUTHOR]

The synthesis of carbon nanoarchitectures from pre-organized precursor complexes with appropriate bonding patterns, here squaric acid and urea, is described. It is shown that depending on the precursor ratio, different crystal morphologies are formed, which can be transformed into nitrogen-containing carbons with either lamellar or hollow tube-like morphology. It is noted that despite the very different architecture, the composition of the final carbons is always close to a 'C2N' stoichiometry. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

One of the greatest challenges in modern chemical processing is to achieve enantiospecific control in chemical reactions using chiral media such as chiral mesoporous materials. Herein, we describe a novel and effective synthetic pathway for the preparation of enantioselective nanoporous carbon, based on chiral ionic liquids (CILs). CILs of phenylalanine (CIL(Phe)) are used as precursors for the carbonization of chiral mesoporous carbon. We employ circular dichroism spectroscopy, isothermal titration calorimetry (ITC), and chronoamperometry in order to demonstrate the chiral nature of the mesoporous carbon. The approach presented in this paper is highly significant for the development of a new type of chiral porous materials for enantioselective chemistry. In addition, it contributes significantly to our understanding of the structure and nature of chiral nanoporous materials and surfaces. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis of nitrogen-doped monolithic carbon aerogels derived from sustainable precursors (i.e.d-glucose and ovalbumin) is presented. The protein acts as nitrogen donor and surface stabilizing agent in this saccharide hydrothermal carbonization, to generate high surface area aerogels (>240 m2g−1) composed of functional continuous large diameter mesopores with excellent hierarchical transport architecture. Post-carbonization treatment controls surface chemistry (e.g.C or N condensation), facilitating tuneable physicochemical properties on a unique continuous 3D carbonaceous pore structure. This highly flexible synthesis lays the basis for the development of a new generation of sustainable (heteroatom-doped) porous carbon aerogels suitable for a range of high value applications. [ABSTRACT FROM AUTHOR]

Mesoporous nitrogen-doped carbon materials with high surface areas up to 1500 m² g-1 were conveniently made by the carbonization of nucleobases dissolved in an all-organic ionic liquid (1-ethyl-3-methylimidazolium dicyanamide). Using hard templating with silica nanoparticles, this process yields high- surface-area nitrogen-doped carbon, materials with nitrogen contents as high as 12 wt %, narrow mesopore size distribution of ca. 12 nm diameter, and local graphitic carbon structure. It is demonstrated that the resulting nitrogen-doped carbons show very high catalytic activity, even in the metal-free case in the oxygen reduction reaction (ORR) for fuel cells. Specifically, the as-prepared materials exhibit a low onset voltage for OAR in alkaline medium and a high methanol tolerance, compared with those of commercial 20 wt % Pt/C catalyst. We regard this as a first step toward an all-sustainable fuel cell, avoiding noble metals. [ABSTRACT FROM AUTHOR]

A facile and sustainable synthesis of hollow carbonaceous nanospheres is presented, offering a scalable and multifunctional route to the generation of useful nanocontainers, which critically possess the stability not offered by polymeric equivalents and functionality not afforded by other nanocarbons. Carbonization temperature provides a subtle but elegant mechanism to control structure and thereby hydrophobicity, nanopartitioning, and permeation between the inner and outer space. [ABSTRACT FROM AUTHOR]

Abstract: We describe the production and catalytic application of highly functionalized mesoporous carbonaceous materials, obtained via a one step green and cheap process relying on the hydrothermal carbonization of carbohydrates (e.g. glucose) in the presence of functional organic monomers (e.g. vinyl imidazole). The resulting materials could be further functionalized to feature imidazolium bromides on their surface and be used for various transesterification, Knoevenagel and Aldol reactions. [Copyright &y& Elsevier]

This paper reports on the one-pot synthesis of main-chain imidazolium-containing polymers, some of which show unusually high thermal stability. The imidazolium polymers are obtained by modified Debus-Radziszewski reactions for the chain build-up from simple organic compounds, here pyruvaldehyde, formaldehyde, acetic acid, and a variety of diamines. The reactions are performed in aqueous media at ambient conditions, being synthetically elegant, convenient, and highly efficient. Finally, a simple anion-metathesis reaction is conducted to replace the acetate anion with dicyanamide, and the thermal properties of the main-chain polyimidazoliums before and after anion exchange are studied in detail, which demonstrate chain cross-linking by the counterion and a coupled unusually high carbonization yield of up to 66 wt% at 900 °C. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) of carbohydrates in general has been reported as a sustainable and green technique to produce novel carbon materials. Traditional HTC of carbohydrates leads to irregular carbonaceous particles with low porosity due to inevitable aggregation induced by the high surface energy and the failure of classical templates. The accrescent understanding of the reaction mechanism in the HTC "dark box" provides possibilities of engineering HTC carbonaceous materials in a refined way. In the past decades, some unprecedented carbonaceous structures were achieved via modified HTC processes. Those progresses reflect the mightiness of HTC for precise synthesis however the last specialized review on this topic is over a decade old. In this review, we summarize the advances in the precise engineering of carbonaceous materials with specific morphologies and structures by the bottom-up HTC of carbohydrates, especially monosaccharides and disaccharides. This review elucidates the HTC set screws for the shaping of and/or the pore-creation within the targeted nanostructured carbonaceous materials. The benefits for applications arised from the special control of HTC carbon are also discussed. This review could inspire further insight into the HTC process and broader application of carbon nanostructures made from renewable resources. [ABSTRACT FROM AUTHOR]

Carbon films and coatings are industrially very versatile and have a multiplicity of applications, such as conductive coatings or chemical and thermal protection layers. However, in most cases they are fabricated by the expensive vapor process, which has prevented a wider commercialization of these products. Herein, carbon films are fabricated using an inexpensive polymer-solution-based or sol–gel coating process, exemplified by spin coating of thin layers. As carbon precursor, the oligomeric form of acrodam, a high nitrogen-containing and non-volatile compound which is known to have excellent carbon yields, was employed. The oligomer is synthesized from commercially available starting materials (diaminomaleonitrile (DAMN) and acrolein) and dissolves in various organic solvents. The carbonized films were found to be homogeneous, optically flat, void- and crack-free, and were fabricated with up to 800 nm thickness after a carbonization step. High conductivities (up to 334 S cm −1 ) were achieved at the carbonization temperature of 1000 °C. [ABSTRACT FROM AUTHOR]

Herein we report a facile and scalable synthesis of highly nitrogen-doped porous carbon materials with tunable morphology. Bio-based imidazolium derivatives made from natural amino acids and dioxo-derivatives are employed as precursors, exhibiting an analogous behavior during carbonization to classical ionic liquids. Utilization of systematically controlled salt templating methods yields nitrogen-doped carbon materials with high surface areas of up to 2650 m 2 g −1 and morphology-engineered structures such as monolithic or highly extended, sheet-like carbons. We believe that the presented approach represents an alternative and sustainable platform towards the rational design of carbon materials possessing controlled nanoporosity and functionality. [ABSTRACT FROM AUTHOR]

Poröse N ‐ dotierte Kohlenstoffmaterialien (HTC ‐ Kohlenstoff mit PILs) aus kugelförmigen Nanopartikeln und solche mit eingebetteten Au/Pd ‐ Kern/Schale ‐ Nanopartikeln (Au/Pd@N ‐ Kohlenstoff) wurden synthetisiert. Sie sind erhältlich durch hydrothermale Verkohlung von Zuckern (160 – 200 °C) in Gegenwart polymerer ionischer Flüssigkeiten (PILs), die als Stabilisatoren, Porenbildner und Stickstoffquelle fungieren. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped carbons were produced using hydrothermal carbonization of nitrogen-containing carbohydrates under mild temperature (180°C). The resulting materials contain significant amounts of nitrogen and display a high degree of aromatization. The nitrogen contents are also retained after further calcination at higher temperatures. All the resulting materials have been thoroughly characterized using X-ray photoelectron spectroscopy, solid state 15N and 13C-nuclear magnetic resonance, elemental chemical analysis, nitrogen adsorption, scanning and transmission electron microscopy. The nitrogen-doped materials proved to have superior performance with respect to their nitrogen-free counterparts in terms of electrical conductivity. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped carbon particles were produced using the hydrothermal carbonization of a nitrogen-containing carbohydrate, namely glucosamine, under mild temperature conditions (180 °C) followed by further calcination under a stream of inert gas at 750 °C. The resulting materials contain significant amounts of nitrogen doping within their structure, mainly as quaternary N involved in an aromatized/graphitized carbon structure according to X-ray photoelectron spectroscopy. This nitrogen-doped material was dispersed with nanolatexes having a high affinity for carbon. The resulting hybrid dispersions could be conveniently cast into dense and stable films for thermal and electrical conductivity measurements. The conductivities were commensurate with technical carbon nanotube latex-based films. A morphological analysis of the dispersing mechanism suggests that the potential for high performance materials realized in this contribution is very competitive, but still far from being fully exploited. [Copyright &y& Elsevier]

Abstract: Greenhouse gas mitigation options include the production of carbonized materials and their addition to soils for longer term storage. Hydrothermal carbonization (HTC) is a novel way to produce carbonized materials. The goal here was to test if HTC material, in our case derived from beet root chips, has adverse effects on plant growth or that of root associated symbionts such as arbuscular mycorrhizal fungi. We carried out several studies, and found that increasing concentrations of HTC material could be deleterious for plant growth of Taraxacum, starting at 10vol% additions. Conversely, root colonization of the fungal symbiont was stimulated at an addition of 20vol%. Soil pH changes occurring during the study could be traced to microbial reduction reactions, and these led to a pH increase of the medium despite the quite acidic nature of the HTC material itself. In separate assays, we showed that spore germination of the AM fungus Glomus intraradices was stimulated by the HTC material, suggesting that direct effects on the fungi are likely in addition to those mediated by the host plant. A third experiment with a different plant species (Trifolium repens) confirmed the major conclusions, and showed also neutral to stimulatory effect on nodulation. Our results suggest that HTC materials should be carefully tested and optimized to reduce negative effects on plant growth before applications in the field are undertaken, particularly at high addition rates. [Copyright &y& Elsevier]

Sugars can be directly …︁ …︁ transformed into porous nitrogen‐doped carbon materials in the presence of poly(ionic liquid)s. In their Communication on page 6028 ff., J. Yuan, Y. Wang, and co‐workers describe the application of this method to synthesize carbon particles 20–50 nm in size and also to synthesize, in one step, nitrogen‐doped carbon materials embedded with core–shell Au–Pd nanoparticles. [ABSTRACT FROM AUTHOR]