Nitrogen Functionalities Research Articles

Free-standing cross-linked activated carbon nanofibers with nitrogen functionality for high-performance supercapacitors

Flexible, heteroatoms-rich activated carbon nanofibers with fascinating cross-linked architectures are successfully gained in a facile and controllable way via electrospinning polyacrylonitrile (PAN) /dicyandiamide (DICY) composite nanofibers followed by carbonation and a CO2 activation process. The unique inter-bonded structures and heteroatoms contents could be easily controlled by adjusting the preoxidation temperature applied in the calcining procedure and the addition of DICY. Significantly, the resultant samples display hierarchical pores with micro/meso/macropores, abundant N, O species doped and unique fiber–fiber interconnections, which considerably boost the electrochemical properties. As an electrode material, the activated N-doped cross-linked carbon nanofibers (ANCLCNFs) show a high capacitance of 323 F g−1 with a current density of 0.5 A g−1, excellent rate capacity (230.1 F g−1 at 20 A g−1) and long-term duration (over 95% after 10000 cycles). Furthermore, the symmetrical supercapacitor delivers a maximum energy density of 14.3 Wh kg−1 at a power density of 162.5 W kg−1.

Tristaniopsis merguensis Griff. Extract as Inhibitor for Corrosion of Stainless Steel

Green inhibitors are inhibitors that utilize secondary metabolites of plant to reduce the rate of corrosion. Secondary metabolites with heteroatom content phosphate, nitrogen, oxygen and sulfur function as ligands and adsorption centers to bind metals. These metabolites compounds include alkaloids, flavonoids, and tannins. Tristaniopsis merguensis Griff. is a local plant of Bangka Belitung which contains alkaloid, flavonoids and tannins. The focus of this research is to analyze the effect of T. merguensis leaf extract on corrosion rate of stainless steel. T. merguensis extract was obtained by maceration for 3 x 24 hours using ethanol solvent. Determination of corrosion rate using the mass reduction method. Then, functional group analysis contained in extract uses the Fourier Transform Infrared (FT-IR) at wavenumber region 4000–400 cm−1. The results obtained that at the highest concentration of 1000 mg/L the extract of T. merguensis was able to inhibit the corrosion rate of stainless steel until the corrosion rate was 0.3826 mmpy equal to inhibition efficiency 85.27%. This inhibiting ability is more likely because T. merguensis leaf extract containing phenolic compounds. Therefor T. merguensis extract can be used as a green inhibitor.

Structural study of functional hierarchical porous carbon synthesized from metal-organic framework template

In this work, nitrogen-doped hierarchical porous carbon (NPC) was obtained from an effective and facile synthesis route based on metal-organic framework (MOF)-drive approach using Zr-metal-organic framework (UiO-66-NH2) as a template. The structural analysis of synthesized NPC using different heat treatment was performed through X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption isotherm at 77K characterization. The results achieved indicate that Zr-MOF is an appropriate starting precursor to attain functional carbon materials with remarkable physicochemical properties for potential advanced applications. Thereby, it was evidenced that the NPC synthesis temperature has an influence on resulting structural properties as well as nitrogen functionalities and amount. Thereby, the obtained NPC exhibits a disorder porous structure with high BET surface area (765–867 m2/g), pore size from microporous to mesoporous, and 3–4% of N content. Related to nitrogen functionalities, the heteroatom corresponds to quaternary, pyrrolic, and pyridinic bonding, indicating that it was successfully incorporated into the carbon framework.

Nitrogen conversion during the rapid pyrolysis of raw/torrefied wheat straw

Nitrogen functionalities play an important role on the conversion of fuel-N during pyrolysis of raw and torrefied biomass while the influences haven’t been clarified yet. The conversion of fuel-N during the rapid pyrolysis of wheat straw (WS) and different torrefied WS was investigated using a fixed-bed reactor at 600–1000 °C and the change of fuel characteristics and nitrogen-containing functional groups in samples were analyzed by TG and XPS. Results showed that the N content of samples increased gradually with torrefaction temperature. The main N functionality of WS was amide-N (N-A), while part of the N-A was converted to pyrrole-N (N-5), pyridine-N (N-6), and quaternary-N (N-Q) during torrefaction. CO2 and O2 can inhibit the transformation of N-A to N-5 and promote the transformation of N-A to N-6. During WS pyrolysis, NH3 was the main NOx precursors at 600–700 °C, while HCN became the main nitrogen-containing gas species at 800–1000 °C and the conversion of (NH3 + HCN)-N was 18.15%–32.0%. After torrefaction, the conversion of NH3-N decreased in varying degrees, especially at low pyrolysis temperature (600–700 °C). The conversion of HCN-N increased with temperature during torrefied WS pyrolysis which was similar to that of WS, but the conversion decreased greatly at 800–1000 °C. Torrefaction atmosphere has a substantial effect on the conversion of fuel-N. In particular, WS torrefied in CO2 of O2 atmosphere can promote the conversion of fuel-N to harmless N2 during pyrolysis.

Structure based design, synthesis and in vitro antitumour activity of tiazofurin stereoisomers with nitrogen functions at the C-2′ or C-3′ positions

Three novel tiazofurin analogues having d-arabino stereochemistry and nitrogen functionalities at the C-2′ position (5–7) have been designed and synthesized in multistep sequences, starting from d-glucose. The known d-xylo stereoisomer of 1 (compound 2) along with two new analogues bearing nitrogen functions at the C-3′ (3 and 4) has also been synthesized from the same sugar precursor. The synthetic sequence consisted of the following three stages: (i) the multistep synthesis of suitably protected pentofuranosyl cyanides, (ii) the construction of ethyl thiazole-4-carboxylate part by cyclocondensation of thus obtained glycofuranosyl cyanides with l-cysteine ethyl ester followed by dehydrogenation, and (iii) the final transformation of the ethyl thiazole-4-carboxylates into the target tiazofurin analogues using the esters ammonolysis. The tiazofurin analogues were evaluated for their antitumour activities in cell-culture-based assays. Compounds 3, 4 (d-xylo) and 7 (d-arabino), showed remarkable antitumour activities, with IC50 values in the range of 4–7 nM. Preliminary structure-activity relationship allowed identification of two analogues with antiproliferative activities exceeding that of the parent compound 1 for several orders of magnitude (e.g. 4: 1354-fold against Raji, 7: 309-fold against K562). Flow cytometry data and Western blot analysis suggested that cytotoxic effects of d-xylo stereoisomers in the culture of K562 cells caused changes in the cell cycle distribution, as well as the induction of apoptosis in caspase-dependent way. The increase of apoptotic cells percentage in treated samples is also confirmed with fluorescent double-staining method. Genotoxicity testing showed that the analogues with the xylo-configuration (2–4) are far less genotoxic than tiazofurin.

Synthesis N-Doped Activated Carbon from Sugarcane Bagasse for CO2 Adsorption

Nitrogen-doped activated carbon (SBACN) was synthesized from sugarcane bagasse waste as acarbon source and urea as nitrogen source through potassium hydroxide (KOH) activation for 2 h at high temperature via two step methods. The synthesized SBCN was characterized using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Fourier Transform Infrared (FTIR). The results showed that the SBCN has low degree crystallinity and graphitization with highly developed micropores due to synergistik activation effect of KOH and urea. These characteristics provide an important contribution to carbon dioxide adsorption capacity, which can reach up to 11,20% wt and this value is higher than pristine activated carbon. The results indicating that the presence of this nitrogen functionalities is found to have a beneficial influence on the carbon dioxide adsorption characteristic in standart condition and exhibit considerable potential in solid adsorption.

Nitrogen Doped Carbon–Silica Based Cu(0) Nanometal Catalyst Enriched with Well-Defined N-moieties: Synthesis and Application in One-Pot Synthesis of 1,4-Disubstituted-1,2,3-triazoles

A novel, air stable, water dispersible and efficient catalyst based on copper nanoparticles immobilized on nitrogen doped carbons derived from inorganic–organic composite [Cu(0)@NDC-Sil] has been prepared. Doping of carbons i.e. inorganic–organic (silica–starch) composite using 5-phenyl-1,2,3,4-tetrazole, a nitrogen-rich precursor imparts a variety of nitrogen functionalities even at moderate temperature and enables the generation of active sites for the immobilization of Cu(0) nanoparticles. The novel catalyst system has been well characterized by various techniques like SEM, HRTEM, STEM, TGA, CHN, EDX, ICP-AES, XRD and XPS and was found to be highly efficient for the one-pot synthesis of 1,4-disubstituted-1,2,3-triazoles via click chemistry approach with a wide range of substrate scope such as benzyl/allyl halides and alkyl bromides. Moreover, it could be easily recovered by filtration and reused without significant loss in its activity.

Effects of activation on the properties of electrospun carbon nanofibers and their adsorption performance for carbon dioxide

Microporous carbon nanofibers were prepared by stabilization, carbonization, and activation of electrospun polyacrylonitrile-based nanofibers. The average fiber diameters of activated electrospun carbon nanofibers (AECNF) samples, ranging from 280 to 500 nm, generally decreased with increasing activation degree. The evolution of nitrogen was observed during the fabricated processes, and the predominant nitrogen functionalities were shifted to those at higher binding energies when the activation degree increased. The N/C ratios on the surface of the samples were affected significantly by the activation temperature and activation time. The AECNF samples were featured with microporosity and the ultramicropores were also newly formed with increasing activation degree. It was expected that the activation process involved a three-step predominant reaction: the transformation from ultramicropores to submicropores, the micropore enlargement reaction followed by the micropore formation reaction. The equilibrium CO2 adsorption capacities could achieve 1.2 mmole/g (0.15 atm) and 3.2 mmole/g (1 atm) at 298 K. The CO2 uptake at low partial pressure and ultramicroporosity of the adsorbents were related to the isosteric heat of adsorption. The AECNF samples for CO2 adsorption had an energetically heterogeneous surface and Freundlich equation provided a satisfactory fit. Synergetic effects of microporosity and nitrogen content of AECNF on CO2 uptakes at low pressure were observed.

(Invited) Nitrogen Functionalization and Doping of Conductive Carbons By Means of Low Temperature Plasmas

Nanomaterials, such as nanocomposites, nanorods, nanotubes and graphenes, are nowadays almost past the title “novel materials”, they have been widely investigated and used as either promising or already proven materials for various applications ranging from electronics and black body coatings to fuel cells and supercapacitors. Such advanced nanomaterials, independently of their chemical composition, are also used for the delivery of therapeutic agents, including biomolecules targeting disease sites, for bioimaging, or in general for biomedical engineering.This contribution presents several examples of plasma synthesized and plasma functionalized carbon based nanomaterials (nanostructures), CBNs, which nowadays play an important role for biomedical engineering, and in particular for the development of novel biosensors. The examples presented in this paper concern materials which are synthesized in low pressure RF plasmas from hydrocarbon precursors, like ethylene, with or without nitrogen presence during their growth. Most of the examples are vertically aligned graphene flakes. The post-treatment of these materials is performed in low pressure radio frequency capacitively coupled plasma and microwave plasma. In this contribution we will focus on surface treatment by nitrogen and ammonia plasma. The goal of such surface treatments with nitrogen containing plasma is doping and functionalization, very often simultaneously obtained. Plasmas were controlled by means of mass spectroscopy.The method of choice for the analysis of the bonding situation of the materials before and after treatment in this presentation is near edge X-ray absorption fine structure spectroscopy (NEXAFS), and X ray photoemission spectroscopy (XPS) performed on HESGM beamline, HBZ Bessy II Germany. Acknowledgments The authors would like to acknowledge the support obtained by French National Research Agency via projects ANR PlasBioSens and PlasmaBond, APR Apropore, French Regionals support by APR Capt’Eau, and PIVOT. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730872 (CALYPSO plus for the work at the HZB BESSY II synchrotron, Berlin, Germany) and grant agreement No766894 (FET-OPEN project PEGASUS).

Effect of Carbon Support on Fe-N3/C Model Active Site for the Oxygen Reduction Reaction

Non-precious metal catalysts for the oxygen reduction reaction (ORR) are of great interest for fuel cell technology due to their low cost and wide availability of materials. Development of these catalysts has been a constantly growing area. However, there have been very few literature reports that provide insights into the precise nature of the structure and geometry of the catalytically active sites formed in these materials. In the current literature, the most commonly proposed catalytically active site(s) for ORR corresponds to Fe-N2+2/C geometry. This is typically produced through a high temperature pyrolysis step to obtain this desired configuration in the active sites[1]. However, the pyrolysis step is very disadvantageous due to the production of a distribution of nitrogen functional groups on the surface which can negatively affect the activity of the catalyst, since only nitrogen functionalities with specified geometry are considered to be the most active for ORR[2,3]. As well, high temperature treatments increase the cost of production, and can be quite energy demanding. Thus, high-temperature treatment makes it difficult to design a surface rich in a specific active site for the desired application. The work presented here demonstrates a model system for a non-precious metal catalyst for the ORR achieved by covalently functionalizing a conventional carbon support with a nitrogen-rich ligand. The terpyridine ligand geometry allows the formation of well-defined active catalytic sites when covalently attaching an N3/C functionality to the carbon surface, leaving exposed the most active sites for the ORR. Room temperature metal-ligand coordination with Fe results in desired Fe-N3/C moieties on the surface. We demonstrate that this system can be prepared using mild reaction conditions and does not require high temperature treatment for improved activity, in fact heat treatment to this system was detrimental to the activity. The Fe-N3/C support was subjected to electrochemical studies in both acidic and basic aqueous media and demonstrates the potential of this system to be used as a model for an Fe-N3/C active site for ORR.

Adsorption of CO2 on KOH activated carbon adsorbents: Effect of different mass ratios

Nitrogen and oxygen enriched carbons were prepared by the cost-effective synthesis route of carbonization of polyacrylonitrile (PAN) and subsequent KOH activation for CO2 capture. The effect of four impregnation mass ratios (KOH: PAN = 1–4) and activation temperatures (600–900 °C) on the synthesized carbon adsorbent properties was explored by different analyses. The X-ray photoelectron spectroscopy (XPS) revealed the existence of basic nitrogen and oxygen functionalities on the adsorbent's surface which increases the adsorption rate for CO2 by providing its basic sites. By increasing mass ratio (KOH:PAN) from 1:1 to 3:1, the surface area increased from 1152.4 to 1884.2 m2 g−1 and the dynamic CO2 adsorption capacity also increased from 2.1 to 2.5 mmol g−1 respectively, at 30 °C (approximately ten times the adsorption capacity of untreated PAN, 0.22 mmol g−1). Physisorption and exothermic nature of the process were confirmed by the decrease in the adsorption capacity of the adsorbents with the increase in adsorption temperature. Moreover, good cyclic stability and regenerability over 5 adsorption-desorption cycles were obtained for the adsorbents. The fractional order kinetic and Temkin isotherm models fitted best with the adsorption data. A heterogeneous interaction between CO2 and the surface of adsorbents was suggested by the isosteric heat of adsorption values. Combined with the simple method for the preparation of activated carbon adsorbents, efficient CO2 adsorption and excellent regeneration make it appropriate adsorbents for post-combustion CO2 capture.

Ultrafast Proton Transport between a Hydroxy Acid and a Nitrogen Base along Solvent Bridges Governed by the Hydroxide/Methoxide Transfer Mechanism.

Aqueous proton transport plays a key role in acid–base neutralization and energy transport through biological membranes and hydrogen fuel cells. Extensive experimental and theoretical studies have resulted in a highly detailed elucidation of one of the underlying microscopic mechanisms for aqueous excess proton transport, known as the von Grotthuss mechanism, involving different hydrated proton configurations with associated high fluxional structural dynamics. Hydroxide transport, with approximately 2-fold-lower bulk diffusion rates compared to those of excess protons, has received much less attention. We present femtosecond UV/IR pump–probe experiments and ab initio molecular dynamics simulations of different proton transport pathways of bifunctional photoacid 7-hydroxyquinoline (7HQ) in water/methanol mixtures. For 7HQ solvent-dependent photoacidity, free-energy–reactivity correlation behavior and quantum mechanics/molecular mechanics (QM/MM) trajectories point to a dominant OH–/CH3O– transport pathway for all water/methanol mixing ratios investigated. Our joint ultrafast infrared spectroscopic and ab initio molecular dynamics study provides conclusive evidence for the hydrolysis/methanolysis acid–base neutralization pathway, as formulated by Manfred Eigen half a century ago. Our findings on the distinctly different acid–base reactivities for aromatic hydroxyl and aromatic nitrogen functionalities suggest the usefulness of further exploration of these free-energy–reactivity correlations as a function of solvent polarity. Ultimately the determination of solvent-dependent acidities will contribute to a better understanding of proton-transport mechanisms at weakly polar surfaces and near polar or ionic regions in transmembrane proton pump proteins or hydrogen fuel cell materials.

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

N-doped porous carbon film electrodes for electrochemical capacitor, made by electrospray of sol precursors

Heteroatom doping in carbon structure enhances surface wettability, electrical conductivity, and electron-donor/acceptor properties that in turn, improves the electrochemical performance of carbon electrodes. In this article, in situ grown carbon film electrodes are obtained through electrospray of polymeric sol on carbon paper, followed by curing, and carbonization. The nitrogen functionality in these binder-free carbon film electrodes is successfully incorporated from melamine addition in resorcinol-formaldehyde sol. The film electrode shows a capacitance of 223 mF cm−2 (446 F g−1), and volumetric energy density of 15.2 mWh cm−3 at 1 mA cm−2 in a symmetric cell with 2 M KOH as electrolyte. Furthermore, these electrodes exhibit excellent cyclic stability even after 5000 charge-discharge cycles with almost complete capacitance retention at 5 mA cm−2. The outstanding electrochemical performance of carbon film electrodes are due to the combined effect of following steps: (i) incorporation of nitrogen and oxygen in right amount, (ii) retention of the desired pore size distribution, and fraction of micropores through systematic balancing of resorcinol to melamine ratio in precursor sol, (iii) disintegration of sol by electrospray prior to deposition on carbon paper, that in turn produces a porous three-dimensional interconnected network of nanoparticulate film, and (iv) lyophilization of wet gel layer that retains the pore spaces during solvent removal.

Effect of nitrogen functionalization of graphite felt electrode by ultrasonication on the electrochemical performance of vanadium redox flow battery

In this paper, facile approach for preparing nitrogen-functionalized graphite felt (GF) as electrodes in vanadium redox flow battery was developed and investigated. Modification was done via ultrasonication-assisted self-polymerization and subsequent pyrolysis of dopamine to produce nitrogen-functionalized graphite felt. The electrode surface changed from hydrophobic to hydrophilic and charge transfer resistance was reduced upon nitrogen functionalization, leading to improved electrochemical properties. To achieve high electrochemical performance, the degree of nitrogen functionalization was optimized by evaluating the characteristics, such as surface area, porosity, and cyclic voltammogram, of GF and various nitrogen-functionalized GF (NGF) samples. All NGF samples showed improved energy efficiency in a VRFB single cell test. Specifically, the optimized sample, NGF05 (containing 0.5 mM dopamine), had a higher energy efficiency (75.5%) than GF (69.2%) at a current density of 150 mA cm−2. Moreover, the electrolyte utilization efficiency of NGF05 (68.1%) was higher than that of GF (58.2%). Thus, nitrogen functionalization of GF by ultrasonication is a simple, practical approach to produce high-performance VRFBs.

Direct Synthesis of Amides by Acceptorless Dehydrogenative Coupling of Benzyl Alcohols and Ammonia Catalyzed by a Manganese Pincer Complex: Unexpected Crucial Role of Base.

Amide synthesis is one of the most important transformations in chemistry and biology. The direct use of ammonia for the incorporation of nitrogen functionalities in organic molecules is an attractive and environmentally benign method. We present here a new synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia. The reaction is catalyzed by a pincer complex of earth-abundant manganese in the presence of a stoichiometric base, making the overall process economical, efficient, and sustainable. Interesting mechanistic insights based on detailed experimental observations, indicating the crucial role of the base, are provided.

Functional properties of bacterial communities in water and sediment of the eutrophic river-lake system of Poyang Lake, China.

In river-lake systems, sediment and water column are two distinct habitats harboring different bacterial communities which play a crucial role in biogeochemical processes. In this study, we employed Phylogenetic Investigation of Communities by Reconstruction of Unobserved States to assess the potential functions and functional redundancy of the bacterial communities in sediment and water in a eutrophic river-lake ecosystem, Poyang Lake in China. Bacterial communities in sediment and water had distinct potential functions of carbon, nitrogen, and sulfur metabolisms as well as phosphorus cycle, while the differences between rivers and the lake were inconspicuous. Bacterial communities in sediment had a higher relative abundance of genes associated with carbohydrate metabolism, carbon fixation pathways in prokaryotes, methane metabolism, anammox, nitrogen fixation, and dissimilatory sulfate reduction than that of water column. Bacterial communities in water column were higher in lipid metabolism, assimilatory nitrate reduction, dissimilatory nitrate reduction, phosphonate degradation, and assimilatory sulfate reduction than that of sediment bacterial communities. Furthermore, the variations in functional composition were closely associated to the variations in taxonomic composition in both habitats. In general, the bacterial communities in water column had a lower functional redundancy than in sediment. Moreover, comparing to the overall functions, bacterial communities had a lower functional redundancy of nitrogen metabolism and phosphorus cycle in water column and lower functional redundancy of nitrogen metabolism in sediment. Distance-based redundancy analysis and mantel test revealed close correlations between nutrient factors and functional compositions. The results suggested that bacterial communities in this eutrophic river-lake system of Poyang Lake were vulnerable to nutrient perturbations, especially the bacterial communities in water column. The results enriched our understanding of the bacterial communities and major biogeochemical processes in the eutrophic river-lake ecosystems.

Tailoring the Adsorption of ACE-Inhibiting Peptides by Nitrogen Functionalization of Porous Carbons.

Bioactive peptides, such as isoleucyl-tryptophan (IW), exhibit a high potential to inhibit the angiotensin-converting enzyme (ACE). Adsorption on carbon materials provides a beneficial method to extract these specific molecules from the complex mixture of an α-lactalbumin hydrolysate. This study focuses on the impact of nitrogen functionalization of porous carbon adsorbents, either via pre- or post-treatment, on the adsorption behavior of the ACE-inhibiting peptide IW and the essential amino acid tryptophan (W). The commercially activated carbon Norit ROX 0.8 is compared with pre- and postsynthetically functionalized N-doped carbon in terms of surface area, pore size, and surface functionality. For prefunctionalization, a covalent triazine framework was synthesized by trimerization of an aromatic nitrile under ionothermal conditions. For the postsynthetic approach, the activated carbon ROX 0.8 was functionalized with the nitrogen-rich molecule melamine. The batch adsorption results using model mixtures containing the single components IW and W could be transferred to a more complex mixture of an α-lactalbumin hydrolysate containing a huge number of various peptides. For this purpose, reverse-phase high-pressure liquid chromatography with fluorescence detection was used for identification and quantification. The treatment with the three different carbon materials leads to an increase in the ACE-inhibiting effect in vitro. The modified surface structure of the carbon via pre- or post-treatment allows separation of IW and W due to the certain selectivity for either the amino acid or the dipeptide.

Enhancing the performance of microbial fuel cells (MFCs) with nitrophenyl modified carbon nanotubes-based anodes

Modification of carbon based-nanomaterials has been proven to be efficient for improving the MFCs performance, since the anode material significantly impacts the biofilm formation and the electron transfer between the microorganism and the electron acceptor. Surface treatment or functionalization is frequently employed to enhance the chemical reactivity and modify the hydrophobic surface of carbon nanotubes (CNTs).This work aims to explore the modification of CNTs with nitrophenyl groups for the improvement of the performance of MFC through anode modifications. Two procedures, involving 4-nitroaniline or 4-nitrobenzenediazonium tetrafluoroborate, were used for the chemical modification of CNTs. The X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry were used for the characterizations of nitrophenyl modified CNTs. The maximum power density was obtained when 4-nitrobenzenediazonium tetrafluoroborate was used for the modification of the surface of CNTs. The introducing of nitrogen functionality on the anode surface and the control of the nitrogen content provide considerable encouragements for enhancing the MFCs performance through anode modifications.

One-Pot Synthesis of Sulfur and Nitrogen Co-Functionalized Graphene Material using Deep Eutectic Solvents for Supercapacitors.

A green approach to the synthesis of sulfur and nitrogen co-functionalized reduced graphene oxide (SN-rGO) is presented; it involves the reduction of graphene oxide (GO) using a deep eutectic solvent (DES) as chemical reducing agent and dopant. For the first time, a DES of choline chloride and sodium sulfide comprising cheap and safe components is introduced, and is both highly effective and reusable as a reducing agent for the production of SN-rGO. The DES is utilized as a solvent as well as reducing agent and dopant to generate SN-rGO. This DES is highly efficient in removing oxygen functionalities from GO and for subsequent sulfur and nitrogen functionalization for high energy-storage efficiency. The reduction ability of this DES is confirmed with five consecutive cycles, which adds to its sustainability and recyclability in the development of energy-storage devices. SN-rGO exhibits a high specific capacitance of 509 F g-1 at 1 A g-1 , which corresponds to high energy and power densities of 57.3 Wh kg-1 and 1804.7 W kg-1 , respectively. This simple and green method for direct reduction of GO with sulfur and nitrogen functionalization on the graphene surface can provide cost-effective bulk production of a nanocarbon template for energy storage applications.