Nitrogen-doped Ordered Mesoporous Carbon Research Articles

Improving Stability of CO2 Electroreduction by Incorporating Ag NPs in N-Doped Ordered Mesoporous Carbon Structures.

The electroreduction of carbon dioxide (eCO2RR) to CO using Ag nanoparticles as an electrocatalyst is promising as an industrial carbon capture and utilization (CCU) technique to mitigate CO2 emissions. Nevertheless, the long-term stability of these Ag nanoparticles has been insufficient despite initial high Faradaic efficiencies and/or partial current densities. To improve the stability, we evaluated an up-scalable and easily tunable synthesis route to deposit low-weight percentages of Ag nanoparticles (NPs) on and into the framework of a nitrogen-doped ordered mesoporous carbon (NOMC) structure. By exploiting this so-called nanoparticle confinement strategy, the nanoparticle mobility under operation is strongly reduced. As a result, particle detachment and agglomeration, two of the most pronounced electrocatalytic degradation mechanisms, are (partially) blocked and catalyst durability is improved. Several synthesis parameters, such as the anchoring agent, the weight percentage of Ag NPs, and the type of carbonaceous support material, were modified in a controlled manner to evaluate their respective impact on the overall electrochemical performance, with a strong emphasis on operational stability. The resulting powders were evaluated through electrochemical and physicochemical characterization methods, including X-ray diffraction (XRD), N2-physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy (SEM-EDS), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-EDS, electron tomography, and X-ray photoelectron spectroscopy (XPS). The optimized Ag/soft-NOMC catalysts showed both a promising selectivity (∼80%) and stability compared with commercial Ag NPs while decreasing the loading of the transition metal by more than 50%. The stability of both the 5 and 10 wt % Ag/soft-NOMC catalysts showed considerable improvements by anchoring the Ag NPs on and into a NOMC framework, resulting in a 267% improvement in CO selectivity after 72 h (despite initial losses) compared to commercial Ag NPs. These results demonstrate the promising strategy of anchoring Ag NPs to improve the CO selectivity during prolonged experiments due to the reduced mobility of the Ag NPs and thus enhanced stability.

Exploration on magnetic and electrochemical properties of nitrogen and phosphorus Co-doped ordered mesoporous carbon for supercapacitor applications

A series of heteroatom doped ordered mesoporous carbons (HOMCs) such as ordered mesoporous carbon (OMC), nitrogen doped ordered mesoporous carbons (NOMC), phosphorus doped ordered mesoporous carbons (POMCs), and nitrogen and phosphorus co-doped ordered mesoporous carbon (NPOMC) were synthesized via a chemical vapor deposition nanocasting (CVD nanocasting) route using SBA-15 as the template at 800 °C for high-performance supercapacitor. The formation of the template and HOMCs were confirmed by various physicochemical characterization techniques such as XRD, RAMAN, BET, SEM-EDAX, HR-TEM and XPS. The magnetic properties of prepared HOMCs were measured. Also, the electrochemical properties of HOMCs were evaluated using electrochemical analyses such as CV, EIS and GCD in 1 M H2SO4 medium. Among the various prepared HOMCs, sample NPOMC showed a high specific capacitance of 355 Fg-1 at a current density of 0.5 Ag-1 due to the heteroatoms. Moreover, the symmetric device fabricated using NPOMC exhibited 98% columbic efficiency with 98% capacitance retention after 1000 cycles at 2 Ag-1 current density.

Highly Efficient Electrochemical Synthesis of Hydrogen Peroxide (H2O2) Enabled by Amino Acid Glycine-Derived Metal-Free Nitrogen-Doped Ordered Mesoporous Carbon

Highly Efficient Electrochemical Synthesis of Hydrogen Peroxide (H₂O₂) Enabled by Amino Acid Glycine-Derived Metal-Free Nitrogen-Doped Ordered Mesoporous Carbon

Efficient removal of H2S with zinc oxide/nitrogen-doped ordered mesoporous carbons at room temperature

Nitrogen-doped ordered mesoporous carbon (NMC) was prepared via an organic–inorganic co-assembly method to support ZnO for the efficient removal of H 2 S at room temperature. NMCs with large BET specific surface areas, copious ordered mesopores, and controllable nitrogen doping worked cooperatively with uniformly dispersed ZnO, to improve desulfurization capability at room temperature. Among these, NMC-2 possessed a BET surface area as high as 1172 m 2 /g, a large pore volume of 1.09 cm 3 /g, and a conducive nitrogen content. The appropriate residual ordered mesopores after ZnO loading provided a fast–H 2 S–diffusion channel in NMC-2-20%, an accessible interfacial area (925 m 2 /g), and a sufficient space for product storage (0.9 cm 3 /g). The introduction of nitrogen as Lewis basic sites not only promoted the dissociation of H 2 S but also accelerated the lattice diffusion rate during the desulfurization process. The synergy of the above advantages resulted in an excellent desulfurization performance of 151.2 mg/g. This study presents the effective application of NMC as a support for ZnO for a fine desulfurization at room temperature. • NMC was prepared via the organic-inorganic co-assembly method. • The ordered mesopores improve H 2 S diffusion and provide sufficient space for product. • N doping could promote the H 2 S dissociation and accelerate lattice diffusion rate. • NMC-2-20% has well desulfurization performance.

Glycine-derived nitrogen-doped ordered mesoporous carbons with a bimodal mesopore size distribution for supercapacitors and oxygen reduction

Nitrogen-doped carbon materials are promising for electrochemical energy storage and conversion. Dopant control and pore engineering play important roles in improving their performance. We have synthesized nitrogen-doped ordered mesoporous carbons (N-OMCs) with a bimodal mesopore size distribution using a solvent-free nanocasting method. The simplest amino acid (glycine, Gly) was used as the only carbon precursor and ordered mesoporous silica SBA-15 as the hard template. The confined pyrolysis of Gly in SBA-15 leads to efficient carbonization, nitrogen doping and an interesting structure. The N-OMCs have high surface areas (923–1374 m2·g−1), large pore volumes (1.32–2.21 cm3·g−1), a bimodal distribution of mesopore sizes (4.8 and 6.2–20 nm) and high nitrogen contents (3.66%–12.23%). The effects of the Gly/SBA-15 mass ratio (1–3) and carbonization temperature (700–1000 °C) on the physicochemical properties of the N-OMCs were studied. When used as electrode materials the N-OMCs have a high performance in supercapacitors. A typical sample has a large specific capacitance of 298 F·g−1, a good rate capability (70% retention at 30 A·g−1) and high stability. The different capacitances and rate capabilities of the N-OMCs are discussed by correlating them with their physicochemical properties. A balance of surface area, degree of graphitization, nitrogen doping, and an open mesoporous structure is essential to achieve the best performance. The N-OMCs also have a good performance in the electrocatalytic oxygen reduction reaction. A typical sample has a high onset of 0.92 V, a high half-wave potential of 0.83 V and a large limiting current density of 5.06 mA·cm−2.

Efficient spinel iron-cobalt oxide/nitrogen-doped ordered mesoporous carbon catalyst for rechargeable zinc-air batteries

A robust oxygen-related electrocatalyst, composed of spinel iron-cobalt oxide and nitrogen-doped ordered mesoporous carbon (NOMC), was developed for rechargeable metal-air batteries. Electrochemical tests revealed that the optimal catalyst Fe0.5Co/NOMC exhibits superior activity with a half-wave potential of 0.89 V (vs. reversible hydrogen electrode) for the oxygen reduction reaction and an overpotential of 0.31 V at 10 mA cm−2 for the oxygen evolution reaction. For demonstration, the catalyst was used in the assembly of a rechargeable zinc-air battery, which exhibited an exceptionally high energy density of 820 Wh kg−1 at 100 mA cm−2, a high power density of 153 mW cm−2 at 1.0 V, and superior cycling stability up to 432 cycles (144 h) under ambient air

Metal-Free Bifunctional Ordered Mesoporous Carbon for Reversible Zn-CO2 Batteries.

The fabrication of Zn-CO2 batteries is a promising technique for CO2 fixation and energy storage. Herein, nitrogen-doped ordered mesoporous carbon (NOMC) is adopted as a bifunctional metal-free electrocatalyst for CO2 reduction and oxygen evolution reaction in the near-neutral electrolyte. The ordered mesoporous structures and abundant N-dopings of NOMC facilitate the accessibility and utilization of the active sites, which endow NOMC with excellent electrocatalysis performance and outstanding stability. Especially, a nearly 100% CO Faradaic efficiency is achieved at an ultralow overpotential of 360 mV for CO2 reduction. When constructed as an aqueous rechargeable Zn-CO2 battery using NOMC as the cathode, it yields a high peak power density of 0.71mW cm-2 , a good cyclability of 300 cycles, and excellent energy efficiency of 52.8% at 1.0mA cm-2 .

A highly sensitive electrochemical sensor containing nitrogen-doped ordered mesoporous carbon (NOMC) for voltammetric determination of l-tryptophan

This study developed a novel electrochemical sensor containing nitrogen-doped ordered mesoporous carbon (NOMC) for the sensitive and selective quantification of l-tryptophan (Trp). The electro-oxidation mechanism of Trp on the NOMC/Nafion/glass carbon electrode (GCE) was first investigated, and was found to follow a two-electron/two-proton transfer mechanism. Subsequently, the analytical operation conditions were optimized. Under the optimum testing conditions, the oxidation current was found to increase linearly with Trp concentration in the ranges 0.5–70.0 μM and 70.0–200.0 μM (different slopes in each range), with the limit of detection determined to be 35.0 nM (S/N = 3). In addition, the sensor was highly selective for Trp and showed good repeatability and long-term stability. Studies of Trp in real world systems, such as an 18 amino acid mixture and an enzymatic protein hydrolysate, showed excellent recoveries (99.30–103.60%). Results suggest that NOMC/Nafion/GCE sensor has excellent performance characteristics for routine Trp analysis.

Hydrothermal synthesis of nitrogen-doped ordered mesoporous carbon via lysine-assisted self-assembly for efficient CO2 capture.

Nitrogen-doped ordered mesoporous carbons (NOMCs) were synthesized by single-step hydrothermal self-assembly using F127 as a soft template, hexamine as a formaldehyde source, l-lysine as a polymerization catalyst, and 3-aminophenol as both carbon and nitrogen sources. The microstructure of the NOMCs was characterized by XRD, N2 adsorption/desorption, TEM, FTIR, and XPS. The results indicated that the obtained NOMCs exhibited a large specific surface area, uniform pore size distribution and highly ordered 2-D hexagonal mesostructure (P6mm). Besides, the nitrogen was uniformly doped into the carbon framework in the form of various nitrogen species. The adsorption isotherms of CO2 and N2 were also determined and could be well fitted by a DSL model. The capture capacity of CO2 was affected by both the nitrogen content and mesostructure of the adsorbents. Overall, NOMC-L-0.5 displayed excellent CO2 capture capacity (0 °C, 3.32 mmol g−1; 25 °C, 2.50 mmol g−1), and still demonstrated great regenerability with only 2% loss after several CO2 adsorption/desorption cycles. Moreover, the CO2/N2 selectivity calculated by IAST was as high as 43.2 at 25 °C in a typical composition of flue gas (binary mixtures with 15% CO2). The superior adsorption performance enables NOMCs to be a promising CO2 adsorbent in practical applications.

Dual nitrogen sources co-doped mesoporous carbon with ultrahigh rate capability for high-performance supercapacitors

Nitrogen-doped ordered mesoporous carbon (N-OMC) was synthesized through evaporation induced self-assembly (EISA) technique by using pyrrole and carbamide as N sources. The obtained N-OMC has high-ordered 2D-hexagonal mesostructures with uniform pore size and high specific surface area. When pyrrole and carbamide were simultaneously employed as N sources, the sample shows higher subtotal percentage of pyridinic and pyrrolic N, leading to better electrochemical performance. As-prepared N-OMC with dual N sources (N12-OMC-1) possesses an ultra-high specific capacitance of 310 F g−1 at the current density of 1.0 A g−1 and remains 245 F g−1 (nearly 80% of its capacitance at 1.0 A g−1) at 20 A g−1, achieving both high rate capability and high specific capacitance. N12-OMC-1 based symmetrical supercapacitor demonstrates the highest energy density of 17.8 Wh kg−1 at a power density of 225 W kg−1 and maintains 12.2 Wh kg−1 at a very high output power density of 13500 W kg−1 in 1 M Na2SO4 electrolyte. Moreover, the N12-OMC-1 based symmetrical supercapacitor exhibits an excellent long-term electrochemical stability with 96.2% capacitance retention and 97% coulombic efficiency after 5000 cycles. Outstanding performances of N12-OMC-1 make it a potential candidate for supercapacitor applications.

Fabrication and electrochemical properties of well-dispersed molybdenum oxide nanoparticles into nitrogen-doped ordered mesoporous carbons for supercapacitors

Environment-friendly supercapacitors demand the high-performance electrode materials working with neutral aqueous electrolyte. In this work, the nitrogen-doped ordered mesoporous carbons (NOMCs) have been synthesized and subsequently modified with molybdenum oxide nanoparticles (NPs) by a self-developed temperature controlled impregnation method. The prepared hybrids possess ordered mesoporous structure, high specific surface area (600–1000 m2 g−1), favorable pore size (∼4 nm) and well-dispersed uniform molybdenum oxide NPs. The results demonstrate that the nano-sized molybdenum oxides encapsulated in the ordered mesoporous channels exhibit significant electrochemical activity with an enhanced specific capacitance up to 410 F g−1, which can be attributed to the nanosize effects from the nanopore confinement and efficient surface area of molybdenum oxide NPs under well dispersion. The hybrids exhibit quasi-rectangular CV curves within the enlarged potential window compared with the pristine NOMCs together with pairs of redox peaks owing to the multi-valance changes of molybdenum corresponding to the Faradaic reactions. Thus, the synthesized hybrids demonstrate not only the synergistic contribution of electrical double-layer capacitance and pseudocapacitance but also superior cycling stability in aqueous neutral electrolyte.

Low-dimensional nitrogen-doped carbon for Br2/Br− redox reaction in zinc-bromine flow battery

Nitrogen-doped ordered mesoporous carbon (NOMC) is developed for the Br2/Br− redox couple, and the effect of the characteristic dimension is investigated. The resultant carbon is extensively investigated by electron microscope, nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy and electrochemical methods. Salient findings are as follows. First, the template determines the morphology of the resultant carbon, which features high specific surface area. Second, the nitrogen-doped carbon, in which the heteroatom-activated carbon act as the active sites, yields a decent electrocatalytic activity towards the Br2/Br− redox couple. The standard reaction rate constant is calculated by using rotating disk electrode method. Third, as compared with NOMC-3D, the lamellar morphology of NOMC-2D favors the exposure of the active sites and mass transfer of the reactive species, yields a high energy efficiency of 84.3% in zinc-bromine flow battery at the current density of 80 mA cm−2. In addition, NOMC-2D shows negligible degradation after 200-cycle test at 80 mA cm−2, revealing its superior electrochemical stability in ZBFB.

Auto-programmed heteroarchitecturing: Self-assembling ordered mesoporous carbon between two-dimensional Ti3C2Tx MXene layers

Two-dimensional (2D) materials have attracted significant research interests for energy-storage applications owing to their unique structural and electronic properties. The modification of 2D materials with ordered mesoporous carbon (OMC) offers great opportunities for increasing the ion-accessible surface area and improving the ion diffusion. Herein, we report an unprecedented type of heterostructured MXene (Ti3C2Tx)/nitrogen-doped OMC (NOMC) hybrid, which is prepared via the self-assembly of melamine resol-P123 micelles with exfoliated Ti3C2Tx nanosheets. The NOMC exhibits well-ordered mesopores which are aligned with Ti3C2Tx nanosheet surface. This novel structure not only prevents the stacking of MXene nanosheets, but also provides a fast ion-diffusion path. When used as an electrode material for supercapacitors, the Ti3C2Tx-NOMC hybrid exhibits a high gravimetric capacitance of 329 F g−1 and a volumetric capacitance of 823 F cm−3. Furthermore, the Ti3C2Tx-NOMC composite also displays excellent rate capability and good cycling stability, thus highlighting the benefit of hybridizing MXene with ordered mesoporous carbon for for enhancing the energy storage performance.

Nitrogen-Dopped Ordered Mesoporous Carbon Anchored Pd Nanoparticles for Solvent Free Selective Oxidation of Benzyl Alcohol to Benzaldehyde by Using O2.

Introducing electron-rich nitrogen atoms to ordered mesoporous carbons (OMC) as supports for noble metal catalysts, not only improves the hydrophilic properties of a mesoporous carbon surface, but also enhances the coordination and binding abilities of metal ion. In the present work, nitrogen-doped ordered mesoporous carbons (NOMCs) were successfully fabricated via a facile hydrothermal self-assembly. The prepared NOMCs were characterized through powder X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm. The analyses demonstrated that the NOMCs prepared at a pyrolysis temperature of 750°C possessed an ordered 2D hexagonal mesoporous structure, a high graphitization degree, large surface area, and a well-distributed pore size. In particular, NOMCs could anchor Pd nanoparticles uniformly because of the introducing N atoms with strong electronegativity, which were selected as efficient catalysts for the partial oxidation of benzyl alcohol to benzaldehyde. Approximately 24.63% conversion with 85.71% selectivity to benzaldehyde was obtained without using any solvent by molecular O2 oxidation. Most importantly, the TOF value of the catalyst in the reaction system was up to 8698 h−1. After five runs reaction, TOF and selectivity of the catalyst remained essentially same. Hence, the proposed catalyst has a potential engineering application value.

Nitrogen-Doped Ordered Mesoporous Carbons Supported Co3O4 Composite as a Bifunctional Oxygen Electrode Catalyst

It is increasingly useful to develop bifunctional catalysts for oxygen reduction and oxygen evolution reaction (ORR and OER) for fuel cells, metal-air rechargeable batteries, and unitized regenerative cells. Here, based on the excellent conductivity and stability of ordered mesoporous carbons, and the best ORR and OER activity of Co3O4, the composite Co3O4/N-HNMK-3 was designed and manufactured by means of a solvothermal method, using ordered N-doped mesoporous carbon (N-HNMK-3) as substrate, and then the bifunctional electrocatalytic performance corresponding to ORR, OER in alkaline media was carefully investigated. The results showed that Co3O4/N-HNMK-3 composite, a non-precious metal centered electrocatalyst, displayed excellent ORR performance (activity, selectivity, and stability) close to that of commercial 20 wt.% Pt/C and a promising OER activity near 20 wt.% RuO2/C. The outstanding bifunctional activities of Co3O4/N-HNMK-3 was assessed with the lowest △E value of 0.86 V (EOER,10 mA cm−2-EORR,−3 mA cm−2) with respect to the two commercial precious metal-based electrocatalysts.

Voltammetric Biosensor Based on Nitrogen-doped Ordered Mesoporous Carbon for Detection of Organophosphorus Pesticides in Vegetables

Background: Pesticides residues in agricultural products have posed a serious threat to food safety and human health, so it is necessary to develop a rapid and accurate method to detect pesticide in the environment. N-OMC with excellent electroconductivity, high biocompatibility and the functional amino group that can be covalently attached to the enzyme can be applied to construct a sensitive and stable acetylcholinesterase biosensor for rapid and accurate detection of organophosphorus pesticides with the help of L-cysteine self-assembled monolayer and AuNPs. Methods: Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption measurements are used to characterize materials. Electrochemical impedance spectroscopy and cyclic voltammetry are used to study the surface features of modified electrodes. Differential pulse voltammetric is used to measure the peak current of modified electrodes. GC-MS is applied to verify the reliability of the prepared biosensor for organophosphorus pesticides detection. Results: N-OMC was synthesized and applied to constructed stable and sensitive acetylcholinesterase biosensors. The combination of N-OMC, L-cysteine self-assembled monolayer and AuNPs to modify the electrode surface has greatly improved the conductivity of biosensor and provided a stable platform for acetylcholinesterase immobilization. The linear detection range of paraoxon was from 3 to 24 nM with a lower detection limit of 0.02 nM. Conclusion: The biosensor exhibited satisfactory reproducibility, repeatability and stability, and was successfully employed to determine the paraoxon in vegetables as well as tap water samples, providing a promising tool for rapid and sensitive detection of organophosphorus pesticides in agricultural products.

Selenium-infiltrated mesoporous carbon composite cathode for a high-capacity lithium-chalcogen battery: Effects of carbon structure and dopant on the rate-capability and cyclic stability

A selenium/carbon (Se/C) composite has been suggested as an excellent substitute cathode material due to its high theoretical volumetric capacity. However, it exhibits severe capacity decay, which is caused by the dissolution of active materials as well as shuttle effect. One effective strategy to alleviate this dissolution is to confine the Se within porous carbon frameworks. Here, we report the effects of carbon structure and dopant on the electrochemical performances of Se infiltrated carbon composites with three types carbons; (i) nitrogen-doped ordered mesoporous carbon (NOMC), (ii) sulfur-doped ordered mesoporous carbon (SOMC), and (iii) macroporous spherical carbon, which have different porosities and dopants. The Se/C cathodes are prepared by meting selenium-sulfur compound and then evaporating sulfur from the compound, providing nanoscale space for efficient electrolyte access to the reaction site. Among the three composite cathodes, the Se/NOMC exhibits the highest rate-capability and cyclic stability due to an abundance of cylindrical mesopores (4–5 nm pore diameter) that can provide enough electrolyte diffusion path and effectively impede the dissolution of selenium. As a result, the Se/NOMC has a high volumetric capacity of 1605 mAh cm−3 and excellent capacity retention of 100% during 500 cycles at 0.648 A h cm−3 (C-rate of C/2.5).

The Selenium-Sulfide Infiltrated Carbon Cathodes for Lithium-Sulfur Batteries: Effects of Carbon Framework Structure and Dopants on the Electrochemical Performances

The Selenium-Sulfur/Carbon(Se-S/C) composites containing Se, which has much higher electrical conductivity (10-3 S cm-1) than S (5*10-28 S cm-1), have been suggested as a new cathode material instead of S/C composites [1-3]. Specifically, SeS2/C composites delivers competitive volumetric capacity (4026 mAh cm-3) compared to sulfur (3296 mAh cm-3) due to larger density of Se (4.82 g cm-3). Despite of these advantages of the Se-S/C, the material could not be used practically due to a severe capacity decay, which is induced by Shuttle Effect in the Se-S/C composites as well as in the S/C composites. It has been considered that one of the good solutions is that the Se-S are confined effectively within the carbon framework during cycling [1-4]. Zhen et al [2]. introduced CMK/SeS2@PDA cathode material, which utilized the well-aligned mesoporous carbon and the conductive polymer coating to confine soluble intermediates physically, but it showed only 55 % of capacity retention after 500 cycles at 0.2 A g-1. Even though it exhibited better long-term cyclic performance in comparison with previously reported Se-S/C works, its capacity retention was still low and the extra coating process was also ineffective way to confine Se-S into pores [2]. In this study, we aimed to demonstrate the effects of the structure and dopants of the carbon framework on the electrochemical performances of the Se-S/C cathode. We prepared the SeS2/C composites by a facile melt-diffusion and an evaporation method employing 4 different carbon frameworks; (i) mesoporous carbon(OMC), (ii) nitrogen-doped ordered mesoporous carbon(NOMC), (iii) sulfur-doped ordered mesoporous carbon(SOMC), and (iv) ketjen black 600JD (KB600, commercial carbon). When preparing the SeS2/C composites, we intended that the SeS2 was partially filled on the carbon frameworks by making an inside hole of SeS2 inside pores of carbon framework, as shown in Fig. 1-2. We believed that it would be beneficial to suppressing volume expansion of chalcogen materials and utilization of the active materials. From the half-cell tests of four SeS2/C cathodes (SeS2/OMC, SeS2/NOMC, SeS2/SOMC, and SeS2/KB600) (Fig.3), the SeS2/KB600 showed the highest initial capacity due to its largest surface area that provides sufficient electrochemical reaction sites. However, it exhibited a poor cyclic stability due to the continuous dissolution of lithium polysulfides and polyselenides, originated from relatively large mean pore diameter (8.67 nm >) that is not suitable to trap the Se and S physically. Meanwhile, the SeS2 in the 3 types of ordered mesoporous carbons (OMC, NOMC, and SOMC), which have a large length to pore diameter ratio (L/D), delivered better rate-capability than the spherical KB600 (Fig. 3a). It implies that a long diffusion path for Li ions and partially filled SeS2 in the ordered mesoporous carbons are favorable to ion transportation inside pores [4]. Among all the SeS2/C cathodes, SeS2/NOMC exhibited the best electrochemical performance; nearly 99.99 % coulombic efficiency (no capacity fading during 500 cycles) presumably due to its N dopant that contribute to chemical adsorption of the soluble intermediates (Fig. 3b, 4).

Sulfur Diffusion within Nitrogen-Doped Ordered Mesoporous Carbons Determined by in Situ X-ray Scattering.

The low intrinsic conductivity of sulfur necessitates conductive additives, such as mesoporous carbons, to the cathode to enable high-performance metal-sulfur batteries. Simultaneous efforts to address polysulfide shuttling have introduced nitrogen-doped carbons to provide both conductivity and suppressed shuttling because of their strong interaction with sulfur. The strength of this interaction willimpact the ability to fill the mesopores with sulfur via melt infusion. Here, we systematically investigate how nitrogen doping influences the rate that molten sulfur can infiltrate the mesopores and the overall extent of pore filling of highly ordered mesoporous doped carbons using in situ small angle X-ray scattering (SAXS). The similarity in electron density between molten sulfur and the soft carbon framework of the mesoporous material leads to a precipitous decrease in the scattered intensity associated with the ordered structure as voids are filled with sulfur. As the nitrogen doping increases from 1 to 20 at. %, the effective diffusivity of sulfur in the mesopores decreases by an order of magnitude (2.7 × 10-8 to 2.3 × 10-9 cm/s). The scattering becomes nearly invariant within 20 min of melt infiltration at 155 °C for all but the most doped carbon, which indicates that submicron-sized mesoporous carbon particles can be filled rapidly. Additionally, the nitrogen doping decreases the sulfur content that can be accommodated within the mesopores from 95% of the mesopores filled without doping to only 64% filled with 20 at. % N as determined by the residual scattering intensity. Sulfur does not crystallize within the mesopores of the nitrogen-doped carbons, which is further indicative of the strong interactions between the nitrogen species and sulfur that can inhibit polysulfide shuttling. In situ SAXS provides insights into the diffusion of sulfur in mesopores and how the surface chemistry of nitrogen-doped carbon appears to significantly hinder the infiltration by sulfur.

Synthesis and Supercapacitor Performance of Polyaniline/Nitrogen-Doped Ordered Mesoporous Carbon Composites

The electrochemical property of ordered mesoporous carbon (OMC) can be changed significantly due to the incorporating of electron-donating heteroatoms into OMC. Here, we demonstrate the successful fabrication of nitrogen-doped ordered mesoporous carbon (NOMC) materials to be used as carbon substrates for loading polyaniline (PANI) by in situ polymerization. Compared with NOMC, the PANI/NOMC prepared with a different mass ratio of PANI and NOMC exhibits remarkably higher electrochemical specific capacitance. In a typical three-electrode configuration, the hybrid has a specific capacitance about 276.1 F/g at 0.2 A/g with a specific energy density about 38.4 Wh/kg. What is more, the energy density decreases very slowly with power density increasing, which is a different phenomenon from other reports. PANI/NOMC materials exhibit good rate performance and long cycle stability in alkaline electrolyte (~ 80% after 5000 cycles). The fabrication of PANI/NOMC with enhanced electrochemical properties provides a feasible route for promoting its applications in supercapacitors.