Nitrogen Co-doped Carbon Materials Research Articles

Selective Aerobic Oxidation of Csp3-H Bonds Catalyzed by Yeast-Derived Nitrogen, Phosphorus, and Oxygen Codoped Carbon Materials.

Nitrogen, phosphorus, and oxygen codoped carbon catalysts were successfully synthesized using dried yeast powder as a pyrolysis precursor. The yeast-derived heteroatom-doped carbon (yeast@C) catalysts exhibited outstanding performance in the oxidation of Csp3-H bonds to ketones and esters, giving excellent product yields (of up to 98% yield) without organic solvents at low O2 pressure (0.1 MPa). The catalytic oxidation protocol exhibited a broad range of substrates (38 examples) with good functional group tolerance, excellent regioselectivity, and synthetic utility. The yeast-derived heteroatom-doped carbon catalysts showed good reusability and stability after recycling six times without any significant loss of activity. Experimental results and DFT calculations proved the important role of N-oxide (N+-O-) on the surface of yeast@C and a reasonable carbon radical mechanism.

Metal-Organic Framework Derived Zinc and Nitrogen Co-Doped Porous Carbon Materials for High Performance Zinc-Ion Hybrid Supercapacitors

Metal-Organic Framework Derived Zinc and Nitrogen Co-Doped Porous Carbon Materials for High Performance Zinc-Ion Hybrid Supercapacitors

Ethanol Dehydrogenation to Acetaldehyde over Co@N-Doped Carbon

Cobalt and nitrogen co-doped carbon materials (Co@CN) have recently attracted significant attention as highly efficient noble-metal-free catalysts exhibiting a large application range. In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts. The catalyst samples were synthesized by a variety of affordable techniques, ensuring generation of various types of Co species incorporated in carbon, such as subnanosized cobalt sites and nano-sized particles of metallic cobalt and cobalt oxides. The catalytic activity was tested under both oxidative and non-oxidative gas-phase conditions at 200–450 °C using a fixed-bed flow reactor. The non-oxidative conditions proved to be much more preferable for the target reaction, competing, however, with ethanol dehydration to ethylene. Under specified reaction conditions, ethanol conversion achieved a level of 66% with 84% selectivity to acetaldehyde at 400 °C. The presence of molecular oxygen in the feed led mainly to deep oxidation of ethanol to COx, giving acetaldehyde in a comparatively low yield. The potential contribution of carbon itself and supported cobalt forms to the observed reaction pathways is discussed.

Organic Dye-Derived N, S Co-Doped Porous Carbon Hosts for Effective Lithium Polysulfide Confinement in Lithium-Sulfur Batteries.

Lithium–sulfur batteries are considered as attractive candidates for next-generation energy storage systems originating from their high theoretical capacity and energy density. However, the severe shuttling of behavior caused by the dissolution of lithium polysulfide intermediates during cycling remains a challenge for practical applications. Herein, porous carbon materials co-doped with nitrogen and sulfur atoms were prepared through a facile hydrothermal reaction of graphene oxide and methylene blue to obtain a suitable host structure for regulating the lithium polysulfide shuttling behavior. Experimental results demonstrated that the abundant heteroatom-containing moieties in the carbon frameworks not only generated favorable active sites for capturing lithium polysulfide but also enhanced redox reaction kinetics of lithium polysulfide intermediates. Consequently, the corresponding sulfur composite electrodes exhibited excellent rate performance and cycling stability along with high Columbic efficiency. This work highlights the approach for the preparation of nitrogen and sulfur co-doped carbon materials derived from organic dye compounds for high performance energy storage systems.

Synergistic effect of PMS activation by Fe0@Fe3O4 anchored on N, S, O co-doped carbon composite for degradation of sulfamethoxazole

High efficient activator is highly desired in the field of persulfate-based advanced oxidation process. In comparison with the previous studies, this study adopted nitrogen, sulfur and oxygen co-doped carbon material to support Fe0 encapsulate in Fe3O4 to prepare iron-based modified carbon composite (Fe0@Fe3O4-MC) by a facile two-step pyrolysis. Fe0@Fe3O4-MC was then used for degradation of sulfamethoxazole. The results showed that Fe0@Fe3O4-MC had superior catalytic activity for PMS activation due to the synergistic effect of iron-based compound and modified carbon. In the presence of 0.1 g/L of Fe0@Fe3O4-MC, SMX (0.04 mM) could be completely degraded within 120 min at pH 3.4 and 3 mM of PMS. The SMX degradation followed pseudo first-order kinetic model, with the rate constant of 0.12 min−1, and the mineralization of SMX achieved 48.4%. Sulfate radicals dominated in the SMX degradation. In addition to Fe0 and Fe3O4, carbon defects, graphitic N, sulfur and FeN4 also contributed to PMS activation. Fe0 oxidation was the rate-limiting step for PMS activation. Dissolved oxygen made a minor contribution to Fe0 oxidation. The intermediate products of SMX degradation were identified, and two pathways of SMX degradation were proposed. The influencing factors on SMX degradation were studied, including pH, temperature, PMS concentration, Fe0@Fe3O4-MC dosage, chloridion, carbonate and humic acids, and the influencing mechanism was discussed. This study could provide an efficient PMS activator for the degradation of emerging organic pollutants in water and wastewater.

Identifying active sites of boron, nitrogen co-doped carbon materials for the oxygen reduction reaction to hydrogen peroxide

The electrochemical synthesis of hydrogen peroxide (H2O2) from two-electron oxygen reduction reaction (2e- ORR) is a promising alternative for producing chemicals on demand, but its widespread application is still hampered by the low efficiency. Here, we successfully prepared a boron and nitrogen co-doped porous carbon (B/NC) aerogel with a tunable B, N co-doped configuration by the gelation of PVA-graphene, borax and PANI, followed by pyrolysis. Due to a hierarchical porous structure and optimized B, N co-doping, B/NC aerogel showed an excellent electrocatalytic performance for H2O2 production in alkaline solution with a high H2O2 selectivity (94.16%) at positive applied potential (0.6 V vs. RHE), superior than most of the other reported electrocatalysts. Density functional theory (DFT) calculations reveal that the hexagonal boron nitride (hBN) coupled with neighboring pyridinic-N species act as the active sites to lower free energy barrier for formation of HOO* intermediate, thus facilitating H2O2 production. Practically, B 2p electron plays an important role for the adsorption of HOO* intermediates. B and Nco-doping into carbon materials provides an effective and facile method to reasonably construct carbon-based catalysts for electroreduction of O2 to H2O2.

Biomass-derived precious metal-free porous carbon: Ca-N,P-doped carbon materials and its electrocatalytic properties

The search for non-noble metal catalysts drive from biomass materials for oxygen reduction reactions (ORR) is highly desirable but challenging. Here, we have designed and synthesized three-dimensional hierarchical porous Ca-modified nitrogen and phosphorus co-doped carbon materials (Ca@NP6C4) derived from biomass hydrogel. Notably, the resulting Ca@NP6C4 material has high content of nitrogen (29.71 wt%)，and relatively high content percentage of pyridinic and graphitic nitrogen. As an efficient non-noble metal electrocatalyst, Ca@NP6C4 exhibits a high onset potential (0.94 V vs RHE) and a four-electron pathway for oxygen reduction reaction as well as good durability and outstanding methanol poisoning tolerance. Besides, it also performs as a good support for Pt particles (NPs). Pt/Ca@NP6C4 catalyst displayed remarkable catalytic performance and high stability for methanol electrooxidation reaction in acid medium. This work provides a feasible approach to develop cost-effective and highly efficient non-precious metal electrochemical catalysts for oxygen reduction.

Hazardous Petroleum Sludge-Derived Nitrogen and Oxygen Co-Doped Carbon Material with Hierarchical Porous Structure for High-Performance All-Solid-State Supercapacitors.

Rational design and sustainable preparation of high-performance carbonaceous electrode materials are important to the practical application of supercapacitors. In this work, a cost-effective synthesis strategy for nitrogen and oxygen co-doped porous carbon (NOC) from petroleum sludge waste was developed. The hierarchical porous structure and ultra-high surface area (2514.7 m2 g−1) of NOC electrode materials could provide an efficient transport path and capacitance active site for electrolyte ions. The uniform co-doping of N and O heteroatoms brought enhanced wettability, electrical conductivity and probably additional pseudo-capacitance. The as-obtained NOC electrodes exhibited a high specific capacitance (441.2 F g−1 at 0.5 A g−1), outstanding rate capability, and cycling performance with inconspicuous capacitance loss after 10,000 cycles. Further, the assembled all-solid-state MnO2/NOC asymmetrical supercapacitor device (ASC) could deliver an excellent capacitance of 119.3 F g−1 at 0.2 A g−1 under a wide potential operation window of 0–1.8 V with flexible mechanical stability. This ASC device yielded a superior energy density of 53.7 W h kg−1 at a power density of 180 W kg−1 and a reasonable cycling life. Overall, this sustainable, low-cost and waste-derived porous carbon electrode material might be widely used in the field of energy storage, now and into the foreseeable future.

Preparation of iron and nitrogen co-doped carbon material Fe/N-CCM-T for oxygen reduction reaction

In this paper, iron and nitrogen co-doped carbon material with nanotube structure (Fe/N-CCM-T) was synthesized by pyrolyzing a mixture of Fe salt, chitosan and melamine and displayed high electrocatalytic performance for oxygen reduction reaction (ORR). The structure of the Fe/N-CCM-T was characterized and their ORR performance in alkaline media was investigated by linear sweep voltammetry, cyclic voltammetry and chronoamperometry. Fe/N-CCM-T displayed better ORR performance than other carbon materials like Fe/N-CC-800. The Fe/N-CCM-800 with a large surface area (302.5 m2/g) especially exhibited the best ORR electrocatalytic performance among the prepared carbon materials, which was also proved by its similar Tafel slope (76 mV decade−1) to Pt/C catalyst (74 mV decade−1). Fe/N-CCM-800 showed similar ORR activity as commercial Pt/C catalyst, but superior tolerance to methanol and stability. Such high ORR performance of the Fe/N-CCM-T can be attributed to its nanotube structure, high specific surface area (SSA), high graphitic-N and pyridinic-N contents.

Clarification of Active Sites for Oxygen Reduction Reaction on Silver and Nitrogen Co-Doped Carbon Materials

The oxygen reduction reaction (ORR) is one of the most important reactions in both fuel cells and metal-air batteries [1]. ORR needs catalysis to lower the electrochemical overpotential for high-voltage output for these technologies and, so far, platinum (Pt) has been the main catalyst of choice. However, as the expensive, traditional Pt/C catalysts are not viable in the long term, much effort has been focused on heteroatom doped and non-precious metal catalysts [2]. Metal-nitrogen co-doped carbon materials have emerged as the main candidates for replacing the platinum-based catalysts. Among these materials, silver and nitrogen co-doped catalysts have proven to exhibit high electrocatalytic activity for the ORR in alkaline media. However, no clear understanding exists about the exact catalytic mechanism and rational design of these catalysts.In this work, we synthesized model catalyst of silver and nitrogen co-doped carbon (Ag-N-C) by using simple precursors. Silver phthalocyanine and multi-walled carbon nanotubes have been used for the one-pot synthesis of Ag-N-C material. The morphology of the catalyst was studied by the transmission electron microscopy and the surface elemental composition was examined with X-ray photoelectron spectroscopy (XPS). The catalysts‘ activity towards ORR in 0.1 M KOH is assessed using the rotating disk electrode (RDE) method and the results are compared to those of commercial Pt/C catalysts (Figure 1). The created Ag-N-C model catalyst reveal a highly enhanced activity via the synergistic, doubly beneficial effects of the support material and formed catalytic centers, which were studied by density functional theory (DFT). Our theoretical calculations, which matched with the experimental findings, provide necessary hints on ORR mechanistic issues on the developed Ag-N-C model catalyst and will guide how to design and prepare better active non-Pt catalyst materials for fuel cell and metal-air battery electrodes, as well as providing deeper insight into the ORR mechanism occurring on this type of catalysts.

From bulk to porous: Structure transformation of nitrogen and phosphorous co-doped carbon material via sodium chloride assistance and its application in lithium-sulfur batteries

Carbon materials with porous structure and high conductivity are popular scaffold in lithium-sulfur batteries. However, the difficulty in fabrication restricts their application. In this work, a facile method to fabricate nitrogen and phosphorus co-doped multi-scaled porous carbon is reported. The porous carbon (named as CPANiP-NaCl) with highly interconnected network structure was fabricated by pyrolysis of phytic acid cross-linked polyaniline aerogels with the assistance of sodium chloride (NaCl). NaCl served as a hard template before melting, which helps to keep the interconnected framework of precursor and prevent the generated carbon intermediates stacking into bulks. Molten NaCl provides an inner media to facilitate dissolved oxysalt (PO43−) to partially oxidize the carbon intermediates and generate micro-pores. Improved specific surface area and porous volume promote the impregnation of sulfur and electrolyte, and the high conductivity of CPANiP-NaCl enhances the electron transportation. Besides that, physical absorption of micro-pores and chemical anchoring of doped heteroatoms accelerate the transformation of polysulfide species. The simultaneously enhanced confinement to polysulfide species with different polarities helps realize the superior cyclic stability and rate performance of CPANiP-NaCl/Sulfur. Finally, the cells maintain the capability of 652 mAh⋅g−1 (1 C = 1675 mAh⋅g−1) at 0.5 C and 94% capacity retention after 120 cycles.

Pyrolysis of a flash nanoprecipitated tannic acid–metal@polymer assembly to create an electrochemically active metal@nanocarbon catalyst

Herein, hydrophobic tannic acid–iron (TA–Fe) coordination composites were encapsulated within polystyrene-copolyacrylonitrile (PS-c-PAN) nanospheres using the flash nanoprecipitation (FNP) technique. Carbon materials with uniform and dense distributions of metal NPs were obtained after carbonization under the protection and confinement of the polymer matrix. The as-prepared Fe and nitrogen codoped carbon materials exhibited enhanced electrocatalytic performance in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In addition, the catalytic ability of the carbon/metal composites could be affected by tuning the morphology and composition. TA–Fe@PS-c-PAN NPs were synthesized via a typical FNP procedure. During the process, the water solution containing Fe3+ and the organic solution containing polymer and TA diffused into each other under turbulent mixing. As a result, the hydrophobic TA–Fe complex quickly formed and co-assembled into TA–Fe@PS-c-PAN NPs. After carbonization, carbon materials with uniformly dispersed metal NPs were finally and used as effective catalysts for oxygen reduction and evolution reactions.

Micelle-template synthesis of a 3D porous FeNi alloy and nitrogen-codoped carbon material as a bifunctional oxygen electrocatalyst

The sluggish kinetics of oxygen reduction reaction and oxygen evolution reaction (ORR/OER) are the key scientific issues that need to be addressed for the application of renewable energy technologies. Rational coupling transition metal with porous heteroatom-doped carbon is extensively investigated as an efficient strategy to achieve high performance ORR/OER nonprecious metal electocatalysts. In this study, a FeNi alloy coated with N-doped carbon material (namely FeNi/NC) was designed by using triblock copolymer Pluronic F127 as a surfactant co-assembly with g-C3N4. This strategy enabled FeNi/NC possessing a high BET surface area in terms of three-dimensional hierarchical porous structure together with abundant defect sites. The optimized FeNi/NC catalyst displays an excellent oxygen electrode electrocatalytic activity with a potential gap △E of 0.77 V in alkaline media which substantially outperformed benchmark Pt/C + RuO2 (△E = 0.80 V). Furthermore, it shows almost no decay after long-time cycling tests for ORR/OER. The excellent catalytic performance along with the low cost for FeNi/NC catalyst makes it possible to commercialize the renewable energy devices.

Nitrogen and Cobalt Co-Coped Carbon Materials Derived from Biomass Chitin as High-Performance Electrocatalyst for Aluminum-Air Batteries

Development of convenient, economic electrocatalysts for oxygen reduction reaction (ORR) in alkaline medium is of great significance to practical applications of aluminum-air batteries. Herein, a biomass chitin-derived carbon material with high ORR activities has been prepared and applied as electrocatalysts in Al-air batteries. The obtained cobalt, nitrogen co-doped carbon material (CoNC) exhibits the positive onset potential 0.86 V vs. RHE (reversible hydrogen electrode) and high-limiting current density 5.94 mA cm−2. Additionally, the durability of the CoNC material in alkaline electrolyte shows better stability when compared to the commercial Pt/C catalyst. Furthermore, the Al-air battery using CoNC as an air cathode catalyst provides the power density of 32.24 mW cm−2 and remains the constant discharge voltage of 1.17 V at 20 mA cm−2. This work not only provides a facile method to synthesize low-cost and efficient ORR electrocatalysts for Al-air batteries, but also paves a new way to explore and utilize high-valued biomass materials.

Efficient oxygen reduction to H2O2 in highly porous manganese and nitrogen co-doped carbon nanorods enabling electro-degradation of bulk organics

The direct synthesis of hydrogen peroxide using sustainable energy and molecular oxygen is a promising alternative approach to the conventional batch synthesis. Here we present a manganese and nitrogen co-doped carbon material which catalyzes the selective reduction of dioxygen in an acidic environment to hydrogen peroxide. The onset potential is close to 0.7 V, with >98% H2O2 selectivity in the range of 0.7–0.5 V vs RHE. This is the highest reported to date, outperforming many bimetallic noble metal catalysts. Besides, this doped carbon material is hierarchically porous, featuring both a large mesopore volume (4.54 mL g−1) and a high specific surface area (1333 m2 g−1). This enables the effective adsorption of bulky organics such as methylene blue (385 mg g−1). Combined with the formation of hydroxyl radicals during electrochemical H2O2 generation, this material also enables the efficient electrochemical degradation of methylene blue, as evidenced by in situ UV–vis spectrometry.

Three-dimensional porous Ni, N-codoped C networks for highly sensitive and selective non-enzymatic glucose sensing

Carbon materials have received intensive attention due to their unique property in the field of electrochemical analysis. As transition metallic heteroatom and nitrogen-codoped carbon (M-N-C) materials commonly exhibit enhanced electrochemical activity for the tuned electronic structure, therefore, fabricating a novel structure of M-N-C material for electrochemical analysis is highly pursued. Herein, an in-situ self-growth NaCl-templated strategy is proposed to fabricate three-dimensional porous Ni, N-codoped carbon material (3D Ni-N-C). The as-obtained 3D Ni-N-C demonstrates superior electrochemical performance toward glucose oxidation and sensing, and a highly sensitive and selective non-enzymatic glucose sensor is subsequently developed for human serums with a wide linear range of 0.001–1.20 mM, low detection limit of 0.15 μM, and high sensitivity of 1181.0 μA mM−1 cm-2. It is believed that the unique structural properties of 3D Ni-N-C (abundant N-doped and Ni-N coordinated active sites, large surface area, open micro-porous structure) are conducive to the formation and exposure of highly catalytic centers and improvement of electron-transfer rate.

Controllable Sulfur, Nitrogen Co-doped Porous Carbon for Ethylbenzene Oxidation: The Role of Nano-CaCO3.

Heteroatom-doped porous carbon materials have exhibited promising applications in various fields. In this work, sulfur, nitrogen co-doped carbon materials (SNCs) with abundant pore structure were prepared by pyrolysis of sulfur, nitrogen-containing porous organic polymers (POPs) mixed with nano-CaCO3 at high temperature. Among the resultant materials, SNC-Ca-850 possesses a relatively high level of doped heteroatoms and exhibits an excellent catalytic performance for the selective oxidation of benzylic C-H bonds. It is noteworthy that nano-CaCO3 increases the doped sulfur content in the synthesized carbon materials to a large extent and impacts the existence modes of sulfur. In addition, it enhances the porous structure and specific surface area of the resultant SNCs significantly. This work provides a viable strategy to promote the doping of sulfur into carbon materials during the pyrolysis process.

Nitrogen and oxygen co-doped glucose-based carbon materials with enhanced electrochemical performances as supercapacitors

Nitrogen and oxygen co-doped glucose-based porous carbon materials were successfully synthesized using ethylenediamine as nitrogen source through hydrothermal treatment and KOH activation. The activation has an obvious impact on the porosity and porous structure, which leads to remarkable increasement in the specific surface area from 99.63 to 1105.58 m2 g−1 and high nitrogen content of 1.727% and oxygen content of 8.000%. The specific capacitance of the nitrogen and oxygen co-doped glucose-based active electrode material at appropriate weight ratio (carbon material/KOH) of 1:1 was up to 324 F g−1 at a current density of 1.0 A g−1. Moreover, the specific capacitance remains 172 F g−1 and the specific capacitance retention is 101.2% after 5000 charge-discharge cycles at 10 A g−1, indicating its good rate capability and excellent electrochemical stability. These results indicate that nitrogen and oxygen co-doped glucose-based porous carbon material is a promising electrode material for high-performance supercapacitors.

Well-defined gradient Fe/Zn bimetal organic framework cylinders derived highly efficient iron- and nitrogen- codoped hierarchically porous carbon electrocatalysts towards oxygen reduction

The development of highly active and durable non-precious metal electrocatalysts (NPMCs) for the oxygen reduction reaction (ORR) is crucial for the sustainable commercialization of fuel cell technologies. In this work, we have synthesized a new class of bimetallic zeolitic imidazolite framework (Fe,Zn-ZIF) materials with a cylindrical morphology and a well-defined Fe/Zn composition gradient. The Fe/Zn gradient in the Fe,Zn-ZIF cylinders—with a Zn-rich core and a Fe-rich shell—results from a balance of the kinetics and thermodynamics of Fe– and Zn–benzimidazole coordination reactions. Pyrolysis of Fe,Zn-ZIF results in evaporation of Zn from the core of the cylinders generating an inter-connected hierarchical microporous–mesoporous structure, and the concomitant formation of highly exposed and accessible Fe-N4 sites on the surface of the resulting carbonized material, which retains the cylindrical morphology of the precursor. The as-obtained iron- and nitrogen-codoped carbon material thus has both high porosity, favoring mass transport of reactants, and an abundance of sites that are known to be active for the ORR on its surface. Indeed, when used as an ORR electrocatalyst the material outperforms a commercial Pt/C catalyst in alkaline electrolyte (with a half-wave potential ~50 mV higher) and possesses comparable activity to that of Pt/C in acidic electrolytes. Extension of this strategy to other gradient MOFs with diverse compositions and morphologies offers a new avenue for the design and synthesis of a variety of carbon-based materials with targeted functionalities.

Porous nitrogen and oxygen co-doped carbon microtubes derived from plane tree fruit fluff for high-performance supercapacitors

Porous nitrogen and oxygen co-doped carbon microtubes (PCMTs) were prepared via carbonization followed by activation of plane tree fruit fluffs (PTFFs) and employed as high-performance supercapacitor electrode materials. The pore structures, surface chemistry and degree of graphitization of the final products can be facilely tailored by adjusting the activation temperature, which changed remarkably as the activation temperature increased from 650 to 900 °C. The PCMT-850 obtained by activating at 850 °C possessed despite the second largest specific surface area (1533 m2/g), but the highest mesopore ratio (9.13%), the maximal nitrogen content (2.20 at.%) and highest degree of graphitization as well as excellent electrical conductivity. The PCMT-850-based carbon electrode exhibited the highest charge storage capacity with a specific capacitance of 257.6 F/g at a current of 1 A/g and the lowest internal resistance in 6 M KOH. The high supercapacitor performance can be attributed to the combined effects of its pore structure, heteroatom doping effects and degree of crystallinity. The favorable capacitive performance render the waste biomass PTFFs serve as novel resources of nitrogen and oxygen co-doped carbon materials for high-performance supercapacitors.