Nitrogen-doped Graphene Aerogel Research Articles

Boosting bioelectricity generation in bioelectrochemical systems with nitrogen-doped three-dimensional graphene aerogel anode

Bioelectricity generation by electrochemically active bacteria has become particularly appealing due to its vast potential in energy production, pollution treatment, and biosynthesis. However, developing high-performance anodes for bioelectricity generation remains a significant challenge. In this study, a highly efficient three-dimensional nitrogen-doped macroporous graphene aerogel anode with a nitrogen content of approximately 4.38 ± 0.50 at% was fabricated using hydrothermal method. The anode was successfully implemented in bioelectrochemical systems inoculated with Shewanella oneidensis MR-1, resulting in a significantly higher anodic current density (1.0 A/m2) compared to the control one. This enhancement was attributed to the greater biocapacity and improved extracellular electron transfer efficiency of the anode. Additionally, the N-doped aerogel anode demonstrated excellent performance in mixed-culture inoculated bioelectrochemical systems, achieving a high power density of 4.2 ± 0.2 W/m², one of the highest reported for three-dimensional carbon-based bioelectrochemical systems to date. Such improvements are likely due to the good biocompatibility of the N-doped aerogel anode, increased extracellular electron transfer efficiency at the bacteria/anode interface, and selectively enrichment of electroactive Geobacter soli within the NGA anode. Furthermore, based on gene-level Picrust2 prediction results, N-doping significantly upregulated the conductive pili-related genes of Geobacter in the three-dimensional anode, increasing the physical connection channels of bacteria, and thus strengthening the extracellular electron transfer process in Geobacter.

Nitrogen Doped Graphene Aerogel Inserted By Carbon Black As Novel Catalyst Support for Low Temperature Hydrogen Fuel Cells

Carbon supported Pt nanocatalysts, which are commonly used in hydrogen fuel cells, suffer from Pt degradation and carbon corrosion. That causes the high cost and limited lifetime of the fuel cell1. Developing catalyst support materials with high surface area, high electrical conductivity, stability and good interaction with catalyst is an effective solution to address this issue.To enhance the activity and durability of Pt-based catalysts for hydrogen fuel cells, graphene aerogels (GA) are a prospective material with rich porous 3D-structure, large surface area, high electrical conductivity, and good electrochemical stability. They also can improve the tolerance of catalyst CO poisoning and avoid graphene stacking by integrating 2D sheet structure into 3D aerogel structure2, 3. Some research show that the nitrogen doped on the surface of carbon materials could improve ORR activity and electronic conductivity by changing the local electronic structure as well as providing a stable anchor point for pt nanoparticles to enhance the durability of catalysts4, 5.However, most GAs are made from graphene oxide (GO) produced by Hummers method which may lead to safety and environmental issue due to the usage of highly toxic and corrosive chemicals2, 5. Also, there are few articles on the application of GA in fuel cells. It may be limited by the collapse and loss of pore structure caused by compression in a fuel cell setup.In this work, graphene oxide produced by electrochemical exfoliation (EGO) was used to prepare N-doped graphene aerogel (NGA) via hydrothermal treatment with ammonia solution as nitrogen source. Moreover, NGA was mixed with carbon black (CB) as a hybrid support material that can avoid collapse of the macropore and generate a graphene-carbon network to provide large surface area for Pt nanoparticles and improve the performance of the fuel cell. Figure1 shows preliminary characterization results of NGA and performance of NGA-CB supported Pt catalysts with different content of NGA. Rich macro-mesoporous structure of NGA can be observed in the SEM image (Figure 1 (a)). Pt catalyst with 20% NGA has a maximum power density of 838 mw cm-2 which is a 31% improvement over that of Pt/CB (Figure 1 (b)).In conclusion, this study presents a fast, efficient and environmentally friendly way to synthesize nitrogen doped GA. The introduction of NGA into CB as catalyst supports can improve the electrochemical active surface area and performance of fuel cells due to graphene aerogel's high conductivity and porosity. Besides, it is effective to enhance the utilization of Pt and durability of catalysts. This will help to reduce the cost of fuel cells and facilitate their commercialization in various fields of application.Figure 1 (a) SEM images of dried NGA. (b) Performance of Pt/NGA-CB with various content of NGA compared to Pt/CB catalyst in a hydrogen fuel cell at 60 ℃ with 100% RH. References Liu, J.; Wu, X.; Yang, L.; Wang, F.; Yin, J., Unprotected Pt nanoclusters anchored on ordered mesoporous carbon as an efficient and stable catalyst for oxygen reduction reaction. Electrochimica Acta 2019, 297, 539-544.Sarac Oztuna, F. E.; Barim, S. B.; Bozbag, S. E.; Yu, H.; Aindow, M.; Unal, U.; Erkey, C., Graphene Aerogel Supported Pt Electrocatalysts for Oxygen Reduction Reaction by Supercritical Deposition. Electrochimica Acta 2017, 250, 174-184.Wu, Z.-S.; Yang, S.; Sun, Y.; Parvez, K.; Feng, X.; Müllen, K., 3D Nitrogen-Doped Graphene Aerogel-Supported Fe3O4 Nanoparticles as Efficient Electrocatalysts for the Oxygen Reduction Reaction. Journal of the American Chemical Society 2012, 134 (22), 9082-9085.Li, O. L.; Chiba, S.; Wada, Y.; Panomsuwan, G.; Ishizaki, T., Synthesis of graphitic-N and amino-N in nitrogen-doped carbon via a solution plasma process and exploration of their synergic effect for advanced oxygen reduction reaction. Journal of Materials Chemistry A 2017, 5 (5), 2073-2082.Xie, B.; Zhang, Y.; Zhang, R., Coassembly and high ORR performance of monodisperse Pt nanocrystals with a mesopore-rich nitrogen-doped graphene aerogel. Journal of Materials Chemistry A 2017, 5 (33), 17544-17548 Figure 1

Porous graphene with high porosity derived from nitrogen-doped graphene aerogel for vapor adsorption and lithium–sulfur batteries

Porous graphene with high porosity derived from nitrogen-doped graphene aerogel for vapor adsorption and lithium–sulfur batteries

Soft-Hard segments regulated framework of Nitrogen-Doped reduced graphene oxide aerogel for efficient adsorption of pollutants

Graphene aerogel (GA) is recognized for its high porosity, rendering it a promising candidate for water treatment applications. However, its reuse potential is hampered due to inherent limitations. To address this, the present study introduces a nitrogen-doped graphene aerogel (NGA) developed by integrating polydopamine soft segments and polyaniline hard segments into the GA matrix. This approach promotes the formation of a cohesive and durable 3D network by bridging reduced graphene oxide (rGO) nanosheets, with the hard segments of polyaniline interposed among rGO layers to mitigate significant restacking, thereby enhancing surface area and adsorption sites. NGA demonstrates remarkable properties including strength (67 kPa), reversible compressibility under 64 % strain, low density (12.26 mg/cm3), and thermal stability (Tdecomposition = 679.6 °C in air), which collectively enhance its adsorption capacity and recyclability. This study further examines the influence of various factors such as pH, adsorbates (dyes and organic solvents), initial concentration, and cycle times on the aerogel’s adsorption efficacy. Additionally, simulation outcomes reveal that NGA’s adsorption kinetics and thermodynamics align more closely with the endothermic pseudo-first-order kinetic model, indicative of predominant physical adsorption mechanisms. Given its superior adsorption capabilities for pollutants, NGA holds significant promise for application in water treatment.

Electron-interactive 1D porous vertical NiCo2O4 nanowire and 3D N-doped graphene aerogel enable high hydroxyl-ion adsorption capacity for superior energy storage

Supercapacitors are a kind of highly efficient energy-storage device with long cycle life and high power density, however, their specific capacitance is insufficient for further application and development. In this work, a novel composite with one-dimensional (1D) NiCo2O4 nanowire arrays (NiCo2O4-NWA) vertically supported on three-dimensional (3D) nitrogen-doped graphene aerogel (NGA) is designed and facilely realized by hydrothermal reaction and thermal treatment. The NiCo2O4 nanowires, with length of ∼1 μm and diameter of ∼25 nm, display a porous structure and are regularly arranged on both sides of the sheets in nitrogen-doped graphene aerogel. The aerogel-supporting NiCo2O4 nanowires demonstrate a remarkably high specific capacitance of 2742 F g−1 at 1 A g−1, and an outstanding cyclic stability with capacitance retention of 90% even after 10,000 cycles at 80 A g−1. The density functional theory calculation shows the narrow band gap (0.32 eV) and strong electronic interaction and hydroxyl-ion adsorption effect of NiCo2O4 supported on NGA, resulting in superior specific capacitance and energy storage performance. The 3D nitrogen-doped graphene aerogel supporting 1D nanowire arrays represent a promising high-performance electrode material for application in the supercapacitors and other electrochemical energy-conversion and storage equipment.

Nitrogen-doped carbon aerogel supported SnO2 anode for electrocatalytic degradation of phenol: Enhanced generation of free radicals

To obtain a high-efficiency and low-cost electrocatalytic anode for environmental pollutant degradation, a nitrogen doped graphene aerogel supported tin oxide (SnO2-NGA) composite catalyst was prepared and SnO2-NGA/Ti anode was fabricated. The influence of nitrogen doping content on electrocatalytic activity of the catalysts was investigated. The effects of current density and initial solution pH on degradation efficiency were studied. The SnO2-N3.0GA/Ti anode shows good catalytic activity for phenol degradation. The conversion of phenol and COD removal by SnO2-N3.0GA/Ti reached 83.6% and 61.2% within 4 h when applied current density was 5.00 mA/cm2 and initial pH was 3.0. The SnO2-N3.0GA/Ti electrode has higher specific surface area, and lower charge transfer resistance. The nitrogen atoms doping increased the content of pyridinic N species, which is beneficial for providing more in-situ catalytic active sites and enhancing the production of reactive oxygen species, especially hydroxyl radical (•OH). This work provides a novel strategy for synthesis of electrocatalytic anode with enhanced activity for degradation of refractory organic pollutants in water.

Construction of site-specific magnetic Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 with porous structure: enhanced catalytic performance in photo-Fenton reaction.

The development of composite photocatalysts with high charge transfer efficiency, great visible light absorption, and quick recovery has aroused the interest of many researchers. Herein, based on the hydrothermal assisted vacuum freeze drying method, CdS, Fe3O4, and N-TiO2 were, respectively, fixed in the inner, middle, and outer layers of nitrogen-doped graphene aerogel for preparation of the site-specific magnetic porous Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 (CdS/Fe3O4@NGAM/N-TiO2) photocatalyst. For the composite, Fe3O4@NGAM carrier with porous and tubular structure not only helps the recycle and reactants/productions mass transport in the photocatalytic process but also ensures the well-steered transfer of electrons and holes from CdS and N-TiO2 in the Z-type heterojunction system, greatly improving the separation of photogenerated carriers. Besides, Fe3O4 can also work as a Fenton catalyst to activate hydrogen peroxide which is generated in situ by CdS. Thus, the CdS/Fe3O4@NGAM/N-TiO2 composite presents excellent degradation efficiencies towards methyl orange ((MO) 98% removal rate within 50min), bisphenol A ((BPA) 96% removal rate within 50min), tetracycline hydrochloride ((TCH) 96% removal rate within 120min) and strong stabilities after 6 cycles. The free radical removal experiments show that ·O2- and ·OH are the main active substances of catalysis, which further confirms the synergistic effect of photocatalysis and Fenton catalysis.

Materials space-tectonics methodology of conductive mesoporous carbon nanohorns embedded graphene aerogels anchoring Pd nanocrystalline for an efficient ethanol oxidation reaction

Materials space-tectonics (MST) methodology is a powerful strategy to design catalytic materials synthesis to overcome the limitation of monotonous pore geometries and develop functional structures with surface-specific functions. Based on the MST, herein, carbon nanohorns (CNH) as “spacers” inserted into three-dimensional (3D) nitrogen-doped graphene aerogel (NG) anchoring Pd nanocrystalline (Pd/CNH@NG) was constructed through a facile hydrothermal approach and wet chemical reduction method without surfactant and employed as electrocatalyst for ethanol oxidation reaction (EOR). The introduction of CNH can provide important mesopore and macropore characters and generate more active sites to anchor Pd nanocrystalline on the basis of unique internal and interstitial nanopore structures, high surface area and conductive graphitic structure, then enhancing the electrocatalytic efficiency, stability and poison tolerance of catalysts. Meanwhile, the role of CNH doped NG also includes accelerating the reaction of the intermediate (CH3COads) manufactured on the Pd-based aerogels surface with adsorbed hydroxyl (OHads) due to coordination effect from Pyridinic-nitrogen and pyrrolic-nitrogen species. The electrochemical results reveal that the specific and mass activities of the obtained Pd/CNH@NG-2 aerogel (the mass ratio of graphene oxide and CNH is 1:3) are 1.38 and 2.86 times higher than those of the commercial Pd/C for EOR. Simultaneously, the current density of Pd/CNH@NG-2 still maintains 70 % after 500 cycles of complete CV, but commercial Pd/C only maintains 22.6 % of the initial activity. The synthesis of Pd/CNH@NG not only offers a porous three-dimensional aerogel for the EOR but also optimizes a facile strategy to fabricate superior supports for promoting the commercialization of DEFCs.

Polyaniline/Polydopamine-Regulated Nitrogen-Doped Graphene Aerogel with Well-developed Mesoporous Structure for Supercapacitor Electrode

Graphene-based materials have been widely studied in the field of supercapacitors. However, their electrochemical properties and applications are still restricted by the susceptibility of graphene-based materials to curling and agglomeration during production. In this study, a nitrogen-doped graphene aerogel (NGA) based on the regulation of polydopamine (PDA) and polyaniline (PANI) is proposed for the development of supercapacitors using industrial grade graphene oxide (GO, 2.67 m2/g) as raw material. Due to the rigidity of the PANI, agglomeration is prevented during the reduction of GO sheets. Meanwhile, the flexibility and adhesion of the PDA ensure a stable interaction between the graphene sheets and the PANI. NGAs feature a well-developed mesoporous structure and a high content of nitrogen, which enables the rapid transfer of ions inside them. As revealed by density functional theory (DFT) calculations, NGA heterojunction is characterized by high electronic conductivity, fast electron transfer, and low adsorption energy. For this reason, the supercapacitor obtained with NGA as an electrode produces an excellent capacitive performance, achieving a high area capacitance (123.6 mF·cm−2 at 0.5 mA·cm−2) and a superior long-cycle compression performance (80.7%, 5000 cycles). This study provides an effective solution for the development of supercapacitor electrodes using low-cost GO as raw materials.

Ultralight, superhydrophobic and fire-resistant nitrogen-doped graphene aerogel for oil/water separation

The simultaneous achievement of graphene aerogels with low density, high adsorption capacity and selectivity, as well as high mechanical strength, holds great significance but remains a challenging task. By adjusting the concentration and ratio of graphene oxide, dopamine and L-ascorbic acid, the hydrogel without obvious volume shrinkage and stability was synthesized by hydrothermal reaction at low temperature, after freeze-drying and calcination, nitrogen doped graphene aerogel (NGA) with ultralight, superhydrophobic, superoleophilic, fire-resistant, and compressible/recoverable were obtained. The density of NGA is only about 1.9 mg/cm3, and the water and oil contact angles in air are 153.3° and 0°, respectively. Given the aforementioned beneficial features, NGA can efficiently select and adsorb multifarious of oils and organic solvents in oil/water mixtures so as to achieve oil/water separation. Remarkably, NGA exhibits an impressive adsorption capacity of up to 150–305 times its own weight, and it also possesses excellent adsorption recyclability. Therefore, NGA has great potential in the treatment of oil pollution in the water environment.

Towards metal-free nitrogen-doped graphene aerogels as efficient electrocatalysts in hydrogen evolution reaction

Graphene-based materials have been researched to substitute traditional Pt-based electrocatalysts in the hydrogen evolution reaction (HER) due to its strong electrical conductivity, easy functionalization, and cheaper synthesis. Doping graphene with heteroatom is a simple way of obtaining original and active electrocatalysts. Moreover, the nitrogen on it had a positive effect on HER performance. By using a reducing agent with nitrogen while synthesising graphene-based aerogels nitrogen-doped catalysts were obtained. In addition, a better reduction rate, higher crystallography parameters and a more porous material structure were reached. The aerogels were synthesised in an one-pot hydrothermal process, in which the graphene sheets were assembled. This was followed by freeze-drying, which fixed the carbon matrix structure. As a result, the final aerogel had a 3D structure that eased mass transfer and enhanced catalytic activity, reaching an overpotential of −10 mAcm−2 at 101 mV vs RHE (η10 = 101 mV). The amount of quaternary type nitrogen generated during synthesis had a strong influence on electrocatalytic behaviour in HER. Then, quaternary nitrogen and surface area (up to 397 m2/g) were maximized to ensure a higher current density. Moreover, an effective aerogel was prepared with half the solvent per batch, as this was essential for expanding the synthesis to an industrial scale. A final calcination step resulted crucial to improve the metal-free aerogel HER performance.

A Review of Nitrogen-Doped Graphene Aerogel in Electromagnetic Wave Absorption.

Graphene aerogels (GAs) possess a remarkable capability to absorb electromagnetic waves (EMWs) due to their favorable dielectric characteristics and unique porous structure. Nevertheless, the introduction of nitrogen atoms into graphene aerogels can result in improved impedance matching. In recent years, nitrogen-doped graphene aerogels (NGAs) have emerged as promising materials, particularly when combined with magnetic metals, magnetic oxides, carbon nanotubes, and polymers, forming innovative composite systems with excellent multi-functional and broadband absorption properties. This paper provides a comprehensive summary of the synthesis methods and the EMW absorption mechanism of NGAs, along with an overview of the absorption properties of nitrogen-doped graphene-based aerogels. Furthermore, this study sheds light on the potential challenges that NGAs may encounter. By highlighting the substantial contribution of NGAs in the field of EMW absorption, this study aims to facilitate the innovative development of NGAs toward achieving broadband absorption, lightweight characteristics, and multifunctionality.

Nanoarchitectonics of nest-like Co3O4 nanowires embedded nitrogen-doped graphene aerogel as electrochemical sensing platform for Pb2+ and Cd2+ trace detection

Nano Co3O4 embedded nitrogen-doped graphene aerogel (Co3O4@NGA) was directly prepared by one-pot hydrothermal synthesis method with ammonia water acting as both precipitant of Co3O4 and nitrogen source of nitrogen-doped graphene aerogel (NGA). This novel method leaved out the calcination process which was necessary for most methods to prepare Co3O4 nanomaterials. The effects of hydrothermal temperature on both morphologies and Pb2+/Cd2+ electrochemical detection performances of Co3O4@NGA were explored. As the hydrothermal temperature rising from 140 °C to 200 °C, the shapes of Co3O4 changed from nanoparticles to nanowires and then to nanoflowers, and nest-like Co3O4 nanowires were architected on NGA sheets at 180 °C. The electrochemical sensor based on the optimized Co3O4@NGA-180 exhibited low limit of detection (LOD) for Pb2+ (7.2 nM) and Cd2+ (10.06 nM) and high sensitivity for Pb2+ (10.51 μA·μM−1) and Cd2+ (8.053 μA·μM−1). The excellent performances were attributed to the synergistic effect of Co3O4 nanowires and porous NGA, which leaded to the fast electrochemical reaction rate in the detection process. Moreover, the Co3O4@NGA-180/GCE sensor had excellent selectivity, repeatability and stability, and could be used to detect traces of Pb2+ and Cd2+ in real water sample.

Ultralight, fire-resistant, lamellar nitrogen-doped graphene aerogels for highly efficient selective organic pollutant cleanup

Ultralight, fire-resistant, lamellar nitrogen-doped graphene aerogels for highly efficient selective organic pollutant cleanup

Correction: Copper chromite decorated on nitrogen-doped graphene aerogel as an efficient catalyst for thermal decomposition of ammonium perchlorate particles

Correction: Copper chromite decorated on nitrogen-doped graphene aerogel as an efficient catalyst for thermal decomposition of ammonium perchlorate particles

Preparation of cobalt-ruthenium nanocatalysts supported on nitrogen-doped graphene aerogel and carbon nanotubes in Fischer-Tropsch synthesis

In this study, cobalt-ruthenium nanocatalysts supported on nitrogen-doped graphene aerogel (NGA) and carbon nanotubes (CNT) were synthesized using the wet impregnation method for Fischer-Tropsch process with a cobalt to ruthenium ratio of 1:50. The synthesized catalysts underwent various characterizations such as FTIR, ICP, BET, XRD, EDX, TPR and TEM. The performance of the synthesized catalysts was compared to that of a cobalt-ruthenium nanostructured catalyst supported on NGA and CNTs. The catalysts were evaluated in a fixed-bed reactor at 25 bar, with a gas ratio H2/CO: 2 and Gas Hourly Space Velocity (GHSV) 10,000 mlg-1h-1, at temperatures of 260 °C and 280 °C. The use of NGA as a cobalt catalyst support led to a 70.5% conversion of carbon monoxide and higher methane selectivity. Conversely, the use of CNTs led to 63.7% conversion of carbon monoxide and higher selectivity towards C5+ production.

Boosting CO2 Electroreduction on Bismuth Nanoplates with a Three-Dimensional Nitrogen-Doped Graphene Aerogel Matrix

Electrochemical CO2 reduction reaction (CO2RR), which uses renewable electricity to produce high-value-added chemicals, offers an alternative clean path to the carbon cycle. However, bismuth-based catalysts show great potential for the conversion of CO2 and water to formate, but their overall efficiency is still hampered by the weak CO2 adsorption, low electrical conductivity, and slow mass transfer of CO2 molecules. Herein, we report that a rationally modulated nitrogen-doped graphene aerogel matrix (NGA) can significantly enhance the CO2RR performance of bismuth nanoplates (BiNPs) by both modulating the electronic structure of bismuth and regulating the interface for chemical reaction and mass transfer environments. In particular, the NGA prepared by reducing graphene oxide (GO) with hydrazine hydrate (denoted as NGAhdrz) exhibits significantly enhanced strong metal-support interaction (SMSI), increased specific surface area, strengthened CO2 adsorption, and modulated wettability. As a result, the Bi/NGAhdrz exhibits significantly boosted CO2RR properties, with a Faradaic efficiency (FE) of 96.4% at a current density of 51.4 mA cm-2 for formate evolution at a potential of -1.0 V versus reversible hydrogen electrode (vs RHE) in aqueous solution under ambient conditions.

Tuning the Electronic Structure of a Novel 3D Architectured Co-N-C Aerogel to Enhance Oxygen Evolution Reaction Activity

Hydrogen generation through water electrolysis is an efficient technique for hydrogen production, but the expensive price and scarcity of noble metal electrocatalysts hinder its large-scale application. Herein, cobalt-anchored nitrogen-doped graphene aerogel electrocatalysts (Co-N-C) for oxygen evolution reaction (OER) are prepared by simple chemical reduction and vacuum freeze-drying. The Co (0.5 wt%)-N (1 wt%)-C aerogel electrocatalyst has an optimal overpotential (0.383 V at 10 mA/cm2), which is significantly superior to that of a series of M-N-C aerogel electrocatalysts prepared by a similar route (M = Mn, Fe, Ni, Pt, Au, etc.) and other Co-N-C electrocatalysts that have been reported. In addition, the Co-N-C aerogel electrocatalyst has a small Tafel slope (95 mV/dec), a large electrochemical surface area (9.52 cm2), and excellent stability. Notably, the overpotential of Co-N-C aerogel electrocatalyst at a current density of 20 mA/cm2 is even superior to that of the commercial RuO2. In addition, density functional theory (DFT) confirms that the metal activity trend is Co-N-C > Fe-N-C > Ni-N-C, which is consistent with the OER activity results. The resulting Co-N-C aerogels can be considered one of the most promising electrocatalysts for energy storage and energy saving due to their simple preparation route, abundant raw materials, and superior electrocatalytic performance.

Ultralight, superhydrophobic, low-cost nitrogen-doped graphene aerogels with a “honeycomb” porous structure for efficient oil removal

Scheme of the synthetic procedure for the preparation of the CGA or NCGA porous aerogel.

Synthesis of nitrogen-doped graphene aerogels modified by magnetic Fe3O4/Fe/C frameworks as excellent dual-band electromagnetic absorbers

Nitrogen-doped reduced graphene oxide/ferroferric oxide/iron/carbon composite aerogels were prepared, which had a unique three-dimensional porous network structure and excellent dual-band electromagnetic absorption performance.