Nitrogen-doped Carbon Aerogels Research Articles

Innovative Mn3−xO4−y@NCA design: Leveraging Mn/O vacancies and amorphous architecture for enhanced sodium-ion storage

Manganese-based oxide electrode materials suffer from severe Jahn-Teller (J-T) distortion, leading to severe cycle instability in sodium ion storage. However, it is difficult to adjust the electron at d orbitals exactly to a low spin state to eliminate orbital degeneracy and suppress J-T distortion fundamentally. This article constructed concentration-controllable Mn/O coupled vacancy and amorphous network in Mn3O4 and coated it with nitrogen-doped carbon aerogel (Mn3−xO4−y@NCA). The existence of Mn/O vacancies has been confirmed by scanning transmission electron microscopy (STEM) and positron annihilation lifetime spectroscopy (PALS). Atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS) determine the most optimal ratio of Mn/O vacancies for sodium ion storage is 1:2. Density functional theory (DFT) calculations prove that Mn/O coupled vacancies with the ratio of 1:2 could exactly induce a low spin states and a d4 electron configuration of Mn, suppressing the J-T distortion successfully. The abundant amorphous regions can shorten the transport distance of sodium ions, increase the electrochemically active sites and improve the pseudocapacitance response. From the synergetic effect of Mn/O coupled vacancies and amorphous regions, Mn3−xO4−y@NCA exhibits an energy density of 37.5 W h kg−1 and an ultra-high power density of 563 W kg−1 in an asymmetric supercapacitor. In sodium-ion batteries, it demonstrates high reversible capacity and exceptional cycling stability. This research presents a new method to improve the Na+ storage performance in manganese-based oxide, which is expected to be generalized to other structural distortion.

Iron-Cobalt Nanoparticles Embedded in B,N-Doped Chitosan-Derived Porous Carbon Aerogel for Overall Water Splitting.

Given their intriguing properties, porous carbons have surfaced as promising electrocatalysts for various energy conversion reactions. This study presents a unique approach where iron-cobalt (FeCo) is confined in a boron, nitrogen-doped chitosan-derived porous carbon aerogel (BNPC-FeCo) to serve as an electrocatalyst for the hydrogen evolution and oxygen evolution reactions (HER and OER). The BNPC-FeCo-900 electrocatalyst demonstrates excellent catalyst activity, with very low overpotentials of 186 and 320 mV at 10 mA cm-2, low Tafel slopes of 82 and 55 mV dec-1, and low charge transfer resistance of 2.68 and 9.25 Ω for HER and OER, respectively. Density functional theory (DFT) calculations further reveal that the cooperation between the boron, nitrogen codoped porous carbon, and the FeCo nanoparticles reduces intermediates' energy barriers, significantly enhancing the HER and OER performance. In conclusion, this work offers significant and informative perspectives into the potential of porous carbon materials as dual-purpose electrocatalysts for water splitting.

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.

Preparation of nanocellulose-based nitrogen-doped carbon aerogel electrocatalysts through hydrothermal pretreatment for zinc–air batteries

A cellulose-based nitrogen-doped carbon aerogel with abundant micro-mesopores for zinc–air batteries with high open-circuit voltage and long cycle stability was prepared by hydrothermal pretreatment and simple carbonization.

Synthesis of Metal-Free Carbon Aerogel with Nitrogen-Doped from Pyrolysis of Cellulose Aerogels Based on Coir Fibers Using Ammonia-Urea System as Electrocatalyst of Oxygen Reduction Reaction for Cathode in Seawater Batteries

Performance of seawater batteries is still limited by the sluggish nature of oxygen reduction reaction (ORR). One way to optimize the performance of the battery is by utilizing an electrocatalyst with the ability to increase the ORR rate of reaction. Nitrogen-doped carbon aerogel based on coir fiber is one of the alternatives because of its excellent electrocatalytic performance and was made from an abundant material. Carbon aerogel was obtained from pyrolyzing coir fiber-based aerogel cellulose. Nitrogen atom structure in carbon aerogel was affected by the temperature of cellulose aerogel pyrolysis. Pyridinic N content in the Nitrogen-doped carbon aerogel has effective for the activity of the ORR. The electrocatalytic performance of the carbon aerogel synthesized from coir fiber with nitrogen doping at the pyrolysis temperature of 600 °C was investigated in this study. The research process began with the synthesis of cellulose aerogel using urea-ammonia crosslinking precursor. Next, cellulose aerogel was pyrolyzed at 600 °C to create carbon aerogel. FTIR, XRD, CV, LSV, and LP were used to characterize the samples. The carbon aerogel was N-doped with pyridinic N, according to an analysis of the FTIR spectra. The carbon aerogel shows 4-electron ORR with kinetic current density (ik) of 0.74 mA/cm2 and current density (io) of 0.583 μA/cm2, according to electrochemical performance analysis in 3.5% NaCl as electrolyte.

Synthesis and Characterization of N-Doped Carbon Aerogel Based on Oil Palm Empty Fruit Bunch as Oxygen Reduction Reaction Electrocatalyst in Seawater Batteries

Some areas in Indonesia have difficulty accessing electricity [1]. One of the alternative is sea water battery because of its good theoretical performance and great seawater potential in Indonesia [2]. However the performance is limited by the sluggish Oxygen Reduction Reaction, therefore electrocatalyst is needed to increase the rate of reaction [2]. Oil palm empty fruit bunch carbon aerogel is one of the alternative because of its excellent electrocatalytic performance and can be made from abundant material with high content of cellulose [3]. Carbon aerogel can be obtained from pyrolizing oil palm empty fruit bunch based aerogel cellulose. Activity of the Oxygen Reduction Reaction can be determined from pyridinic N concentration in the carbon aerogel [4]. This research focuses on synthesizing nitrogen-doped carbon aerogel from oil palm empty fruit bunch and characterized its electrocatalytic performance. Research started with synthesizing cellulose aerogel with urea-ammonia crosslinking precursor and followed by pyrolysis of cellulose aerogel to carbon aerogel at 600°C. Samples were characterized using FTIR, XRD, CV, LSV, and LP. The FTIR Spectra analysis shows that the carbon aerogel was N-doped with pyridinic N. Electrochemical performance analysis in 3.5% NaCl as electrolyte shows that carbon aerogel undergoes 2-electron ORR pathway with kinetic current density of ik=0.107 mA/cm2 and current density of io=0.295 μA/cm2.

Metal–Organic Gel Leading to Customized Magnetic-Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

HighlightsFe3+, Co2+, H3BTC, and collagen peptide are used to achieve a one-step assembly of stable FeCo-MOG/CP by manipulating the complexation effect and solution polarity.By optimizing pyrolysis, two kinds of nitrogen-doped carbon aerogels loaded with virus-shaped and nanospherical magnetic particles are obtained.FeCo/Fe3O4/NC and FeCo/NC aerogels exhibit excellent electromagnetic wave absorbing and radar stealth performances.

Scale-up biomass strategy to macro-microporous nitrogen-doped carbon aerogels for ionic liquid supercapacitors with high efficiency

Ionic liquids are commonly employed as supercapacitor electrolytes owing to their wide voltage windows. However, ion transport in a carbon electrode is limited by the larger viscosity and larger ion size of an ionic liquid, which reduces the energy density of supercapacitors. In this work, we fabricated macro-microporous nitrogen-doped carbon aerogels (H-A-C-N) as electrode materials by scale-up biomass strategy for high-energy-density supercapacitors. The macroporous structure ensures the rapid transport of ions in the ionic liquid, particularly under high-current charging and discharging conditions. We fabricated a symmetric supercapacitor using the H-A-C-N as the electrode and 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4) as the electrolyte. The developed supercapacitor presents an energy density of 68.8 Wh kg−1. The results of this study present considerable potential for the preparation of high-performance electrode materials in future studies.

Improved DMFC water management via superwetting, high-performance catalyst synthesized by nanocapsule method

In this paper, an effective water management structure for direct methanol fuel cell (DMFC) is designed based on the super-hydrophilicity of nitrogen-doped carbon aerogel which functions as the support of Pt catalyst. Considering the case where Pt nanoparticles deposited into the nanopores of the support are difficult to contact with the ionomer, the catalyst is synthesized by nanocapsule method, and the experimental results prove that a favorable improved oxygen reduction reaction activity of the prepared catalyst has been achieved. The produced hydrophilic catalyst is used to construct a two-layered cathode catalyst layer (CCL) with hydrophilic inner layer and hydrophobic outer layer as water management structure, since a single-layered hydrophilic CCL shows poor performance due to serious water flooding. A mathematical model is developed to study the influence of two-layered CCL, and its effect on cell performance is also analyzed by polarization tests. For the improved liquid-feed DMFCs, high hydraulic pressure is formed in CCL to promote water recovery and inhibit methanol crossover. For the improved vapor-feed DMFC, the enhanced water recovery secures the water required for the anodic oxidation reaction, which increases the output performance and stability greatly. This study provides a new method for the optimization of DMFC.

Nitrogen-doped carbon aerogel framework with in situ encapsulated ZrO2 nanoparticles as pseudocapacitive anode for phosphorus uptake

Phosphorus reduction is crucial for controlling eutrophication and protecting the aquatic environment. Nonetheless, traditional methods suffer from secondary pollution and high costs. Capacitive deionization (CDI) is a novel electrochemical approach for phosphorus removal, which is low-cost and environmentally friendly. Its performance is highly correlated with the electrode material. Herein, a novel nitrogen-doped carbon aerogel framework encapsulated with ZrO2 nanoparticles (ZrNC) was rationally fabricated and employed as an anode for phosphorus removal. The experimental results revealed that the N site and ZrO2 could enhance the physicochemical properties, electrochemical activity, and additional pseudocapacitive contribution, thus raising the phosphorus removal capacity. The optimal ZrNC-3 electrode demonstrated superior phosphorus capture (18.26 mg P/g), low energy consumption at 1.2 V (0.0256 kWh/m3 and 4.159 kWh/kg), outstanding phosphorus selectivity, and excellent stability. Mechanism investigation suggested phosphorus can form mono- or bi-dentate inner-sphere complexes (Zr–O–P) by ligand exchange with ZrO2 sites under an electric field and combined with unsaturated Zr sites and N species by electrostatic attraction. This study presents a promising conception for designing and applying metal oxide/carbon complexes in selective phosphorus uptake electrodes.

3D-printed N-doped porous carbon aerogels for efficient flow-through degradation and disinfection of wastewater

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have great potential for water treatment. Herein, a 3D nitrogen-doped porous carbon (3D-NPC) aerogel has been prepared by direct ink writing of a hydrogel containing agarose, urea, sodium chloride and hydroxypropyl methylcellulose, and subsequent freeze-drying and pyrolysis. The obtained 3D-printed aerogel exhibits multiple desirable properties including self-supportability, hierarchical porous structure, and good structural stability, and thus can be used as a monolithic catalytic filter in flow-through experiments. The 3D-NPC catalysts have demonstrated excellent PMS-based performances toward degradation of organic dyes and disinfection of bacterial culture. The degradation efficiency of Rhodamine B by 3D-NPC is as high as 97.2% within 5 min and the high degradation efficiency can be sustained for 5 h. Moreover, 100% inactivation of bacteria by 3D-NPC can also be maintained for at least 5 h, which far exceeds those of traditional catalysts. The key reactive species of the 3D-NPC + PMS system is found to be singlet oxygen in both Rhodamine B degradation and antibacterial disinfection, where the non-radical pathway contributes to the majority of the catalytic activity. Our work has innovatively presented a 3D-printed monolithic catalyst for efficient flow-through degradation and disinfection.

Cobalt-nitrogen-carbon sites on carbon aerogels for enhanced electrocatalytic CO2 activity

Developing highly-efficient electrocatalysts with metal-nitrogen-carbon (M−NxC) sites for electrochemical CO2 reduction reaction (CO2RR) towards carbon monoxide (CO) is an effective way towards carbon neutralization. Herein, nitrogen-doped carbon aerogels (N-CA) supported Co-NxC sites with cobalt phthalocyanine (CoPc) as precursor via pyrolysis (500 ℃) strategy is reported. The CoPc@N-CA-500 catalyst with the average pore size of 8.57 nm, displays a wide potential window from −0.5 to −0.9 V vs. RHE with the CO Faradaic efficiency (FECO) over 80%. It also exhibits the maximal FECO of 92.48%, the CO partial current density of 21.72 mA cm−2, CO turnover frequency (TOFCO) of 1.23 s−1 and stability over 20 h (under −0.8 V vs. RHE), which is significantly higher than that of CoPc@CB-500 (53.91%, 4.47 mA cm−2, 0.14 s−1) with the average pore size of 2.54 nm, while selecting commercial carbon black (CB) as the carrier. The superior activity of CoPc@N-CA-500 could be attributed to its unique porous system, which not only promotes the mass transfer of CO2 molecules to facilitate the CO2RR kinetic, but is beneficial to expose Co active sites. Meanwhile, a home-made zinc-CO2 battery with CoPc@N-CA-500 as cathode achieved a peak power density of 0.69 mW cm−2 and maximum FECO of 87.41%.

The origin of selective nitrate-to-ammonia electroreduction on metal-free nitrogen-doped carbon aerogel catalysts

Electrocatalytic nitrate reduction reaction (NitRR) to NH3 provides an appealing route to reform the energy-consuming ammonia industry. Considerable studies have demonstrated transition-metal-based catalysts for the NitRR, while most of them suffer from high cost, poor stability, and unsatisfactory selectivity. In this work, a group of carbon-based aerogel catalysts with regulated N species have been developed for highly efficient nitrate-to-ammonia reduction. The results show that the electrocatalytic performance is dependent on the graphitic-N moiety, where the catalyst with the highest content of graphitic-N moiety exhibits a maximum NH3 yield rate of 1.33 mgNH3 h−1 cm−2 with the faradaic efficiency of ca. 95%. The theoretical investigation further reveals the strong adsorption of nitrate on graphitic-N moiety as the reason for the enhanced NO3ˉ-to-NH3 activity. This study, thus, provides a fundamental understanding of the intrinsic mechanism of the NitRR on nitrogen-doped carbon structures, facilitating the rational design of metal-free catalysts for advanced electrosynthesis.

Electronic Modulation of the 3D Architectured Ni/Fe Oxyhydroxide Anchored N-Doped Carbon Aerogel with Much Improved OER Activity.

It remains a big challenge to develop non-precious metal catalysts for oxygen evolution reaction (OER) in energy storage and conversion systems. Herein, a facile and cost-effective strategy is employed to in situ prepare the Ni/Fe oxyhydroxide anchored on nitrogen-doped carbon aerogel (NiFeOx(OH)y@NCA) for OER electrocatalysis. The as-prepared electrocatalyst displays a typical aerogel porous structure composed of interconnected nanoparticles with a large BET specific surface area of 231.16 m2·g-1. In addition, the resulting NiFeOx(OH)y@NCA exhibits excellent OER performance with a low overpotential of 304 mV at 10 mA·cm-2, a small Tafel slope of 72 mV·dec-1, and excellent stability after 2000 CV cycles, which is superior to the commercial RuO2 catalyst. The much enhanced OER performance is mainly derived from the abundant active sites, the high electrical conductivity of the Ni/Fe oxyhydroxide, and the efficient electronic transfer of the NCA structure. Density functional theory (DFT) calculations reveal that the introduction of the NCA regulates the surface electronic structure of Ni/Fe oxyhydroxide and increases the binding energy of intermediates as indicated by the d-band center theory. This work provides a new method for the construction of advanced aerogel-based materials for energy conversion and storage.

Preparation of nitrogen-doped hierarchical porous carbon aerogels from agricultural wastes for efficient pollution adsorption

The development of green, economic and high-performance pollutant adsorption materials is an important way to meet severe environmental challenges. Herein, aerogel-like N-doped hierarchical porous carbon materials (NHCs) were prepared by rapid pyrolysis of corn straw and urea using KHCO3 as the activator. A series of characterizations including SEM, (HR)TEM, N2 absorption and desorption, FTIR, Raman, XPS, and elemental analysis were carried out to explore influences of activation temperature on the physicochemical properties of NHCs. It is found that NHC-800 prepared at 800 °C has a well-developed hierarchical pore structure, a high specific surface area (1871 m2/g) and a very low density (0.032 g/cm3). Influences of various parameters including activation temperature, urea and KHCO3 ratio, biomass type on the NHC adsorption performance were investigated. The material naming NHC-800 prepared from corn straw (corn straw: KHCO3: urea is 1:4:1) has the best methylene blue adsorption performance, with a maximum adsorption capacity of 1009.6 mg/g. Adsorption kinetics and thermodynamic analysis were carried out, and mechanism research was performed. It is found that urea not only provides pyridinic N chemisorbent sites, but also provides more activable sites for NHCs to generate more pore structures for physical adsorption. Performances on the adsorption of acid fuchsin, methyl orange, tetracycline, Cr6+, Cu2+ and actual wastewater were also studied, and it is found that NHC-800 can selectively and effectively remove organic pollutants while retaining metal ions.

Template-assisted synthesis of ultrathin graphene aerogels as bifunctional oxygen electrocatalysts for water splitting and alkaline/neutral zinc-air batteries

Low-cost, high-performance oxygen catalysts are critical for electrochemical water splitting and metal-air batteries. Herein, carbon aerogels with skeletons consisting of few-layer graphene are derived pyrolytically from a hydrogel precursor using an array of NaCl crystals as the template, exhibiting a high electrical conductivity (869 S m−1) and an ultralow mass density (11.1 mg cm−3). The deposition of NiFe layered double hydroxide (NiFe-LDH) nanocolloids renders the aerogels active towards both the oxygen reduction/evolution reactions (ORR/OER), with the performances highly comparable to those of commercial benchmarks in both alkaline and neutral media. Results from operando Raman spectroscopy measurements and first principles caculations suggest that Fe(OH)3 colloids facilitate the oxidation of Ni2+, which lowers the energy barrier to 0.42 eV for OER, whereas the nitrogen-doped carbon aerogels are responsible for the ORR activity. With the composites used as bifunctional oxygen catalysts for electrochemical water splitting and rechargeable zinc-air batteries, the performances in both alkaline and neutral media are markedly better than those based on the mixture of commercial Pt/C and RuO2. Results from this study highlight the unique advantages of ultrathin graphene aerogels in the development of effective catalysts for electrochemical energy devices.

Three-dimension in-situ nitrogen doping porous cellulosic biomass-based carbon aerogel for electrocatalytic CO2 reduction

As components of biomass, cellulose has great utilization value. In this study, the three-dimensional interconnected porous structure of carbon aerogel was easily prepared from cellulose on the electrocatalytic reduction reaction of CO2 (CO2RR). However, carbon materials have fewer active sites resulting in poor catalytic activity. Therefore, in order to improve the conductivity and active sites of carbon materials, melamine as nitrogen source was added into carbon aerogel by in-situ synthesis method to prepare nitrogen uniform distribution catalyst at different pyrolysis temperature. Results showed that with the increase of pyrolysis temperature, abundant pore structures were gradually formed from inside to outside, which provided enough transport channels for CO2 and products. N3–750 had the maximum CO faradaic efficiency (FE) of 75.90% due to the largest surface area of 1038.02 m2/g and the highest surface N/C ratio of 5.15%. Meanwhile, the high content of pyridinic N provided sufficient active sites on forming the *COOH intermediate rather than the pyrrolic N. Furthermore, after eight hours of reaction, the FE of CO changed from 75.90% to 68.26%, indicating good stability. Therefore, nitrogen-doped cellulosic biomass-based carbon aerogel has the potential to become a stable and efficient CO2RR catalyst.

Nitrogen-doped carbon aerogels derived from polyimide for high-performance supercapacitor

Nitrogen-doped carbon aerogels derived from polyimide for high-performance supercapacitor

Highly durable iron single-atom catalysts for low-temperature zinc-air batteries by electronic regulation of adjacent iron nanoclusters

Durability of carbon-supported Fe single-atom catalysts has remained a critical issue for metal-air batteries. Herein, Fe single atoms with adjacent Fe nanoclusters supported on nitrogen-doped carbon aerogels (NCA/FeSA+NC) are prepared via a facile two-step pyrolysis procedure using biomass hydrogels as the precursor and template. The Fe atomic centers are found to exhibit an increased 3d electron density and decreased magnetic moment by the nanoclusters. This markedly enhances the oxygen reduction reaction activity and anti-oxidation stability of the FeN4 sites, as compared to the nanocluster-free counterparts. With NCA/FeSA+NC as the cathode catalysts, a flexible zinc-air battery delivers a remarkable performance even at −40 °C, with an open circuit voltage as high as 1.47 V, power density 49 mW cm−2, and excellent durability after 2300 continuous recharging/charging cycles. The performance is even higher at ambient temperature. These results highlight the significance of electronic manipulation in enhancing the durability of single atom catalysts.

Rational Design of Carbon-Based Porous Aerogels with Nitrogen Defects and Dedicated Interfacial Structures toward Highly Efficient CO2 Greenhouse Gas Capture and Separation.

CO2 capture from flowing flue gases through adsorption technology is essential to reduce the emission of CO2 to the atmosphere. The rational design of highly efficient carbon-based absorbents with interfacial structures containing interconnected porous structures and abundant adsorption sites might be one of the promising strategies. Here, we report the synthesis of nitrogen-doped carbon aerogels (NCAs) via prepolymerized phenol-melamine-formaldehyde organic aerogels (PMF) by controlling the addition amount of ZnCl2 and the precursor M/P ratio. It has been revealed that NCAs with a higher specific surface area and interconnected porous structures contain a large amount of pyridinic nitrogen and pyrrolic nitrogen. These would act as the intrinsic adsorption sites for highly effective CO2 capture and further improve the CO2/N2 separation efficiencies. Among the prepared samples, NCA-1-2 with a high micropore surface area and high nitrogen content exhibits a high CO2 adsorption capacity (4.30 mmol g-1 at 0 °C and 1 bar) and CO2/N2 selectivity (36.5 at 25 °C, IAST). Under typical flue gas conditions (25 °C and 1.01 bar), equilibrium gas adsorption analysis and dynamic breakthrough measurement associated with a high adsorption capacity of 2.65 mmol g-1 at 25 °C and 1.01 bar and 0.81 mmol g-1 at 25 °C and 0.15 bar. This rationally designed N-doped carbon aerogel with specific interfacial structures and high CO2 adsorption capacity, high selectivity, and adsorption performance remained pretty stable after multiple uses.