N-doped Carbon Aerogel Research Articles

Highly branched Pt-Ni-Co core-shell nano-dendrites anchored on N-doped carbon aerogel: Synergism between meso-porosity and surface morphology for enhanced ORR performance

Dendritic nanostructures are seizing growing interest in electrocatalysis owing to their unique structural features and low density. Under unique branched structures with the symbiotic effect of N-doped carbon aerogel (N-AC), the obtained core-shell nano-dendrites (NDs) showed excellent oxygen reduction performance. In detail, the mass and specific activities of Pt-Ni-Co/N-AC were found to be 1.88 A mgPt−1 / 0.78 mA cm−2 which is 9.9/2.5 times greater than commercial Pt/C. Furthermore, Pt-Ni-Co/N-AC demonstrated the best performance with the lowest activity loss across 1k, 3k, and 5k cycles and 40k sec testing, (40k testing repeated 4 times). At the 5k cycle and 40k sec testing, the ECSA loss is 13.47 % and the current loss is 10.1 %, the smallest among all tested NDs. This indicates that they exhibit superior stability and durability over extended cycles. The catalyst's large surface area, effective exposure and accessibility of active sites in NDs, high Pt-N/Ni-Co content, and predominance of pyridinic-N over pyrrolic-N collectively add to ND's activity. Highly branched, porous interconnected structures supported by chemical active sites of N-AC and sustained performance of Pt-Ni-Co/N-AC NDs make them a reliable choice for fuel cell technology.

Recyclable wood-structured bimetallic carbon aerogel for high-performance bulk catalytic antibiotic decomposition

Harnessing renewable low-cost, bulk wood-structured materials with highly porous, anisotropic and compressible properties that fulfills sustainable water purification is imperative yet still challenging to push forward a circular bioeconomy. In this work, a bimetallic Fe-Co implanted, N-doped wood carbon aerogel (Fe-Co/NWCA) is constructed to guarantee the facile regeneration in high-performance catalytic antibiotic decomposition via activating peroxymonosulfate (PMS). A rapid, reversible and excellent tetracycline (TC) elimination performance (∼90% in 12 min) within a wide pH range of 3–11 is achieved by Fe-Co/NWCA-mediated system. Importantly, the as-prepared hydrophilic Fe-Co/NWCA not only delivers a favorable robustness to interfering anions (e.g., Cl−, H2PO4− and HCO3−), but also presents a superior recyclability with over 90% retention after the fourth cycling operation via a convenient squeezing behavior. Integration of radical quenching experiments and electron paramagnetic resonance demonstrates the participation of reactive oxygen species (ROS) into catalytic TC oxidation, wherein the dominant contributor is 1O2 followed by O2•‾, SO4•‾ and •OH. As an important non-radical route, the directly interfacial electron transfer is confirmed by electrochemical measurements and density-functional-theory computations. In the context of activating PMS, the multi-valent Fe, Co-coordinated species function as the redox reactive site to trigger diversiform ROS with accelerated kinetics, while N, O-associated surface defects and unsaturated functional groups (e.g., −COOH and ketonic C=O) contribute to the 1O2 formation and electron shuttling. This universal approach paves a critical avenue to manufacture the reactive wood-based aerogels with hierarchical microchannels in the practical pollutant remediation, shedding the valuable insights on multifunctional biomass-water nexus.

Chitosan derived N-doped carbon aerogel nanostructures for high-performance supercapacitors

This study presented a chitosan-derived activated carbon aerogel material (ACAM), which was prepared via a sol–gel method, freeze-drying, and carbonization. The prepared nitrogen-doped carbon materials had nanopore structures with a highly specific surface area of 2341 m2 g−1 that was expected to be suitable as active electrode materials for supercapacitors). The prepared electrode exhibited a high capacitance of 215 F g−1 at 1.0 A g−1. Moreover, the electrode could retain almost 93% of the original capacitance, and the Coulombic efficiency remains over 97% after 5,000 cycles. The findings suggest a low-price and high-performance material for supercapacitors.

Size tuning of vanadium nitride particles from atomic to micron level as efficient catalysts for zinc-air battery

Transition metal nitrides present superior electrocatalytic activities on the air electrode for fuel cells or metal-air batteries. Despite that, the weak intrinsic activity and ease of aggregation have hampered their catalytic kinetic properties and practical application. Herein, vanadium nitride (VN) particles of different sizes, micron to molecular level, have been fabricated using a facile, in-situ urea-nitridation method, and embedded in an N-doped graphitic carbon aerogel electrocatalyst (VN@CA), the doped material serving as an oxidation catalyst. Having a balance of atomic-level dispersed VN clusters and a high active site density, the obtained VN@CA catalytic material exhibits enhanced catalytic efficiency for the oxygen reduction reaction (ORR), the values of onset and half-wave voltages were measured to be 0.97 V and 0.90 V, respectively, compared to Pt/C (which had voltages of 0.95 V and 0.87 V). Furthermore, the assembled Zn-air battery using VN@CA as catalyst exhibits a high-power density of 176 mW cm−2, a substantial specific discharge capacity of 851 mAh gZn−1 at 20 mA cm−2, a narrow gap between charging and discharging voltages (0.73 V at 50 mA cm−2), and an excellent charge-discharge cycling stability, exceeding 270 cycles with a 66 % round-trip efficiency. This work confirms that the particle size and the density both are responsible for the enhanced electrochemical activity.

Deep removal of COS by carbon aerogel in natural gas: A 3D network structure of nitrogen doped and Cu based adsorbent

For the purpose of overcoming the difficulty of low removal rate of COS at low temperatures, N-doped copper oxide-supported carbon aerogels were prepared with sodium alginate as a carbon source for deep removal of COS (about 20 ppm) from natural gas. By exploring the effects of different nitrogen sources (urea, melamine and p-phenylenediamine), carbon–nitrogen ratio and carbonization temperature, p-phenylenediamine-doped copper oxide-loaded carbon aerogels (PPD-Cu/CA) with both excellent catalytic hydrolysis of COS and adsorption were prepared. The COS adsorption capacity of optimized PPD-Cu/CA was 18.6 mg·g−1 with 0.94 %Vol of water content at 40 °C, meanwhile, the COS removal efficiency at 40,000 and 70,000 mL·g−1·h−1 could reach 100 % and 94.6 %, respectively, showing excellent high space velocity resistance. Combined with characterization and experimental results, the introduction of p-phenylenediamine enriched the pore structure of the carbon carrier, increased the neutral base site, and played a positive role in the adsorption and hydrolysis of COS. This study provides a new insight into the removal of carbonyl sulfur from natural gas.

Carbon aerogel capsulated cobalt oxides with nanomicro-hierarchical architectures as anodes for lithium-ion batteries

N-doped carbon aerogel capsulated Co3O4 (Co3O4@NCA) is prepared via a hydrothermal method using an N-doped carbon aerogel (NCA) as a conductive carbon matrix and coating layer.

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.

Cu-Alginate/Graphene Aerogels Derived Electrocatalyst for Oxygen Reduction Reaction

In this work, the Cu-alginate/graphene aerogels were prepared by using alginate, graphene and copper chloride as precursors by a freeze-drying process. Finally, N-doped carbon aerogels supported by Cu nanoparticles (NPs) (Cu/N-CAs) were obtained through annealing in the NH3 atmosphere. The morphology, microstructures, specific surface area, and pore size distribution were studied by SEM, XRD, and BET analysis. The results showed that a significant amount of Cu NPs were uniformly disseminated on the aerogels’ surface, and the catalysts’ specific surface area reached 141 m2/g. Electrochemical tests revealed good catalytic capabilities for the oxygen reduction reaction (ORR) of the as-obtained Cu/N-CAs. Compared to the commercial 20%Pt/C, the Cu/N-CAs exhibited comparable catalytic performance, superior catalytic stability and methanol resistance. The transfer of 3.94 electrons indicated that the Cu/N-CAs were undergoing a four-electron (4e-) ORR process.

Ru-promoted NiFe oxyhydroxide anchored on the hierarchical porous N-doped carbon aerogel: Electronic structures modulation for much enhanced OER/HER dual-functional characteristics

Herein, we have demonstrated a novel Ru-promoted NiFe oxyhydroxide anchored on N-doped carbon aerogel (RuNi7FeOx(OH)y @NCA) aerogel electrocatalyst via a facile sol-gel process, combined with a supercritical drying technique. The optimal RuNi7FeOx(OH)y @NCA shows a typical "pearl-like" aerogel nanostructure with a three-dimensional network, showing a large specific surface area of 227.7 m2·g−1. The achieved RuNi7FeOx(OH)y @NCA exhibits high OER activity with a low overpotential of 278.0 mV at 10 mA·cm−2 and a high TOF of 0.107 s−1. Moreover, the RuNi7FeOx(OH)y @NCA aerogel displays excellent hydrogen evolution reaction (HER) activity under alkaline conditions, with a small overpotential of 99.0 mV at a current density of 10 mA·cm−2, and a small Tafel slope of 61.1 mV·dec−1. DFT calculations show that the enhanced OER activity is attributed to the improved binding strength of *OOH intermediate on the catalyst surface, and the introduced Ru with larger electron density and weaker spin density leads to the improved HER activity.

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.

Sustainable chitosan hydrogen derived platinum/N-doped carbon aerogel for efficient oxygen reduction and hydrogen evolution reactions

Platinum (Pt)-based catalysts play a key role in electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), and reducing Pt content and maintaining high electrocatalytic activity and durability are essential to its promoted application. In this work, low content of Pt (10.5 wt%) loaded defective N-doped carbon aerogel (Pt/D-NCA) was synthesized using natural protonated chitosan complexed chloride platinate ion (chitosan-PtCl62-) as precursor. Pt/D-NCA exhibits better ORR (half-wave potential of 0.89 V vs RHE) and HER (57 mV vs RHE overpotential at 100 mA/cm2) performance than commercial 20 wt% Pt/C, and can be used as efficient cathode for Zn-air battery and water spitting. The defective N-doped carbon support can effectively reduce energy barrier of Pt sites through interface effect to inducing high intrinsic ORR and HER catalytic activity. This work provides a sustainable route to synthesize low Pt consumption electrocatalyst through a sustainable and environmentally friendly pathway.

N, O-diatomic dopants activate catalytic activity of 3D self-standing graphene carbon aerogel for long-cycle and high-efficiency Li-CO2 batteries

Carbon-based metal-free materials are regarded as viable cathode catalysts for Li-CO2 batteries due to their low costs and lightweight. And heteroatom doping (such as N atom) has great potential to improve the catalytic activity of carbon-based catalysts. However, the underlying catalytic mechanism is yet unclear, which hinders the construction of high-efficiency catalysts and further improvements in electrochemical performance. Especially, the role of oxygen-containing groups prevalent in carbon-based catalysts has never been explored. In this work, guided by theoretical simulation, a self-standing N-doped graphene carbon aerogel with certain oxygenic groups was well-designed and synthesized by a straightforward, one-step thermal approach as the cathode catalyst. N dopant can effectively regulate the electronic structure of graphene and thus lower the free energy change of reactants/intermediate species. The intrinsic oxygen-containing functional groups still presented in graphene aerogel can further stabilize CO2-related intermediate species and improve the catalytic activity through a synergistic coupling effect with N dopant. This effect was originally discovered and clarified in the Li-CO2 battery system. Additionally, intriguing 3D hierarchical pores of as-obtained graphene carbon aerogel not only guarantee good conductivity but also offer a vast surface area to expose numerous accessible active sites. The resulting Li-CO2 batteries showed a significantly enhanced initial energy efficiency of approximately 78.46% and remarkable cyclic stability of more than 1500 h at 20 μA cm−2. This fundamental understanding of the structure-performance relationship gives new ideas for creating extremely effective carbon-based metal-free catalysts for Li-CO2 batteries.

Chemical vapor deposition strategy for inserting atomic FeN4 sites into 3D porous honeycomb carbon aerogels as oxygen reduction reaction catalysts in high-performance Zn-air batteries

Fe-NxC single-atom catalysts have been immensely explored as the most promising ORR catalysts for replacing noble metals. Nevertheless, how to precisely introduce Fe atoms to optimize their spatial distribution and coordination environment in carbonaceous matrices while constructing the hierarchical porous structures to facilitate the mass transport process and ensure the accessibility of Fe-Nx sites remain significant challenges. Here, we propose a strategy to prepare porous N-doped carbon aerogels anchored with single atomic Fe sites (Fe-SA@PNC) as highly efficient ORR electrocatalysts via directional freeze-casting and chemical vapor deposition. Fe-SA@PNC exhibit remarkable ORR activity and stability due to the highly stable honeycomb morphology and hierarchical pore structure, as well as the atomically dispersed Fe-N4 sites in the carbon support. Furthermore, the practical application of Fe-SA@PNC catalysts as cathode materials in Zn-air batteries was demonstrated with encouraging performance. This study provides a promising approach for constructing high-efficiency ORR single-atom catalysts.

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.

A diatomite-derived N-doped carbon aerogel with 98% sulfur loading for the enhancement of Li–S battery performance

The ultralight carbon material with diatomite as template can drive 98 wt% sulfur material with only 2 wt%, and it still has high performance when used as the cathode material for lithium sulfur batteries.

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.

Polyamide aerogel-derived n-doped carbon aerogel decorated with platinum nanoparticles as highly active and stable electrocatalysts for oxygen reduction reaction

We prepared polyamide aerogel (PA)-derived carbon aerogel (CA) supported Pt nanoparticles with the supercritical CO2 deposition (SCD) technique as electrocatalysts for the oxygen reduction reaction (ORR). PAs were pyrolyzed at 800 °C to yield CPA and some CPA monoliths were subsequently etched with CO2 at 1000 °C to yield etched CPA (ECPA) to increase micro-mesoporosity and surface area in order to investigate their effect on the Pt nanoparticle dispersion and electrocatalytic performance towards ORR. The N-rich backbone of PAs yielded homogenously distributed N atoms in the CA structure enabling homogenous distribution of Pt nanoparticles, efficient dispersion of the Nafion ionomer and possible creation of ORR-active sites. Highly dispersed Pt nanoparticles with average size of 1.5 and 3.0 nm were obtained on CPA and ECPA, respectively. Pt-ECPA electrocatalysts showed enhanced electrochemically active surface area (ESA) and ORR mass activity when compared with commercial Pt-C. Pt-CPA showed similar ESA, mass and specific activity to that of commercial Pt-C due to lower mesopore volume and higher average Pt nanoparticle size. Accelerated stability tests (AST) revealed superior stability of Pt-CPA electrocatalyst due to favorable initial Pt nanoparticle size enabling successful immobilization Pt nanoparticles on CPA through the N-functionalities. Two important parameters, pore structure of carbon aerogel and initial Pt nanoparticle size, can be controlled through the powerful combination of sol-gel and supercritical deposition techniques to achieve both highly active and stable electerocatalysts.

Silk fibroin derived porous carbon aerogels confined hyperdispersed Rh nanoparticles to achieve electrocatalytic hydrogen evolution under high current density

In order to meet the current demand for clean energy and realize industrial application, it is urgent to develop highly efficient catalysts for hydrogen production from electrolytic water. Herein, we successfully synthesize hyperdispersed Rh nanoparticles on silk fibroin derived porous N-doped carbon aerogels (N-Rh/CA) using environment friendly silk fibroin as precursor material. The bonding between Rh and N anchored Rh nanoparticles uniformly super-dispersed on the substrate, exposing plentiful active sites. This N-Rh/CA with ultra-low metal content (2 wt %) exhibits the Pt-like electrocatalytic activity for hydrogen evolution, delivering current density of 10 and 100 mA cm−2 at a ultrasmall overpotential of 65 mV and 210 mV, respectively. Meanwhile, N-Rh/CA possesses a mass activity of 196.81 A g−1 at potential of 150 mV, and exhibits outstanding economic efficiency compared with Pt/C and reported Rh-based electrocatalyst. Furthermore, the electrocatalyst showed superior stability for the hydrogen evolution reaction, paving way for its potential industrial application.

Tunable high-performance electromagnetic interference shielding of intrinsic N-doped chitin-based carbon aerogel

Heteroatom doping of carbon aerogels is a promising strategy to dissipate electromagnetic waves (EMWs) and it is still a daunting challenge to establish the relationship between heteroatomic structure and EMI shielding performance. In our work, intrinsic N-doped biomass-based carbon aerogel was successfully prepared by freeze-drying and a specific two-stage pyrolysis using chitin and chitosan as carbon and nitrogen source. The content and type of doping elements and electrical conductivity could be accurately manipulated by controlling the content of precursors and carbonization temperature. The intrinsic N-doped induced a dipole polarization, and the unique three-dimensional porous architecture of biomass-based carbon aerogel was conducive to multiple reflection/scattering of EMWs. The as-prepared biomass-based carbon aerogel at 1300 °C exhibited an optimal EMI performance of 82 dB, and the absorption coefficients could be tuned in the range of 0.31–0.88. The excellent EMI performance originated from a variety of mechanisms involving conduction loss, dipole polarization loss, and interface polarization loss. The novel heteroatomic doping strategy not only provides new insight into the contribution of heteroatomic structure to EMI shielding performance, but also opens a new avenue to develop biomass-based carbon aerogels with tunable EMI shielding performances.

Thermal derived bismuth nanoparticles on nitrogen-doped carbon aerogel enable selective electrochemical production of formate from CO2

Producing formate via electrochemical carbon dioxide reduction reaction (CO2RR) is an attractive approach to carbon neutrality but suffers from low selectivity and energy conversion efficiency. Herein, we develop an efficient CO2RR electrocatalyst composed of Bi nanoparticles supported on N-doped carbon aerogel (Bi@NCA). Based on experimental and computational results, the carbon support serves as dual roles, one is to stabilize Bi nanoparticles by nitrogen dopants, the other function is to provide high porosity with abundant active sites to enhance CO2 adsorbability. Because of the synergistic effect between Bi nanoparticles and N-doped carbon framework, the as-obtained Bi@NCA delivers remarkable performance with moderate overpotential, and high selectivity towards formate with Faradaic efficiency surpassing 95% in a wide potential range.