Nitrogen-doped Hierarchical Carbon Research Articles

Rational Construction of Honeycomb-like Carbon Network-Encapsulated MoSe2 Nanocrystals as Bifunctional Catalysts for Highly Efficient Water Splitting.

The scalable fabrication of cost-efficient bifunctional catalysts with enhanced hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance plays a significant role in overall water splitting in hydrogen production fields. MoSe2 is considered to be one of the most promising candidates because of its low cost and high catalytic activity. Herein, hierarchical nitrogen-doped carbon networks were constructed to enhance the catalytic activity of the MoSe2-based materials by scalable free-drying combined with an in situ selenization strategy. The rationally designed carbonaceous network-encapsulated MoSe2 composite (MoSe2/NC) endows a continuous honeycomb-like structure. When utilized as a bifunctional electrocatalyst for both HER and OER, the MoSe2/NC electrode exhibits excellent electrochemical performance. Significantly, the MoSe2/NC‖MoSe2/NC cells require a mere 1.5 V to reach a current density of 10 mA cm-2 for overall water splitting in 1 M KOH. Ex situ characterizations and electrochemical kinetic analysis reveal that the superior catalytic performance of the MoSe2/NC composite is mainly attributed to fast electron and ion transportation and good structural stability, which is derived from the abundant active sites and excellent structural flexibility of the honeycomb-like carbon network. This work offers a promising pathway to the scalable fabrication of advanced non-noble bifunctional electrodes for highly efficient hydrogen evolution.

Hierarchical Nitrogen-Doped Carbon: A Bifunctional Catalyst for Oxygen Reduction and Evolution Reactions

This study presents the synthesis and characterization of hierarchical nitrogen-doped carbon (HCN-900), demonstrating remarkable electrocatalytic performance for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), outperforming traditional catalysts like RuO₂ and Pt/C. HCN-900 exhibits an onset potential of 0.98 V and a half-wave potential of 0.85 V for ORR, closely matching Pt/C performance while achieving an electron transfer number of 4.0, indicative of a four-electron pathway. For OER, HCN-900 achieves a current density of 10 mA cm⁻2 at an overpotential of 223 mV, significantly lower than RuO₂ (288 mV) and Pt/C (363 mV). The material also shows a Tafel slope of 87 mV dec⁻¹, indicating rapid kinetics and efficient electron transfer. This impressive performance is attributed to the optimized structural and electronic properties of HCN-900, including its high surface area, hierarchical porosity, and nitrogen doping, which enhance active site density and promote electron transport. Furthermore, HCN-900 retains approximately 96.72% of its initial performance after 10 h of continuous operation, demonstrating excellent long-term stability. The comprehensive analysis highlights HCN-900 as a promising bifunctional catalyst for advanced energy applications, providing a cost-effective and sustainable alternative to conventional catalysts. Its superior electrocatalytic properties make HCN-900 an excellent candidate for integration into next-generation energy conversion and storage systems.

MOF-derived high-density carbon nanotubes “tentacle” with boosting electrocatalytic activity for detecting ascorbic acid

Accurate detection of ascorbic acid (AA) plays a significant role in food and human physiological processes. Herein, a three-dimensional flexible leaf-like nitrogen-doped hierarchical carbon nanoarrays with high-density carbon nanotube “tentacle” architecture (NC/CNT-Co), which possesses high specific surface area, plenty of active defect sites, and various pore size distributions, was synthesized by the pyrolysis of zeolitic imidazolate framework (ZIF(Co)), while g-C3N4 acted as carbon source and heteroatom doping agent. Benefiting from its unique structure and surface properties, a selective and highly sensitive AA sensor was developed using this material. Compared to powder materials, NC/CNT-Co modified CF (CF@NC/CNT-Co) which don't be extra decorated, exhibits lower detection limit (1 μM), a wider linear range (20–1400 μM), and better stability, showing higher performance in electrocatalysis and detection of AA. Furthermore, CF@NC/CNT-Co also demonstrates high resistance to interference and fouling in AA detection. Particularly, the prepared CF@NC/CNT-Co electrode could determine AA in beverage samples with a recovery rate of 96.3–103.5 %. Therefore, the three-dimensional NC/CNT-Co hierarchical structure can be provided as an original electrode nanomaterial suitable for the selective and sensitive detection of AA, with a wide range of practical applications from food analysis to the pharmaceutical industry.

Hierarchical Carbon Nanocages as Superior Supports for Photothermal CO2 Catalysis.

The exploitation of hierarchical carbon nanocages with superior light-to-heat conversion efficiency, together with their distinct structural, morphological, and electronic properties, in photothermal applications could provide effective solutions to long-standing challenges in diverse areas. Here, we demonstrate the discovery of pristine and nitrogen-doped hierarchical carbon nanocages as superior supports for highly loaded, small-sized Ru particles toward enhanced photothermal CO2 catalysis. A record CO production rate of 3.1 mol·gRu-1·h-1 with above 90% selectivity in flow reactors was reached for hierarchical nitrogen-doped carbon-nanocage-supported Ru clusters under 2.4 W·cm-2 illumination without external heating. Detailed studies reveal that the enhanced performance originates from the strong broadband sunlight absorption and efficient light-to-heat conversion of nanocage supports as well as the excellent intrinsic catalytic reactivity of sub-2 nm Ru particles. Our study reveals the great potential of hierarchical carbon nanocages in photothermal catalysis to reduce the fossil fuel consumption of various industrial chemical processes and stimulates interest in their exploitation for other demanding photothermal applications.

Self-enhanced localized alkalinity at the encapsulated Cu catalyst for superb electrocatalytic nitrate/nitrite reduction to NH3 in neutral electrolyte.

The electrocatalytic nitrate/nitrite reduction reaction (eNOx-RR) to ammonia (NH3) is thermodynamically more favorable than the eye-catching nitrogen (N2) electroreduction. To date, the high eNOx-RR-to-NH3 activity is limited to strong alkaline electrolytes but cannot be achieved in economic and sustainable neutral/near-neutral electrolytes. Here, we construct a copper (Cu) catalyst encapsulated inside the hydrophilic hierarchical nitrogen-doped carbon nanocages (Cu@hNCNC). During eNOx-RR, the hNCNC shell hinders the diffusion of generated OH- ions outward, thus creating a self-enhanced local high pH environment around the inside Cu nanoparticles. Consequently, the Cu@hNCNC catalyst exhibits an excellent eNOx-RR-to-NH3 activity in the neutral electrolyte, equivalent to the Cu catalyst immobilized on the outer surface of hNCNC (Cu/hNCNC) in strong alkaline electrolyte, with much better stability for the former. The optimal NH3 yield rate reaches 4.0 moles per hour per gram with a high Faradaic efficiency of 99.7%. The strong-alkalinity-free advantage facilitates the practicability of Cu@hNCNC catalyst as demonstrated in a coupled plasma-driven N2 oxidization with eNOx-RR-to-NH3.

Highly Dispersed Quasi-1 nm Ruthenium Nanoclusters on Hierarchical Nitrogen-Doped Carbon Nanocages Constructed by Surface-Constrained Sintering for Alkaline Hydrogen Evolution

Highly Dispersed Quasi-1 nm Ruthenium Nanoclusters on Hierarchical Nitrogen-Doped Carbon Nanocages Constructed by Surface-Constrained Sintering for Alkaline Hydrogen Evolution

Oxygen-Bridged Cu Binuclear Sites for Efficient Electrocatalytic CO2 Reduction to Ethanol at Ultralow Overpotential.

Electrocatalytic CO2 reduction (CO2RR) to alcohols offers a promising strategy for converting waste CO2 into valuable fuels/chemicals but usually requires large overpotentials. Herein, we report a catalyst comprising unique oxygen-bridged Cu binuclear sites (CuOCu-N4) with a Cu···Cu distance of 3.0-3.1 Å and concomitant conventional Cu-N4 mononuclear sites on hierarchical nitrogen-doped carbon nanocages (hNCNCs). The catalyst exhibits a state-of-the-art low overpotential of 0.19 V (versus reversible hydrogen electrode) for ethanol and an outstanding ethanol Faradaic efficiency of 56.3% at an ultralow potential of -0.30 V, with high-stable Cu active-site structures during the CO2RR as confirmed by operando X-ray adsorption fine structure characterization. Theoretical simulations reveal that CuOCu-N4 binuclear sites greatly enhance the C-C coupling at low potentials, while Cu-N4 mononuclear sites and the hNCNC support increase the local CO concentration and ethanol production on CuOCu-N4. This study provides a convenient approach to advanced Cu binuclear site catalysts for CO2RR to ethanol with a deep understanding of the mechanism.

A novel approach for facile synthesis of cost-optimal catalyst for high-performance lithium-air battery

We have developed a novel and efficient cathode for advanced lithium-air batteries by employing a new approach and facile strategy. In this method, we prepared core-shell structured ZIF-8@ZIF-67 crystals with epitaxial growth using a hydrothermal technique. By subjecting these crystals to carbonization at a temperature 200 °C higher than the degradation initiation temperature (i.e. 600 °C according to thermogravimetric results), we successfully obtained functionalized nanoporous hybrid carbon materials. These hybrid carbon materials consist of hierarchical nitrogen-doped carbon @ cobalt anchored/nitrogen doped carbon (NC@CNC), where the nitrogen-doped carbon (NC) serves as the core and the cobalt anchored/nitrogen doped carbon (CNC) forms the shell. It is worth noting that electrochemical characterization data strongly support the superior performance of this nanoporous hybrid carbon material. It combines the advantageous properties of individual mesopores of nitrogen-doped carbon and the catalytic activity of cobalt‑nitrogen doped carbon. In particular, the cathode material, i.e. NC@CNC, exhibits a remarkable specific capacitance of 10,000 mAh·g−1, as calculated from the galvanostatic charge-discharge curves obtained at a current density of 50 mA·g−1. This impressive performance highlights the potential of our developed material in enhancing the efficiency and overall performance of lithium-air batteries.

Constructing Gold Single-Atom Catalysts on Hierarchical Nitrogen-Doped Carbon Nanocages for Carbon Dioxide Electroreduction to Syngas.

Precious-metal single-atom catalysts (SACs), featured by high metal utilization and unique coordination structure for catalysis, demonstrate distinctive performances in the fields of heterogeneous and electrochemical catalysis. Herein, gold SACs are constructed on hierarchical nitrogen-doped carbon nanocages (hNCNC) via a simple impregnation-drying process and first exploited for electrocatalytic carbon dioxide reduction reaction (CO2RR) to produce syngas. The as-constructed Au SAC exhibits the high mass activity of 3319Ag-1 Au at -1.0V (vs reversible hydrogen electrode, RHE), much superior to the Au nanoparticles supported on hNCNC. The ratio of H2/CO can be conveniently regulated in the range of 0.4-2.2 by changing the applied potential. Theoretical study indicates such a potential-dependent H2/CO ratio is attributed to the different responses of HER and CO2RR on Au single-atom sites coordinating with one N atom at the edges of micropores across the nanocage shells. The catalytic mechanism of the Au active sites is associated with the smooth switch between twofold and fourfold coordination during CO2RR, which much decreases the free energy changes of the rate-determining steps and promotes the reaction activity.

Alloyed Pt-Sn nanoparticles on hierarchical nitrogen-doped carbon nanocages for advanced glycerol electrooxidation

Alloyed Pt-Sn nanoparticles on hierarchical nitrogen-doped carbon nanocages for advanced glycerol electrooxidation

High-Rate Lithium-Selenium Batteries Boosted by a Multifunctional Janus Separator Over a Wide Temperature Range of -30 °C to 60 °C.

Lithium-selenium batteries are characterized by high volumetric capacity comparable to Li-S batteries, while ≈1025 times higher electrical conductivity of Se than S is favorable for high-rate capability. However, they also suffer from the "shuttling effect" of lithium polyselenides (LPSes) and Li dendrite growth. Herein, a multifunctional Janus separator is designed by coating hierarchical nitrogen-doped carbon nanocages (hNCNC) and AlN nanowires on two sides of commercial polypropylene (PP) separator to overcome these hindrances. At room temperature, the Li-Se batteries with the Janus separator exhibit an unprecedented high-rate capability (331 mAh g-1 at 25 C) and retain a high capacity of 408 mAh g-1 at 3 C after 500 cycles. Moreover, the high retained capacities are achieved over a wide temperature range from -30 °C to 60 °C, showing the potential application under extreme environments. The excellent performances result from the "1+1>2" synergism of suppressed LPSes shuttling by chemisorption and electrocatalysis of hNCNC on the cathode side and suppressed Li-dendrite growth by thermally conductive AlN-network on the anode side, which can be well understood by the "Bucket Effect". This Janus separator provides a general strategy to develop high-performance lithium-chalcogen (Se, S, SeS2 ) batteries.

Electrical properties of hierarchical nitrogen-doped multi-walled carbon nanotubes obtained using cobalt nanoparticles

In this work, for the first time, both initial and secondary branches of hierarchical nitrogen-doped multi-walled carbon nanotubes (h-N-MWCNTs) were obtained using chemical vapor deposition due to the decomposition of ace-tonitrile over Co-based nanoparticles. The results of a study of the electrical conductivity of h-N-MWCNTs for a wide temperature range of 300−4.2 K are presented. It was shown that fluctuation-assisted tunneling between delocalized states is the dominant conduction mechanism at temperatures above 50 K. An analysis of the temperature and electric field dependences of the resistance indicates that the transfer of electric charges below 50 K occurs due to hoppings between localized states located in the vicinity of the Fermi level. It was shown that the Coulomb interaction affects the charge carrier transport. The width of the Coulomb gap estimated from the temperature dependence of the resistance is 0.5 meV. The electrical conductivity of h-N-MWCNTs in the temperature range of 50−4.2 K occurs by the Efros–Shklovskii variable range hopping conduction mechanism. It was found that the charge localization length is ≈150 nm. Electrical property analysis indicates that the dielectric constant of the h-N-MWCNTs is ≈ 100.

MoO2 Nanoclusters Embedded in Hierarchical Nitrogen Doped Carbon Nanoflower as Electrocatalytic Mediators in Aqueous Zinc-Tellurium Batteries: Enhancing Electrochemical Kinetics of Tellurium Redox Reaction.

Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising devices for large-scale energy storage systems owing to their high theoretical capacity, environmental friendliness, and safety. However, the ionic intercalation or surface redox mechanisms in conventional cathode materials generally result in unsatisfactory capacities. Conversion-type aqueous zinc-tellurium (Zn-Te) batteries have recently gained widespread attention owing to their high theoretical specific capacities. However, it remains an enormous challenge to improve the slow kinetics of the aqueous Zn-Te batteries. Here, MoO2 nanoclusters embedded in hierarchical nitrogen-doped carbon nanoflower (MoO2 /NC) hosts are successfully synthesized and loaded with Te in aqueous Zn-Te batteries. Benefitting from the highly dispersed MoO2 nanoclusters and hierarchical nanoflower structure with a large specific surface area, the electrochemical kinetics of the Te redox reaction are significantly improved. As a result, the Te-MoO2 /NC electrode exhibits superior cycling stability and a high specific capacity of 493 mAh g-1 at 0.1 A g-1 . Meanwhile, the conversion mechanism is systematically explored using a variety of ex situ characterization methods. Therefore, this study provides a novel approach for enhancing the kinetics of the Te redox reaction in aqueous Zn-Te batteries.

Photothermal-Responsive Intelligent Hybrid of Hierarchical Carbon Nanocages Encapsulated by Metal-Organic Hydrogels for Sensitized Photothermal Therapy.

Hierarchical carbon nanocages as emerging nanomaterials have a great potential for photothermal therapy due to their unique porous structure, high specific surface area, and excellent photothermal property. Herein, a hierarchical nitrogen-doped carbon nanocage (hNCNC) is introduced as a second near-infrared photothermal agent, and then functionalizes it with metal-organic hydrogel (MOG) to form a thermal-responsive switch for sensitized photothermal therapy. Upon 1064nm light irradiation, the hNCNCs exhibit a remarkable photothermal conversion efficiency of 65.9% owing to a high near-infrared extinction coefficient. Meanwhile, due to the hierarchical structure, hNCNCs show 60.2% (wt./wt.) loading efficiency of quercetin, a heat shock protein (Hsp70) inhibitor. Through thermal-driven dry-gel transformation, the coating MOGs intelligently release the encapsulated quercetin for sensitizing cancer cells to heat. Based on the synergistic effect of hyperthermia elevation and thermal-driven drug release, the dual thermal utilization platform achieves effective photothermal tumor ablation in vivo under low concentration of hNCNCs and mild irradiation, which provides a new diagram of intelligent responsive photothermal agents for enhanced photothermal therapy.

Loss-free pulverization by confining copper oxide inside hierarchical nitrogen-doped carbon nanocages toward superb potassium-ion batteries.

Taking the advantages of hierarchical nitrogen-doped carbon nanocages (hNCNCs) with nanocavities for encapsulation and multiscale micro-meso-macropores/high conductivity for mass/electron synergistic transportation, a conversion-type CuO anode material is confined inside hNCNCs for potassium storage. The so-obtained yolk-shelled CuO@hNCNC hybrids have tunable CuO contents in the range of 11.7-63.7 wt%. The unique architecture leads to the loss-free pulverization of the active components during charge/discharge, which increases the surface-controlled charge storage, shortens the K+ solid diffusion lengths with an enlarged K+ diffusion coefficient, and meanwhile enhances the rate capability and durability. Consequently, the optimized CuO@hNCNC delivers a high specific capacity of 498 mA h g-1 at 0.1 A g-1 and 194 mA h g-1 at 10.0 A g-1 based on the total mass of CuO@hNCNC, and a long-term stability. The capacity based on the CuO active component reaches a record-high 522 mA h g-1 at 1.0 A g-1 after 2000 cycles, which is ca. 2.5 times the state-of-the-art value in the literature. The evolution of the cycling performance with CuO loading is well understood based on the loss-free pulverization. This study demonstrates a new strategy to turn the generally harmful pulverization of active components into a beneficial factor for K+ storage, which paves the way for exploring high-performance anodes for rechargeable batteries.

Facile template-free synthesis of 3D cluster-like nitrogen-doped mesoporous carbon as metal-free catalyst for selective oxidation of H2S

Construction of metal-free carbon-based materials for efficient sulfur resource recovery in pollutant H2S is very critical for both applied environmental catalysis and fundamental material exploration. Herein, we report a template-free hydrothermal method to prepare hierarchical nitrogen-doped mesoporous carbon (HNMCs) materials with abundant nitrogen sites and large BET surface area. The representative HNMC-800 achieves a H2S conversion of ∼100% and sulfur selectivity of ∼95% at 150 °C in H2S selective oxidation. Moreover, HNMCs catalysts are resistant to sulfur poisoning, displaying good catalytic durability, with no significant loss of sulfur yield in the run of 80 h, outperforming the pure active carbon, g-C3N4, and commercial Fe2O3. This work provides the possibility of utilizing hierarchical nitrogen-doped carbon materials as metal-free catalysts for the selective oxidation of H2S.

Hierarchical Nitrogen-Doped Graphitic Carbon Spheres Anchored with Amorphous Cobalt Nanoparticles as High-Performance and Ultrastable Anode for Potassium-Ion Batteries

As one of the most promising electrochemical energy-storage devices after lithium-ion batteries, potassium-ion batteries (KIBs) have been restricted by the limited capacity of carbon-based anodes. Herein, we design and prepare three-dimensional nitrogen-doped graphitic carbon spheres anchored with cobalt nanoparticles (CoNC) via self-sacrifice template method. The CoNC spheres exhibit a uniform spherical morphology with an inner hierarchical structure. The final calcination temperature is changed to obtain CoNC-700, CoNC-800, and CoNC-900, in which CoNC-700 is verified to combine amorphous cobalt nanoparticles with graphitic carbon spheres successfully and presents excellent rate capability and good potassium-storage performance. Nitrogen-doping and amorphous cobalt nanoparticle-loading can effectively introduce rich defects to the CoNC electrode, enhance electrical conductivity, and accelerate potassium-storage kinetics, which leadto a reversible specific capacity of 382 mA h g–1 at a current density of 0.5 A g–1 and 330 mA h g–1 at a current density of 1 A g–1 after 1000 cycles, suggesting the potential of the high-capacity, ultrastable anode for potassium-ion batteries.

Tailored design of well-defined hierarchical nitrogen-doped carbon via salt-confined strategy for selective Cd(Ⅱ) adsorption

Efficient cadmium (Cd) removal is vital to ensure freshwater safety, yet it still lacks high-efficiency treatment technologies, especially for the technique with simple-operation and eco-friendliness. Herein, three different carbon-based nanomaterials of hierarchical nitrogen-doped carbon (h-NC-750, h-NC-800 and h-NC-850) were successfully synthesized, via carbonizing the sealed ZIF-8 particles in NaCl crystals at various carbonization temperatures of 750, 800 and 850 °C in Ar atmosphere. Amongst them, the acquired dual-carbon of h-NC-800 harvesting a total nitrogen content of 15.5% rendered the maximum Cd(Ⅱ) adsorption capacity of 356.4 mg g−1, which was 12.5 and 48.3% higher than that of h-NC-750 and h-NC-850 counterparts. The density functional theory (DFT) simulations in combination with characterizations unveiled that the exceptional Cd(Ⅱ) removal of h-NC-800 was derived from the harmonized edge- to graphitic-nitrogen ratio that strengthened the binding energies between Cd(Ⅱ) and h-NC. Impressively, thus-optimized adsorbents afforded the favorable and stabilized removal efficiency (>92%) toward Cd(Ⅱ) in realistic water and five-consecutive regeneration cyclicality. This work is anticipated to offer an innovative insight into the molecular-level architecture design of h-NC with well-defined nitrogen doping and controllable edge- to graphitic-nitrogen ratio, targeting high performance in aqueous Cd(Ⅱ) removal.

Encapsulating atomic molybdenum into hierarchical nitrogen-doped carbon nanoboxes for efficient oxygen reduction

Construction of single-atom catalysts (SACs) with maximally exposed active sites remains a challenging task mainly because of the lack of suitable host matrices. In this study, hierarchical N-doped carbon nanoboxes composed of ultrathin nanosheets with dispersed atomic Mo (denoted as hierarchical SA-Mo-C nanoboxes) were fabricated via a template-engaged multistep synthesis process. Comprehensive characterizations, including X-ray absorption fine structure analysis, reveal the formation of Mo-N4 atomic sites uniformly anchored on the hierarchical carbon nanoboxes. The prepared catalysts offer structural and morphological advantages, including ultrathin nanosheet units, unique hollow structures and abundant active Mo-N4 species, that result in excellent activity with a half-wave potential of 0.86 V vs. RHE and superb stability for the oxygen reduction reaction in 0.1 M KOH; thus, the catalysts are promising air–cathode catalysts for Zn-air batteries with a high peak power density of 157.6 mW cm−2.

Controlled preparation of nitrogen-doped hierarchical carbon cryogels derived from Phenolic-Based resin and their CO2 adsorption properties

Nitrogen-doped hierarchical carbon cryogels with good monolithic structure are synthesized from phenol (P), melamine (M), and formaldehyde (F) by sol-gel, freeze-drying, and carbonization process with different molar ratios of F/(P + M). The synthesized cryogels have the characteristics of cost-effective and abundant hierarchical pores. The pore structures, chemical properties, and CO2 adsorption performance of the prepared carbon cryogels are investigated. The results reveal that the PF carbon cryogel without N doping shows poor porosity characteristics, which leads to lower CO2 adsorption performance. For the N-doped PMF carbon cryogels, with the increase in the molar ratio of F/(P + M), the specific surface area and micropore volume decreases from 1160.6 to 874.1 m2/g and from 0.47 to 0.35 cm3/g, respectively, indicating that a lower formaldehyde content is conducive to the formation of more micropores and higher specific surface area. The carbon cryogel PMF2.0 (F/(P + M) = 2.0) exhibits a CO2 adsorption capacity as high as 5.79 mmol/g, and it also has a high CO2/N2 adsorption selectivity (13.43) and isosteric adsorption heat (33.06 kJ/mol). Thus, the PMF carbon cryogel exhibits immense potential as an adsorbent for CO2 capture, and its excellent performance is attributed to the synergistic effect of N doping and abundant micropores with appropriate size.