Nitrogen-doped Carbon Nanocages Research Articles

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

ZIF67-derived ultrafine Co9S8 nanoparticles embedded in nitrogen-doped hollow carbon nanocages for enhanced performances of trifunctional ORR/OER/HER and overall water splitting

ZIF67-derived ultrafine Co9S8 nanoparticles embedded in nitrogen-doped hollow carbon nanocages for enhanced performances of trifunctional ORR/OER/HER and overall water splitting

Nanocage confined nitrogen-rich MOF-derived Co/CoN heterostructure for overall water splitting

Of great significance is the study towards replacing precious metal electrocatalysts with transition metal electrocatalysts for the electrocatalytic hydrogen evolution from water, regarding clean energy utilization. The precise design and engineering of catalysts at the nanoscale, with a focus on their structural and functional attributes, have garnered significant attention and research interest as pivotal approaches to optimizing their catalytic performance. Among those strategies, fabricating transition metals and their corresponding nitrides has lately gained extensive attentions for electrocatalytic water decomposition, because of their adjustable distribution of electrons. In this study, ZIF-67@MAT-6 precursor was formed by coating ZIF-67 with triazole ligand (MAT-6) based on ligand exchange strategy, followed by confining Co/CoN heterostructure nanoparticles in nitrogen-doped carbon nanocages upon heat treatment under nitrogen flow. The resulting electrocatalyst exhibited outstanding electrocatalytic performance for hydrogen and oxygen evolution reactions in alkaline media, with overpotentials of 115 mV and 290 mV to reach 10 mA·cm−2 in 1 M KOH electrolyte, respectively. In addition, the electrocatalyst showed great durability with only 2.16 % current decay during 24 h potentiostatic electrolysis for water decomposition. The density functional theory (DFT) theoretically supported that the accelerated interfacial charge transfer and promoted electrical conductivity were responsible for the remarkable electrocatalytic performance, caused by the synergic effect between the heterogeneous Co and CoN.

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 direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

A direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

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.

A bi-functional catalyst strategy to selectively regulate sulfur redox kinetics in lithium–sulfur batteries

Designing electrochemical catalysts has become a research hotspot due to their accelerating the polysulfide conversion of the sulfur cathode to inhibit the “shuttle effect” in lithium–sulfur batteries. However, it is still a great challenge to design the heterogeneous selective electrochemical catalyst for inhibiting the “shuttle effect”. Herein, nickel cobalt phosphide and cobalt phosphide as the heterogeneous catalyst active sites embedded in the nitrogen-doped hollow carbon nanocages (NiCoP@CoP/NC) are reported, used for multi-step and multi-phase sulfur electrode reaction, and it is found that metal-sulfur d-p hybridization can effectively indicate the intrinsic catalytic activity of metal site. Division of labor and cooperation of the bi-active NiCoP@CoP as heterogeneous catalysts propel the stepwise polysulfide conversion. NiCoP and CoP sites preferentially accelerate the long-chain polysulfide conversion reaction (S8⇌LiPSs) and the short-chain polysulfide conversion reactions (LiPSs⇌Li2S), respectively. Moreover, the hollow and porous N-doped carbon structure can successfully suppress the volume effect and improve the conductivity of the sulfur cathode. The unique design can obtain an effective inhibition of the shuttle effect and rapid electrode reaction. As a result, LiS batteries demonstrate a high initial capacity of 1063 mAh g−1 and a low-capacity decay of 0.04% per cycle within 1000 cycles. Our work provides a feasible idea for the design of host materials in Li–S batteries.

Hierarchical construction of MoSe2 nanoparticles anchored on N-doped porous carbon nanocages with Mo-C bonding for enhanced potassium-ion storage

Molybdenum selenide (MoSe2) is considered as a promising anode material for potassium ion batteries (PIBs) due to its high theoretical capacity and large interlayer spacing. However, the low intrinsic conductivity and large volume expansion impede its practical application. Herein, hierarchical nanostructure of MoSe2 nanoparticles tightly anchored on hollow porous nitrogen-doped carbon nanocages (MoSe2/NCC) is constructed as an anode material for PIBs. Nitrogen-doped carbon nanocages not only improve the conductivity, provide more active sites, and alleviate the volume expansion during K+ insertion and desertion, but also serve as a nucleation substrate for suppressing the agglomeration of MoSe2 nanoparticles. Importantly, the structural stability and electron/ion transfer kinetics are significantly enhanced by strong interfacial coupling between MoSe2 and carbon via the formation of Mo-C bonding. Consequently, MoSe2/NCC electrode exhibits a reversible capacity of 321 mA h g−1 at 0.1 A g−1, excellent cycling stability with a retention of 323 mA h g−1 after 80 cycles, and rate capability of 173 mA h g−1 at 5 A g−1. In addition, the storage mechanism and transfer kinetics of potassium ions during the charging and discharging process are investigated. This work paves the ideas for the design of novel anode materials for high-rate and stable PIBs.

Energetic metal–organic frameworks derived porous nitrogen-doped carbon nanocages for highly efficient peroxymonosulfate activation

Porous nitrogen-doped carbon nanocages (PNCCs) are fabricated by one-step pyrolysis of energetic Zn-based MOF (MET-6) and employed as highly efficient PMS activator to decompose organic micropollutants. PNCCs-900 exhibits extraordinary catalytic activity for RhB degradation due to its high specific surface area (894.9 m2 g−1), N-doping level (13.1%), and optimum N configuration ratio. This work opens a new avenue for the development of efficient PMS activators for water remediation.

Cobalt nanoparticles-embedded porous carbon nanocages uniformly dispersed hollow carbon fibers as the accelerated electrocatalysts toward water splitting

The fast, low-cost, and efficient design of zeolite imidazolate frameworks (ZIF) based derivatives with perfect hollow channels is an effective method for enhancing their full water-splitting catalytic activities and achieving their commercial use. In this study, the novel cobalt nanoparticles embedded in nitrogen-doped porous carbon nanocages uniformly dispersed over two curved surfaces of biomass-derived hollow carbon fibers (Co@NC nanocage/HCF) were synthesized via the carbonization of the ZIF-67/hollow biomass fiber precursors. After the usage amounts of biomass fibers were optimized, the optimal Co@NC nanocage/HCF200 exhibited a larger surface area and higher dispersion states of Co@NC nanocages than the tightly packed pure Co@NC nanocages. Particularly, owing to the hollow and porous structures of Co@NC nanocages, more electrocatalytic active centers (i.e. the pyridinic-N, Co-Nx-C, pyrrolic-N, graphitic-N, high-valence Co, and other oxygen-containing functional groups) were exposed along surfaces of the Co@NC nanocage/HCF200 catalyst. In an alkaline solution, the hydrogen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 165 mV more negative than that of 20 wt% Pt/C. Particularly, the oxygen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 17 mV more negative than that of RuO2. For overall water splitting, the bifunctional Co@NC nanocage/HCF200 catalyst-based electrolysis cell achieved a current density of 10 mA cm−2 at a cell voltage of 1.618 V, which is 4 mV smaller than that of the state-of-the-art 20 wt% Pt/C||RuO2 cell (1.614 V). The perfect hollow and porous structures, uniformly dispersed Co@NC nanocages (locked by vast in situ formed carbon nanotubes), and abundant electrocatalytic active sites along the inner and outer surfaces of Co@NC nanocage/HCF200 contributed to the excellent water splitting catalysis. Particularly, owing to the excellent stabilities of hollow structures and uniformly dispersed porous Co@NC nanocages, the Co@NC nanocage/HCF200 exhibited higher stability toward water electrolysis.

Amorphous Nitrogen-Doped Carbon Nanocages with Excellent SERS Sensitivity and Stability for Accurate Identification of Tumor Cells.

The surface-enhanced Raman scattering (SERS) bioprobe's strategy for identifying tumor cells always depended on the intensity difference of the Raman signal compared with that of normal cells. Hence, exploring novel SERS nanostructure with excellent spectra stability, a high enhancement factor (EF), and good biocompatibility is a primary premise for boosting SERS signal reliability and accuracy of tumor cells. Here, high SERS EF (5.52 × 106) is acquired by developing novel amorphous nitrogen-doped carbon (NDC) nanocages (NCs), whose EF value was in a leading position among carbon-based SERS substrates. In addition, a uniform SERS signal was obtained on NDC NCs due to homogeneous morphology and size. The delocalized carbon-conjugated systems of graphitic-N, pyrrole-N, and pyridine-N with lone pair electrons increase the electronic density of states and reduce the electron localization function of NDC NCs, thereby promoting the charge transfer process. The electron-donor platform of the NDC NCs facilitates the thermodynamic process of charge transfer, resulting in multimode vibrational coupling in the surface complexes, which greatly amplifies the molecular polarizability. Importantly, the good biocompatibility and signal stability endow these NDC NC SERS bioprobes unique superiority in distinguishing tumor cells, and quantitative recognition of two triple-negative breast cancer cells based on SERS detection mode has been successfully realized.

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.

Defect-stabilized platinum single atoms and clusters in bilayer nitrogen-doped porous carbon nanocages for synergistic catalysis of basic hydrogen evolution

Alkaline water electrolysis is a safe and efficient method for producing hydrogen that is favored by the industry. At present, single-atom catalysts have attracted extensive attention due to their extremely high atom utilization. However, studies on the single-atom site catalytic mechanism of the Volmer step, the rate-determining step of the cathodic HER reaction, are lacking. Here, we used ZIF-8 to obtain double-layer N-doped porous carbon nanocages, and successfully achieved the co-loading of Pt single atoms and their clusters (NPCN–Pt). The turnover frequency (TOF) and mass activity of NPCN–Pt are 5 and 7.2 times higher than those of commercial Pt/C, respectively, and the former exhibits significantly better stability than Pt/C. Theoretical calculations show that Pt clusters have a lower activation energy barrier for water molecules compared to Pt single atoms, which favors the Volmer step. The ΔGH* of Pt single-atom sites is smaller than that of Pt clusters, which is more conducive to the release of H2. The study shows that Pt clusters and single atoms can synergistically catalyze the HER reaction, providing new ideas for the development of efficient HER catalysts.

Sub‐Nanometer Fe Clusters Confined in Carbon Nanocages for Boosting Dielectric Polarization and Broadband Electromagnetic Wave Absorption (Adv. Funct. Mater. 31/2022)

Subnanometer Clusters In article number 2204370, Yixing Li, Xuefeng Zhang, and co-workers fabricate sub-nanometer iron clusters within nitrogen-doped carbon nanocages. Benefitting from their unique structures, the energy transformation between the relatively complex permeability and permittivity can be realized, which thus boosts the dielectric polarization and improves the electromagnetic wave absorption performance.

Sub‐Nanometer Fe Clusters Confined in Carbon Nanocages for Boosting Dielectric Polarization and Broadband Electromagnetic Wave Absorption

AbstractCompositing dielectric and magnetic components have been proven effective in optimizing electromagnetic (EM) wave absorption, in which the dielectric loss capacity can be reinforced by the polarization effects of hetero‐substitutions. Here, the dielectric polarization through the energy transformation between the relatively complex permeability and permittivity in nitrogen‐doped carbon nanocages (NCNs) with sub‐nanometer Fe clusters is further boosted. As a transition state between single Fe atoms and Fe3O4 nanoparticles hetero‐substitutions, these subnanometer Fe clusters confined in NCNs can be achieved by carbonizing FePc@ZIF‐8 composites at 900 °C. Benefitting from their unique structures, an enhanced dielectric loss tangent of 1.57 is obtained at 10 GHz, which is 3.0 and 1.6 times higher than those of single Fe atoms and Fe3O4 nanoparticles hetero‐substitutions, respectively. Furthermore, the minimum reflection loss can reach −64.75 dB at 7.1 GHz (2.7 mm) and the effective absorption bandwidth is 6.2 GHz (11.8–18 GHz, covering the full P‐band) at 1.7 mm. The present study provides intrinsic insight into the dielectric polarization behaviors in subnanometer hetero‐substitutions, inspiring the design of high‐performance EM absorption materials.

Self-supported hierarchically porous 3D carbon nanofiber network comprising Ni/Co/NiCo2O4 nanocrystals and hollow N-doped C nanocages as sulfur host for highly reversible Li–S batteries

Hierarchically porous nitrogen-doped carbon nanofibers (P-N-CNF) comprise well-embedded metallic-Ni/Co and spinel-type NiCo2O4 nanocrystals (Ni-Co/NiCo2O4) along with metal-organic framework-derived hollow nitrogen-doped carbon nanocages (HNC), denoted as P-N-CNF@NCO/HNC, are rationally designed as cathode substrates for advanced lithium-sulfur batteries with feasible parameters. The highly conductive and porous N-CNF matrix provides numerous conductive channels for rapid ionic and electronic transfer. HNC guarantees efficient impregnation of a large volume of active material along with high loading, channelizing the volume variation stress, and ensuring efficient electrolyte percolation, which is crucial for uniform dispersion and high active sulfur utilization, especially at low electrolyte/sulfur (E/S) ratios. The metallic-Ni/Co and polar spinel-type NiCo2O4 nanoparticles offer sufficient chemisorption sites to prevent polysulfide migration towards the anode. Li-S cells assembled using P-N-CNF@NCO/HNC as an advanced host and lithium polysulfide catholyte as the starting material displayed stable electrochemical performance even with strident battery parameters, including high sulfur content (79.8 wt%), high sulfur loading (7.7 mg cm−2), and low E/S ratio (8.0 µL mg−1). The cell displays a maximum areal capacity of 5.4 mA h cm−2 that stabilizes to 2.8 mA h cm−2 after 160 cycles at 0.1 C and is comparable to the theoretical threshold of presently available commercial systems.