N-doped Carbon Nanotubes Research Articles

Heterostructure Engineering Enables MoSe2 with Superior Alkali-Ion Storage

Molybdenum diselenide (MoSe2) is a promising anode for alkali-ion storage due to its intrinsic advantages. However, MoSe2 still encounters the issues of structural instability and poor rate performance caused by drastic volume change and sluggish reaction kinetics. Reasonable design of electrode structure is crucial for achieving superior electrochemical performance. Herein, a novel hierarchical structure coupled with 1D/1D subunits is elaborately designed and constructed, in which the MoSe2/CoSe2 heterostructure is the “trunk” and the N-doped carbon nanotubes are the “branches” (MoSe2/CoSe2/NCNTs). Benefiting from the properties endowed by unique configurations, MoSe2/CoSe2/NCNTs electrodes manifest faster reaction kinetics and better structure durability. Evaluated as an anode for LIBs and SIBs, MoSe2/CoSe2/NCNTs deliver high reversible capacity, superior rate capability (452 at 10 A g−1 in LIBs and 296 at 10 A g−1 in SIBs), and prominent cycle life (553 after 2000 cycles at 5 A g−1 in LIBs and 310 after 2000 cycles at 5 A g−1 in SIBs). Such design conception can also provide guidance for the development of other high-performance electrodes.

Highly Dispersed Mn-Doped Ceria Supported on N-Doped Carbon Nanotubes for Enhanced Oxygen Reduction Reaction.

The weak adsorption of oxygen on transition metal oxide catalysts limits the improvement of their electrocatalytic oxygen reduction reaction (ORR) performance. Herein, a dopamine-assisted method is developed to prepare Mn-doped ceria supported on nitrogen-doped carbon nanotubes (Mn-Ce-NCNTs). The morphology, dispersion of Mn-doped ceria, composition, and oxygen vacancies of the as-prepared catalysts were analyzed using various technologies. The results show that Mn-doped ceria was formed and highly dispersed on NCNTs, on which oxygen vacancies are abundant. The as-prepared Mn-Ce-NCNTs exhibit a high ORR performance, on which the average electron transfer number is 3.86 and the current density is 24.4% higher than that of commercial 20 wt % Pt/C. The peak power density of Mn-Ce-NCNTs is 68.1 mW cm-2 at the current density of 138.9 mA cm-2 for a Zn-air battery, which is close to that of 20 wt % Pt/C (69.4 mW cm-2 at 106.1 mA cm-2). Density functional theory (DFT) calculations show that the oxygen vacancy formation energies of Mn-doped CeO2(111) and pure CeO2(111) are -0.55 and 2.14 eV, respectively. Meanwhile, compared with undoped CeO2(111) (-0.02 eV), Mn-doped CeO2(111) easily adsorbs oxygen with the oxygen adsorption energy of only -0.68 eV. This work provides insights into the synergetic effect of Mn-doped ceria for facilitating oxygen adsorption and enhancing ORR performance.

N-doped carbon nanotube arrays Encapsuled with cobalt‑nickel alloy as superior free-standing electrodes for ultrahigh-rate hydrogen peroxide production

Electrocatalytic oxygen reduction via the two-electron pathway (2e−-ORR) is an environmentally friendly and promising route for hydrogen peroxide (H2O2) production. Carbon-based catalysts with transition metal species have been widely investigated due to their high tunability. However, the H2O2 production performance of such catalysts is still far from the requirement of practical applications, owing to their contradiction between durability and ORR activity/selectivity. In this work, metal alloy is encapsulated within the free-standing N-doped carbon nanotube arrays, named NiCo-CNTs-x (x represents the duration of the cation substitution process in hours), to precisely regulate the activity and selectivity of nitrogen sites on the surface of the carbon layer, meanwhile hindering the dissolution of alloy inside the CNTs, thus realizing long-term stability and high-activity catalysis for 2e−-ORR. Therefore, the NiCo-CNTs-30 demonstrates high activity (onset potential around 0.7 V) and selectivity (greater than 85% within the range of 0–0.8 V), and delivers a high yield of 11.7 mg L−1 h−1 with no current decay or structural damage within 24 h, showcasing its exceptional long-term stability. The catalyst can also effectively degrade organic dyes, making it highly promising for industrial applications.

ZIF-L/PBA-derived transition metal-based N-doped CNT modified membranes for lithium-sulfur batteries

The dual MOF framework ZIF-L/X-PBA (X = Fe, Co, and Ni) was formed by combining ZIF-L with Prussian blue (PBA), from which Fe3C-NCNT, Co-NCNT, and Ni-NCNT were derived. The effect of NCNT derived from different transition metals PBA on batteries performance was studied. Tests showed that the Li–S batteries using Fe3C-NCNT obtained an initial discharge capacity of 1456 mAh g−1 at 0.2 C, while the batteries using Co-NCNT and Ni-NCNT had inferior performance in all aspects compared to Fe3C-NCNT. It was found that Fe3C-NCNT had the best performance, and that the inhibitory effect of MOF derivatives on LiPS varied due to the different characteristics of the metal centers, but they all could suppress shuttle effect and extend the life of the batteries.

In Situ Encapsulation of Cobalt Selenide Nanoparticles in N-Doped Carbon Nanotubes with a Full Sulfiphilic Surface as a Catalytic Interlayer for Lithium–Sulfur Batteries

In Situ Encapsulation of Cobalt Selenide Nanoparticles in N-Doped Carbon Nanotubes with a Full Sulfiphilic Surface as a Catalytic Interlayer for Lithium–Sulfur Batteries

Controlled Construction of a N-Doped Carbon Nanotube Network Endows Carbon Felt with Superior Performances for High-Rate Vanadium Flow Batteries

Controlled Construction of a N-Doped Carbon Nanotube Network Endows Carbon Felt with Superior Performances for High-Rate Vanadium Flow Batteries

Portable wireless electrochemical sensing of breviscapine using core-shell ZIFs-derived Co nanoparticles embedded in N-doped carbon nanotube polyhedra-modified electrode.

Acore-shell ZIF-67@ZIF-8-derived Co nanoparticles embedded in N-doped carbon nanotube polyhedra (Co/C-NCNP) hybrid nanostructure was preparedby a pyrolysis method. The synthesized Co/C-NCNP was modified on the screen-printed carbon electrode and used for the portable wireless sensitive determination of breviscapine (BVC) by differential pulse voltammetry. The Co/C-NCNP had a large surface area and excellent catalytic activity with increasing Co sites to combine with BVC for selective determination, which led to the improvement of the sensitivity of the electrochemical sensor. Under optimized conditions, the constructed sensor had linear ranges from 0.15 to 20.0µmol/L and 20.0 to 100.0µmol/L with the limit of detection of 0.014µmol/L (3S0/S). The sensor was successfully applied to BVC tablet sample analysis with satisfactory results. This work provided the potential applications of zeolitic imidazolate framework-derived nanomaterials in the fabrication of electrochemical sensors for the sensitive detection of drug samples.

FeNi alloys incorporated N-doped carbon nanotubes as efficient bifunctional electrocatalyst with phase-dependent activity for oxygen and hydrogen evolution reactions

Electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are two important half-cell reactions for overall water splitting. The rational design and fabrication of efficient electrocatalysts involving nonprecious-metals and carbon matrix is highly attractive. Herein, a series of N-doped carbon nanotubes encapsulated FeNi alloy nanoparticles (FeNi@NCNTs) are synthesized via a simple pyrolysis treatment of Fe-doped Ni(OH)2 precursors under the assistance of dicyandiamine source. The results reveal that the Fe/Ni ratio has an obvious influence on the morphology and phase composition of FeNi@NCNTs series, thus affecting the electrocatalytic performance. The highest electrocatalytic activity is achieved for the Fe1Ni4@NCNTs product with a Fe/Ni molar ratio of 1:4, which delivers low overpotentials of 278 and 279 mV for OER and HER at 10 mA cm−2 in 1.0 mol/L KOH, respectively. The intriguing electrocatalytic performance is mainly ascribed to the advantageous integration of rambutan-like hierarchically porous structure and composition optimization, significantly facilitating the fast mass/charge transfer as well as promoting the adsorption ability for intermediates. The present method may open a facile avenue for developing cost-effective, high-activity, and stable electrocatalysts for the application of overall water splitting.

2-Amino-terephthalic acid derived N-doped CNTs to modify Na3V2(PO4)3 with enhanced pseudocapacitance behavior

The compound Na3V2(PO4)3 (NVP) shows potential as a viable option owing to its notable stability and three-dimensional framework. Nevertheless, its effective use is impeded by its inadequate inherent electron conductivity. In this study, we have introduced a novel approach to overcome this limitation. We synthesized a Na3V2(PO4)3 material (NVP/C/N) coated with N-doped carbon nanotubes (CNTs) using 2-amino-terephthalic acid (NPTA) as the carbon source. The presence of the amino functional group serves a dual purpose: catalyzing the in-situ growth of a CNTs coating layer and incorporating N into the CNTs coating layer. When utilized as cathode materials, NVP/C/N exhibit exceptional rate capability, with discharge capacities of 108.8 mAh g−1 at 0.5C and 87.6 mAh g−1 at 50C, respectively, as well as remarkable cycling stability over long periods of time, maintains its capacity for 10,000 cycles at 50C, with only 0.00094 % capacity decay each cycle. The remarkable characteristics of this compound can be attributed to the enhanced conductivity and augmented active sites resulting from the coating layer of N-doped CNTs, as well as the enhanced pseudocapacitance behavior and reduced volume expansion during charge and discharge. Overall, this work holds immense potential for the advancement of energy storage systems that are both high-performing and reliable.

Self-Catalyzed Growth of Co4N and N-Doped Carbon Nanotubes toward Bifunctional Cathode for Highly Safe and Flexible Li-Air Batteries.

The practical application of high-energy density lithium-oxygen (Li-O2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g-1) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at ∼3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.

Enhanced interfacial evaporation of CF@NC fabric via coupled photo-thermal and Joule-heating effect

To address the challenges of global water pollution and scarcity, solar-driven interfacial water evaporation has emerged as a viable method for producing clean water. Nevertheless, the efficacy of most extant interfacial evaporation systems were contingent upon abundant sunlight, thereby constraining their utility. To surmount the limitation, this study introduced a coupled tunable photo-thermal and Joule-heating process for interfacial evaporation utilizing carbon fiber (CF) modified by N-doped carbon nanotubes (NC). The CF@NC had highly graphitized structure, excellent light-absorbing ability and hydrophilicity, which made it suitable for photo-thermal and Joule-heating conversion. Under the coupled effect of photo-thermal and Joule-heating, the evaporation rate reached 10.37 kg·m−2·h−1 with 1 sun and 2.5 V, while the rate was 1.81 kg·m−2·h−1 under only 1 sun and 7.63 kg·m−2·h−1 with 2.5 V. Meanwhile, the CF@NC fabric evaporator also showed promising potential in salt tolerance and dye wastewater treatment. Under continuous all-day operation, a superior purification performance was achieved, which realized long periods of no salt operation and effectively remove the Rhodamine B and methyl orange in the water. Considering the high evaporation rate and reliable water yields obtained from simulated seawater and dye wastewater, the CF@NC fabric evaporator hold great promise for highly efficient purification.

Controllable fabrication of N-doped carbon nanotubes coated Co4N nanoparticles to boost hydrogen evolution reaction

Transition metal nitrides (TMNs) have attracted great attention as ideal active materials in the field of electrocatalysts in recent years due to their excellent electrical conductivity, wide band gap and adjustable morphology. Pure phase Co4N nanoparticles encapsulated nitrogen-doped carbon (NC) nanotubes (Co4N@NC) were in-situ synthesized by one-pot method. In this paper, the morphology of carbon nanotubes is controlled by adjusting the pyrolysis time, so that more active sites are exposed on carbon nanotubes. Thus, the cobalt nitride catalyst with excellent catalytic performance for hydrogen evolution reaction (HER) in acidic electrolyte was obtained. In summary, due to the protection of mesoporous nitrogen-doped carbon to Co4N nanoparticles, large electrochemically active surface area, good conductivity and more exposed active sites, Co4N@NC possesses excellent HER performance in acidic electrolytes. The overpotential of Co4N@NC at the current density of 10 mA cm−2 is 117 mV (η10), and it shows long-term stability in 0.5 M H2SO4 solution for 50 h. This study provides a strategy for the development of catalysts for the controllable synthesis of high-performance transition metal nitrides.

N-Doped Carbon Nanotubes Nucleated through Cobalt Nanoparticles as Bifunctional Catalysts for Zinc–Air Batteries

N-Doped Carbon Nanotubes Nucleated through Cobalt Nanoparticles as Bifunctional Catalysts for Zinc–Air Batteries

Fabrication of CNT-N@Manganese Oxide Hybrid Nanomaterials through a Versatile One-Pot Eco-Friendly Route toward Engineered Textile Supercapacitors.

The expansion of the Internet of Things market and the proliferation of wearable technologies have generated a significant demand for textile-based energy storage systems. This work reports the engineered design of hybrid electrode nanomaterials of N-doped carbon nanotubes (CNT-N) functionalized with two types of manganese oxides (MOs)-birnessite (MnO2) and hausmannite (Mn3O4)-and their application in solid-state textile-based hybrid supercapacitors (SCs). A versatile citric acid-mediated eco-friendly one-pot aqueous precipitation process is proposed for the fabrication of the hybrids. Remarkably, different types of MOs were obtained by simply changing the reaction temperature from room temperature to 100 °C, without any post-thermal treatment. Asymmetric textile SCs were developed using cotton fabrics coated with CNT-N and the hybrids as textile electrodes, and poly(vinyl) alcohol/orthophosphoric acid as the solid-gel electrolyte. The asymmetric devices presented enhanced energy storage performance relative to the symmetric device based on CNT-N and excellent cycling stability (>96%) after 8000 charge/discharge cycles owing to synergistic effects between CNT-N and the MOs, which endowed nonfaradaic and pseudocapacitive features to the SCs. The asymmetric SC based on CNT-N@MnO2 featured 47% higher energy density and comparable power density to the symmetric CNT-N-based device (8.70 W h cm-2 at 309.01 μW cm-2 vs. 5.93 W h cm-2 at 346.58 μW cm-2). The engineered hybrid CNT-N@MO nanomaterials and the eco-friendly citric acid-assisted one-pot precipitation route open promising prospects not only for energy storage, but also for (photo)(electro)catalysis, wastewater treatment, and (bio)sensing.

A universal synthesis strategy for facile and scalable of magnetic biochar composite materials for PMS activation: Catalytic mechanisms

Biochar-based catalysts have shown great promise for application in AOPs due to their wide source and good performance, while its development is limited by its complicated preparation process and large variation in performance. Herein, a series of magnetic biochar composites(Fe@NC-XX) based on different biomass (duckweed, shrimp shell, peanut shell, corncob, and pomelo peel) were fabricated via one-pot pyrolysis method. The removal of sulfadiazine (SDZ) by all materials reached more than 90% within 20 min. The characterization results indicated that the special structure of Fe encapsulated in nitrogen-doped carbon nanotubes (CNTs) was the main reason why this approach is not limited to specific biomass. Acts as a catalytic center, Fe catalyzes the formation of CNTs during annealing. Meanwhile, graphene sheets and carbon nanoparticles formed by melamine and biomass decomposition migrate to the nucleus surface to form a hollow structure of CNTs. In addition, the results of quenching experiments and ESR tests elucidated that surface-bound radicals accumulated on the surface of CNTs, which can remarkably boost the efficient removal of SDZ. Consequently, the synthetic strategy of Fe nanoparticles anchored in N-doped CNTs that are not selective for biomass provides a new pathway for a universal synthesis method of biochar-based catalysts.

Ni─Co─O─S Derived Catalysts on Hierarchical N-doped Carbon Supports with Strong Interfacial Interactions for Improved Hybrid Water Splitting Performance.

Simultaneously improving electrochemical activity and stability is a long-term goal for water splitting. Herein, hierarchical N-doped carbon nanotubes on carbon nanowires derived from PPy are grown on carbon cloth, serving as a support for NiCo oxides/sulfides. The hierarchical electrodes annealed in N2 or H2/N2 display improved intrinsic activity and stability for hydrogen evolution reaction (HER) and glucose oxidation reaction. Compared with Pt/C||Ir/C in alkaline media, the glucose electrolysis assembled with electrodes exhibits a cell voltage of 1.38V at 10mAcm-2, durability for >12h at 50mAcm-2, and resistance to glucose/gluconic acid poisoning. In addition, electrocatalysts can also be applied in ethanol oxidation reactions. Systematic characterizations reveal the strong interactions between NiCo and N-doped carbon support-induced partial charge transfer at the interface and regulate the local electronic structure of active sites. Density functional theory calculations demonstrate that the synergistic effect between N-doped carbon supports, metallic NiCo, and NiCo oxides/sulfides optimize the adsorption energy of H2O and the H* free energy for HER. The energy barrier of the dehydrogenation of glucose effectively decreased. This work will attract attention to the role of metal-support interactions in enhancing the intrinsic activity and stability of electrocatalysts.

Encapsulated cementite enhances catalytic performance of carbon nanotubes for oxygen reduction reaction

Nonprecious-metal-based materials show great potential to be highly efficient catalysts for oxygen reduction reaction (ORR). There is still room for improvement in the performances of nonprecious-metal-based catalysts for ORR. In this paper, we investigated the catalytic performances of N-doped carbon nanotubes (CNTs) with encapsulated cementite (Fe3C@CNT) for ORR. The encapsulation structure was confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses. The catalytic performances of Fe3C@CNT for ORR were investigated by cyclic voltammetry, linear sweep voltammetry, Tafel analysis, rotating disk electrode, and rotating ring-disk electrode tests. The results showed that both the onset potential and half-wave potential of Fe3C@CNT-catalyzed ORR were 60 mV higher than those of 20 wt% Pt/C catalyst. Fe3C@CNT catalyzed ORR mainly happened through a four-electron pathway. The long-time running stability of the Fe3C@CNT was also superior to that of the 20 wt% Pt/C catalyst. The eutectic layers between the CNTs and cementite enhanced the electron transfer from the inner-layer CNT to the surface-layer N-doped CNT. Calculations revealed that the iron and carbon in the cementite were in positive and negative electronic states, respectively. The encapsulated cementite promoted the formation of equipotential circles on the surface-layer CNT, which greatly enhanced the catalytic performance of the Fe3C@CNT for ORR. N-doped CNTs with encapsulated cementite show great potential to be high-performance catalysts for ORR.

CoS2 nanoparticles embedded in N-doped hollow carbon nanotubes as anode materials for high performance lithium-ion battery

CoS2 nanoparticles are effectively incorporated into N-doped hollow carbon nanotubes (CoS2@HC) through a combination of a straightforward oil bath method and a high-temperature sulfurization process. The CoS2@HC composite demonstrates exceptional electrochemical performance as an anode material in Li-ion batteries. The outstanding performance of this system can be attributed to the ingeniously designed hollow carbon nanotubes. These nanotubes not only possess high electrical conductivity, thus facilitating efficient electron transfer, but also provide ample space to accommodate volume changes. Furthermore, the ultrafine CoS2 nanoparticles embedded within the hollow carbon nanotubes offer a large surface area for effective electrolyte wetting and rapid ion diffusion during the cycling process. As a result, the CoS2@HC composite delivers a high capacity of 356.2 mAh·g−1 at 2000 mA·g−1 even after 1500 cycles, demonstrating remarkable cyclic stability.

N-DMBI Doping of Carbon Nanotube Yarns for Achieving High n-Type Thermoelectric Power Factor and Figure of Merit.

The application of carbon nanotube (CNT) yarns as thermoelectric materials for harvesting energy from low-grade waste heat including that generated by the human body, is attracting considerable attention. However, the lack of efficient n-type CNT yarns hinders their practical implementation in thermoelectric devices. This study reports efficient n-doping of CNT yarns, employing 4-(1, 3-dimethyl-2, 3-dihydro-1H-benzimidazole-2-yl) phenyl) dimethylamine (N-DMBI) in alternative to conventional n-dopants, with o-dichlorobenzene emerging as the optimal solvent. The small molecular size of N-DMBI enables highly efficient doping within a remarkably short duration (10s) while ensuring prolonged stability in air and at high temperature (150°C). Furthermore, Joule annealing of the yarns significantly improves the n-doping efficiency. Consequently, thermoelectric power factors (PFs) of 2800, 2390, and 1534µWm-1K-2 are achieved at 200, 150, and 30°C, respectively. The intercalation of N-DMBI molecules significantly suppresses the thermal conductivity, resulting in the high figure of merit (ZT) of 1.69×10-2 at 100°C. Additionally, a π-type thermoelectric module is successfully demonstrated incorporating both p- and n-doped CNT yarns. This study offers an efficient doping strategy for achieving CNT yarns with high thermoelectric performance, contributing to the realization of lightweight and mechanically flexible CNT-based thermoelectric devices.

Synergistic promotion for the performance of photocatalytic carbon dioxide reduction by vacancy engineering and N-doped carbon nanotubes

The structural devise of photocatalytic materials are closely related to the separation of photogenerated carriers and the transport of charge, which is crucial to enhance the performance of photocatalytic carbon dioxide reduction reaction (CO2RR). Here, a photocatalyst (CdS-SV@Co@NCNT) has been successfully prepared by growing cadmium sulfide nanoparticles with sulfur vacancies on N-doped carbon nanotubes through a simple solvothermal method. The intrinsic electronic structure is regulated by sulfur vacancies to promote photocatalytic activity. Meanwhile, a larger specific surface area of Co@NCNT could expose more reaction sites and shorten the transfer distance of photogenerated carriers. Furthermore, the combination with Co@NCNT could effectively suppress the photocorrosion of CdS. The possible photocatalytic CO2RR path is further speculated by in-situ infrared test results, in which CO2 molecules adsorbed on sulfur vacancies preferentially generate important intermediate COOH*, which is then reduced to CO and CH4. Therefore, it exhibits a high CO yield of 263.3 μmol·g−1·h−1 and trace of CH4 while showing excellent stability. This research provides a novel idea for designing the photocatalysts with highly active and stability for CO2RR.