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[Display omitted] Silicon-air batteries (SABs) have become promising candidates for energy conversion and storage devices due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, the slow kinetics of the 4e− transfer in the oxygen reduction reaction (ORR) at the cathode during discharge, coupled with severe polarization, reduces the battery's capacity and hinders the development of silicon-air batteries. The cathodes of currently developed SABs primarily rely on commercial Pt/C and MnO 2 , with limited research on low-cost, efficient, and stable air cathodes for SABs. To address this issue, we synthesized nitrogen-doped carbon nanotubes containing FeMn alloy particles (FeMn@NCNTs) as cathode ORR catalysts using a simple high-temperature pyrolysis method combined with chemical vapor deposition. In an alkaline medium, the catalyst's half-wave potential (E 1/2) reached 0.83 V. Moreover, the FeMn@NCNTs air cathode exhibited excellent compatibility with the silicon anode, and the constructed aqueous silicon-air battery demonstrated a high specific capacity (165 Ah kg−1) and power density (3.69 mW cm−2). Additionally, the quasi-solid-state SABs constructed with FeMn@NCNTs showed stable operation over a wide temperature range, providing a new solution for the development of low-cost, efficient silicon-air batteries suitable for a wide range of applications. [ABSTRACT FROM AUTHOR]

[Display omitted] The high theoretical specific energy and environmental friendliness of zinc-air batteries (ZABs) have garnered significant attention. However, the practical application of ZABs requires overcoming the sluggish kinetics associated with oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, 3D self-supported nitrogen-doped carbon nanotubes (N -CNTs) arrays encapsulated by CoNi nanoparticles on carbon fiber cloth (CoNi@ N -CNTs/CFC) are synthesized as bifunctional catalysts for OER and ORR. The 3D interconnected N -CNTs arrays not only improve the electrical conductivity, the permeation and gas escape capabilities of the electrode, but also enhance the corrosion resistance of CoNi metals. DFT calculations reveal that the co-existence of Co and Ni synergistically reduces the energy barrier for OOH conversion to OH, thereby optimizing the Gibbs free energy of the catalysts. Additionally, analysis of the change in energy barrier during the rate-determining step suggests that the primary catalytic active center is Ni site for OER. As a result, CoNi@ N -CNTs/CFC exhibits superior catalytic activity with an overpotential of 240 mV at 10 mA cm−2 toward OER, and the onset potential of 0.92 V for ORR. Moreover, utilization of CoNi@ N -CNTs/CFC in liquid and solid-state ZABs exhibited exceptional stability, manifesting a consistent cycling operation lasting for 100 and 15 h, respectively. [ABSTRACT FROM AUTHOR]

This work utilizes defect engineering, heterostructure, pyridine N‐doping, and carbon supporting to enhance cobalt‐nickel selenide microspheres' performance in the oxygen electrode reaction. Specifically, microspheres mainly composed of CoNiSe2 and Co9Se8 heterojunction rich in selenium vacancies (VSe·) wrapped with nitrogen‐doped carbon nanotubes (p‐CoNiSe/NCNT@CC) are prepared by Ar/NH3 radio frequency plasma etching technique. The synthesized p‐CoNiSe/NCNT@CC shows high oxygen reduction reaction (ORR) performance (half‐wave potential (E1/2) = 0.878 V and limiting current density (JL) = 21.88 mA cm−2). The JL exceeds the 20 wt% Pt/C (19.34 mA cm−2) and the E1/2 is close to the 20 wt% Pt/C (0.881 V). It also possesses excellent oxygen evolution reaction (OER) performance (overpotential of 324 mV@10 mA cm−2), which even exceeds that of the commercial RuO2 (427 mV@10 mA cm−2). The density functional theory calculation indicates that the enhancement of ORR performance is attributed to the synergistic effect of plasma‐induced VSe· and the CoNiSe2‐Co9Se8 heterojunction. The p‐CoNiSe/NCNT@CC electrode assembled Zinc‐air batteries (ZABs) show a peak power density of 138.29 mW cm−2, outperforming the 20 wt% Pt/C+RuO2 (73.9 mW cm−2) and other recently reported catalysts. Furthermore, all‐solid‐state ZAB delivers a high peak power density of 64.83 mW cm−2 and ultra‐robust cycling stability even under bending. [ABSTRACT FROM AUTHOR]

Despite significant progress, precise control of the dispersion of ruthenium (Ru) nanoparticles (NPs) on the carrier, reduction of their aggregation and leaching during water splitting is always a challenging issue. In this work, metal-organic frameworks (MOFs) derived Co 7 Fe 3 alloy/Co NPs embedded in nitrogen-doped carbon and nitrogen-doped carbon nanotubes (FeCoSG/NCNT) with a three-dimensional (3D) spider-egg structure are synthesized by chemical vapor deposition (CVD) technique. Then, Ru NPs are uniformly loaded on the FeCoSG/NCNT through impregnation and reduction. The obtained FeCoSG/NCNT@Ru possesses enriched mesopore and high conductivity. In addition, the Ru NPs synergize with non-precious metal active sites to promote hydrogen-evolution-reaction (HER), which lowers the need for precious metals while maintaining excellent performance. The obtained FeCoSG/NCNT@Ru only requires a low overpotential of 21.1 mV to attain a current density of 10 mA cm−2 in 1 M KOH towards HER, which is smaller than the benchmark catalyst Pt/C (∼30.1 mV). Moreover, it shows ultra-high stability, which can work continuously at current densities of 10, 20, and 30 mA cm−2 for 25 h without degradation, respectively. The study presents insight on the design of advanced support and the construction of highly active and durable electrocatalysts. [Display omitted] • Co 7 Fe 3 alloy/Co NPs embedded in MOF-derived NC encapsulated by NCNT. • The N doping brings a favorable effect on the regulation of Ru distribution. • The unique spider-egg structure provides an abundance of Ru attachment sites. • FeCoSG/NCNT@Ru is a highly efficient and stability HER catalyst. • It exhibits an extremely small overpotential of 21.1 mV at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

One of the main challenges potassium‐ion batteries (PIBs) face is the lack of structurally stable anodes with high reactivity and fast kinetics for reversible potassium insertion/extraction. Herein, nitrogen‐doped carbon nanotubes (N‐CNTs) are synthesized using a straightforward method assisted by a Co‐based catalyst. The as‐synthesized N‐CNTs possess interlayer distances up to 0.38 nm and nitrogen‐doping content of 2.2 at.%. Compared to the undoped CNTs (U‐CNTs), N‐CNTs exhibit a promising initial specific capacity of 568 mAh g−1 at 0.1 A g−1, as well as excellent long‐term cycling performance of 104, 82, and 76 mAh g−1 at a high current of 0.5, 1, and 2 A g−1 for 500 cycles. The cyclic voltammetry (CV) measurements reveal the potassium storage mechanism of N‐CNTs, which combines the major capacitive mechanisms and the secondary diffusion, and successfully avoids inconspicuous voltage plateau. The kinetic analysis of the galvanostatic intermittent titration technique and ex situ X‐ray photoelectron spectroscopy spectra show fast reaction kinetics and low side effects and degradation for the N‐CNTs anodes during the potassiation/de‐potassiation process. This study provides a straightforward method to synthesize heteroatom‐doped carbonaceous anode materials and achieves superior electrochemical properties with cost‐effectiveness and material sustainability. [ABSTRACT FROM AUTHOR]

Highlights Iron sulfide-based heterostructure in situ hybridized with nitrogen-doped carbon nanotubes was prepared through a successive pyrolysis and sulfidation approach. The as-prepared Fe7S8/FeS2/NCNT electrode exhibits superior sodium storage performance in both ester and ether-based electrolytes. The structure advantages of the electrode contribute to high electrochemical performance in the ester-based electrolyte, while fast ionic diffusion and favorable capacitive behavior result in the robust sodium storage performance in the ether-based electrolyte.

Highlights: Iron sulfide-based heterostructure in situ hybridized with nitrogen-doped carbon nanotubes was prepared through a successive pyrolysis and sulfidation approach. The as-prepared Fe7S8/FeS2/NCNT electrode exhibits superior sodium storage performance in both ester and ether-based electrolytes. The structure advantages of the electrode contribute to high electrochemical performance in the ester-based electrolyte, while fast ionic diffusion and favorable capacitive behavior result in the robust sodium storage performance in the ether-based electrolyte. Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe7S8/FeS2/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe7S8/FeS2/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g−1 up to 100 cycles at 1.0 A g−1 and superior rate capability (273.4 mAh g−1 at 20.0 A g−1) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g−1 after 1,000 cycles at 5.0 A g−1) and outstanding rate capability (536.5 mAh g−1 at 20.0 A g−1) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte. [ABSTRACT FROM AUTHOR]

Electrode materials for flexible supercapacitors possessing exceptional and maintaining electrical properties have garnered significant attention in academic research. The graphene oxide (GO) and polypyrrole-derived nitrogen-doped carbon nanotubes (N-CNTs) were mixed to obtain a GO/N-CNTs film. The GO/N-CNTs film was then reduced to prepare a flexible reduced GO (rGO)/N-CNTs film. The specific capacitance of the rGO/N-CNTs film electrode was 223.2 F g−1 at a current density of 0.5 A g−1. The rGO/N-CNTs supercapacitor exhibited a specific capacitance of 130 F g−1 and energy density of 18.04 Wh·kg−1 at a current density of 0.5 A g−1. Furthermore, the capacitance retention of the supercapacitor was 68.7 % when the current density increased to 20 A g−1. In addition, the cyclic voltammetry test indicated that the capacitance retention of the supercapacitor remained at 82.7 % after 8000 cycles, and the capacitance retention still reached 70 % even after bending 600 times. The present study successfully presented the remarkable electrical characteristics of supercapacitors based on rGO/N-CNTs films. Additionally, the investigation has highlighted the noteworthy flexibility of supercapacitors, a feature of considerable significance for applications in wearable technology, portable electronic devices, and flexible displays. [Display omitted] • RGO/N-CNTs hybrid film is fabricated. • The effect of N-CNTs on the film is investigated. • The as-prepared film possesses a good capacitance of 130 F g−1 at 0.5 A g−1. • The film expresses high cyclic stability of 82.7 % after 8000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] At present, construction of economical, efficient and stable electrocatalysts for oxygen reduction reaction (ORR) is critical to alleviate the energy shortage. Theophylline (THP) can be easily extracted from natural plants, whose nitrogen atoms can chelate with metal ions. With assistance of THP, FeCo alloy was confined in N-doped carbon nanotubes (FeCo/NCNTs-800) by one-step pyrolysis of a mixture of the metal precursors, g-C 3 N 4 and THP. The resulting FeCo/NCNTs-800 showed a better ORR performance (onset potential, E onset = 1.09 V; half-wave potential, E 1/2 = 0.87 V) than commercial Pt/C (50 wt %) in a 0.1 M KOH solution, with a limiting current density as high as –5.54 mA cm−2. This work offers a feasible strategy for developing transitional bimetal-based carbon catalysts in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeNi-NCNT was prepared by carbonizing Ni2+/Zn2+-PAT-[Fe(CN) 6 ]3− complex precursor. • FeNi-NCNT offered high ORR/OER activities with E 1/2 = 0.835 V and E j = 10 = 1.560 V. • FeNi-NCNT-based aqueous RZAB showed ultralong cycle life (400 h at 25 mA cm−2). • FeNi-NCNT-based solid RZAB exhibited excellent stability and flexibility. In this work, we present an efficient bifunctional electrocatalyst comprising iron-nickel (FeNi) alloy nanoparticles confined in nitrogen-doped carbon nanotubes (denoted FeNi-NCNT) for zinc-air batteries. The FeNi-NCNT electrocatalyst is fabricated by anion-exchange of nickel(II) ion/zinc(II) ion-2,4,6-tris-(di(pyridin-2-yl)amino)-1,3,5-triazine complex with ferricyanide anion followed by mixing with melamine and then carbonization. The resultant FeNi-NCNT electrocatalyst displays excellent bifunctional activity with a low reversible oxygen electrode index of 0.725 V. The rechargeable aqueous zinc-air battery fabricated with FeNi-NCNT air cathode manifests both high specific capacity (819 mAh g−1 Zn at 5.0 mA cm−2) and long cycle life (1500 cycles/1000 h at 10 mA cm−2, 600 cycles/400 h at 25 mA cm−2, and 165 cycles/110 h at 50 mA cm−2). Moreover, flexible solid-state zinc-air battery assembled with FeNi-NCNT air cathode can deliver a specific capacity of 765 mAh g−1 Zn at 5.0 mA cm−2, a power density of 84.8 mW cm−2, and a cycle life of 110 h (330 cycles) at 2.0 mA cm−2. [ABSTRACT FROM AUTHOR]

Aqueous batteries exhibite great potential for large-sacle energy storage due to their intrinsic safety, eco-friendliness, and low cost. However, the inadequate capacity and poor cycling stability impede the futher development. Herein, FeS 2 compounded with three-dimensional carbon fibers are designed as the self-supporting cathodes in aqueous copper ion system, where the microporous/mesoporous (within 10 nm) are proposed to improve the rapid electron transfer and strengthen the electrolyte wettability. The results reveal that FeS 2 @CNFs700 exhibits a specific capacity of 462 mAh g−1 after 1600 cycles at 5 A g−1 with low capacity degradation of only 0.022 % and 385 mAh g−1 after 4000 cycles with high coulombic efficiency of 97.5 %, prossessing superior rate performance (387 mAh g−1 at 15 A g−1). Furthermore, the reversible reaction pathway of FeS 2 → CuS → Cu 7 S 4 → Cu 2 S is demonstrated by a series of ex-situ testing, proving the feasibility of FeS 2 in aqueous batteries at ambient temperature. In addition, the assembled Zn//FeS 2 @CNFs hybrid battery exhibits a stable reversible specific capacity of 510 mAh g−1 and a specific energy of 459 Wh kg−1 at 1 A g−1 with an excellent cycling stability (capacity decay: 2.77 % after 50 cycles). This work offers unique insights about stable FeS 2 -aqueous batteries designing. [Display omitted] • Self-supporting cathode is designed by electrostatic spinning. • Microporous (within 10 nm) can efficiently improve the rapid electron transfer. • FeS 2 @CNFs demonstrates excellent stability during long cycle test at 5 A/g. • The reversible reaction pathway of FeS 2.→ CuS → Cu 7 S 4 → Cu 2 S is proved in FeS 2 //Cu battery. • Hybrid battery of FeS 2 //Zn is designed to improve the operational voltage. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (HMF) has great promise as a versatile platform chemical for the synthesis of a wide range of other chemical compounds. The preparation of HMF from carbohydrates for industrial applications, especially fuels and fine chemicals, has received much more attention. In the present study, metal/nitrogen-doped carbon nanotubes (M/N-CNTs) were produced using a one-step carbonization method and used as an exceptional catalyst for converting fructose to HMF. The catalyst structure was determined using Energy-dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), High-resolution X-ray Photoelectron Spectrometer (HRXPS), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), and Fourier-transform Infrared Spectroscopy (FT-IR) techniques. The effects of temperature, catalytic loading, substrate feed concentrations, solvents, reusability, and scalability were carried out. This work achieved an excellent yield of HMF (91 % ± 2) utilizing Cr/N-CNTs as a catalyst for producing HMF at 120 °C for 180 min. Furthermore, the Cr/N-CNTs could be recovered and reused in industrial applications without significant loss of the catalytic activity. [Display omitted] • A highly efficient catalytic metal/nitrogen-doped carbon nanotube has been developed to convert fructose to HMF. • An excellent HMF yield of 91 ± 2 % was obtained in DMSO at 120 °C for 3 h. • The catalyst has the ability to be recycled and employed in industrial applications. [ABSTRACT FROM AUTHOR]

The pivotal challenge of electrocatalysis remains the development of highly effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, a universal strategy of preparing the encapsulation of Co-based multimetallic alloys/oxide nanoparticles in nitrogen-doped carbon nanotubes (named CoM@CNTs, M = Ni/Mn/Fe) was induced by annealing mixtures of the as-synthesized precursor, ethanol and different metallic acetates, including binary CoNi@CNTs, ternary CoNi/MnO@CNTs and quaternary CoNiFe/MnO@CNTs. By virtue of its unique structure with a high electrical conductive network based on CNT substrates, abundant catalytic active sites supplied by multimetallic nanoparticles and protection against nanoparticle corrosion by N-doped carbon layers, the as-synthesized CoNiFe/MnO@CNTs electrocatalyst has remarkable HER properties with a low overpotential of 122 mV and OER activity with a low overpotential of 275 mV at 10 mA cm−2 and excellent stability and durability under long-term testing in alkaline solutions. Therefore, this strategy will provide a new route for fabricating multimetallic-based CNTs as HER/OER electrocatalysts with excellent stability and high catalytic activity. [Display omitted] • The self-reduction of precursor Co–U and ethanol were creatively used to form Co-based CoM@CNTs. • The synthesis strategy for CoM@CNTs was simple and universal. • Unique structure of CNTs networks endowed CoM@CNTs a high electrical conductivity. • Abundant catalytic active sites endowed CoNiFe/MnO@CNTs electrocatalyst with remarkable HER/OER properties. [ABSTRACT FROM AUTHOR]

[Display omitted] For development of green and sustainable energy, it is of importance to search highly efficient and low-cost electrocatalysts of oxygen reduction reaction (ORR) in energy conversion devices. Herein, CoFe alloyed nanocrystals embedded in N -doped bamboo-like carbon nanotubes (CoFe@NCNTs) were facilely synthetized by one-step co-pyrolysis with the mixture of triamterene, metal chlorides and graphitic carbon nitride (g-C 3 N 4). The resultant CoFe@NCNTs exhibited excellent ORR activity with the positive shifts in the onset potential (E onset = 0.97 V) and half-wave potential (E 1/2 = 0.88 V), outperforming commercial Pt/C (E onset = 0.96 V; E 1/2 = 0.84 V). Compared to metal organic frameworks (MOFs)-based strategy for synthesis of low-cost carbon-based ORR catalysts, this method is simple and convenient, coupled by avoiding the complicated synthesis of MOFs and its ligands. This work provides a promising route to fabricate advanced transition-metal-based carbon catalysts in the researches correlated with energy conversion devices. [ABSTRACT FROM AUTHOR]

• Monolithic TS-1 was prepared via dry gel conversion in the vapor of ammonia. • The crystallization time was shortened to 18 h compared to normal method (72 h). • Nitrogen doped carbon nanotubes provided sufficient nucleation sites for TS-1. TS-1 is a mild and efficient catalyst for olefin epoxidation reactions. To improve the catalytic performance, a monolithic TS-1 was successfully synthesized by dry gel conversion using nitrogen-doped carbon nanotubes grown on nickel foam surface as the carrier in an ammonia gas phase environment. The nitrogen atoms in the carrier could form hydrogen bonds with the silicon species in the raw material, providing nucleation sites for crystallization, resulting in uniform particle dispersion. The binding energy sequence of the four nitrogen atoms with the silicon species was: nitrogen oxides > pyrrole nitrogen > pyridine nitrogen > graphite nitrogen. Nitrogen-doped carbon nanotubes grown at 550 °C by chemical vapor deposition owned the highest content of pyridine nitrogen and nitrogen oxides, which provided the most nucleation sites for TS-1. Compared with powder TS-1 obtained by hydrothermal method, the crystallization time of monolithic TS-1 was shortened from 72 h to 18 h. There was an optimal amount of ammonia, if the amount of ammonia was little, the molecules in the solid gel were difficult to move, and crystallization was difficult to occur, but excessive ammonia reduced the degree of supersaturation, resulting in a transformation to hydrothermal crystallization. [Display omitted] [ABSTRACT FROM AUTHOR]

Electron transfer between metal‐oxides and supports considerably affects the oxidative desulfurization (ODS) performance of catalysts, while this is far from being well understood. Herein, molybdenum dioxide with oxygen vacancies (VO‐MoO2) catalysts derived from Mo‐based metal‐organic frameworks are anchored on electron‐rich nitrogen‐doped carbon nanotubes (NC) to obtain excellent ODS activity and reusability. Results show that either dibenzothiophene (DBT) or 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) is removed 100% on the composite catalyst (VO‐MoO2@NC) within 40 min of reaction when cumene hydroperoxide is chosen as an oxidant. After five cycles of reaction, DBT and 4,6‐DMDBT removal still exceeded 99.5 and 95.0%, respectively. Results from density functional theory calculations and characterizations confirm that the strong electron‐donating effect of NC on VO‐MoO2 can promote the dispersion of VO‐MoO2 and reduce the bond energy of the MoO bond, leading to exposure of active sites and enrichment of oxygen vacancies (VO). Furthermore, the strong interfacial electrostatic interaction caused by the electron transfer from NC to VO‐MoO2 can reduce the leaching of active sites of the catalyst. This study provides a versatile strategy of constructing strong electronic interaction between metal‐oxide and support via anchoring on NC for the design of high‐performance ODS catalysts. [ABSTRACT FROM AUTHOR]

Vertically-aligned nitrogen-doped carbon nanotubes (v-N-CNTs) were synthesized \textit{via} the chemical vapour deposition (CVD) technique. 1-ferrocenylmethyl(2-methylimidazole) was employed as the source of the Fe catalyst and was dissolved in different ratios of acetonitrile/benzophenone feedstock which served as both the carbon, nitrogen, and oxygen sources. The morphological difference in N-CNTs was as a result of increased oxygen concentration in the reaction mix and not due to water vapour formation as observed in the oxygen-free experiment, indicating specifically, the impact of oxygen. Raman and X-ray photoelectron spectroscopy (XPS) revealed surface defects and grafting of oxygen functional groups on the sidewall of N-CNTs. The FTIR data showed little or no effect as oxygen concentration increases. XPS analysis detected the type of nitrogen species (\textit{i.e.} pyridinic, pyrrolic, graphitic, or molecular nitrogen forms) incorporated in the N-CNT samples. Pyrrolic nitrogen was dominant and increased (from 8.6 to 11.8 at.\%) as oxygen concentration increases in the reaction precursor. An increase in N content was observed with the introduction of a lower concentration of oxygen, followed by a gradual decrease at higher oxygen concentration. Our result suggested that effective control of the reactant mixtures can manipulate the morphology of N-CNTs.

Abstract Water electrolysis is an emerging energy conversion technology, which is significant for efficient hydrogen (H2) production. Based on the high‐activity transition metal ions and metal alloys of ultrastable bifunctional catalyst, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the key to achieving the energy conversion method by overall water splitting (OWS). This study reports that the Co‐based coordination polymer (ZIF‐67) anchoring on an indium–organic framework (InOF‐1) composite (InOF‐1@ZIF‐67) is treated followed by carbonization and phosphorization to successfully obtain CoP nanoparticles–embedded carbon nanotubes and nitrogen‐doped carbon materials (CoP‐InNC@CNT). As HER and OER electrocatalysts, it is demonstrated that CoP‐InNC@CNT simultaneously exhibit high HER performance (overpotential of 153 mV in 0.5 m H2SO4 and 159 mV in 1.0 m KOH) and OER performance (overpotential of 270 mV in 1.0 m KOH) activities to reach the current density of 10 mA cm−2. In addition, these CoP‐InNC@CNT rods, as a cathode and an anode, can display an excellent OWS performance with η10 = 1.58 V and better stability, which shows the satisfying electrocatalyst for the OWS compared to control materials. This method ensures the tight and uniform growth of the fast nucleating and stable materials on substrate and can be further applied for practical electrochemical reactions.

It's still an ongoing research challenge to explore non-precious metal-based catalysts for substituting precious metal catalysts during full water electrocatalysis. Herein, we reported the partially oxidized cobalt species in nitrogen-doped carbon nanotubes hierarchical structures to produce dual-functionality towards oxygen/hydrogen evolution reactions. The in situ transformation of carbon nanotubes and well-exposed metal-oxide contributes to mass diffusion and greater electrolyte-accessible surface area. The as-synthesized catalyst displays low overpotentials of 287 mV and 171 mV for oxygen and hydrogen evolution reactions at 10 mA cm−2 of current density with remarkable performance during long-term stability. Furthermore, when employed as cathode and anode, a respectable performance of 1.68 V demonstrated our catalyst as an efficient bifunctional material for conducting water-splitting operation. Image 1 • Nanostructure engineering by surficial induced approach. • The strong interface connection of active sites and conducting carbon matrix. • In situ formation of CNTs anchored Co-O x. • An efficient bifunctional material for conducting water-splitting. [ABSTRACT FROM AUTHOR]

This study sheds light on the effect of nitrogen (N) doping of carbon nanotubes (CNTs) on medium-amplitude oscillatory shear (MAOS) response of CNT/polyvinylidene fluoride (PVDF) nanocomposites within a rheologically percolated concentration regime. Custom-synthesized CNTs without and with nitrogen heteroatom (at a nitrogen atomic percent of 3.85 at. %) were incorporated into a PVDF matrix using a miniature melt-mixer at different concentrations. In both cases, as confirmed by TEM investigations, a nanoscopic state of dispersion in the PVDF matrix was achievable using the applied melt mixing procedure. Our results indicated that N-doped nanocomposites, well below their electrical percolation, form a hybrid, load-bearing network structure where network interconnectivity is driven by N-doped CNT domains and near-surface regions of the PVDF phase. This hybrid network formation behavior combined with N-doped CNTs inferior aspect ratio and their higher susceptibility to breakage and length loss during the melt mixing process have led to delayed electrical percolation. In contrast, localized clustering and contact aggregation in a submicrometer scale was the dominant mode of network formation in the undoped CNT/PVDF nanocomposites. These microstructural inferences were further validated in the frame of molecular simulations and optical microscopy investigations. [ABSTRACT FROM AUTHOR]

Searching for inexpensive, efficient and durable electrocatalysts with earth-abundant elements toward the hydrogen evolution reaction (HER) is of vital importance for the future sustainable hydrogen economy, yet still remains a formidable challenge. Herein, a facile template-engaged strategy is demonstrated for the direct in-situ growth of Ni nanoparticles and N-doped carbon nanotubes on carbon nanorod substrates, forming a hierarchically branched architecture (abbreviated as Ni@N-C NT/NRs hereafter). The elaborate construction of such unique hierarchical structure with tightly encapsulated Ni nanoparticles and open configuration endows the as-fabricated Ni@N-C NT/NRs with abundant well-dispersed active sites, enlarged surface area, reduced resistances of charge transfer and mass diffusion, and reinforced mechanical robustness. As a consequence, the optimal Ni@N-C NT/NR catalyst demonstrates superior electrocatalytic activity with relatively low overpotential of 134 mV to deliver a current density of 10 mA·cm−2 and excellent stability for HER in 0.1 M KOH, holding a great promise for practical scalable H2 production. More importantly, this work offers a reliable methodology for feasible fabrication of robust high-performance carbon-based hierarchical architectures for a variety of electrochemical applications. [ABSTRACT FROM AUTHOR]

Water electrolysis is an emerging energy conversion technology, which is significant for efficient hydrogen (H2) production. Based on the high‐activity transition metal ions and metal alloys of ultrastable bifunctional catalyst, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the key to achieving the energy conversion method by overall water splitting (OWS). This study reports that the Co‐based coordination polymer (ZIF‐67) anchoring on an indium–organic framework (InOF‐1) composite (InOF‐1@ZIF‐67) is treated followed by carbonization and phosphorization to successfully obtain CoP nanoparticles–embedded carbon nanotubes and nitrogen‐doped carbon materials (CoP‐InNC@CNT). As HER and OER electrocatalysts, it is demonstrated that CoP‐InNC@CNT simultaneously exhibit high HER performance (overpotential of 153 mV in 0.5 m H2SO4 and 159 mV in 1.0 m KOH) and OER performance (overpotential of 270 mV in 1.0 m KOH) activities to reach the current density of 10 mA cm−2. In addition, these CoP‐InNC@CNT rods, as a cathode and an anode, can display an excellent OWS performance with η10 = 1.58 V and better stability, which shows the satisfying electrocatalyst for the OWS compared to control materials. This method ensures the tight and uniform growth of the fast nucleating and stable materials on substrate and can be further applied for practical electrochemical reactions. [ABSTRACT FROM AUTHOR]

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 Co 4 N nanoparticles encapsulated nitrogen-doped carbon (NC) nanotubes (Co 4 N@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 Co 4 N nanoparticles, large electrochemically active surface area, good conductivity and more exposed active sites, Co 4 N@NC possesses excellent HER performance in acidic electrolytes. The overpotential of Co 4 N@NC at the current density of 10 mA cm−2 is 117 mV (η 10), and it shows long-term stability in 0.5 M H 2 SO 4 solution for 50 h. This study provides a strategy for the development of catalysts for the controllable synthesis of high-performance transition metal nitrides. [Display omitted] [ABSTRACT FROM AUTHOR]

Constructing Co-based carbon nanotubes/g-C 3 N 4 structure via integrated strategy remains a challenge in cobalt-based electrocatalysis. We firstly proposed a coordination-polymerization integrated strategy for the preparation of Co@N-CNT@g-C 3 N 4 with efficient hydrogen evolution reaction at all pH values. In Co@N-CNT@g-C 3 N 4 , Co nanoparticles were encapsulated in the tip of carbon nanotubes and carbon nanotubes grew on g-C 3 N 4 to bridge Co particles and g-C 3 N 4. More importantly, Co particles, carbon nanotubes, and g-C 3 N 4 were assembled simultaneously skillfully to construct a closely integrated interface, thereby enhancing electron transfer efficiency. Electrochemical tests showed that the structure has high catalytic activity, with overpotentials of 61, 145, and 170 mV in 1 M KOH, 0.5 M H 2 SO 4 and 1.0 M phosphate buffer saline (PBS), respectively, to drive 10 mA cm−2. Additionally, the Gibbs free energy for hydrogen adsorption (∆G H *) on the Co surface of Co@N-CNT@g-C 3 N 4 was only − 0.13 eV, which was conducive to H 2 formation. [Display omitted] • A unique coordination-polymerization integrated strategy was firstly proposed. • Co@CNT@CN showed low overpotentials (61, 145, and 170 mV) in different electrolytes. • The high capability was due to Co@carbon nanotubes and closely integrated CNT/g-C 3 N 4. • Co NPs. CNTs. g-C 3 N 4 served as H* combination. e- migration, H 2 O adsorption sites. [ABSTRACT FROM AUTHOR]

The development of efficient and durable non-precious metal-based bifunctional oxygen electrocatalysts is pivotal in realizing cost-effective and high-performance rechargeable Zinc-Air Batteries (ZABs). In this study, a straightforward hydrothermal-melamine-assisted carbonization method is employed to synthesize a hierarchical core-shell structure comprising Mo 2 C/MoC intertwined with cobalt-incorporated N-doped carbon nanotubes (Mo 2 C/MoC/Co@CNTs). The synergy between Mo 2 C/MoC and Co@CNTs is harnessed to achieve remarkable bifunctional OER/ORR activities, as evidenced by a small potential gap (ΔE = E j = 10 – E 1/2) of 0.74 V between OER and ORR. When integrated into a liquid ZAB, the assembled battery delivers a remarkable peak power density of 134 mW cm−2 and exhibits a robust cycling performance, sustaining continuous operation for 275 h at a current density of 10 mA cm−2. This work not only presents a strategic approach to developing electrocatalysts with specific components, but also underscores the significance of multi-component synergy in electrocatalytic applications. This research provides a multi-component synergy strategy for designing and synthesizing bifunctional ORR/OER electrocatalysts for rechargeable Zn-air battery. [Display omitted] • Developed a hierarchical Mo 2 C/MoC/Co@CNTs oxygen electrocatalyst. • Multi-component synergy boosts electrocatalytic performance. • Heterostructure controls bifunctional electrocatalyst activity. • The electrocatalyst exhibits high performance for rechargeable Zn-air battery. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (N-CNTs) show promise in several applications related to catalysis and electrochemistry. In particular, N-CNTs with a single nitrogen dopant in the unit cell have been extensively studied computationally, but the structure-property correlations between the relative positions of several nitrogen dopants and the electronic transport properties of N-CNTs have not been systematically investigated with accurate hybrid density functional methods. We use hybrid density functional theory and semiclassical Boltzmann transport theory to systematically investigate the effect of different substitutional nitrogen doping configurations on the electrical conductivity of N-CNTs. Our results indicate significant variation in the electrical conductivity and the relative energies of the different dopant configurations. The findings can be utilized in the optimization of electrical transport properties of N-CNTs.

Nitrogen-doped carbon nanotubes (NCNTs) were used as a support for iron (Fe) nanoparticles applied in carbon dioxide (CO2) hydrogenation at 633 K and 25 bar (1 bar = 105 Pa). The Fe/NCNT catalyst promoted with both potassium (K) and manganese (Mn) showed high performance in CO2 hydrogenation, reaching 34.9% conversion with a gas hourly space velocity (GHSV) of 3.1 L·(g·h)−1. Product selectivities were high for olefin products and low for short-chain alkanes for the K-promoted catalysts. When Fe/NCNT catalyst was promoted with both K and Mn, the catalytic activity was stable for 60 h of reaction time. The structural effect of the Mn promoter was demonstrated by X-ray diffraction (XRD), temperature-programmed reduction (TPR) with molecular hydrogen (H2), and in situ X-ray absorption near-edge structure (XANES) analysis. The Mn promoter stabilized wüstite (FeO) as an intermediate and lowered the TPR onset temperature. Catalytic ammonia (NH3) decomposition was used as an additional probe reaction for characterizing the promoter effects. The Fe/NCNT catalyst promoted with both K and Mn had the highest catalytic activity, and the Mn-promoted Fe/NCNT catalysts had the highest thermal stability under reducing conditions.

Titanium, either in the form of a Ti foil or in form of a Ti mesh, was used as a novel substrate to grow nitrogen‐doped carbon nanotubes (NCNTs) through chemical vapor deposition at moderate temperatures over electrodeposited iron particles. The thus‐prepared high‐surface‐area electrodes were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS). The electrochemical performance towards the V(IV)/V(V) redox couple was investigated by cyclic voltammetry. The parameters for iron particle electrodeposition were adjusted towards high and uniform substrate coverage. Nanotube growth from acetonitrile at moderate temperatures (600 °C) led to N‐containing CNTs with a high amount of graphitic nitrogen. NCNTs grown over Ti substrates provide promising performances towards the V(IV)/V(V) as well as the V(III)/V(IV) redox pair. In general, the results of this study show that Ti might be a suitable electrocatalyst substrate for various applications in electrochemical energy conversion. [ABSTRACT FROM AUTHOR]

A novel N‐doped carbon nanotube aerogel has been synthesized by pyrolysis of the three‐dimensional tubular polypyrrole networks and evaluated as a metal‐free electrocatalyst for the oxygen reduction reaction. The carbon aerogel catalysts are pyrolyzed at 500 °C (PPy/C‐500), 700 °C (PPy/C‐700), 900 °C (PPy/C‐900) and 1050 °C (PPy/C‐1050), and display the pyrolyzed temperature‐dependent activity and stability. The catalytic activity is increased with the increase of pyrolysis temperature from 500 °C to 1050 °C, ascribed to the high electronically conductive graphitic phases, the thin wall of the three‐dimensional tubular carbon aerogel framework and the increased effective active sites. The nitrogen content is reduced with the increase of pyrolysis temperature, and which plays an important role in the stability of the pyrolyzed catalyst. After 1500 cycles, the PPy/C‐1050 catalyst shows more positive half‐wave potential than the commercial Pt/C catalyst, and displays a quasi‐four‐electron pathway toward the oxygen reduction reaction in the acid solution. This work provides an effective strategy for preparing the low cost and metal‐free N‐doped carbon aerogel catalyst from the conjugated conducting polymer, to achieve high activity and stability. [ABSTRACT FROM AUTHOR]

In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid followed by stabilizing in water by employing the ultrasonic bath. Investigation on the stability of the samples showed a high stability level for the prepared water/N-CNT nanofluids in which the zeta potential of − 43.5 mV was obtained for the best sample. Also for studying the heat transfer properties, the thermal conductivity in the range of 0.1–0.5 mass% and convection heat transfer coefficients of nanofluids in the range of 0.1–0.5 mass%, and Reynolds number in the range of 4000–9000 were evaluated. The results showed 32.7% enhancement of the convection heat transfer coefficients at Reynolds number of 8676 and 27% increase in the thermal conductivity at 0.5 mass% and 30 °C. [ABSTRACT FROM AUTHOR]

Values of specific electric conductivity are determined for nitrogen-doped carbon nanotubes (N‑CNTs) and N-CNTs oxidized with 68 wt % HNO3. It is established that the electrical conductivity of the material falls considerably along with nitrogen content in the tubular structure of the N-CNTs and an increase in the number of oxygen-containing groups on their surfaces due to a rise in the concentration of defects in their structure. The electrical conductivity of all types of samples rises along with pressure. [ABSTRACT FROM AUTHOR]

Graphical abstract Nitrogen-doped carbon nanotubes with well-defined tubular morphology and controllable shell thickness as efficient nonprecious oxygen reduction reaction electrocatalysts have been reported. Highlights • Halloysite nanotubes were used as the template for the synthesis of uniform N-CNTs. • The shell thickness of N-CNTs can be well-controlled. • N-CNTs showed excellent catalytic activity toward the oxygen reduction reaction. • N-CNTs with the pyridinic N content of 21.6% showed the best oxygen reduction reaction performance. Abstract Halloysites were applied as the template to form halloysite/polyaniline core/shell hybrids through an oxidative polymerization route, where the amount of aniline monomer could be adjusted to precisely control the shell thickness of polyaniline. The pyrolysis process was then applied to ensure the carbonization of the polyaniline to form halloysite/nitrogen-doped carbon core/shell hybrids. Finally, halloysites were removed, resulting in the formation of nitrogen-doped carbon nanotube with a uniform morphology and a controlled shell thickness. The shell thickness and pyrolysis temperature of nitrogen-doped carbon nanotubes were optimized to improve the electrocatalytic performance involved in oxygen reduction reaction. The nitrogen-doped carbon nanotubes showed good electrocatalytic activities toward oxygen reduction reaction in 0.1 mol L−1 KOH aqueous solution, making them a promising cathode catalyst for alkaline fuel cell applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A CVD-based protocol simultaneously achieving microstructure design and SMSIs is reported. • The SMSIs are manifested by partial embedment of Ru nanoparticles in the carbon support and charge modulation. • The SMSIs optimize H* adsorption, lower energy barriers and enhance catalyst robustness. • The hierarchical microstructure, hydrophilic/aerophobic surface, high Ru dispersion render superior high-rate HER activity. Strong metal-support interactions (SMSIs) play a pivotal role in enhancing the catalytic activity and stability of supported metal catalysts in heterogeneous thermal catalysis, but construction of effective SMSIs remains challenging in electrocatalysis. As a ubiquitous and versatile support for electrocatalysts, carbon materials are generally too inert to generate SMSIs with the loaded metal active sites. We hereby report a CVD-based method to prepare Ru nanoparticles on arrays of oxygen- and nitrogen-doped CNTs grown on the fibers of carbon paper (Ru/ONCNT@CP). The SMSIs were manifested by electronic structure tuning of Ru nanoparticles and their partial embedment in the carbon support. The SMSIs result in optimized Gibbs free energy of H*, lowered energy barrier of H 2 O dissociation, and enhanced catalyst robustness. Combined with the hierarchical microstructure, high surface area and hydrophilic/aerophobic nature, the Ru/ONCNT@CP electrode displays excellent HER catalytic activity in 1 M KOH, requiring overpotentials of only 73, 180, and 252 mV to achieve current densities of 100, 500, and 800 mA cm−2, respectively. Moreover, the Ru/ONCNT@CP electrode exhibits outstanding stability, with negligible current decay after 120 h HER operation at 100 mA cm−2. This work features an effective and scalable approach for preparation of metal-loaded-carbon electrocatalysts with engineered microstructure and SMSIs. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction plays a major role in fuel cell applications to generate electricity by an electrochemical reaction. In this study, functionalised graphene composited with Fe-NCNT or NCNT were investigated on its ORR activity using a physical mixing method. Initially, functionalised graphene was produced via oxidation of graphene. NCNT and Fe-NCNT was obtained from the previously prepared samples using chemical vapour deposition technique and electrochemical reduction method for Fe-NCNT. The physical mixing between functionalised graphene and NCNT or Fe-NCNT was performed using sonication with the presence of pyrrole to produce the desired nanocatalyst. The surface morphologies and microstructures of the synthesised nanocatalysts were studied using field emission scanning electron microscopy. Surface chemical functionality of the nanocatalysts was investigated using X-ray photoelectron microscopy. Meanwhile, the ORR performance of nanocatalysts in a half cell were investigated using cyclic voltammetry techniques in both alkaline and acidic electrolytes. From this study, agglomeration of functionalised graphene (f-graphene) was observed on the Fe-NCNTs indicating a hindrance in transfer of electrons within the catalyst surface. NCNT/f-graphene showed to contain higher percentage of pyridinic-N which claimed to have favored the catalytic activity compared to Fe-NCNT/f-graphene. Likewise, a higher onset potential was recorded for NCNT/f-graphene which indicated a higher ORR activity than the Fe-NCNT/f-graphene.

A nitrogen‐doped carbon nanotubes/graphene (NCNTs‐G) composite as the sulfur host for a lithium‐sulfur battery has been fabricated by in situ growth of NCNTs on graphene in a one‐step nickel‐catalyzed thermolysis. The graphene sheet can function as a robust support to anchor NCNTs so that the specific surface area of the composite can be increased and the charge‐transfer resistance is reduced. These features, together with the high N‐doping level, impart the NCNTs‐G/S cathode a high utilization of sulfur, and the polysulfide shuttle effect can be effectively inhibited by both physical confinement and chemical adsorption. Therefore, the NCNTs‐G/S cathode shows high reversible capacities of 1484 mA h g−1 and 985 mA h g−1 at the current rate of 0.1 C and 0.5 C, respectively. It also exhibits a good cycling stability; 82 % of its initial capacity is retained after 150 cycles at 0.5 C, and a very small capacity decay rate of 0.06 % per cycle resulted in 400 cycles at 1 C. Based on the above structural characteristics and battery performance results, the NCNTs‐G/S is a promising cathode for a high‐performance Li−S battery. Dropping anchor on graphene: N‐doped carbon nanotubes/graphene (NCNTs‐G) was prepared by the in situ growth of NCNTs on graphene oxide with Ni as the catalyst and cyanamide as the carbon and nitrogen source. The graphene sheets provide anchoring sites for NCNTs, avoiding their aggregation, increasing the surface area and reducing the charge transfer resistance. The NCNTs‐G shows a high discharge capacity and good cycling stability for a Li−S battery. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) constitute an interesting material for nanomedicine applications because of their unique properties, especially their ability to penetrate membranes, to transport drugs specifically and to be easily functionalized. In this work, the energies of the intermolecular interactions of single-walled CNTs and the anticancer drug doxorubicin (DOX) were determined using the AMBER 12 molecular dynamics MM/PBSA and MM/GBSA methods with the aim of better understanding how the structural parameters of the nanotube can improve the interactions with the drug and to determine which structural parameters are more important for increasing the stability of the complexes formed between the CNTs and DOX. The armchair, zigzag, and chiral nanotubes were finite hydrogen-terminated open tubes, and the DOX was encapsulated inside the tube or adsorbed on the nanotube surface. Pentagon/heptagon bumpy defects and polyethylene glycol (PEG) nanotube functionalization were also studied. The best interaction occurred when the drug was located inside the cavity of the nanotube. Armchair and zigzag nanotubes doped with nitrogen, favored interaction with the drug, whereas chiral nanotubes exhibited better drug interactions when having bumpy defects. The π-π stacking and N-H...π electrostatic interactions were important components of the attractive drug-nanotube forces, enabling significant flattening of the nanotube to favor a dual strong interaction with the encapsulated drug, with DOX-CNT equilibrium distances of 3.1-3.9 Å. These results can contribute to the modeling of new drug-nanotube delivery systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fe 3 C@NCNTs/GNS is simply obtained by a direct pyrolysis of K 4 Fe(CN) 6. • Fe 3 C@NCNTs/GNS exhibits excellent performance for Bisphenol A (BPA) degradation. • 1O 2 and O 2 − are responsible for BPA removal instead of classical OH and SO 4 −. • Graphitic carbon framework together with N doping induces the non-radical pathway. • Influences of anions, humic acid, and actual sewages are investigated in detail. Abstract Developing novel carbocatalysts with available strategies for peroxymonosulfate (PMS) activation has become a popular topic in environmental remediation and protection fields. Herein, using commercial K 4 Fe(CN) 6 as the precursor, Fe 3 C@nitrogen-doped carbon nanotubes/graphene nanosheets (Fe 3 C@NCNTs/GNS) is synthesized by a direct high-temperature pyrolysis. Characterization results prove that Fe 3 C@NCNTs/GNS has a relatively high graphitization degree and rich nitrogen doping content, which endow it with excellent catalytic efficiency in PMS activation for powerful removal of Bisphenol A (BPA). Influences of catalyst/oxidant dosages, some inorganic anions, humic acid, and practical sewages are investigated in detail. For mechanism studies, it is found that tert-butyl alcohol (TBA)/methanol fails to inhibit BPA degradation, and the primary reactive oxidative species (ROS) are superoxide radical (O 2 −) and singlet oxygen (1O 2). Discussion on the origin of 1O 2 confirms that moderate modification of N atoms in graphitic carbon frameworks plays an essential role in inducing the non-radical mechanism. This work will provide new insights for the preparation of high-performance carbocatalysts in PMS activation and exploring critical roles of N-doping during non-radical processes. [ABSTRACT FROM AUTHOR]

Using the methods of scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, the influence of concentration, time, and the procedure for the oxidative treatment of the surface of carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) in the mixture with calcium nitrate was studied. All prepared materials were tested as supports of cobalt-supported catalysts in the Fischer–Tropsch process. It is shown that an increase in the Ca(NO3)2 concentration from 15 to 25 wt % leads to the destruction of CNTs, and the time of treatment and oxygen concentration in the oxidizing mixture have almost no effect on the morphology and physicochemical characteristics of the materials. It is found that heterosubstitution in nanotubes and a change in the surface relief of the carbon support lead to an increase in CO conversion, and the catalyst activity increases in the series: Co/CNTs → Co/N-CNTs → Co/CNTs(Ca) → Co/N-CNTs(Ca). [ABSTRACT FROM AUTHOR]

Abstract A novel Ni-doped TiN modified N-doped CNTs hybrid nanotubes (N-CNTs@TiNiN) is constructed and serves as hybrid support for the platinum (Pt) catalyst. We prepare the N-CNTs@TiNiN support by a solvothermal process followed by a nitriding process. It is used as anodic catalyst support to test methanol electrooxidation. By contrast, the current density of Pt/N-CNTs (0.34 A mgpt−1) is nearly 1.31 times more than Pt/CNTs (0.26 A mgpt−1) while Pt/TiNiN (0.56 A mgpt−1) is almost 1.33 times as much as Pt/TiN (0.42 A mgpt−1). What's more, among all the catalysts investigated in this work, the novel Pt/N-CNTs@TiNiN (0.86 A mgpt−1) shows the highest reactivity for methanol oxidation, which is also much more active and durable than the commercial JM Pt/C catalyst, showing only slight activity variation even after 12 000 potential cycles. The synthetic Pt/N-CNTs@TiNiN catalyst is researched on its electrocatalytic performance toward methanol electrooxidation and the high activity and durability might be mainly attributed to the electron transfer due to the synergistic effect of the robust TiNiN NPs and N-CNTs by inducing both co-catalytic and electronic effects. Graphical abstract A fancy N-CNTs@TiNiN hybrid is successfully synthesized and used as the support for Pt, and the experimental results show that Pt/N-CNTs@TiNiN have a much higher catalytic activity and durability than conventional Pt/C (JM) catalyst for methanol electrooxidation. Image 1 Highlights • N-CNTs@TiNiN support with an interactive structure and high surface area was synthesized. • Pt nanoparticles with small size were well dispersed on N-CNTs@TiNiN support. • Pt/N-CNTs@TiNiN shows remarkably enhanced methanol oxidation activity and durability. [ABSTRACT FROM AUTHOR]

A set of novel catalysts FeMn/N‐CNTs that partly maintain the core‐shell structure have been prepared successfully by calcination of analogous MOF‐74, which has bimetallic species (Fe and Mn) and a cheap organic ligand (2, 5‐dihydroxylbenzoic acid, DHBA) with melamine as additional nitrogen source. These catalysts exhibit a distinctive microstructure of Fe−Mn alloys surrounded by N‐doped carbon nanotubes (CNTs). Electrochemical methods have been employed to investigate their activity in oxygen reduction reaction (ORR) in alkaline solution. The highest ORR performance of Fe3Mn1/N‐CNTs‐100 shows that the half wave potential is at 0.865 V and the kinetic current density (at 0.9 V) is 1.447 mA cm−2, which are higher than those of commercial Pt/C (0.855 V, 0.946 mA cm−2). In addition, Fe3Mn1/N‐CNTs‐100 is much more durable than commercial Pt/C under the conditions tested. The highly efficient ORR performance may be attributed to the unique microstructure and large surface area with appropriate pore size, as well as to the synergistic effects between the pyridinic N species and the Fe−Nx species that play important roles in ORR in alkaline solution. However, in acid medium, only Fe−Nx species catalyze ORR and pyridinic N species are limited to work as the active sites. This study may prompt others to explore the development of heteroatom‐doped CNTs surrounding particles as efficient catalyst for ORR and fuel cell applications. All for one: A novel catalyst FeMn/N‐CNTs was prepared by annealing bimetallic (Fe and Mn) analogous MOF‐74 precursor with melamine, to yield Fe−Mn alloys contained in N‐doped CNTs, which are highly active and durable ORR catalysts. The excellent performance is the result of the unique microstructure of the catalyst and its large surface area with appropriate pore size, in addition to the synergistic effects of the bimetallic species, and those between the pyridinic N species and the Fe−Nx species. [ABSTRACT FROM AUTHOR]

Shaped carbon nanomaterials (SCNMs) were synthesized via the chemical vapour deposition (CVD) technique by using typical metallocenes (ferrocene, nickelocene, cobaltocene, and ruthenocene), and more interestingly, by use of novel ferrocenyl imidazolium derivatives, containing -Cl (FcImCl), -NO 2 (FcImNO 2 ) and -CH 3 (FcImCH 3 ) substituents as catalysts. Acetonitrile was applied both as a carbon and nitrogen source at temperatures 800–900 °C. The SCNMs, namely, carbon nanotubes (CNTs), carbon spheres (CS), carbon fibres (CF) and amorphous carbons (ACs) were obtained in varying ratios depending on the catalyst and carbon sources. The ferrocenyl imidazolium catalysts produced nitrogen-doped CNTs (N-CNTs) with bamboo-like structures. The yields of various reactions were temperature-dependent, with the highest amount of N-CNTs obtained at 850 °C. In all samples, the composition was mainly of CS and N-CNTs except for nickelocene at 800 °C that gave CFs as a “minor” product. Ferrocene and nickelocene in acetonitrile produced well-aligned N-CNTs while cobaltocene and ruthenocene gave ‘spaghetti-like’ structures. In the case of ferrocenyl imidazolium catalyst, a coiled N-CNTs morphology was produced from FcImCl catalyst. Also, higher percentage of N-CNTs with traces of CS were obtained from the FcImCl and FcImCH 3 catalysts in acetonitrile at 850 °C, while higher percentage of CS and AC were obtained for FcImNO 2 catalyst. In all the catalysts, the use of acetonitrile promoted nitrogen-doping (samples with more disordered and with smaller outer-diameters). Thus, this study demonstrates that the synthesis of N-CNTs from nitrogen-containing ferrocenyl imidazolium compounds as catalyst sources, provided higher percentage of N-CNTs which can be suitable for various application. [ABSTRACT FROM AUTHOR]

Large reversible capacitance and rapid rate capability are crucial to the realization of the manganese dioxide (MnO 2 ) based electrode material but have been proved to be challenging to achieve due to the poor electronic conductivity of MnO 2 . Herein, the N-CNTs/MnO 2 composites are prepared by using PPy-derived nitrogen-doped carbon nanotubes (N-CNTs) as the support frameworks to load nanosized MnO 2 . Benefitting from the high electronic conductivity of N-CNTs and the large pseudocapacitance of MnO 2 , the N-CNTs/MnO 2 -2 electrodes exhibit high specific capacitance of 366.5 F g −1 at a current density of 0.5 A g −1 which maintains 245.5 F g −1 (67.0%) at 25 A g −1 , indicating excellent rate capability. Moreover, the as-fabricated asymmetric supercapaitors using N-CNTs/MnO 2 -2 and N-CNTs as the positive and negative electrodes achieve a wide stable operating voltage of 1.8 V and a high energy density of 20.9 Wh kg −1 , as well as outstanding cycling stability of 91.6% retention after 5000 cycles at a current density of 5 mA cm −2 . Therefore, these composites are promising electrode materials for the further high-power output energy storage and conversion devices. [ABSTRACT FROM AUTHOR]