Bamboo-like Carbon Research Articles

Catalytic carbon-bed sintering of CNTs/calcium aluminate cement and its effects on thermal mechanical properties of refractory castables

To improve the dispersion of carbon nanotubes in refractory castables and exert the strengthening effect of carbon nanotubes on castables, the core-shell CNTs/CAC (carbon nanotubes/calcium aluminate cement) was synthesized by the catalytic carbon-bed sintering method. The effects of catalyst content on the microstructure of CNTs/CAC powders were evaluated by Raman spectroscopy, SEM, and HRTEM. The results suggested that the optimal addition amount of catalyst was 0.75 wt%. The diameter of the bamboo-like carbon nanotubes was ∼50 nm and the length of the carbon nanotubes was ∼120 μm. Carbon nanotubes and small calcium aluminate particles were interspersed with each other and wrapped in a compact calcium aluminate shell with a thickness of 3∼5 μm. Moreover, the DFT calculation was employed to investigate the growth mechanism of carbon nanotubes. Electrons were transferred from Ni to H, O, and C atoms, increasing bond length and weakening the strength of C–H and CO bonds which was conducive to the growth of carbon nanotubes. The formation of the core-shell structure was in direct connection with the liquid-phase eutectic phase. Calcium carbonate and alumina reacted preferentially to form C12A7, and then C12A7 continued to react with alumina to form CA and CA2. With the increase of sintering temperature, a large amount of liquid phase was formed. Carbon nanotubes were wrapped by the liquid phase of calcium aluminate to form a core-shell structure. The CNTs/CAC cement bonded Al2O3–SiC castables had great mechanical properties and thermal shock resistance. Compared with Al2O3–SiC castables bonded with Secar71, the HMOR and thermal shock residual strength ratio of Al2O3–SiC castables bonded with CNTs/CAC cement were increased by 24.7% and 22.1%, respectively.

Dual-MOFs-Derived Fe and Mn Species Anchored on Bamboo-like Carbon Nanotubes for Efficient Oxygen Reduction as Electrocatalysts

The development of efficient non-precious metal electrocatalysts for oxygen reduction reaction (ORR) to replace Pt-based methods is crucial for the applications of fuel cells and metal–air batteries. In this study, a bimetallic M-N-C catalyst with highly dispersed dual-atom Fe/Mn-Nx sites immobilized on N-doped bamboo-like carbon nanotubes is prepared by the ball-milling and calcination of dual-MOFs as precursors. The rich N-doping and abundant M–Nx species contribute to the excellent intrinsic ORR activity of the catalyst, and the unique bamboo-like nanotubes morphology is beneficial for facilitating electron transfer and mass transport while simultaneously enabling the exposure of active sites. As expected, the optimized Z-Fe1Mn1-NC catalyst exhibits efficient ORR activity with a half-wave potential (E1/2) of 0.80 V in acid and 0.82 V in alkaline, and a higher electrochemical stability with the current density maintained at 91% (in 0.1 M KOH) and 86% (0.1 M HClO4) of its initial current density after 15 h of a chronoamperometric test at a high potential of 0.7 V. When further applied to Zn–air batteries, the catalyst also delivers a high open-circuit voltage, large power density, and outstanding rate performance. This work provides a novel means of designing dual metal M–Nx site-based M-N-C catalysts for ORR sustainable energy applications.

Ni3Fe@N-doped carbon nanotubes 3D network induced by nanoconfined symmetry breaking for high-performance microwave absorption, corrosion protection, and pollutant purification

It remains challenging to develop multifunctional electromagnetic wave (EMW) absorbers with anti-corrosion and pollutant purification capabilities suitable for extremely harsh ocean environments. This study exploits symmetry breaking to construct a three-dimensional (3D) network of bamboo-like N-doped carbon nanotubes (NCNT) encapsulated with magnetic Ni3Fe nanocatalysts via facile coordination and catalytic chemical vapor deposition process. The resulting Ni3Fe@NCNT composite demonstrates outstanding EMW absorption performance, anti-corrosion behavior, and adsorption purification function. Its excellent EMW absorption performance, including a minimum reflection loss of −57.3 dB and a maximum effective absorption bandwidth of 6.0 GHz, is achieved by magnetic-dielectric match, inert space platform, and porosity architecture. The Ni3Fe@NCNT composite also shows corrosion resistance and self-cleaning function simultaneously because of the physical shield provided by the intrinsically impermeable, inert NCNT shells and their considerable chemically active site and high porosity. For the first time, the EMW absorber is endowed with cooperative multi-functionalities. Our findings may pave the way to manufacture versatile EMW materials for applications in complicated environments.

Bamboo-like N-doped carbon tubes encapsulated Co2P–Fe2P derived from zeolitic imidazolate framework as an efficient trifunctional electrocatalyst for water splitting and Zn-air batteries

The development of high-performance and stable trifunctional electrocatalysts is a pressing challenge for the practical application of water splitting and regenerative Zn-air batteries. Herein, bamboo-like N-doped carbon tubes encapsulated Co2P–Fe2P nanoparticles (CoFe-PN/C) was fabricated via a facile template-sacrificial approach by using CoZn-ZIF trapping Fe3+ (CoFeZn/C) as the precursor. The incorporation of Fe3+ was achieved by the one-pot synthesis approach during crystallization of ZIF, which led to the generation of the unique bamboo-like tube structure under the condition of simultaneous phosphating and carbonization. Benefiting from the large surface area, the optimized electronic structure of active sites and the unique bamboo-like nanotube, the resultant CoFe-PN/C can be used as the trifunctional electrocatalyst possessing a small overpotential at 10 mA cm−2 for the HER (178 mV) and OER (300 mV), as well as a high half-wave potential of 0.884 V for ORR (40 mV more positive than that of commercial 20 wt% Pt/C). Moreover, the self-designed CoFe-PN/C||CoFe-PN/C alkaline electrolyzer driving 50 mA cm−2 only need operating potential of 1.84 V and the maximum discharge power density of the CoFe-PN/C-assembled ZABs could achieve 152.0 mW cm−2, superior to those of Pt/RuO2 couple. This work will facilitate the development and application of trifunctional electrocatalysts based on bi-transition metallic phosphides for energy conversion and storage technology.

Ni Nanoclusters Anchored on Ni-N-C Sites for CO2 Electroreduction at High Current Densities.

Transition metal catalyst-based electrocatalytic CO2 reduction is a highly attractive approach to fulfill the renewable energy storage and a negative carbon cycle. However, it remains a great challenge for the earth-abundant VIII transition metal catalysts to achieve highly selective, active, and stable CO2 electroreduction. Herein, bamboo-like carbon nanotubes that anchor both Ni nanoclusters and atomically dispersed Ni-N-C sites (NiNCNT) are developed for exclusive CO2 conversion to CO at stable industry-relevant current densities. Through optimization of gas-liquid-catalyst interphases via hydrophobic modulation, NiNCNT exhibits as high as Faradaic efficiency (FE) of 99.3% for CO formation at a current density of -300 mA·cm-2 (-0.35 V vs reversible hydrogen electrode (RHE)), and even an extremely high CO partial current density (jCO) of -457 mA·cm-2 corresponding to a CO FE of 91.4% at -0.48 V vs RHE. Such superior CO2 electroreduction performance is ascribed to the enhanced electron transfer and local electron density of Ni 3d orbitals upon incorporation of Ni nanoclusters, which facilitates the formation of the COOH* intermediate.

Ru Catalysts Supported on Bamboo-like N-Doped Carbon Nanotubes: Activity and Stability in Oxidizing and Reducing Environment.

The catalysts with platinum-group metals on nanostructured carbons have been a very active field of research, but the studies were mainly limited to Pt and Pd. Here, Ru catalysts based on nitrogen-doped carbon nanotubes (N-CNTs) have been prepared and thoroughly characterized; Ru loading was kept constant (3 wt.%), while the degree of N-doping was varied (from 0 to 4.8 at.%) to evaluate its influence on the state of supported metal. Using the N-CNTs afforded ultrafine Ru particles (<2 nm) and allowed a portion of Ru to be stabilized in an atomic state. The presence of Ru single atoms in Ru/N-CNTs expectedly increased catalytic activity and selectivity in the formic acid decomposition (FAD) but had no effect in catalytic wet air oxidation (CWAO) of phenol, thus arguing against a key role of single-atom catalysis in the latter case. A remarkable difference between these two reactions was also found in regard to catalyst stability. In the course of FAD, no changes in the support or supported species or reaction rate were observed even at a high temperature (150 °C). In CWAO, although 100% conversions were still achievable in repeated runs, the oxidizing environment caused partial destruction of N-CNTs and progressive deactivation of the Ru surface by carbonaceous deposits. These findings add important new knowledge about the properties and applicability of Ru@C nanosystems.

Co3C-stabilized-CoFe heterostructure wrapped by bamboo-like N-doped carbon nanotubes for highly-efficient oxygen electrocatalysis

Bimetallic alloys have been showing unexpectedly high activity for oxygen reduction reaction (ORR) in alkaline electrolytes. However, many fundamental questions regarding the ORR stability and poor oxygen evolution reaction (OER) performance of bimetallic alloys remain unresolved. Here, we prepare a cobalt carbide-stabilized CoFe alloy wrapped by hollow bamboo-like nitrogen-doped carbon nanotubes (CoFe-Co3C@NCNTs) using bimetallic Prussian-blue-analogue and dicyandiamide as precursors. Interestingly, the spherical CoFe-Co3C heterojunctions are always encapsulated at one end of the tube. The as-marked CoFe-Co3C@NCNTs-20 catalyst exhibits an ultra-high ORR activity (half-wave potential of 0.934 V) and a relatively good OER activity (overpotential of 0.320 V), which are superior to Pt/C and RuO2, respectively. CoFe-Co3C@NCNTs-20 also shows excellent ORR/OER stabilities and potential difference between ORR and OER (0.616 V). Excellent activity and stability benefit from the synergies between CoFe-Co3C and NCNTs, while the hollow structure/conductive skeleton enhances the mass/charge transfers, respectively. The NCNTs coating greatly enhances the stability of the CoFe-Co3C heterojunctions to avoid the corrosion of active sites in alkaline media. Moreover, rechargeable zinc-air battery assembled with CoFe-Co3C@NCNTs-20 cathode shows high power-density (209.15 mW cm−2) and open-circuit voltage (1.505 V). It provides a new reference for promoting the development of bimetallic alloy-coupled transition metal carbide catalysts.

Cobalt Nanoparticles Encapsulated with N-Doped Bamboo-Like Carbon Nanofibers as Bifunctional Catalysts for Oxygen Reduction/Evolution Reactions in a Wide pH Range

Nonprecious bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) catalysts in wide pH electrolytes are crucial for the versatile use of electrochemical energy storage and conversion devices. Non-noble metal/nitrogen-doped carbon (M–N/C) has been reported as a promising candidate for efficient and cost-effective bifunctional catalysts. Nevertheless, the stability and catalytic activity of M–N/C bifunctional catalysts in a wide pH range are still limited, especially in neutral and acidic electrolytes. Here, we synthesized directly grown N-doped bamboo-like carbon nanofiber-encapsulated cobalt nanoparticles on carbon flakes (Co–N/C fiber) via pyrolysis of 2D cobalt–zeolitic imidazolate framework and tubular g-C3N4. The in situ growth of N-doped carbon nanofiber incorporated with Co nanoparticles exposes large active sites and enhances charge transfer. Moreover, abundant mesopores with high loading of pyridinic-N, graphitic-N, Co@N/C, and Co–Nx facilitate high catalytic activity in a wide pH condition. Co–N/C fiber shows superior ORR performance in alkaline, neutral, and acidic electrolytes with high onset potentials of 1.003, 0.820, and 0.800 V vs RHE, respectively. A comparable OER performance of Co–N/C fiber to the Ir/C benchmark in alkaline and neutral conditions can be obtained with 397 and 570 mV overpotentials at 10 mA cm–2. Utilizing Co–N/C fiber in alkaline and neutral Zn–air batteries exhibits power densities of 155 and 67 mW cm–2, with excellent stability for over 180 h. This study offers a strategy for developing a bifunctional M–N/C catalyst that is applicable across a wide pH range via hybrid nanostructuring.

Efficient synergistic effect of trimetallic organic frameworks derived as bifunctional catalysis for the rechargeable zinc-air flow battery

Precise design of oxygen electrode catalysts can alleviate the problems of slow kinetic reaction and high overpotential in the rechargeable zinc-air flow batteries (ZAFBs). Herein, an ideal 3D carbon-based material for FeCo alloy inlaid to Fe/Co and N co-doped bamboo-like carbon nanotubes (CNTs) is prepared by means of a one-pot high-temperature pyrolysis strategy of three metal organic frameworks (MOFs) mixed-precursors. The concentration of active metal species, the amount of conductive CNTs and the hierarchical porous structure with high specific surface area in this material are regulated. The optimal catalyst, Fe/12Zn/Co-NCNTs, demonstrates excellent electrochemical activity with a high half-wave potential of 0.879 V for oxygen reduction reaction (ORR) and low overpotential of 340 mV at 10 mA cm−2 for oxygen evolution reaction (OER) in the half-cell. Moreover, the smaller bifunctional ΔE value of Fe/12Zn/Co-NCNTs and Fe/(12Zn/Co)-NCNTs catalyst are 0.693 V and 0.717 V, respectively, less than the commercial Pt/C+IrO2 (ΔE = 0.77 V). The ZAFB yields a high open circuit voltage of 1.518 V, peak power density of 166 mW cm−2, and specific capacity of 809.1 mAh g−1 when employing Fe/12Zn/Co-NCNTs as air cathode because of the synergistic effect that improves both OER and ORR. More importantly, both Fe/12Zn/Co-NCNTs and Fe/(12Zn/Co)-NCNTs as the bifunctional catalysts produce a low charge-discharge voltage gap and high cycle lifespan of more than 320 h at 10 mA cm−2. This work provides a facile strategy for fabricating high-efficiency and low-cost bifunctional electrocatalysts for ZAFBs and other clean energy applications.

Supramolecular complex derived carbon nanotubes decorated with iron single atoms and nanoclusters as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

The great attention of rechargeable Zn-air battery has motivated extensive research on the development of inexpensive, highly efficient, and robust noble-metal-free bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a supramolecular complex derived strategy was used to prepare bamboo-like carbon nanotubes with abundant Fe single atoms and sub-nanometer clusters anchored on tube walls. When served as a bifunctional ORR/OER electrocatalyst, this hybrid showed a small overpotential gap of 0.713 V and excellent stability. More importantly, a large power density of 213 mW cm−2 and stable long-time round-trip charge-discharge performance were achieved for the assembled rechargeable Zn-air batteries. Density functional theory calculations revealed that atomic Fe–N4 moiety in the catalyst could be the essence of high ORR activity, while atomic Fe–N4 moiety coupled sub-nanometer cluster significantly reduces the OER energy barrier. This work provides an effective strategy for the preparation of high-performance and robust oxygen electrode catalysts as well as a significant new insight on the catalytic mechanisms, helping to realize significant advances in energy devices.

Catalytic effect of bamboo-like carbon nanotubes loaded with NiFe nanoparticles on hydrogen storage properties of MgH2

Catalyst doping modification has become an important strategy to solve the high desorption temperature and sluggish kinetics issues of magnesium hydride (MgH2) for further commercial application. Herein, we report a novel strategy by exploiting a catalyst with the “magnesophilic” transition metal and “magnesiphobic” carbon material to construct a MgH2-catalysts-carbon layer hydrogen storage material, where the bimetallic NiFe nanoparticles are supported atop the bamboo-like carbon nanotubes (NiFe@CNT) via calcination. The experimental results show that the built MgH2-NiFe@CNT composite can absorb 4.06 and 3.25 wt% H2 at 373 and 348 K, respectively, while the milled-MgH2 almost no longer absorbs H2 and takes only 0.82 wt% even at 423 K. More importantly, the initial desorption temperature of the MgH2-NiFe@CNT composite reduces to 498 K by 122 K in contrast to the milled-MgH2, and the dehydrogenation activation energy decreases from 151.8 to 49.7 kJ mol−1. Ex situ structural characterization and theoretical calculation show that the synergistic effects of the “hydrogen pump” role of Mg2Ni/Mg2NiH4 and “hydrogen gateway” role of α-Fe, as well as the good dispersion function of carbon nanotubes generated in situ from the NiFe@CNT, contribute the excellent hydrogen storage properties of the MgH2-NiFe@CNT composite. This study provides new insights into the modification of MgH2 by carbon-supported transition metal catalysts.

Large-scale and solvent-free synthesis of magnetic bamboo-like nitrogen-doped carbon nanotubes with nickel active sites for photothermally driven CO2fixation

The development of a method for the large-scale and solvent-free preparation of hierarchical pore single-atom catalysts is highly desirable but challenging.

Synthesis of hierarchically structured Fe3C/CNTs composites in a FeNC matrix for use as efficient ORR electrocatalysts.

Fe-N-C has a high number of FeN x active sites and has thus been regarded as a high-performance oxygen reduction reaction (ORR) catalyst, and combining Fe3C with Fe-N-C typically boosts ORR activity. However, the catalytic mechanism remains unknown, limiting further research and development. In this study, a precipitation-solvothermal process was used in conjunction with pyrolysis to produce a series of Fe-N-C catalysts derived from a zeolitic imidazolate framework (ZIF) that was composited with Fe3C. The prepared catalysts had a multiscale structure of ZIF-like carbon particles and rod-like structures, as well as bamboo-like carbon nanotubes (CNTs) and carbon layers wrapped with Fe3C particles while a series of studies revealed the origin of the rod-like structures and Fe3C phase. The hierarchical structure was beneficial to the enhanced electrocatalytic performance of catalysts for ORR. The optimal sample had the highest half-wave potential of 0.878 V vs. RHE, which was higher than that of commercial Pt/C (0.861 V vs. RHE). The ECSA of the optimal sample was 1.08 cm2 μg-1, with an electron transfer number close to 4, and functioning kinetics. The optimal sample exhibited high durability and methanol tolerance for the ORR. Finally, blocking different Fe active sites with coordination ions demonstrated that Fe(ii) was the main active site, indicating that Fe3C primarily served as a cocatalyst to optimize the electron structure of Fe-N-C, thereby synergistically improving the ORR activity.

Gram-scale production of in-situ generated iron carbide nanoparticles encapsulated via nitrogen and phosphorous co-doped bamboo-like carbon nanotubes for oxygen evolution reaction

Optimizing electrocatalytic activity and recognizing the most reactive sites for oxygen evolution reaction (OER) electrocatalysts are valuable to the order of renewable power. In this research article, we explored an innovative in-situ annealing technique for constructing iron carbide nanoparticles (Fe3C NPs) encapsulated via nitrogen and phosphorous doped bamboo-shape carbon nanotubes (NP-CNTs) for OER. Interestingly, the constructed Fe3C NPs@NP-CNT-800 composite exhibited remarkable electrochemical operation and offered a stable current density of 10 mA/cm2 at a lower overpotential (280 mV) in an alkaline solution. Furthermore, an innovative Fe3C NPs@N,P-CNT-800 hybrid surpassed the standard RuO2 electrocatalyst in terms of OER performance and showed negligible degradation in chronoamperometric (21 h) and chronopotentiometry (3000 cycles) analyses. The remarkable performance and stability are ascribed to the Fe3C NPs, novel tubular bamboo-like morphology of its carbon materials, and heteroatom doping, which contribute to the electrochemical interfaces, large surface area, active catalytic sites, and rapid charge transfer kinetics.

High polarity catalyst of CoFe alloy/fluoride interconnected by bamboo-like nitrogen-doped carbon nanotubes for efficient oxygen evolution reaction

The easy agglomeration and low conductivity of high polarity catalysts restrict the active phase formation for oxygen evolution reaction (OER) in water-splitting reactions, even for the catalysts with conductive NC species derived from MOFs carbonization. Herein, as a proof of concept, the bamboo-like nitrogen-doped carbon nanotube (N-doped CNT) from dicyandiamide pyrolysis was introduced into MOFs-derived high polarity catalyst of CoFe alloy and fluoride, and the performance for OER can be largely improved to low overpotentials of 231 mV to drive 10 mA cm−2 when loaded on the glassy carbon electrode. The structural evolution induced by the N-doped CNT introduction was carefully studied by both spectroscopic analysis and electrochemical measurements, and it was revealed that forming the structure of carbon nanotube interconnected active sites prevented the active site agglomeration and improved the catalytic conductivity, which improved the mass transfer, and active site exposure. The largely improved performance was attributed to the easy active phase formation by high polarity metal fluoride, the synergy between Fe and Co species, and conductivity improvement by N-doped carbon nanotubes derived from dicyandiamide with high graphitic N. The current work showed some novel contributions to catalytic ability boosting for MOF-derived catalysts in OER catalysis.

Autocatalytic formed bamboo-like N-doped carbon nanotubes encapsulated with Co nanoparticles as highly efficient catalyst for activation of peroxymonosulfate toward degradation of tetracycline

Co-based catalysts activated peroxymonosulfate (PMS) for organic pollutants degradation has been extensively studied. Co dissolution of Co-based catalysts would result in secondary environmental contamination. Co autocatalysis the formation of bamboo-like N-doped carbon nanotubes to confine Co nanoparticles (Co NPs). Herein, the N-doped carbon nanotubes encapsulated Co (Co@NCTs) were successfully synthesized through a one-step high-temperature calcination method at different temperatures. Co@NCTs-800 exhibited excellent catalytic performance, the degradation efficiency of tetracycline (TC) could reach 94.5% with only 0.05 g/L catalyst in activating PMS. In addition, the encapsulation of carbon nanotubes inhibits the dissolution of Co, the Co2+ dissolution was 0.0594 mg/L in 40 min in the system of Co@NCTs-800/PMS. Free radical quenching tests, electron paramagnetic resonance, and electrochemical measurements revealed that the non-radical route was dominated by tetracycline degradation, with singlet oxygen (1O2) and electron transfer as the principal active species. The N-doped carbon nanotubes can effectively encapsulate Co, which not only reduces the leaching of Co but also play a synergistic role with Co in degrading organic pollutants. In addition to this, the degradation mechanism and pathways of TC were further investigated. The Co@NCTs-800/PMS system was also able to successfully decompose a variety of organic contaminants, demonstrating that it has real application potential in wastewater.

Nickel coating on carbon nanotubes and PProDOT-2CH2SH supported Pt nanoparticles as the electrocatalyst for methanol oxidation reaction

The electricity generated by direct methanol fuel cells (DMFCs) comes from methanol oxidation reaction (MOR), which is affected by electrocatalytic activity of anode materials. Herein, Pt nanoparticles supported by the composite of thiol group grafted poly(3,4-propylenedioxythiophene) (PProDOT-2CH2SH) and Ni–N co-doped bamboo-like carbon nanotubes (Ni-NCNT) are prepared and proposed as an anode material for DMFCs. The results from morphological analysis show that the Pt nanoparticles uniformly disperse on the surface of support (PProDOT-2CH2SH/Ni-NCNT) with bamboo-like structure, and there is an electronic effect between the Pt and Ni confirmed by X-ray photoelectron spectroscopy analysis. Electrochemical tests reveal that the PProDOT-2CH2SH/Ni-NCNT/Pt catalyst demonstrates good electrocatalytic activity for the MOR in acidic electrolyte, and the catalyst has higher resistance to CO poisoning than commercial Pt/C. The mass activity (MA) of catalyst is up to 1670.54 mA mgPt−1 with an electrochemical active surface area (ECSA) of 98.0 m2 g−1, and the catalyst maintains good performance after 800 cycles. This work provides a high-performance MOR catalyst in practical application for DMFCs.

Cobalt nanoparticles decorated bamboo-like N-doped carbon nanotube as nanozyme sensor for efficient biosensing

• Bamboo-like N doped carbon nanotubes encapsulated with cobalt nanoparticles (Co-BNCNTs) was designed by one-step pyrolysis. • The bamboo-like structure could prevent the self-aggregation of the CoNPs, improve the stability of the CoNPs, and enhance the catalytic activity of the CoNPs. • The hollow tubular structure could shorten the distance for the reactants to reach the electrode surface and accelerate the mass transfer process. In this work, Co nanoparticles decorated bamboo-like N-doped carbon nanotubes (Co-BNCNTs) were design, which exhibited excellent oxidase-mimicking activity and could be served as a novel signal amplification platform for dopamine (DA) sensing. Co nanoparticles (CoNPs) encapsulated in bamboo-like N-doped carbon nanotubes (BNCNTs) could prevent their self-aggregation and expose more active sites. Besides, the N-doping in carbon materials could adjust the charge density and increase active sites. Moreover, the synergistic effect between CoNPs and BNCNTs also could contribute to enhance catalytic activity. In a word, excellent electrical conductivity, large electrochemically active area, multiple catalytically active sites are beneficial for DA detection. The Co-BNCNTs/GCE biosensor showed good stability and selectivity, a wide detection range of 0.5-150 μM, and a lower detection limit of 0.0342 μM. The Co-BNCNTs sensor was employed to detect the DA in the actual sample, which displayed a potential application in clinical diagnosis. Furthermore, our study presented an effective way to the synthesis of metal nanoparticles encapsulated into CNTs catalysts as nanozymes for the application in biosensing.

The preparation of bifunctional Co-N co-doped carbon with bamboo-like hollow tubular as an efficient electrocatalyst for oxygen reduction and methanol oxidation reaction

• Bamboo-like hollow tubular Co-N-C was prepared by direct pyrolysis method. • The Co-N-C catalyst exhibits a high specific surface area. • The Pt@Co-N-C has a high electrochemical surface area. • The Co-N-C and Pt@Co-N-C exhibit excellent ORR and MOR activity and stability. Catalysts with distinguished properties and stability are very important for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) of fuel cells. Herein, we describe a convenient and efficient preparation means to synthesize a bamboo-like hollow tubulous structure Co-N co-doped carbon material (Co-N-C) via a late-model of Co-Imace coordinated compound as the precursor by direct pyrolysis. Additionally, Pt nanoparticles supported by Co-N-C catalysts (Pt@Co-N-C) were prepared using the ethylene glycol reduction procedure. The obtained catalyst exhibited an excellent electro-catalytic property for ORR in alkaline media, which possessed a more positive half-wave potential (0.868V) than commercial Pt/C (0.852V). Moreover, the Co-N-C maintained preeminent long-term stability (91.6 %) after the 21000s and also owned a stronger methanol resistance than Pt/C. The obtained Pt@Co-N-C electrocatalyst exhibited higher MOR activity (96.3 mA cm -2 ), which is 1.6 times greater than that of Pt/C, benefiting from the high electrochemical surface area of Pt@Co-N-C (68 m 2 g -1 ). Furthermore, the Pt@Co-N-C exhibited lower onset potentials, higher I f /I b ratios, and well long-term stability than Pt/C.

Flexible and free-standing electrode for high-performance vanadium redox flow battery: Bamboo-like carbon fiber skeleton from textile fabric

Developing the free-standing and flexible electrodes with high current density and cycle stability is still under debate towards the extensive application of vanadium redox flow batteries (VRFBs). So far, carbon felts, carbon fibers and carbon papers are used which mostly prepared from fossil precursors make them unsustainable. Herein, we first sought to prepare a mechanically flexible and free-standing carbon cloth from terry cloth towel fabric (100% cotton) by using a simple pyrolysis method (TCC). Interestingly, we obtained a bamboo-like carbon fiber structure with a well-balanced micro, -meso, and -macro porosity. Moreover, a low-cost Polyethyleneimine (PEI) is used for Nitrogen doping on carbon cloth skeleton (N-TCC) to improve its electrochemical performance. The as-prepared N-TCC were utilized as efficient electrodes for the VRFBs with higher electrochemical activity towards vanadium species VO2+/VO2+ than TCC and commercial graphite felt (GF) in a 3 electrode electrochemical cell i.e. half-cell. Interestingly, the VRFBs constructed with N-TCCs electrodes (both +ve and –ve half cells) in a full cell configuration at varied current densities from 40 to 160 mA cm−2, we achieved an increased energy efficiency (EE), voltage efficiency (VE), and columbic efficiency (CE) compared to pristine CFs, and TCC based VRFBs. The newly designed cotton based electrodes establishes a unique opportunity for constructing a low-cost, metal-free VRFBs towards a large-scale commercialization of sustainable energy storage system.