Nitrogen-doped Multi-walled Carbon Nanotube Research Articles

Nitrogen-doped carbon nanotube catalytic membrane with peroxymonosulfate activation for the degradation of metronidazole and bisphenol A: Performance and mechanism comparison

As typical pharmaceuticals and personal care products (PPCPs), metronidazole (MNZ) and bisphenol A (BPA) normally presented in sewage effluent and surface water. The nitrogen-doped multi-walled carbon nanotube (NCNT) membrane was prepared and utilized as a peroxymonosulphate (PMS) catalyst to degrade MNZ and BPA. Within the NCNT membrane/PMS catalytic system, MNZ and BPA can be efficiently degraded, while different catalytic degradation mechanism exists related with their structure, adsorption properties and even PMS dosage. The optimal conditions for the degradation of MNZ and BPA were investigated. Quenching tests and electron paramagnetic resonance examination demonstrated that •OH radicals and 1O2 played roles in MNZ degradation, while surface-bound radicals and 1O2 dominated BPA degradation within the NCNT membrane catalytic PMS system. Electrochemical tests proved that an electron-transfer process between NCNT membrane and PMS during MNZ degradation, and the electron-transfer process was further verified with the degradation experiment in the binary-solute system (BPA and MNZ). PMS dosage had little influence on the degradation mechanism of MNZ and BPA.

Enhancement of the diesel fuel characteristics by using nitrogen-doped multi-walled carbon nanotube additives

Nanoparticles are considered promising additives to diesel fuel and significantly affect engine performance and exhaust emission levels. Nitrogen-doped multiwalled carbon nanotubes (N-doped MWCNTs) are one of the effective catalysts owing to their promising properties, which have recently increased their usability in many applications. These features make them good candidates as a catalyst to enhance diesel engine performance. The effects of adding N-doped MWCNTs into diesel fuel for a single-cylinder CI engine working at a rated speed of 1500 rpm and different loads were studied. Four doses of N-doped MWCNTs were added to diesel fuel using ultrasonic dispersion. Multiwalled carbon nanotubes (MWCNTs) were used as reference additives to compare their results with those obtained by N-doped MWCNTs. The results illustrated that most blends of N-doped MWCNTs were preferred in combustion behavior, engine performance, and exhaust emission analysis with respect to diesel and MWCNTs blends. Thus, there was a significant increase in the in-cylinder pressure and heat release rate compared to pure diesel. Also, the brake thermal efficiency was increased, and the brake specific fuel consumption was reduced compared to diesel. For all N-doped MWCNTs blends, there were remarkable reductions in NOx, soot, and CO formations, and it is mainly preferred over MWCNTs/diesel blends in exhaust emissions reduction.

Enhancement of the waste cooking oil biodiesel usability in the diesel engine by using n-decanol, nitrogen-doped, and amino-functionalized multi-walled carbon nanotube

The depletion of fossil fuels makes it necessary to find alternative fuels to diesel. Waste cooking oil biodiesel (WCO) has interesting properties and could replace diesel fuel. However, WCO biodiesel increased nitrogen oxides (NOx) at high loads compared to diesel. Thus, some fuel additives, such as functionalized MWCNTs and decanol, can be used as they are considered promising diesel fuel additives and significantly affect engine performance and exhaust emission levels. The functionalized MWCNTs, mainly Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) and amino-functionalized multi-walled carbon nanotubes (NH2-MWCNTs), are excellent catalysts that have been used recently in many applications and have good properties that can be used in diesel engines. Thus, in the current research, an experimental investigation was performed by a CI engine working at a constant speed and different loads to study the effects of a WCO biodiesel-decanol blend on engine performance and exhaust gas emissions. First, n-Decanol was added to WCO biodiesel to enhance the biodiesel combustion properties (80 % biodiesel + 20 % n-decanol by volume). Then, two doses (50 and 75 ppm) for each type of functionalized MWCNTs were inserted into the WCO biodiesel-decanol blend to enhance the engine performance. The results illustrated that WCO biodiesel-decanol blend was close to diesel in engine performance, where the NOx and soot were reduced by about 8 % and 20 % for WCO biodiesel-decanol blends compared to diesel. Also, the addition of functionalized MWCNTs led to a significant reduction in the NOx, CO, and soot levels by around 35 %, 61 %, and 44 % compared to diesel. BTE was diminished by almost 10 %, and BSFC was raised by 15 % for WCO biodiesel-decanol blend compared to diesel. At the same time, these negative impacts have been alleviated with inserting functionalized MWCNTs into the WCO biodiesel-decanol combination. At 75 % load, WCO biodiesel-decanol blends raised the in-cylinder pressure and advanced the start of combustion by a three-crank angle degree. Therefore, it can be implied that WCODNH75 is a recommended combination considering combustion and emission characteristics.

Hydrothermal synthesis of CuO@MnO2 on nitrogen-doped multiwalled carbon nanotube composite electrodes for supercapacitor applications

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been used to fabricate nanostructured materials for various energy devices, such as supercapacitors, sensors, batteries, and electrocatalysts. Nitrogen-doped carbon-based electrodes have been widely used to improve supercapacitor applications via various chemical approaches. Based on previous studies, CuO@MnO2 and CuO@MnO2/N-MWCNT composites were synthesized using a sonication-supported hydrothermal reaction process to evaluate their supercapacitor properties. The structural and morphological properties of the synthesized composite materials were characterized via Raman spectroscopy, XRD, SEM, and SEM–EDX, and the morphological properties of the composite materials were confirmed by the nanostructured composite at the nanometer scale. The CuO@MnO2 and CuO@MnO2/N-MWCNT composite electrodes were fabricated in a three-electrode configuration, and electrochemical analysis was performed via CV, GCD, and EIS. The composite electrodes exhibited the specific capacitance of ~ 184 F g−1 at 0.5 A g−1 in the presence of a 5 M KOH electrolyte for the three-electrode supercapacitor application. Furthermore, it exhibited significantly improved specific capacitances and excellent cycling stability up to 5000 GCD cycles, with a 98.5% capacity retention.

Highly Sensitive Hybrid Nanostructures for Dimethyl Methyl Phosphonate Detection.

Nanostructured materials synthesized by the hydrothermal and thermal reduction process were tested to detect the dimethyl methylphosphonate (DMMP) as a simulant for chemical warfare agents. Manganese oxide nitrogen-doped graphene oxide with polypyrrole (MnO2@NGO/PPy) exhibited the sensitivity of 51 Hz for 25 ppm of DMMP and showed the selectivity of 1.26 Hz/ppm. Nitrogen-doped multi-walled carbon nanotube (N-MWCNT) demonstrated good linearity with a correlation coefficient of 0.997. A comparison between a surface acoustic wave and quartz crystal microbalance sensor exhibited more than 100-times higher sensitivity of SAW sensor than QCM sensor.

Hydrogel Cryo‐Microtomy Continuously Making Soft Electronic Devices

AbstractStandard fabrication of soft electronic devices with both high controllability and yield is highly desirable but remains a challenge due to the modulus mismatch of component materials through a one‐step process. Here, by mimicking the freeze‐section process of multicomponent biological tissues containing low‐modulus muscles and high‐modulus bones, for the first time, a hydrogel cryo‐microtomy method to continuously making soft electronic devices based on a sol‐solid‐gel transition mechanism is presented. Polyvinyl alcohol (PVA) electrolyte and aligned nitrogen‐doped multi‐walled carbon nanotube (N‐MWCNT) array electrode are demonstrated as low‐ and high‐modulus components to fabricate soft supercapacitors with high performances. Stable interfaces form between frozen PVA electrolyte and N‐MWCNT electrodes with matched moduli at subzero temperature and are well maintained during cryo‐microtomy process. The resulting soft supercapacitors realize controllable patterns, tunable thicknesses from 0.5 to 600 μm, high yields such as 20 devices per minute even at lab scale, and high reproducibility with over 75% devices in 15% performance fluctuation. This cryo‐microtomy method is further generalized to fabricate other soft devices such as sensors with high sensing properties.

Growth of nitrogen-doped carbon nanotubes using Ni/La2Zr2O7 as catalyst: Electrochemical and magnetic studies

The combination of different nanomaterials to achieve particular applications is a topic with an increasing impact on diverse areas of nanotechnology. In particular, the material of La2Zr2O7 (LZO) and NiO could be employed as a source of catalyst for carbon nanotube fabrication. In this work, the Ni/LZO material was utilized to fabricate nitrogen-doped multiwalled carbon nanotube (N-MWCNTs). The N-MWCNTs were produced at 850 °C by the aerosol assisted catalytic chemical vapor deposition method using benzylamine as the sole carbon and nitrogen precursor. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry. Before the synthesis of N-MWCNTs, NiO was reduced to Ni to act as a catalyst and LZO as support. N-MWCNTs exhibited the typical feature bamboo shape morphology with small nanoparticles anchored inside and on its surface. The electrochemical studies show interesting results about charge capacity and a hydroquinone/quinone redox process of oxygen functionalities. The magnetic properties of N-MWCNTs showed a ferromagnetic behavior with a saturated magnetization of 43 emu/g at 0.2 T.

Investigation of the surface properties of different highly aligned N-MWCNT carpets

We investigated the physicochemical surface properties of different highly aligned nitrogen-doped multi-walled carbon nanotube (N-MWCNT) carpets, synthesized using toluene/pyrazine, toluene/benzylamine and acetonitrile via a sublimation-based chemical vapor deposition (SCVD) method at 760 °C. The surfaces of the N-MWCNT carpets synthesized using toluene/pyrazine and toluene/benzylamine were very hydrophobic. In contrast, we observed a complete wetting of the N-MWCNT carpets synthesized using acetonitrile. The difference in the wetting behavior of these N-MWCNT carpets is the main focus in this study and was not investigated before. Here, we show that not only the presence or concentration of nitrogen inside the carbon lattice, but especially it's kind of incorporation have an important influence on the surface polarity.

Development of an Electrochemical Sensor for Determination of Ligustrazine Based on Nitrogen-Doped Multi-Walled Carbon Nanotube

Development of an Electrochemical Sensor for Determination of Ligustrazine Based on Nitrogen-Doped Multi-Walled Carbon Nanotube

Straightforward synthesis of nitrogen-doped carbon nanotubes as highly active bifunctional electrocatalysts for full water splitting

The success of intermittent renewable energy systems relies on the development of energy storage technologies. Particularly, active and stable water splitting electrocatalysts operating in the same electrolyte are required to enhance the overall efficiency and reduce the costs. Here we report a precise and facile synthesis method to control nitrogen active sites for producing nitrogen doped multi-walled carbon nanotube (NMWNT) with high activity toward both oxygen and hydrogen evolution reactions (OER and HER). The NMWNT shows an extraordinary OER activity, superior to the most active non-metal based OER electrocatalysts. For OER, the NMWNT requires overpotentials of only 320 and 360mV to deliver current densities of 10 and 50mAcm−2 in 1.0M NaOH, respectively. This metal-free electrocatalyst also exhibits a proper performance toward HER with a moderate overpotential of 340mV to achieve a current density of 10mAcm−2 in 0.1M NaOH. This catalyst also shows high stability after long-time water oxidation without notable changes in the structure of the material. It is revealed that the electron-withdrawing pyridinic N moieties in the NMWNTs could serve as the active sites for OER and HER. Our findings open up new avenues for the development of metal-free electrocatalysts for full water splitting.

Flexible rewritable organic memory devices using nitrogen-doped CNTs/PEDOT:PSS composites

Nonvolatile rewritable organic memory devices based on poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and nitrogen doped multi-walled carbon nanotube (NCNT) nanocomposites were fabricated on glass and PET substrates.Organic memory devices with bistable resistive switching were obtained using very low NCTN concentration (∼0.002 wt%) in the polymeric matrix. The memory devices exhibited a good ON/OFF ratio of approximately three orders of magnitude, a good retention time of 104 s under operating voltages ≤ |4V| and a few hundredths of write-read-erase-read cycles. The bistable resistive switching is mainly attributed to the creation of oxygen vacancies. These defects are introduced into the thin native Al oxide (AlOx) layer on the bottom electrode during the first voltage sweep. The well-dispersed NCNTs immersed in PEDOT:PSS play a key role as conductive channels for the electronic transport, hindering the electron trapping at the AlOx-polymer interface and inducing a soft dielectric breakdown of the AlOx layer. These PEDOT:PSS + NCNTs memory devices are to easy to apply in flexible low-cost technology and provide the possibility of large-scale integration.

Enhanced oxygen reduction reaction activity of nitrogen-doped graphene/multi-walled carbon nanotube catalysts in alkaline media

In this work, the electroreduction of oxygen on nitrogen-doped graphene and multi-walled carbon nanotube (MWCNT) composite catalysts is investigated. Acid-treated MWCNTs and graphite oxide were doped using biuret, carbohydrazide and semicarbazide hydrochloride as the nitrogen precursors. The reactants were mixed with carbon nanomaterials and pyrolysed in an inert atmosphere at 800 °C. Scanning electron microscopy was used to characterise the surface morphology of catalysts and X-ray photoelectron spectroscopy (XPS) was used to determine the surface content of the catalysts. XPS revealed different contents of nitrogen gained by using different nitrogen precursors, which were tied to electrochemical activities observed in this work by using the rotating disk electrode (RDE) method. The catalysts revealed high oxygen reduction reaction (ORR) activity even at low loadings and excellent stability over 1000 potential cycles. This indicates their applicability as cathode materials in alkaline anion exchange membrane fuel cells.

Pine-tree-like morphologies of nitrogen-doped carbon nanotubes: Electron field emission enhancement

Abstract

Undoped, nitrogen-doped and boron-doped multiwalled carbon nanotube/poly(vinyl alcohol) composite as active layer in simple hydrostatic pressure sensors

We report on hydrostatic pressure sensors prepared using 10 % w/w multiwalled carbon nanotube (MWCNT)/poly(vinyl alcohol) composites. Three types of carbon nanotubes were used in the composites: undoped MWCNTs, nitrogen-doped MWCNTs and boron-doped MWCNTs (B-MWCNTs). The sensor response was tested using an alternating current input, measuring the capacitance and conductance outputs. The sensors based on the three composites show a linear capacitance and conductance sensitivity pressure dependence in the range 50–120 kPa, but a higher sensitivity to pressure dependence above this interval. The highest angular coefficient of the sensitivity, which reached 0.092 kPa−1, was observed for the capacitance sensitivity of the B-MWCNT based composite.

Electrocatalysis of oxygen reduction on nitrogen-containing multi-walled carbon nanotube modified glassy carbon electrodes

The electrochemical reduction of oxygen was studied on nitrogen-doped multi-walled carbon nanotube (NCNT) modified glassy carbon (GC) electrodes employing the rotating disk electrode (RDE) method. Nitrogen doping was achieved by simple pyrolysis of the carbon nanotube material in the presence of urea. The surface morphology and composition of the NCNT samples were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed a rather uniform distribution of NCNTs on the GC electrode substrate. The XPS analysis showed a successful doping of carbon nanotubes with nitrogen species. The RDE results revealed that in alkaline solution the N-doped nanotube materials showed a remarkable electrocatalytic activity towards oxygen reduction. At low overpotentials the reduction of oxygen followed a two-electron pathway on undoped carbon nanotube modified GC electrodes, whereas on NCNT/GC electrodes a four-electron pathway of O2 reduction predominated. The results obtained are significant for the development of nitrogen-doped carbon-based cathodes for alkaline membrane fuel cells.

Magnetoresistance and Phase Breaking Behavior of a Nitrogen Doped Multi-Walled Carbon Nanotube

The low temperature magnetoresistance (MR) has been studied in a nitrogen doped multi-walled carbon nanotube (CNxMWNT) with a four terminal resistance measurement. The phase coherent properties of electron transport in the CNxMWNT have been deduced from results of quantum-transport analysis. A zero-field peak of the weak localization can be observed in the low-temperature MR, however, there exhibits a clear boundary between the phase braking processes around 10 K. The phase coherence has been analyzed and the quasi-one-dimensional properties have been discussed in weakly localized metallic transport with a low temperature MR in terms of quantum interference.

Fabrication of Nitrogen-doped Multi-walled Carbon Nanotube and Their Field Effect Transistor Properties

Fabrication of Nitrogen-doped Multi-walled Carbon Nanotube and Their Field Effect Transistor Properties