Activity Of Nitrogen-doped Carbon Nanotubes Research Articles

Metal-free catalysis based on nitrogen-doped carbon nanomaterials: a photoelectron spectroscopy point of view.

In this review, we discuss the use of doped carbon nanomaterials in catalysis, a subject that is currently intensively studied. The availability of carbon nanotubes since the 1990’s and of graphene ten years later prompted the development of novel nanotechnologies. We review this topic linking fundamental surface science to the field of catalysis giving a timely picture of the state of the art. The main scientific questions that material scientists have addressed in the last decades are described, in particular the enduring debate on the role of the different nitrogen functionalities in the catalytic activity of nitrogen-doped carbon nanotubes and graphene.

Effects of catalyst aging on the growth morphology and oxygen reduction activity of nitrogen-doped carbon nanotubes

This work reports some effects that aging time of the used catalyst (Fe/MgO) has on the produced N-doped carbon nanotubes. In particular, the catalyst age affects the synthesized nanomaterials with respect to morphology, surface composition and electrocatalytic behavior towards the electrochemical oxygen reduction.

The Effect of Metal Catalyst on the Electrocatalytic Activity of Nitrogen-Doped Carbon Nanotubes

Nitrogen-doped and undoped carbon nanotubes (CNTs) were synthesized from ferrocene, nickelocene, and cobaltocene metal catalysts. Electrochemical testing for an oxygen reduction reaction (ORR) showed that nitrogen-doped CNTs synthesized from ferrocene had improved catalytic activity while nanotubes synthesized from nickelocene and cobaltocene, doped with a comparable amount of nitrogen and having similar stacked-cups structure as nitrogen doped CNTs from ferrocene, had a performance only slightly better than that of undoped CNTs. Ferrocene-based nitrogen-doped CNTs also demonstrated similar long-term stability and higher CO tolerance compared to Pt/C catalyst. Detailed ORR mechanisms were also studied and carbon nanomaterials showed different ORR processes as a result of the metal catalyst utilized in the chemical synthesis. Nitrogen-doped and undoped CNTs synthesized from nickelocene show a preferential 4-electron process as compared to materials synthesized from ferrocene and cobaltocene. We believe that the metal used in the growth process regulates the mechanism of oxygen reduction and can be used to develop improved nitrogen-doped carbon nanomaterials as nonprecious-metal catalysts for fuel cells.

Electrocatalytic Activity of Nitrogen-Doped Carbon Nanotubes Decorated with Gold Nanoparticles

Films consisting of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were fabricated by means of chemical vapor deposition technique and decorated with gold nanoparticles (AuNPs) of different diameters (5, 14, and 35 nm). The electrochemical responses of AuNPs-modified N-MWCNTs films, further denoted as N-MWCNTs/AuNPs, were investigated towards ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− redox system in aqueous potassium chloride solutions. The findings reveal strong dependence of film’s electrochemical response on diameter of AuNPs. Namely, the electrochemical response expressed in terms of peak current density enhances and the kinetic of electron transfer tends to be faster with the increase of diameter of AuNPs. Furthermore, an obvious improvement of film’s detecting capability towards [Fe(CN)6]3−/4− occurs with the increase of diameter of AuNPs. The findings demonstrate that by varying the size of AuNPs attached onto N-MWCNTs/AuNPs, the film’s electrochemical response and detection capability can be tuned.

Revealing the enhanced catalytic activity of nitrogen-doped carbon nanotubes for oxidative dehydrogenation of propane

Bulk nitrogen doping can efficiently improve the catalytic performance of carbon nanotubes (CNT) in oxidative dehydrogenation of propane (ODH). The graphitic nitrogen plays a determining role in enhancing their activity by speeding up the activation of oxygen and decreasing the overall activation energy of the reaction.

Activity, Selectivity, and Anion-Exchange Membrane Fuel Cell Performance of Virtually Metal-Free Nitrogen-Doped Carbon Nanotube Electrodes for Oxygen Reduction Reaction

Virtually metal-free, aligned nitrogen-doped carbon nanotubes (N-CNTs) are prepared by an alumina template technique and characterized using XRD, Raman spectroscopy, SEM, and XPS. Highly uniform and aligned nanotubes are identified from SEM. The surface nitrogen concentration in the N-CNTs is estimated to be ∼8.0 at.%. Electrocatalytic oxygen reduction reaction (ORR) activity in alkali media is investigated by rotating disk electrode (RDE) voltammetry and compared with commercial Pt/C (E-TEK). RDE measurements indicated the comparable ORR activity of nitrogen-doped carbon nanotubes with Pt/C. Kinetic analysis reveals that the ORR on nitrogen-doped carbon nanotubes follows the four-electron pathway leading to water. Moreover, during the ORR, nitrogen-doped carbon nanotubes exhibited substantially higher ethanol tolerance than Pt/C. A maximum power density of 37 and 62 mW/cm2 is observed with N-CNT and Pt/C cathodes, respectively, under anion-exchange membrane fuel cell conditions. Durability measurements performed under fuel cell operating conditions for 30 h indicate the good stability of the catalysts.

High reaction activity of nitrogen-doped carbon nanotubes toward the electrooxidation of nitric oxide

Carbon nanotubes doped with N (NCNTs) enable 1.5 times faster electron-transfer kinetics for the oxidation of NO compared to pristine carbon nanotubes (CNTs), which may be due to the low adsorption energy for a NO on pyridinic NCNT(5,5) allowing NO to lose electrons readily and facilitate the following oxidation to nitrate.

Electroreduction of oxygen on nitrogen-doped carbon nanotube modified glassy carbon electrodes in acid and alkaline solutions

The electrochemical reduction of oxygen was studied on vertically aligned N-doped carbon nanotube (NCNT) modified glassy carbon (GC) electrodes in 0.5 M H 2SO 4 and in 0.1 M KOH solutions using the rotating disk electrode (RDE) method. For comparison purposes, the oxygen reduction behaviour of undoped carbon nanotube material has been also investigated. Both catalysts were prepared by chemical vapour deposition (CVD). Acetonitrile was used as the precursor in the synthesis of the NCNT material. The surface morphology and chemical composition of the NCNT catalysts were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The NCNT/GC electrodes showed a significant enhancement of the kinetics of oxygen reduction in both solutions. In acid media the half-wave potential of O 2 reduction on NCNT-modified electrodes shifted by 250 mV to more positive potentials as compared to that of vertically aligned undoped CNT materials. The factors that determine the high electrocatalytic activity of nitrogen-doped carbon nanotubes towards oxygen reduction are discussed.

Nitrogen-Doped Carbon Nanotubes: High Electrocatalytic Activity toward the Oxidation of Hydrogen Peroxide and Its Application for Biosensing

This study compares the electrocatalytic activity of nitrogen-doped carbon nanotubes (NCNTs) with multiwalled carbon nanotubes (MWCNTs). Results indicate that NCNTs possess a marked electrocatalytic activity toward oxygen reduction reaction (ORR) by an efficient four-electron process in the alkaline condition, while the process of MWCNTs is through a two-electron pathway. Meanwhile, NCNTs show a very attractive electrochemical performance for the redox reaction of hydrogen peroxide (H2O2) and could be employed as a H2O2 sensor at a low potential of +0.3 V. The sensitivity of the NCNT-based biosensor reaches 24.5 microA/mM, more than 87 times that of the MWCNT-based one. Moreover, NCNTs exhibit striking analytical stability and reproducibility, which enables a reliable and sensitive determination of glucose by monitoring H2O2 produced by an enzymatic reaction between glucose oxidase/glucose or choline oxidase/choline at +0.3 V without the help of the electron mediator. The NCNT-based glucose biosensor has a linear range from 2 to 140 microM with an extremely high sensitivity of 14.9 microA/mM, and the detection limit is estimated to be 1.2 microM at a signal-to-noise ratio of 3. The results indicate that the NCNTs are good nanostructured materials for potential application in biosensors.