The large-scale practical application of fuel cells will be difficult to realize if the expensive platinum-based electrocatalysts for oxygen reduction reactions (ORRs) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, we report that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells. In air-saturated 0.1 molar potassium hydroxide, we observed a steady-state output potential of –80 millivolts and a current density of 4.1 milliamps per square centimeter at –0.22 volts, compared with –85 millivolts and 1.1 milliamps per square centimeter at –0.20 volts for a platinum-carbon electrode. The incorporation of electron-accepting nitrogen atoms in the conjugated nanotube carbon plane appears to impart a relatively high positive charge density on adjacent carbon atoms. This effect, coupled with aligning the NCNTs, provides a four-electron pathway for the ORR on VA-NCNTs with a superb performance.

http://science.sciencemag.org/content/sci/323/5915/760.full.pdf

Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction.

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Nitrogen-doped graphene (N-graphene) was synthesized by chemical vapor deposition of methane in the presence of ammonia. The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells. To the best of our knowledge, this is the first report on the use of graphene and its derivatives as metal-free catalysts for oxygen reduction. The important role of N-doping to oxygen reduction reaction (ORR) can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, even new catalytic materials for applications beyond fuel cells.

/pdf/nitrogen-doped-graphene-as-efficient-metal-free-2c5sl934bm.pdf

Nitrogen-Doped Graphene as Efficient Metal-Free Electrocatalyst for Oxygen Reduction in Fuel Cells

Zinc oxide is a unique material that exhibits semiconducting and piezoelectric dual properties. Using a solid–vapour phase thermal sublimation technique, nanocombs, nanorings, nanohelixes/nanosprings, nanobelts, nanowires and nanocages of ZnO have been synthesized under specific growth conditions. These unique nanostructures unambiguously demonstrate that ZnO probably has the richest family of nanostructures among all materials, both in structures and in properties. The nanostructures could have novel applications in optoelectronics, sensors, transducers and biomedical sciences. This article reviews the various nanostructures of ZnO grown by the solid–vapour phase technique and their corresponding growth mechanisms. The application of ZnO nanobelts as nanosensors, nanocantilevers, field effect transistors and nanoresonators is demonstrated.

/pdf/zinc-oxide-nanostructures-growth-properties-and-applications-8d5hcz3lg8.pdf

Zinc oxide nanostructures: growth, properties and applications

Recent Advances in Bulk Heterojunction Polymer Solar Cells

A novel approach for chemical modification of carbon nanotubes was developed, which involved radio frequency glow-discharge plasma activation, followed by chemical reactions characteristic of the plasma-generated functional groups. For instance, amino-dextran chains have been immobilized onto acetaldehyde-plasma-treated aligned carbon nanotubes through the formation of Schiff-base linkages, which were further stabilized by reduction with sodium cyanoborohydride. Using the same reaction, we have also chemically grafted periodate-oxidized dextran chains pre-labeled with fluorescein onto ethylenediamine-plasma-treated carbon nanotubes. The fluorescein labeling allows the surface immobilization reaction to be followed simply by photoluminescence measurements. The resulting polysaccharide-grafted carbon nanotubes are very hydrophilic, as demonstrated by X-ray photoelectron spectroscopic and air/water contact angle measurements.

Plasma Activation of Carbon Nanotubes for Chemical Modification

The use of multiwalled aligned carbon nanotubes provides a novel electrode platform for inherently conducting polymer based biosensors. The example used here to highlight the usefulness of such a platform is the polypyrrole based glucose oxidase system for detection of glucose. The use of these three dimensional electrodes offers advantages in that large accessible enzyme loadings can be obtained within an ultrathin layer. It has also been found that the detection of H2O2 at these new electrode structures containing iron loaded nanotube tips can be achieved at low anodic potentials. The result is a sensitive and selective glucose sensor.

/pdf/biosensors-based-on-aligned-carbon-nanotubes-coated-with-3fnxq8k7rl.pdf

Biosensors Based on Aligned Carbon Nanotubes Coated with Inherently Conducting Polymers

One-step roll-to-roll air processed high efficiency perovskite solar cells

Aligned Coaxial Nanowires of Carbon Nanotubes Sheathed with Conducting Polymers

Aligned Coaxial Nanowires of Carbon Nanotubes Sheathed with Conducting Polymers M.G. is grateful for a joint scholarship from Wollongong University and CSIRO; S.H. and L.D. thank the support from the Department of Industry, Science, and Technology (DIST), Australia; R.P.G. and Z.L.W. thank the support of US NSF grants (DMR-9733160), and the NSF of China.

Mei Gao

Papers

Plasma Activation of Carbon Nanotubes for Chemical Modification

Biosensors Based on Aligned Carbon Nanotubes Coated with Inherently Conducting Polymers

One-step roll-to-roll air processed high efficiency perovskite solar cells

Aligned Coaxial Nanowires of Carbon Nanotubes Sheathed with Conducting Polymers