Nitrogen doping has been an effective way to tailor the properties of graphene and render its potential use for various applications. Three common bonding configurations are normally obtained when doping nitrogen into the graphene: pyridinic N, pyrrolic N, and graphitic N. This paper reviews nitrogen-doped graphene, including various synthesis methods to introduce N doping and various characterization techniques for the examination of various N bonding configurations. Potential applications of N-graphene are also reviewed on the basis of experimental and theoretical studies.

Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400°C (designated as LT-LiCoO 2 ) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO 2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800°C (designated as HT-LiCoO 2 ) for the oxygen evolution reaction. Although LT-LiCoO 2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li 1 À x CoO 2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LTLi 0,5 CoO 2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co 4 O 4 cubane subunits and a pinning of the Co 3 þ /4 þ :3d energy with the top of the O 2 À :2p band.

Zinc oxide (ZnO) is an adaptable material that has distinctive properties, such as high-sensitivity, large specific area, non-toxicity, good compatibility and a high isoelectric point, which favours it to be considered with a few exceptions. It is the most desirable group of nanostructure as far as both structure and properties. The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery, solar cells, photocatalysis, biosensors, biomedical and biological applications in the form of bulk crystal, thin film and pellets. The nanosized materials exhibit higher dissolution rates as well as higher solubility when compared to the bulk materials. This review significantly focused on the current improvement in ZnO-based nanomaterials/composites/doped materials for the application in the field of energy storage and conversion devices and biological applications. Special deliberation has been paid on supercapacitors, Li-ion batteries, dye-sensitized solar cells, photocatalysis, biosensors, biomedical and biological applications. Finally, the benefits of ZnO-based materials for the utilizations in the field of energy and biological sciences are moreover consistently analysed.

Electrochemical energy storage has emerged as one of the principal topics of present‐day research to deal with the high energy demands of modern society. Accordingly, besides fuel cells and battery technologies, interesting and challenging results have been observed in the recent past, during the materialization of “supercapacitors” or “ultracapacitors”, which have provoked a sharp increase in research inclination to revisit this aspect of renewable and sustainable energy storage. Supercapacitor performances are largely dependent on electrode materials, the nature of the electrolyte used, and the range of voltage windows employed. Carbon‐based electrode materials have tunable properties such as electrical conductivity, extensive surface area, and faster electron transfer kinetics with low fabrication costs. But their specific capacitances are found to be too low for commercialization. Ruthenium dioxide (RuO2), owing to its high theoretical specific capacitance value (1400–2000 F g−1), has been extensively recognized as a favorable material for supercapacitor devices, but high production cost and agglomeration effects stand as high barriers preventing marketable usage. Consequently, RuO2‐based nanocomposites have been widely studied to optimize the material cost, with simultaneous improvement in the electrochemical performances. This Review describes comprehensively the recent progress in terms of the fabrication and design, electrochemical performance, and achievements of RuO2 and its nanocomposites as electrode materials for supercapacitors, which will be beneficial for further research designing high‐performance supercapacitor devices.

A three-dimensional interconnected graphene monolith was used as an electrode support for pulsed electrochemical deposition of platinum (Pt) nanoparticles. Pt nanoparticles with well-defined morphology and small size can be obtained by controlling electrodeposition potential and time. Electrochemical characterization was carried out to examine the electrocatalytic activity of this monolithic electrode towards methanol oxidation in acidic media. The results show that the carbon material surface and structure have a strong influence on the Pt particle size and morphology. Compared with the three-dimensional scaffold of carbon fibers, the three-dimensional graphene when used as a free-standing electrode support resulted in much improved catalytic activity for methanol oxidation in fuel cells due to its three-dimensionally interconnected seamless porous structure, high surface area and high conductivity.