Raman spectroscopy is among the primary techniques for the characterisation of graphene materials, as it provides insights into the quality of measured graphenes including their structure and conductivity as well as the presence of dopants. However, our ability to draw conclusions based on such spectra is limited by a lack of understanding regarding the origins of the peaks. Consequently, traditional characterisation techniques, which estimate the quality of the graphene material using the intensity ratio between the D and the G peaks, are unreliable for both GO and rGO. Herein we reanalyse the Raman spectra of graphenes and show that traditional methods rely upon an apparent G peak which is in fact a superposition of the G and D’ peaks. We use this understanding to develop a new Raman characterisation method for graphenes that considers the D’ peak by using its overtone the 2D’. We demonstrate the superiority and consistency of this method for calculating the oxygen content of graphenes, and use the relationship between the D’ peak and graphene quality to define three regimes. This has important implications for purification techniques because, once GO is reduced beyond a critical threshold, further reduction offers limited gain in conductivity.

A facile synthesis of nitrogen-doped graphene with high atomic percentages of pyridinic N and graphitic N is reported. The synthesized materials show superior capacitance performance and metal-free bifunctional electrocatalysis of ORR and OER.

A multifunctional nano-heterostructured electrocatalyst of transition metal/metal oxide (nickel/nickel oxide) embedded on nitrogen-doped graphene is reported.

A three-dimensional nanostructured nitrogen-doped graphene/carbon nanotube composite has been synthesized via a thermal annealing process, using the high surface attachment properties of uric acid (solid nitrogen precursor) with graphene oxide and oxidized multiwalled carbon nanotube. In the synthesis procedures, the attachment of uric acid to graphene oxide surfaces and the oxidized multiwalled carbon nanotubes via hydrogen bonding and electrostatic forces in the solution leads to a lamellar nanostructure during thermal annealing by the proper insertion of carbon nanotubes in graphene layers with nitrogen doping. The resultant composite has good atomic percentage of N (11.2 at. %) and shows superior electrochemical energy storage and conversion properties compared with nitrogen-doped graphene only and physically mixed nitrogen-doped graphene and nitrogen-doped carbon nanotube samples. The composite exhibits high gravimetric and volumetric capacitance (324 F g −1 at a current density of 1 A g −1 ) as electrode in solid-state supercapacitors, superior capacitive deionization (440 F g −1 at a current density of 1 A g −1 ) in 1 M sodium chloride solution, and as high-performance anode in lithium-ion batteries (1150 mAh g −1 at 0.1 A g −1 ) with longterm cycling stability. In addition, the composite demonstrates efficient metal-free bifunctional electrocatalysis toward the oxygen reduction and evolution reactions, comparable with the commercial electrocatalysts.

Though feasible for CO methanations in gas-cleaning applications ([CO] < 1%), carbon-nanotube-supported catalysts have never been implemented for the production of synthetic natural gas.

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Reaching beyond the horizon of Li-ion batteries is a formidable challenge, as energy storage will be more important in the future than at any time in the past. This requires the exploration of new chemistry, especially electrochemistry, and new materials. Among the available choices, lithium-sulfur (Li-S) batteries are attractive because of their low cost, environmental friendliness, and superior energy density (theoretically 2500 Wh/kg). Despite their great promise, the commercialization of Li-S batteries is hindered by low cycle stability, fast capacity fading, and low efficiency; these problems are induced by the polysulfide shuttle reaction that occurs through dissolution into electrolyte, the loss of active sulfur material, and the electronically insulating nature of sulfur. To tackle these issues, we synthesized a novel nanostructured composite consisting of Graphene and Carbon Nanotubes (CNT), each pre-doped with Nitrogen (N), as a host material for sulfur impregnation. In this unique composite, not only do CNTs act as the spacer units between the graphene sheets, avoiding losses in performance through restacking and agglomerate formation, but they also contribute to the material activity, overall surface area/nanoporosity, and the composite conductivity over the effective doping method strategy. In the next step, a new method of sulfur impregnating into the composite structure was implemented to effectively confine the sulfur into graphitic clusters, voids, and defects in N-doped graphene–CNT composite. The carbon nanostructured framework serves not only as a conductive layer for encapsulating sulfur and polysulfides without direct contact with electrolyte, but also as a nano-electrochemical reaction chamber. Cyclic voltammetry (CV) of the sulfur-impregnated N-doped graphene-CNT in high-dielectric solvent behaved similar to low-dielectric solvent, indicating that the material was not solvent dependent. Strong interaction between N-doped composite and sulfur or polysulfides enabled us to demonstrate Li–S cells with a high reversible capacity (1005-1592 mAh/g), outstanding cycling stability, and great Coulombic efficiency (~97.5%). The results indicate that the sulfur-impregnated N-doped graphene-CNT nanocomposite is a very promising cathode material for high-performance lithium–sulfur batteries. Figure 1