A Simple Gas–Solid Route To Functionalize Ordered Carbon

The reaction of nitric oxide (NO) and carbonaceous materials generates nitrogen functionalities on and in graphitic carbons and oxidizes some of the carbon. Here, we have exploited these phenomena to provide a novel route to surface-functionalized multiwalled carbon nanotubes (MWCNTs). We investigated the impacts of NO on the physical and chemical properties of industrially synthesized multiwalled carbon nanotubes to find a facile treatment that increased the specific surface area (<i>S</i>_BET) of the MWCNTs by ∼20%, with only a minimal effect on their degree of graphitization. The technique caused less material loss (∼12 wt %) than traditional gas-based activation techniques and grafted some nitrogen functional groups (1.1 at. %) on the MWCNTs. Moreover, we found that Ni nanoparticles deposited on NO-treated MWCNTs had a crystallite size of <i>d</i>_Ni = 13.1 nm, similar to those deposited on acid-treated MWCNTs (<i>d</i>_Ni = 14.2 nm), and clearly much smaller than those deposited under the same conditions on untreated MWCNTs (<i>d</i>_Ni = 18.3 nm)

Patterned Polymer Coatings Increase the Efficiency of Dew Harvesting

Micropatterned polymer surfaces, possessing both topographical and chemical characteristics, were prepared on three-dimensional copper tubes and used to capture atmospheric water. The micropatterns mimic the structure on the back of a desert beetle that condenses water from the air in a very dry environment. The patterned coatings were prepared by the dewetting of thin films of poly-4-vinylpyridine (P4VP) on top of polystyrene films (PS) films, upon solvent annealing, and consist of raised hydrophilic bumps on a hydrophobic background. The size and density distribution of the hydrophilic bumps could be tuned widely by adjusting the initial thickness of the P4VP films: the diameter of the produced bumps and their height could be varied by almost 2 orders of magnitude (1–80 μm and 40–9000 nm, respectively), and their distribution density could be varied by 5 orders of magnitude. Under low subcooling conditions (3 °C), the highest rate of water condensation was measured on the largest (80 μm diameter) hydrophilic bumps and was found to be 57% higher than that on flat hydrophobic films. These subcooling conditions are achieved spontaneously in dew formation, by passive radiative cooling of a surface exposed to the night sky. In effect, the pattern would result in a larger number of dewy nights than a flat hydrophobic surface and therefore increases water capture efficiency. Our approach is suited to fabrication on a large scale, to enable the use of the patterned coatings for water collection with no external input of energy

Self-Assembled N/S Codoped Flexible Graphene Paper for High Performance Energy Storage and Oxygen Reduction Reaction

A novel flexible three-dimensional (3D) architecture of nitrogen and sulfur codoped graphene has been successfully synthesized via thermal treatment of a liquid crystalline graphene oxide–doping agent composition, followed by a soft self-assembly approach. The high temperature process turns the layer-by-layer assembly into a high surface area macro- and nanoporous free-standing material with different atomic configurations of graphene. The interconnected 3D network exhibits excellent charge capacitive performance of 305 F g^–1 (at 100 mV s^–1), an unprecedented volumetric capacitance of 188 F cm^–3 (at 1 A g^–1), and outstanding energy density of 28.44 Wh kg^–1 as well as cycle life of 10 000 cycles as a free-standing electrode for an aqueous electrolyte, symmetric supercapacitor device. Moreover, the resulting nitrogen/sulfur doped graphene architecture shows good electrocatalytic performance, long durability, and high selectivity when they are used as metal-free catalyst for the oxygen reduction reaction. This study demonstrates an efficient approach for the development of multifunctional as well as flexible 3D architectures for a series of heteroatom-doped graphene frameworks for modern energy storage as well as energy source applications

High-Performance Multifunctional Graphene Yarns: Toward Wearable All-Carbon Energy Storage Textiles

The successful commercialization of smart wearable garments is hindered by the lack of fully integrated carbon-based energy storage devices into smart wearables. Since electrodes are the active components that determine the performance of energy storage systems, it is important to rationally design and engineer hierarchical architectures atboth the nano- and macroscale that can enjoy all of the necessary requirements for a perfect electrode. Here we demonstrate a large-scale flexible fabrication of highly porous high-performance multifunctional graphene oxide (GO) and rGO fibers and yarns by taking advantage of the intrinsic soft self-assembly behavior of ultralarge graphene oxide liquid crystalline dispersions. The produced yarns, which are the only practical form of these architectures for real-life device applications, were found to be mechanically robust (Young’s modulus in excess of 29 GPa) and exhibited high native electrical conductivity (2508 ± 632 S m^–1) and exceptionally high specific surface area (2605 m² g^–1 before reduction and 2210 m² g^–1 after reduction). Furthermore, the highly porous nature of these architectures enabled us to translate the superior electrochemical properties of individual graphene sheets into practical everyday use devices with complex geometrical architectures. The as-prepared final architectures exhibited an open network structure with a continuous ion transport network, resulting in unrivaled charge storage capacity (409 F g^–1 at 1 A g^–1) and rate capability (56 F g^–1 at 100 A g^–1) while maintaining their strong flexible nature