Flexible graphene fi ber (GF) stands for a new type of fi ber of practical importance, which integrates such unique properties as high strength, electrical and thermal conductivities of individual graphene sheets into the useful, macroscopic ensembles. GFs possess the common characteristics of fi bers like the mechanical fl exibility for textiles, while maintaining the uniqueness such as low cost, light weight, and ease of functionalization in comparison with conventional carbon fi bers. [1][2][3] Due to the extraordinary challenge to assemble two-dimensional (2D) microcosmic graphene sheets with irregular size and shape into macroscopic fi brillar confi guration, however, the success in fabrication of neat graphene fi bers only comes true recently. [1][2][3][4] In this regard, we have devised a facile one-step dimensionallyconfi ned strategy to fabricate the neat GFs by directly hydrothermally assembling graphene within glass pipeline. [ 2 , 5 ] The as-produced GFs have a density of 0.23 g/cm 3 , 7 times and 85 times lower than that of conventional carbon fi bers ( > 1.7 g/cm 3 ) and Au wire (ca. 20 g/cm 3 ), while remaining strong, fl exible, conductive, weavable and shapeable, and their engineered structures with multifunctionalities can be done readily in an in situ or post-synthesis fashion. [ 2 ] These remarkable features of GFs endow them with prominent advantages over common carbon fi ber and metal wires [ 6 ] for development of unconventional, lightweight, fl exible devices, especially in fi ber shape for wearable electronics.The fl ourishing progress of electronics in the unconventional forms has opened a new prospect of future electronics such as smart skins, human friendly devices, and fl exible/stretchable circuitries and energy devices. [7][8][9][10][11][12][13][14][15][16] This new class of electronics can conformably deform into complex, non-planar shapes under bending, stretching, compressing, twisting process while maintaining good performance, reliability and integration. Flexible energy-storage devices have attracted tremendous attentions in recent years due to their promise in integration into stretchable and wearable electronics. [ 7 , 17-23 ] In particular, supercapacitors are of signifi cant interest as energy storage devices associated with their high power density, long cycling life, and short charging time. [ 24 , 25 ] Conventional supercapacitors are heavy and bulky, targeting for the applications in electric or hybrid vehicles, and auxiliary power sources. However, the development of high-effi ciency miniaturized supercapacitor devices compatible with the fl exible and wearable electronics lags except from several recent paradigms. [26][27][28][29][30] 3D graphene structures possess notable features including highly-exposed surface areas, high electrical conductivity, and good chemical stability, and therefore they have been widely explored as electrode materials for supercapacitor applications. [31][32][33][34][35] Herein, we design and fabricate a unique allgraphene core-sheath f...

Deformation-tolerant devices are vital for the development of high-tech electronics of unconventional forms. In this study, a highly compressible supercapacitor has been fabricated by using newly developed polypyrrole-mediated graphene foam as electrode. The assembled supercapacitor performs based on the unique and robust foam electrodes achieves superb compression tolerance without significant variation of capacitances under long-term compressive loading and unloading processes.

Graphene lite: a density of (2.1 ± 0.3) mg cm(-3), the lowest to date for a graphene framework architecture, is achieved by preparing an ultralight, N-doped, 3D graphene framework (see photo of a block of the material balancing on a dandelion). Its adsorption capacity for oils and organic solvents is much higher than that of the best carbonaceous sorbents, and it is a promising electrode material for supercapacitors (484 F g(-1)) and as a metal-free catalyst for the oxygen reduction reaction.

Rationally designed N, S co-doped graphitic sheets with stereoscopic holes (SHG) act as effective tri-functional catalysts for the oxygen reduction reaction, hydrogen evolution reaction, and oxygen evolution reaction, simultaneously. The multifunctional electrocatalytic activities originate from a synergistic effect of the N, S heteroatom doping and unique SHG architecture, which provide a large surface area and efficient pathways for electron and electrolyte/reactant transports.

Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis.

Graphen light: Ein N‐dotiertes 3D‐Graphen wurde hergestellt, das die bisher niedrigste Dichte einer Graphen‐Architektur aufweist [(2.1±0.3) mg cm−3; siehe Foto einer Probe auf einer Pusteblume]. Die Adsorptionskapazität des Materials für Öle und organische Lösungsmittel ist weit höher als die der besten Kohlenstoffsorbentien, und es ist außerdem ein vielversprechendes Elektrodenmaterial für Superkondensatoren (484 F g−1) und als metallfreier Katalysator für die Sauerstoffreduktionsreaktion.

Enough to make your hair curl! Moisture-responsive graphene (G) fibers can be prepared by the positioned laser reduction of graphene oxide (GO) counterparts. When exposed to moisture, the asymmetric G/GO fibers display complex, well-controlled motion/deformation in a predetermined manner. These fibers can function not only as a single-fiber walking robot under humidity alternation but also as a new platform for woven devices and smart textiles.

Owning to the multiple advantages, including earth abundance, low-cost, high electronic conductivity, structure tenability at the molecular and morphological levels, and strong tolerance to acidic/alkaline media, [6] carbon nanomaterials have the great potential as metal alternatives for highly efficient metal-free catalysis. While metal alloys often suffer from segregation problems, heteroatom-doped carbonbased metal-free catalysts (C-MFCs) with covalent chemical bonds between the carbon and dopant atoms have no segregation issue, leading to a good operational stability. For metal catalysts, the catalytic activities strictly rely on metal element attributes. However, the catalytic active sites on C-MFCs can be modulated by introducing different dopants and structural defects, [8] providing powerful means for creating a large variety of highly efficient, multifunctional catalysts for various reactions. [5] Furthermore, 3D carbon architectures can be constructed from advanced nanocarbons, including carbon nanotubes (CNTs) and graphene sheets, [9,10] to further improve the performance of C-MFCs. Of particular interest, efficient 3D porous C-MFCs exhibit a large surface area with abundant available exposed active sites, excellent conductivity, high electrolyte diffusibility, and good mechanical property [11,12] -essentially impossible for metal catalysts.Great progress has been achieved since the first C-MFC with heteroatom-doping (i.e., vertically aligned N-doped CNT array, VA-NCNT) was developed as a metal-free catalyst for oxygen reduction reaction (ORR) by Dai and co-workers in 2009. [8] It is the doping-induced charge transfer from carbon atoms to their adjacent nitrogen atoms, changing the chemisorption mode of O 2 and weakening the OO bond for improving the ORR performance of VA-NCNT. [8] This groundbreaking work then launched a large number of research activities worldwide. [4,5,7] Since then, C-MFCs have been demonstrated to catalyze hydrogen evolution reaction (HER) for the production of clean fuel (H 2 ) from photo-/electrochemical water-splitting, ORR in fuel cells for energy generation/conversion, [10] and oxygen evolution reaction (OER) in metal-air batteries for energy storage, [7] two-electron transfer ORR to generate H 2 O 2 (an energy carrier and green oxidizer), [13] CO 2 reduction reaction (CO 2 RR) for the direct conversion of CO 2 into fuel, [14] N 2 reduction reaction (NRR) for synthesis of NH 3 under ambient environment, [15] and for the renewable energy generation/conversion from water driven by sunlight. [16] Carbon atoms in the graphitic carbon skeleton can be replaced by heteroatoms with different electronegative from that of the carbon atom (i.e., heteroatom doping) to modulate the charge distribution over the carbon network. The charge modulation can be achieved via direct charge transfer with an electron acceptor/donor (i.e., charge transfer doping) or through introduction of defects (i.e., defective doping). Various doping strategies, including heteroatom doping, charge-transfer dopi...