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.