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Phosphorus-doped (P-doped) graphene with the P doping level of 1.30 at % was synthesized by annealing the mixture of graphene and phosphoric acid. The presence of P was confirmed by elemental mapping and X-ray photoelectron spectroscopy, while the morphology of P-doped graphene was revealed by using scanning electron microscopy and transmission electron microscopy. To investigate the effect of P doping, the electrochemical properties of P-doped graphene were tested as a supercapacitor electrode in an aqueous electrolyte of 1 m H 2 SO 4 . The results showed that doping of P in graphene exhibited significant improvement in terms of specific capacitance and cycling stability, compared with undoped graphene electrode. More interestingly, the P-doped graphene electrode can survive at a wide voltage window of 1.7 V with only 3 % performance degradation after 5000 cycles at a current density of 5 A g À1, providing a high energy density of 11.64 Wh kg À1 and a high power density of 831 W kg À1 .Owing to the accelerating consumption of global energy, research and development on sustainable energy storage technologies have attracted a great deal of interest. Particularly, carbon nanomaterials have shown excellent performance as electrodes, catalysts, and supports in energy-storage devices, such as supercapacitors, batteries, fuel cells and hydrogen storage. [1] In recent years, graphene, a single layer of sp 2 hybridised carbon atoms, has emerged as one of the most promising carbon allotropes for energy storage devices due to its unique structure and excellent properties, [2] for example, high theoretical surface area (2630 m 2 g À1 ), [3] intrinsic carrier mobility (2 10 5 cm 2 V À1 s À1 ), [4] optical transmittance (97.7 %) [5] and superior mechanical strength. [6] To improve the performance of graphene in energy-storage applications, various attempts have been investigated. Among them, introducing heteroatoms (O, N, S, B, and P) is one of the most effective methods to tailor the electrochemical properties of graphene-based materials; [7] and the advantages lie in the modification of the electronic properties of carbon materials and the effect on electronic charge distribution of adjacent carbon atoms. [7a, 8] Nitrogen-doped (N-doped) graphene has been widely studied in supercapacitors, [9] batteries, [10] fuel cells [11] and field-effect transistors.[12] However, only a few studies are available so far regarding graphene doped with other (non-nitrogen) heteroatoms in similar applications.Recently, Zhang prepared phosphorus-doped (P-doped) graphene by a thermal treatment using graphene oxide and triphenylphosphine, and the P doping in graphene significantly improved the electrochemical properties in oxygen reduction reaction (ORR) and lithium ion batteries (LIB).[13] In another work, P/N co-doped graphene was prepared by pyrolysis of a graphene-dicyandiamide mixture in the presence of phosphoric acid, exhibiting significant enhancement of catalytic activity for ORR.[14] P-doped graphene, obtained by anneal...

The recent booming development of wearable electronics urgently calls for high-performance flexible strain sensors. To date, it is still a challenge to manufacture flexible strain sensors with superb sensitivity and a large workable strain range simultaneously. Herein, a facile, quick, cost-effective, and scalable strategy is adopted to fabricate novel strain sensors based on reduced graphene oxide woven fabrics (GWF). By pyrolyzing commercial cotton bandages coated with graphene oxide (GO) sheets in an ethanol flame, the reduction of GO and the pyrolysis of the cotton bandage template can be synchronously completed in tens of seconds. Due to the unique hierarchical structure of the GWF, the strain sensor based on GWF exhibits large stretchability (57% strain) with high sensitivity, inconspicuous drift, and durability. The GWF strain sensor is successfully used to monitor full-range (both subtle and vigorous) human activities or physical vibrational signals of the local environment. The present work offers an effective strategy to rapidly prepare low-cost flexible strain sensors with potential applications in the fields of wearable electronics, artificial intelligence devices, and so forth.

An electrically conductive and electrochemically active composite paper of graphene nanosheet (GNS) coated cellulose fibres was fabricated via a simple paper-making process of dispersing chemically synthesized GNS into a cellulose pulp, followed by infiltration. The GNS nanosheet was deposited onto the cellulose fibers, forming a coating, during infiltration. It forms a continuous network through a bridge of interconnected cellulose fibres at small GNS loadings (3.2 wt%). The GNS/cellulose paper is as flexible and mechanically tough as the pure cellulose paper. The electrical measurements show the composite paper has a sheet resistance of 1063 Ω□(-1) and a conductivity of 11.6 S m(-1). The application of the composite paper as a flexible double layer supercapacitor in an organic electrolyte (LiPF(6)) displays a high capacity of 252 F g(-1) at a current density of 1 A g(-1) with respect to GNS. Moreover, the paper can be used as the anode in a lithium battery, showing distinct charge and discharge performances. The simple process for synthesising the GNS functionalized cellulose papers is attractive for the development of high performance papers for electrical, electrochemical and multifunctional applications.