An efficient polymer moist-electric generator is developed on the basis of conventional polyelectrolyte membrane to output considerable electric power under moisture.

Rationally designed graphene nanomesh assembled foam (GMF) with hierarchical pore arrangement has been successfully fabricated for the first time by a site-localized nanoparticle-induced etching strategy on the basis of hydrothermally self-assembled graphene architecture.The newly developed GMF provides a new material platform for developing high-performance functional devices. Specially, the Nand S-codoped GMF electrode exhibits excellent electrocatalytic activities for oxygen reduction reaction (ORR), better than most of the graphene-based ORR catalysts reported previously.

Converting ubiquitous environmental energy into electric power holds tremendous social and financial interests. Traditional energy harvesters and converters are limited by the specific materials and complex configuration of devices. Herein, it is presented that electric power can be directly produced from pristine graphene oxide (GO) without any pretreatment or additives once encountering the water vapor, which will generate an open-circuit-voltage of up to 0.4-0.7 V and a short-circuit-current-density of 2-25 µA cm on a single piece of GO film. This phenomenon results from the directional movement of charged hydrogen ions through the GO film. The present work demonstrates and provides an extremely simple method for electric energy generation, which offers more applications of graphene-based materials in green energy converting field.

Graphene-based materials have shown great potential in various fields across physics, chemistry, biology, and electronics, due to their unique electronic properties, facile synthesis, and ease of functionalization.

The rise of graphene has triggered the fast increasing research upsurge in both controllable synthesis of graphene and unique applications associated with its miraculous properties. In particular, graphenebased smart devices that can automatically respond to external stimulations are among those attracting our most attention. In this featured article, we summarize some of the recent advances in stimulusresponsive graphene actuation systems contributed by us and others, and discuss the different roles that graphene plays in various actuation circumstances such as under electrical, chemical, photonic, thermal and other stimuli. Impressive progress including graphene-based robots is also presented, demonstrating the great prospects of graphene actuation systems in a wide range of applications including sensors, switches, artificial muscles, nano/micro electromechanical devices, etc. Broader contextAn actuator is a type of device that can operate on a certain source of energy, such as electric current, pressure and chemical energy, and transform that energy into motion. It is desirable to have an actuator with controlled motions upon application ofan environmental stimulus, because such a device could mimic organisms and have wide applications ranging from sensors, switches, and articial muscles to nano/micro electromechanical systems. Meanwhile, graphene, the perfect two-dimensional single-atom-thick carbon sheet, has attracted tremendous research interest due to its huge specic surface area, high electron mobility at room temperature, excellent mechanical exibility, exceptionally high thermal conductivity and environmental stability. These remarkable electrical, thermal and mechanical properties of graphene are important in designing and fabricating future actuation systems, and therefore, it is not surprising that graphene has recently been revealed to be a benecial component in composite polymer actuators and even an outstanding actuating material by itself. In this Perspective, we discuss the exciting developments, emerging applications and existing challenges of stimulus-responsive graphene actuation systems that convert different types of energies such as electrical, chemical, photonic, thermal energies to mechanical energy, aiming to attract increasing research efforts to this interesting yet demanding interdisciplinary eld.

Similar to the paper-making process, the effi cient fl ame retardant graphene paper is conveniently obtained by using graphene oxide (GO) and hexachlorocyclotriphosphazene (HCCP) aqueous pulp. The "paper pulp" can also conceivably be used as ink to make other hydrophilic fi lms become fl ame retardant paper. Further, the as-prepared reduced GO-HCCP paper (RGO-HCCP paper), compared with GO-HCCP paper, can maintain its intact structure for a longer time in an ethanol fl ame. As a consequence of these preparation methods, the bearing temperature of the as-prepared graphene papers shows a signifi cant increase.

Graphitic carbon nitride nanosheet (g-C3N4-NS) has layered structure similar with graphene nanosheet and presents unusual physicochemical properties due to the s-triazine fragments. But their electronic and electrochemical applications are limited by the relatively poor conductivity. The current work provides the first example that atomically thick g-C3N4-NSs are the ideal candidate as the active insulator layer with tunable conductivity for achieving the high performance memory devices with electrical bistability. Unlike in conventional memory diodes, the g-C3N4-NSs based devices combined with graphene layer electrodes are flexible, metal-free and low cost. The functionalized g-C3N4-NSs exhibit desirable dispersibility and dielectricity which support the all-solution fabrication and high performance of the memory diodes. Moreover, the flexible memory diodes are conveniently fabricated through the fast laser writing process on graphene oxide/g-C3N4-NSs/graphene oxide thin film. The obtained devices not only have the nonvolatile electrical bistability with great retention and endurance, but also show the rewritable memory effect with a reliable ON/OFF ratio of up to 105, which is the highest among all the metal-free flexible memory diodes reported so far, and even higher than those of metal-containing devices.

Graphene materials have been attracting significant research interest in the past few years, with the recent focuses on graphene-based electronic devices and smart stimulus-responsive systems that have a certain degree of automatism. Owing to its huge specific surface area, large room-temperature electron mobility, excellent mechanical flexibility, exceptionally high thermal conductivity and environmental stability, graphene is identified as a beneficial additive or an effective responding component by itself to improve the conductivity, flexibility, mechanical strength and/or the overall responsive performance of smart systems. In this review article, we aim to present the recent advances in graphene systems that are of spontaneous responses to external stimulations, such as environmental variation in pH, temperature, electric current, light, moisture and even gas ambient. These smart stimulus-responsive graphene systems are believed to have great theoretical and practical interests to a wide range of device applications including actuators, switches, robots, sensors, drug/gene deliveries, etc.