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A flexible transparent molybdenum trioxide nanopaper, assembled via ultralong molybdenum trioxide nanobelts, displays an excellent average transmittance of ≈90% in the visible region. The free-standing nanopaper electrode delivers an outstanding specific capacitance of 1198 F g(-1) and shows an excellent long-term stability performance over 20 000 cycles with a retention rate of 99.1%.

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Efficient utilization and broader commercialization of alternative energies (e.g., solar, wind, and geothermal) hinges on the performance and cost of energy storage and conversion systems. For now and in the foreseeable future, the combination of rechargeable batteries and electrochemical capacitors remains the most promising option for many energy storage applications. Porous carbonaceous materials have been widely used as an electrode for batteries and supercapacitors. To date, however, the highest specific capacitance of an electrochemical double layer capacitor is only ∼200 F/g, although a wide variety of synthetic approaches have been explored in creating optimized porous structures. Here, we report our findings in the synthesis of porous carbon through a simple, one-step process: direct carbonization of kelp in an NH3 atmosphere at 700 °C. The resulting oxygen- and nitrogen-enriched carbon has a three-dimensional structure with specific surface area greater than 1000 m(2)/g. When evaluated as an electrode for electrochemical double layer capacitors, the porous carbon structure demonstrated excellent volumetric capacitance (>360 F/cm(3)) with excellent cycling stability. This simple approach to low-cost carbonaceous materials with unique architecture and functionality could be a promising alternative to fabrication of porous carbon structures for many practical applications, including batteries and fuel cells.

Thermally reduced graphene oxide (rGO)-wrapped ZnMn 2 O 4 nanorods have been successfully fabricated via a facile bottom-up approach. Characterization results show that porous ZnMn 2 O 4 nanorods are uniformly wrapped by ultrathin rGO sheets. The unique structure of this rGO-ZnMn 2 O 4 composite could facilitate both ion and electron diffusion, thus providing suitable characteristics of an anode material for high performance lithium-ion batteries. Specifically, the conductive rGO sheets could act as an efficient buffer to relax the volume changes from Li + insertion/extraction, and enable the structural and interfacial stabilization of ZnMn 2 O 4 crystals. As a consequence, a high and stable reversible capacity (707 mA h g À1 at 100 mA g À1 over 50 cycles) and an excellent rate capability (440 mA h g À1 at 2000 mA g À1 ) are achieved with this composite material.

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