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Graphene-based fiber-shaped supercapacitors (FSSCs) have received considerable attention as potential wearable energy storage devices owing to their simple operating mechanism, flexibility, and long-term stability. To date, energy storage capacities of supercapacitors have been significantly improved via strategies such as heteroatom doping and the incorporation of pseudocapacitive metal oxides. Herein, we develop a novel and scalable direct-hybridization method that combines heteroatom doping and metal oxide hybridization for the fabrication of high-performance FSSCs. Using porous and highly conductive nitrogen and sulfur co-doped graphene fibers (NS-GFs) as self-heating units, we successfully convert ruthenium hydroxide anchored to the surface into ruthenium oxide nanoparticles after programmed sub-second electrothermal annealing without structural damage of the fibers. The resulting fibers show an increased gravimetric capacitance of 68.88 F g

The conversion of the electrokinetic energy arising from evaporation-induced water flow through nanoporous materials has great potential for renewable energy production. In this study, we prepare a nanocapillary membrane containing both nanopores and nanochannels based on an assembly of holey graphene oxide (HGO) nanosheets, which enables water molecules to permeate and simultaneously evaporate from the nanostructure. In particular, we find that the performance of our HGO membrane-based water evaporation-induced energy harvester (WEEH) can be significantly improved by ensuring (1) a high capillary flow of water through low-friction nanochannels and (2) a high rate of evaporation, which is achieved by the presence of large nanoscale pores with a broad size distribution. Our WEEH yields a maximum voltage of 0.44 V, current of 200 nA, and output energy density of 2.2 μWh cm−2. Furthermore, the use of multiple WEEHs allows for the generation of sufficient energy to charge a 1-F supercapacitor and power a light-emitting diode (2 V × 20 mA). Thus, our proposed nanocapillary, thin-membrane-based WEEH has great practical potential for energy generation, as well as other membrane-based technologies such as water purification.