Micro-supercapacitors are promising energy storage devices that can complement or even replace batteries in miniaturized portable electronics and microelectromechanical systems. Their main limitation, however, is the low volumetric energy density when compared with batteries. Here, we describe a hierarchically structured carbon microfibre made of an interconnected network of aligned single-walled carbon nanotubes with interposed nitrogen-doped reduced graphene oxide sheets. The nanomaterials form mesoporous structures of large specific surface area (396 m(2) g(-1)) and high electrical conductivity (102 S cm(-1)). We develop a scalable method to continuously produce the fibres using a silica capillary column functioning as a hydrothermal microreactor. The resultant fibres show a specific volumetric capacity as high as 305 F cm(-3) in sulphuric acid (measured at 73.5 mA cm(-3) in a three-electrode cell) or 300 F cm(-3) in polyvinyl alcohol (PVA)/H(3)PO(4) electrolyte (measured at 26.7 mA cm(-3) in a two-electrode cell). A full micro-supercapacitor with PVA/H(3)PO(4) gel electrolyte, free from binder, current collector and separator, has a volumetric energy density of ∼6.3 mWh cm(-3) (a value comparable to that of 4 V-500 µAh thin-film lithium batteries) while maintaining a power density more than two orders of magnitude higher than that of batteries, as well as a long cycle life. To demonstrate that our fibre-based, all-solid-state micro-supercapacitors can be easily integrated into miniaturized flexible devices, we use them to power an ultraviolet photodetector and a light-emitting diode.

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Autonomous bubble-propelled catalytic micro- and nanomachines show great promise in the fields of biomedicine, environmental science, and natural resources. It is envisioned that thousands and millions of such micromachines will swarm and communicate with each other, performing desired actions. To date, mainly platinum catalyst surfaces have been used for the decomposition of a fuel, hydrogen peroxide, to oxygen bubbles. Here we propose Pt-free, low-cost inorganic catalysts for powering micromotors based on silver and manganese dioxide surfaces. Such Ag- and MnO2-based bubble-powered micromotors show fast motion even at very low concentrations of fuel, down to 0.1% of H2O2. These catalysts should enable unparalleled widespread use of such motors in real applications, as it will be possible to make them in large quantities at low cost.

This work delineates the first example for controlling product selectivity in metal-catalyzed hydrogenation of biomass by zeolite crystals. The key to this success is to combine the advantages of both Pd nanoparticles (highly active sites) and zeolite micropores (controllable diffusion of reactants and products), which was achieved from encapsulation of the Pd nanoparticles inside of silicalite-I zeolite crystals as a core-shell structure (Pd@S-1). In the hydrogenation of biomass-derived furfural, the furan selectivity over the Pd@S-1 is as high as 98.7%, outperforming the furan selectivity (5.6%) over conventional Pd nanoparticles impregnated with S-1 zeolite crystals (Pd/S-1). The extraordinary furan selectivity in the hydrogenation over the Pd@S-1 is reasonably attributed to the distinguishable mass transfer of the hydrogenated products in the zeolite micropores.

Using CO2 as the soft oxidant for the oxidative dehydrogenation of ethane (ODE) is a potential advancement for ethylene production from ethane. However, the current ODE reaction is primarily operated at high temperatures (e.g., 873 K), and the development of alternative approaches for the ODE reaction under the mild conditions is still a challenge. Herein, we report a photocatalytic ODE using CO2 as the oxidant over Pd/TiO2 catalysts at room temperature. The presence of CO2 significantly promoted the production of C2H4 and syngas, and the 1% Pd/TiO2 catalyst exhibited a C2H4 production rate of 230.5 μmol/gcat·h and syngas of 282.6 μmol/gcat·h. Density functional theory (DFT) calculation verified that the intermediate energy level provided by Pd and the covalent bond in Pd–O stimulated the electron transfer, excitation, and separation. The photoinduced electron, hole, and isolate OH on the surface of TiO2 played essential roles during the whole process. In addition, the possible reaction pathways of photocatalytic ODE with CO2 were proposed on the basis of the experimental data and DFT calculation results.