Recently, multilevel structural carbon aerogels are deemed as attractive candidates for microwave absorbing materials. Nevertheless, excessive stack and agglomeration for low-dimension carbon nanomaterials inducing impedance mismatch are significant challenges. Herein, the delicate “3D helix–2D sheet–1D fiber–0D dot” hierarchical aerogels have been successfully synthesized, for the first time, by sequential processes of hydrothermal self-assembly and in-situ chemical vapor deposition method. Particularly, the graphene sheets are uniformly intercalated by 3D helical carbon nanocoils, which give a feasible solution to the mentioned problem and endows the as-obtained aerogel with abundant porous structures and better dielectric properties. Moreover, by adjusting the content of 0D core–shell structured particles and the parameters for growth of the 1D carbon nanofibers, tunable electromagnetic properties and excellent impedance matching are achieved, which plays a vital role in the microwave absorption performance. As expected, the optimized aerogels harvest excellent performance, including broad effective bandwidth and strong reflection loss at low filling ratio and thin thickness. This work gives valuable guidance and inspiration for the design of hierarchical materials comprised of dimensional gradient structures, which holds great application potential for electromagnetic wave attenuation. "Image missing"

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The development of flexible carbon‐based film electrodes with high loading and sufficient electron/ion transport channels is of great significance but still challenging. Herein, a flexible high‐loading (over 15 mg cm–2) film with 3D hierarchical pores is prepared by an alternate deposition of carbon nanocoils (CNCs) and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The unique alternate architecture of CNC/PEDOT:PSS bilayers possesses porous structure constructed by interconnected CNCs, which serves as transfer channels and storage chambers of ions. Meanwhile, the PEDOT:PSS layers anchoring CNCs function as not only the cement to ensure the stability of the film structure but also the current collectors to improve electron transfer kinetics between interlayers. The film electrode shows excellent flexibility and electrochemical properties. It delivers a high areal capacitance of 1402.5 mF cm–2 at 0.25 mA cm–2 and a superior stability even at an extremely high current density of 50 mA cm–2 after 10 000 cycles. The corresponding solid‐state supercapacitor has great energy storage ability and steady capacitance response under various deformation. The device achieves a superb energy density of 211 μW h cm–2 with a wide potential window of 2 V. This strategy paves a road for the controllable fabrication of high‐performance flexible electrodes and supercapacitors.

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The wearable and self-powered sensors with multiple functions are urgently needed for energy saving devices, economical convenience, and artificial human skins. It is a meaningful idea to convert excess heat sources into power supplies for wearable sensors. In this report, we have fabricated a series of free-standing self-powered temperature-strain dual sensors based on poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PE-DOT:PSS)/carbon nanocoils (CNCs)−poly(vinyl) alcohol composite films by a simple drop casting method. The Seebeck coefficients of the composite films were measured to be 19 μV/K. The sensor, with the addition of CNCs, showed a superior sensing performance to that without CNCs. PEDOT:PSS is used to provide a thermoelectric power to detect temperature changes and strain deformations. The minimum detect limit for the temperature difference was 0.3 K. Under a constant temperature gradient of 30 K, strains from 1 to 10% were detected without any external power supply. The films can be easily made into an array to detect the temperature of the fingers and motions of the wrist by attaching it to the human wrist directly. For the first time, due to the independent action of the thermoelectric material and strain sensing material, the thermoelectric voltage which is generated by a constant temperature difference is maintained under different strains. This kind of free-standing self-powered multifunctional sensors has great application prospects in the fields of healthcare and artificial intelligence in the future.