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Graphene-like two-dimensional carbon nanosheets with properly modulated compositions and porosity are of particular importance for robust capacitance harvesting. Nevertheless, the large-scale and cost-effective production of such nanostructures still remains a great challenge. Herein, we innovatively produce nitrogen-doped porous carbon nanosheets using pine nut shells, an abundant biomass waste, as the precursor, under the synergetic effect of KOH and melamine during the activation process. The sole activation of the precursors with KOH can produce only traditional activated carbon particles of several micrometers, while interestingly, the extra introduction of melamine results in nitrogen-doped porous carbon nanosheets possessing high tunability. By construction of a two-electrode configuration, the supercapacitors with optimal nanosheets as the electrode materials can deliver a superior specific capacitance of 324 F g –1 at 0.05 A g–1, outstanding rate capability of 258 F g–1 at 20 A g–1, and extraordinary cyclic stability of 94.6% after 10 000 cycles at 2 A g–1 in an aqueous electrolyte of 6 M KOH. Such a facile strategy proposed here may contribute to new possibilities of synthesizing graphene-like porous carbon nanosheets in a sustainable manner for energy-related applications.

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The creation of micromotors that can convert stored energy to autonomous movement would be of great value in various applications, ranging from chemical sensing to precision water-quality screening and from cleaning clogged arteries to repairing microscopic cracks. Many of micromotors, based on different propulsion mechanisms (e.g., magnetic fields, ultrasound filed, chemical fuels, light, and bubble propulsion), [1][2][3][4][5][6][7][8][9] have been designed and fabricated over the past decade. Generally, they are built of rigid materials [10] to maintain a good maneuverability, but often with limited body compliance and adaptability in confined spaces. [11][12][13] In contrast to the hard Shape-transformable liquid metal (LM) micromachines have attracted the attention of the scientific community over the past 5 years, but the inconvenience of transfer routes and the use of corrosive fuels have limited their potential applications. In this work, a shape-transformable LM micromotor that is fabricated by a simple, versatile ice-assisted transfer printing method is demonstrated, in which an ice layer is employed as a "sacrificial" substrate that can enable the direct transfer of LM micromotors to arbitrary target substrates conveniently. The resulting LM microswimmers display efficient propulsion of over 60 µm s −1 (≈3 bodylength s −1 ) under elliptically polarized magnetic fields, comparable to that of the common magnetic micro/ nanomotors with rigid bodies. Moreover, these LM micromotors can undergo dramatic morphological transformation in an aqueous environment under the irradiation of an alternating magnetic field. The ability to transform the shape and efficiently propel LM microswimmers holds great promise for chemical sensing, controlled cargo transport, materials science, and even artificial intelligence in ways that are not possible with rigid-bodies microrobots.bodied, nature has created a wide range of biological motors with deformable bodies at small scales. They often have strong ability to actively adapt to their environment, thus can perform various demanding tasks in complex environments. Inspired by nature, researchers have begun to explore the design and control shape-transformable micromotors composed of compliant materials [14,15] (e.g., hydrogels, [16] granular media, [17] lowmelting point alloys, [18,19] and electroactive polymers [14] ) to ensure maneuverability, adaptability and agility in practical applications. Liquid metals (LMs) are typical examples of highly extensible and adaptable compliant materials, [20,21] such as Gallium and gallium-containing alloys (e.g., eutectic gallium-indium (EGaIn): 75% gallium and 25% indium; Galinstan: 68.5% gallium, 21.5% indium, and 10% tin). One of the most striking features of these gallium-based liquid metals is the nearly instant formation of a passivating oxide layer on their surface in the present of oxygen. This oxide layer (mainly composed of Ga 2 O 3 ) mechanically stabilizes the liquid metals into nonequilibrium shapes [22] and can be removed ...

Amorphous carbon is regarded as a promising alternative to commercial graphite as the lithium-ion battery anode due to its capability to reversibly store more lithium ions. However, the structural disorder with a large number of defects can lead to low electrical conductivity of the amorphous carbon, thus limiting its application for high power output. Herein, ultrathin amorphous carbon nanosheets were prepared from petroleum asphalt through tuning the carbonization temperature in a molten-salt medium. The amorphous nanostructure with expanded carbon interlayer spacing can provide substantial active sites for lithium storage, while the two-dimensional (2D) morphology can facilitate fast electrical conductivity. As a result, the electrodes deliver a high reversible capacity, outstanding rate capability, and superior cycling performance (579 and 396 mAh g at 2 and 5 A g after 900 cycles). Furthermore, full cells consisting of the carbon anodes coupled with LiMnO cathodes exhibit high specific capacity (608 mAh g at 50 mA g) and impressive cycling stability with slow capacity loss (0.16% per cycle at 200 mA g). The present study not only paves the way for industrial-scale synthesis of advanced carbon materials for lithium-ion batteries but also deepens the fundamental understanding of the intrinsic mechanism of the molten-salt method.

In this paper, we report on the hydrogen photochromism in Nb2O5 powders with different structures. Four different powder phases were prepared by calcining Nb2O5·nH2O powders at various temperatures, and their morphology, structure, and electronic band structure were characterized by scanning electron microscopy, structural analyses, thermogravimetric analysis, differential scanning calorimetry, and optical spectroscopy. Nb2O5 powders with different structures and very different properties were formed after different high-temperature treatments of the polymorphous oxide. A pronounced photochromic effect was observed in the M and H phases of Nb2O5, whereas the other phases exhibited poor photochromic responses. Because photochromism arises due to the detachment of hydrogen atoms under the action of light from hydrogen donor molecules previously adsorbed on the oxide surface, the electronic band structure and the morphology have strong influences on the photochromic properties of Nb2O5 powders. For these reasons, a pronounced photochromic effect was achieved in the H phase.

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