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.

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.

The carbon dioxide reduction reaction (CO 2 RR) driven by renewable electricity is a promising way to tackle the CO 2 emission woes and recycle use of CO 2 . The synthesis of electrocatalysts with high activity and selectivity for CO 2 RR to ethylene remains a great challenge. Herein, leaf-like CuO nanosheets are fabricated in situ on nitrogen-doped graphene (NG) by using a novel reduction-oxidation-reconstruction process. When used as a catalyst for the CO 2 RR in 0.1 M KHCO 3 , a high faradaic efficiency of approximately 30 % for ethylene with an ultra-high ethylene/methane ratio of 190 was achieved at À 1.3 V vs. the reversible hydrogen electrode. The SEM and TEM images confirm the leaf-like CuO nanosheets display highcurvature structures, while multiple distinguished grain boundaries constructed by CuO(110) and CuO(111) planes are verified by HRTEM. For the first time, we present a facile method to combine the high-curvature structure and the grain boundary to enhance the selectivity of the CO 2 RR to ethylene over a CuO catalyst.

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