Rechargeable zinc-air battery (ZAB) has been regarded as a promising energy storage device owing to its high energy densities, good safety, and environmental friendliness. However, the development of non-precious metal...

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Porous carbon has been one desirable electrode material for supercapacitors, but it is still a challenge to balance the appropriate mesopore volume and a high specific surface area (SSA). Herein, a good balance between a high SSA and mesopore volume in biomass-derived porous carbon is realized by precarbonization of wheat husk under air atmosphere via a chloride salt sealing technique and successive KOH activation. Due to the role of molten salt generating mesopores in the precarbonized product, which can further serve as the active sites for the KOH activation to form micropores in the final carbon material, the mesopore–micropore structure of the porous carbon can be tuned by changing the precarbonization temperature. The appropriate amount of mesopores can provide more expressways for ion transfer to accelerate the transport kinetics of diffusion-controlled processes in the micropores. A high SSA can supply abundant sites for charge storage. Therefore, the porous carbon with a good balance between the SSA and mesopores exhibits a specific gravimetric capacitance of 402 F g−1 at 1.0 A g−1 in a three-electrode system. In a two-electrode symmetrical supercapacitor, the biomass-derived porous carbon also delivers a high specific gravimetric capacitance of 346 F g−1 at 1.0 A g−1 and a good cycling stability, retaining 98.59% of the initial capacitance after 30,000 cycles at 5.0 A−1. This work has fundamental merits for enhancing the electrochemical performance of the biomass-derived porous carbon by optimizing the SSA and pore structures.

To recycle wastes and develop renewable energy, much effort has been focused on converting biowastes into porous carbon for supercapacitors. Porous nanocage-like carbons have excellent capacitive properties, but generally their preparation methods are costly or complex. Herein, a “one-step” strategy of synchronous activation and support through the thermal decomposition of a multifunctional template (magnesium acetate, Mg(Ac)2) is designed to prepare N-, O-, and S-codoped mesoporous hollow biochar nanocages (BNC-700). The BNC-700 prepared displays an interconnected porous structure and a two-dimensional (2D) multilayer wall/three-dimensional (3D) hollow nanocage structure with abundant active heteroatoms and edge defects. Due to their specific structures, high surface areas (1369 m2 g–1), and large pore volumes (1.81 cm3 g–1), the assembled supercapacitor delivers a considerable energy density of 37.4 Wh kg–1 at 212 W kg–1 and cycling stability of 99.5% after 15,000 cycles. The unique structure and N, O, and S codoping characteristics ensure a potential application for BNC-700 in supercapacitors. In summary, a strategy is designed for the green, simple, and cost-effective preparation of high-performance biochar for advanced energy storage devices.

Using electroplating CBN hard gear-honing-tools with standard involute, the vicinity of the workpiece tooth pitch circle will be a “mid concave” error, the root of the tooth will be a “dig root” error generally. For the formation factors of the error are more complex, it is difficult to calculate errors with an exact analytical method. To this end, by using Pro/E and ANSYS software, the contact analysis of electroplating CBN hard honing process was simulated. The honed tooth surface normal deformation analysis was the important means to determine extent of tooth profile error, through the normal deformation analysis based on simulation results, the location and extent of normal deformation was determined. Practice shows that the location and extent of the normal deformation has been a certain relationship with processing gear tooth profile errors. It is provided a theoretical basis to make the gear-honing tooth surface modification as possible.