ZnCl₂-KOH modulation of biomass-derived porous carbon for supercapacitors

With the implementation of carbon neutrality, more and more researchers are devoted to the development of biomass-based porous carbon materials using agricultural and forestry wastes for energy storage applications. However, biomass-derived carbon materials are still suffering from structural instability and difficult to regulate the pore structure, so it is very essential to study the regulation of pore structure in activation process of biochar. Therefore, this work developed an approach to modulate the pore structure of biomass porous carbon. The pyrolyzed biochar was primary activated by ZnCl2 to form the intermediate FC, and the FC was secondary activated by the impregnation method with the addition of trace KOH to form the graded porous carbon FCK-x. The prepared porous carbon exhibited a large specific surface area (2845 m2g−1) and a large pore volume (1.43 cm3g−1), which is very favorable for efficient ion transport in the three-electrode system, FCK-0.6 exhibited a specific capacitance of 321.7 F/g at 1A/g and the assembled supercapacitor exhibited high capacitance retention (95.17%) and charge retention (85%). This work provides a feasible way to modulate biomass pore structure.</p

Autonomous Chitosan-Based Self-Healing Hydrogel Formed through Noncovalent Interactions

A facile strategy was developed for the formation of an autonomous chitosan-based self-healing hydrogel. This hydrogel was fabricated using in situ free radical polymerization of acrylic acid (AA) and acrylamide (AM) in the presence of chitosan in dilute acetic acid aqueous solution under mild conditions. The in situ formed hydrogel is mainly composed of chitosan graft copolymers (CS-g-P­(AM-r-AA)) and a small amount of nongrafted copolymers (P­(AM-r-AA)), which interact with each other through a combination of multiple noncovalent interactions, including the interchain electrostatic complexation between −[AA]– segments and positively charged amino groups of chitosan, the H-bonding between −[AM]– segments, and the H-bonding between −[AM]– segments and the chitosan backbone. Owing to the cooperation of these noncovalent interactions and the reversible nature of the noncovalent network structure, the obtained hydrogel exhibits rapid network recovery, high stretchability, and efficient autonomous self-healing properties. The hydrogel can also dissolve completely in dilute acidic aqueous solution under mild conditions, visibly reflecting the unique network feature of this self-healing hydrogel system

Bioinspired Synthesis of Hierarchical Porous Graphitic Carbon Spheres with Outstanding High-Rate Performance in Lithium-Ion Batteries

Inspired by the biomineralization of unicellular diatoms, a biomimetic approach based on template (pluronic F127 micelle cluster)-induced self-assembly of α-cyclodextrin is developed to create hierarchical porous graphitic carbon spheres via hydrothermal treatment followed by pyrolysis. The as-obtained carbon spheres combine the features required for high-power electrode materials in lithium-ion batteries (LIBs), such as high degree of graphitization, large surface area with hierarchically distributed pore sizes as well as doping with heteroatoms, which synergistically contribute to their impressive electrochemical properties. When applied as an anode for LIBs, the carbon spheres exhibit high reversible capacity (ca. 700 mA h g^–1 at 50 mA g^–1), good cycling stability, and remarkably outstanding high-rate performance (ca. 600, 450, and 290 mA h g^–1 obtained at a current density of 1, 10, and 30 A g^–1, respectively), which is among the best of present pure carbon materials for LIBs applications. The fabrication process is straightforward and cost-effective, providing a new methodology for the tailored design of carbon materials with enhanced power densities for energy storage applications

Insights into thin film blistering of gold coating on metal substrate

Au thin films, up to h ≈ 90 nm thick, have been deposited by direct current sputtering at room temperature to address the effect of coating thickness on film blistering that occurred on Ni-based single crystal (NBSC) superalloy rather than on Si. Transmission electron microscopy provides evidence that the blisters nucleated at the Au/NBSC interface. Statistically, the diameters of the blisters increases while their density decreases with the increase in h; however, the height-to-diameter ratios of the blisters measured from the film surface are rather constant and independent of h. When h is increased from ≤63 nm to ∼90 nm, the size distribution of the blisters turns from a single mode to a bimodal along with an emergence of larger circular blisters and edge-like ones. Mechanical modelling and density-function calculations provide evidence that the formation of blisters is driven by pockets of energy concentration while the nucleation site is influenced by surface absorbents of the substrate.</p

Insights into thin film blistering of gold coating on metal substrate

Au thin films, up to h ≈ 90 nm thick, have been deposited by direct current sputtering at room temperature to address the effect of coating thickness on film blistering that occurred on Ni-based single crystal (NBSC) superalloy rather than on Si. Transmission electron microscopy provides evidence that the blisters nucleated at the Au/NBSC interface. Statistically, the diameters of the blisters increases while their density decreases with the increase in h; however, the height-to-diameter ratios of the blisters measured from the film surface are rather constant and independent of h. When h is increased from ≤63 nm to ∼90 nm, the size distribution of the blisters turns from a single mode to a bimodal along with an emergence of larger circular blisters and edge-like ones. Mechanical modelling and density-function calculations provide evidence that the formation of blisters is driven by pockets of energy concentration while the nucleation site is influenced by surface absorbents of the substrate.</p