Two-dimensional activated carbon nanosheets for rapid removal of tetracycline via strong π-π electron donor receptor interactions.

Two-dimensional carbonaceous materials have sparked extensive attention in organic pollutants adsorption due to their unique structure to facilitate the formation of the physical or chemical bonding. Herein, natural two-dimensional porous activated carbon nanosheets with ultra-high specific surface area (2276.44 m2 g-1) are prepared by alkaline immersion-assisted circulating calcination techniques from corn straw piths. The prepared nanosheets exhibit rapid tetracycline adsorption capacity (633 mg g-1 within 5 min) and high equilibrium adsorption capacity of 804.5 mg g-1. Significantly, the nanosheets can adapt to a wide range of pH (at least between pH = 3-10) and are almost unaffected by coexisting ions. Mechanism studies and theoretical calculations demonstrate that the rapid and high-efficient adsorption of tetracycline mainly depends on the π-π electron donor receptor interactions. In addition, hydrogen bonding and pore filling was also responsible for tetracycline adsorption. This work provides important guidance for the development of the biobased high-performance adsorbents from agricultural waste.

Progress of NiO-Based Anodes for High-Performance Li-Ion Batteries.

Rechargeable lithium-ion batteries (LIBs) are of great significance to the development of renewable energy. The traditional graphite anode is gradually unable to meet increasing demands for high energy density and power density due to its low theoretical capacity. NiO has gained considerable attention because of its high theoretical capacity, low toxicity, and stable chemical properties. This review summarizes the research progress of NiO-based nanomaterials in LIBs and centers on the electrochemical reaction mechanism, synthesis methods, and strategies for improving the electrochemical properties of NiO anodes. The results demonstrate that the electrochemical characteristics highly depend on the synthesis method, morphology, surface area, conductive substrate, etc. Compared with pure NiO, NiO-based composites including NiO/carbon-based materials and NiO/metal oxide often present higher capacity and cycle stability. Furthermore, challenges and future perspectives of NiO-based anodes are also discussed.

Magnesium-regulated oxygen vacancies of cobalt-nickel layered double hydroxide nanosheets for ultrahigh performance asymmetric supercapacitors.

Rational design of layered double hydroxide (LDH) electrodes is of great significance for high-performance supercapacitors (SCs). Herein, ultrathin cobalt-nickel-magnesium layered double hydroxide (CoNiMg-LDH) nanosheets with plentiful oxygen vacancies are synthesized via sacrificial magnesium-based replacement reaction at room temperature. Self-doping and mild reduction of magnesium can significantly increase the concentration of oxygen vacancies in CoNiMg-LDH, which promotes the electrochemical charge transfer efficiency and enhances the adsorption ability of electrolytes. Density functional theory (DFT) calculations also indicate that Mg2+ doping can decrease the formation energy of oxygen vacancies in CoNiMg-LDH nanosheets, which increases the concentration of oxygen vacancies. Thus, the assembled asymmetric supercapacitor CoNiMg-LDH//Actived Carbon accomplishes a superior capacity of âˆ¼ 333 C g-1 (208 F g-1) at 1 A g-1 and presents a gravimetric energy density of 73.9 Wh kg-1 at 0.8 kW kg-1. It presents only 13% capacity loss at 20 A g-1 after 5000 cycles. This discovery emphasizes the positive role of magnesium in regulating oxygen vacancies to improve the performance of supercapacitors, which should be beneficial for extending the scope of superior SCs active materials.

An ultrasonic-assisted synthesis of rice-straw-based porous carbon with high performance symmetric supercapacitors.

Biomass porous carbon materials are ideal supercapacitor electrode materials due to their low price, rich source of raw materials and environmental friendliness. In this study, an ultrasonic-assisted method was applied to synthesize the rice-straw-based porous carbon (UPC). The obtained UPC exhibited a two-dimensional structure and high specific surface area. In addition, the electrochemical test results showed that the UPC with a 1 hour ultrasonic treatment and lower activation temperature of 600 °C (UPC-600) demonstrated optimal performance: high specific capacitances of 420 F g-1 at 1.0 A g-1 and 314 F g-1 at a high current of 10 A g-1. Significantly, the symmetric supercapacitors showed a high energy density of 11.1 W h kg-1 and power density of 500 W kg-1. After 10 000 cycles, 99.8% of the specific capacitance was retained at 20 A g-1. These results indicate that UPC-600 is a promising candidate for supercapacitor electrode materials.

α- and ß-Phase Ni-Mg Hydroxide for High Performance Hybrid Supercapacitors.

Mg-substituted α- and ß-phase nickel hydroxides with high specific capacitance and good stability have been synthesized via sacrificial metal-based replacement reaction. 2D α- and ß-phase nickel-magnesium hydroxide (NiMg-OH) have been synthesized by sacrificing magnesium (Mg) powder with nickel salt aqueous solutions. Interestingly, the phase of the obtained NiMg-OH can be controlled by adjusting the nickel precursor. As well, the Mg powder is used not only as Mg source but also alkali source to form NiMg-OH. The α-phase nickel-magnesium hydroxide sample (α-NiMg-OH) exhibits lager surface area of 290.88 m2 g-1. The electrochemical performances show that the α-NiMg-OH presented a superior specific capacitance of 2602 F g-1 (1 A g-1) and ß-phase nickel-magnesium hydroxide sample (ß-NiMg-OH) exhibits better stability with 87% retention after 1000 cycles at 10 A g-1. The hybrid supercapacitor composed of α-NiMg-OH and activated carbon (AC) display high storage performance and cycle stability, it presents 89.7 F g-1 (1 A g-1) and of 0-1.6 V potential window and it maintains capacitance retention of 84.6% subsequent to 4000 cycles.