Fabrication of chitosan/phenylboronic acid/SiO2 hydrogel composite silk fabrics for enhanced adsorption and controllable release on luteolin.

Due to the growing demand for self-health and safety, eco-friendly health textile products with natural colors and pharmacological functionalities have gained considerable popularity. Rapid adsorption and controlled release of active molecules are important issues for functional health textiles. In this study, a functionalized chitosan-based hydrogel composite silk fabric was prepared using chitosan, 3-carboxyphenylboronic acid, and 3-(2, 3-epoxypropyl oxygen) propyl silane by dip-pad and vacuum freeze-drying techniques. The results showed that the incorporation of chitosan/phenylboronic/SiO2 hydrogel into silk fibers improved the UV protection capacity, mechanical properties, and adsorption properties of silk fabrics. The effects of various parameters on the luteolin adsorption properties of silk fabrics were discussed, including metal salt types, salt dosage, pH value, dyeing temperature, initial luteolin concentration, and dyeing time. Under the dyeing temperature of 60 °C and pH of 6.8, the luteolin exhaustion of the composite silk was more than that of the untreated silk, and the adsorption process followed the quasi-second-order kinetic model and the Langmuir adsorption isotherm model. Furthermore, the luteolin-dyed composite silk materials exhibited strong antioxidant activity and controllable release behavior with various pH levels. The as-prepared chitosan-hydrogel composite silk could be a promising material for the sustained release of drugs in medical and healthcare textiles.

Properties and composition of the spent electrolyte for premium circulation mediated by Al-air batteries.

Al-air batteries can serve as a bridge for high-quality cyclic utilization of aluminum resources. However, limited insights into the spent electrolyte are challenging to accurately adjust the recovery process to obtain premium Al-containing products. Herein, the properties and composition of the spent electrolyte were explored through experiments and theoretical calculations. The results demonstrate that the viscosity of the spent electrolyte increased with the rise in discharge current density, time and temperature under highly alkaline conditions, while the ionic conductivity and causticity obviously decreased. Al(OH)4- was the prime and balanced aluminate species when the battery was discharged at 25 °C and coexisted with a bit of [Al2O(OH)6]2-, [Al2O2(OH)6]4- and Al(OH)63- ions. Especially, the characteristics of the spent electrolyte were mainly dominated by the discharge time and temperature when the current density was continuously increased. There was only Al(OH)4- in the electrolyte at a higher discharge temperature. The DFT results also reveal that the polynuclear aluminate ions were produced by the interaction between the mononuclear aluminate ion Al(OH)4- and OH-. This work manifests a profound insight into the spent electrolyte from Al-air batteries for the efficient recycling of aluminum resources.

High-Density Cationic Defects Coupling with Local Alkaline-Enriched Environment for Efficient and Stable Water Oxidation.

The inferior activity and stability of non-noble metal-based electrocatalysts for oxygen evolution reaction (OER) seriously limit their practical applications in various electrochemical energy conversion systems. Here we report, a drastic nonequilibrium precipitation approach to construct a highly disordered crystal structure of layered double hydroxides as a model OER catalyst. The unconventional crystal structure contains high-density cationic defects coupled with a local alkaline-enriched environment, enabling ultrafast diffusion of OH- ions and thus avoiding the formation of a local acidic environment and dissolution of active sites during OER. An integrated experimental and theoretical study reveals that high-density cationic defects, especially di-cationic and multi-cationic defects, serve as highly active and durable catalytic sites. This work showcases a promising strategy of crystal structure engineering to construct robust active sites for high-performance oxygen evolution in an alkaline solution.

Tuning the coordination environment of Fe atoms enables 3D porous Fe/N-doped carbons as bifunctional electrocatalyst for rechargeable zinc-air battery.

As one of the most promising candidates for power sources, the rechargeable Zn-air batteries have attracted much attention due to their high energy density. However, Zn-air batteries suffer from sluggish kinetics of oxygen reduction (ORR) and oxygen evolution reaction (OER) during the discharge and charge process. Herein, a FeN2-doped carbon with a unique three-dimensional (3D) porous structure (CeO2-FeNC-5) was synthesized as an electrocatalyst for Zn-air batteries by one-step pyrolysis and introducing CeO2 to tune the coordination environment of Fe atoms. Extended X-ray absorption fine structure (EXAFS) results indicate that the introduction of CeO2 can convert FeN3 moieties into FeN2 moieties. The CeO2-FeNC-5 exhibits a more positive half-wave potential of 0.902 V for ORR, and a low overpotential of 0.327 V at 10 mA cm-2 for OER. Furthermore, the Zn-air battery with CeO2-FeNC-5 achieve a maximum power density (169 mW cm-2), a high open voltage platform (1.47 V) and superior cycling stability (200 h). The unique 3D porous structure provides channels for mass transport and exposes sufficient active sites to facilitate the ORR and OER processes. Calculations prove that FeN2 moieties are beneficial to O2 adsorption on Fe/N-doped carbon surface. This work provides an effective strategy for designing and synthesizing FeNx-doped carbon matrix electrocatalysts for sustainable metal-air batteries.

A closed-circuit cycle process for recovery of carbon and valuable components from spent carbon cathode by hydrothermal acid-leaching method.

Spent carbon cathode (SCC) as a hazardous solid waste produced in aluminum electrolysis industry, contains plenty valuable components but generate a seriously threat to the environment. This paper focus on a closed-circuit cycle process for direct treatment of SCC based on the hydrothermal acid-leaching method. Thermodynamic calculation, single factor experiment, orthogonal experiment and kinetic study are utilized to obtain the leaching properties of impurities, optimize the leaching conditions, study the influence of conditions on leaching, and capture the restriction factors of leaching. The results indicate that the carbon content of the treated SCC can reach 97.3% when the leaching condition attach the optimal (liquid-solid ratio of 25 mL/g, temperature of 413 K, time of 270 min and acid concentration of 4 mol/L), and liquid-solid ratio is regarded as the crucial factor influencing on that. In addition, the activation energy of impurities reaches 6.25 kJ/mol and the whole leaching process is controlled by the diffusion extent. Finally, the filtrate after the hydrothermal acid leaching is treated, and calcium fluoride, cryolite and sodium chloride are successfully separated. The proposed process eliminates the harm of SCC to the environment, and completes a closed-circuit cycle for the treatment of SCC and recovery of valuable components. It enriches the hydrometallurgical processes of SCC, and provides an attractive scheme for the treatment of SCC.

Anode Interfacial Layer Construction via Hybrid Inhibitors for High-Performance Al-Air Batteries.

The self-corrosion of aluminum anodes is one of the key issues that hinder the development and application of low-cost and high-energy-density Al-air batteries (AABs). Herein, a hybrid corrosion inhibitor combining ZnO and acrylamide (AM) was developed to construct a dense protective interface on the Al anode to suppress the self-corrosion and enhance the electrochemical performance of AABs. Also, the results show that the hydrogen evolution rate with the optimal combination of hybrid inhibitors is 0.0848 mL cm-2 min-1, corresponding to the inhibition efficiency of 78.03%. The integrated AABs with hybrid inhibitors show remarkable capacities of 1240.6 mA h g-1 (25 mA cm-2) and 2444.1 mA h g-1 (100 mA cm-2) and a high power density of 63.7 mW cm-2. This shows that ZnO dissolves into the electrolyte and forms a loose and porous film on the Al surface. When AM is introduced into the ZnO-containing electrolyte, the adsorption of the amide group of AM on the surface of aluminum and ZnO occurs, which not only controls the growth morphology of ZnO but also enables ZnO to easily aggregate into a layer that is in close contact with the anode, efficiently suppressing self-corrosion. This work opens up the prospect of a corrosion inhibition mechanism for ZnO and AM in alkaline solutions and for developing effective organic/inorganic hybrid inhibitors.

An AlCl3 coordinating interlayer spacing in microcrystalline graphite facilitates ultra-stable and high-performance sodium storage.

Metal chloride-intercalated graphite intercalation compounds (MC-GICs) show a perfect sandwich structure with high electronic conductivity and chemical stability, but there are few applications for MC-GICs in anode materials of sodium ion batteries (SIBs). Herein, we selected a splendid host microcrystalline graphite (MG) to synthesize an AlCl3 intercalated MG intercalation compound (AlCl3-MGIC) anode material and demonstrated that it is suitable for SIBs via electrolyte optimization. The AlCl3-MGIC electrode is primarily compared in four electrolytes. Sodium storage is proposed for co-intercalation and conversion reactions by simultaneously selecting a compatible NaPF6/diethylene glycol dimethyl ether (DEGDME) electrolyte. As a result, the AlCl3-MGIC anode delivers a specific capacity of 202 mA h g-1 at a current density of 0.2 A g-1 after 100 cycles and still exhibits a satisfactory capacity of 198 mA h g-1 after 900 cycles. Density functional theory calculations further illustrate that DEGDME solvent molecules offer moderate adsorption energy to sodium ions that guarantees structure stabilization of GICs during repeated cycling. This work provides a theoretical basis for designing sodium ion storage with a graphite layered structure and unveiling the prospects of MC-GIC materials as high-performance anodes.

Comparison of ultrasound-assisted and traditional caustic leaching of spent cathode carbon (SCC) from aluminum electrolysis.

The spent cathode carbon (SCC) from aluminum electrolysis was subjected to caustic leaching to investigate the different effects of ultrasound-assisted and traditional methods on element fluorine (F) leaching rate and leaching residue carbon content. Sodium hydroxide (NaOH) dissolved in deionized water was used as the reaction system. Through single-factor experiments and a comparison of two leaching techniques, the optimum F leaching rate and residue carbon content for ultrasound-assisted leaching process were obtained at a temperature of 70°C, residue time of 40min, initial mass ratio of alkali to SCC (initial alkali-to-material ratio) of 0.6, liquid-to-solid ratio of 10mL/g, and ultrasonic power of 400W, respectively. Under the optimal conditions, the leaching residue carbon content was 94.72%, 2.19% larger than the carbon content of traditional leaching residue. Leaching wastewater was treated with calcium chloride (CaCl2) and bleaching powder and the treated wastewater was recycled caustic solution. All in all, benefiting from advantage of the ultrasonication effects, ultrasound-assisted caustic leaching on spent cathode carbon had 55.6% shorter residue time than the traditional process with a higher impurity removal rate.