Low vaporization enthalpy of modified chitosan hydrogel for high performance solar evaporator.

The high vaporization enthalpy of water attributed to the strong hydrogen bonds between water molecules is limiting the performance of solar evaporators. This work demonstrates a deliberate attempt to significantly reduce the vaporization enthalpy of water through the introduction of weak water-amine hydrogen bond interactions in hydrogel evaporators. In this article, bio-based chitosan-agarose/multiwalled carbon nanotube hydrogel film evaporators (CAMFEs) exhibit larger vaporization enthalpy reduction with the presence of primary amine groups in chitosan. An interplay between vaporization enthalpy reduction and water diffusivity leads to an optimal ratio of chitosan to agarose = 7:1 (CAMFE7) showing an impressive evaporation rate of 4.13 kg m-2 h-1 under 1 sun irradiation. CAMFE7 also exhibits excellent salt resistance, with a stable water evaporation rate, using brine water of up to 10 % salinity under continuous 1 sun irradiation. The high mechanical robustness together with its scalability makes CAMFE7 a highly promising material for practical drinking water production.

MIL-53(Al) assisted in upcycling plastic bottle waste into nitrogen-doped hierarchical porous carbon for high-performance supercapacitors.

Disposable aluminum cans and plastic bottles are common wastes found in modern societies. This article shows that they can be upcycled into functional materials, such as metal-organic frameworks and hierarchical porous carbon nanomaterials for high-value applications. Through a solvothermal method, used poly(ethylene terephthalate) bottles and aluminum cans are converted into MIL-53(Al). Subsequently, the as-prepared MIL-53(Al) can be further carbonized into a nitrogen-doped (4.52 at%) hierarchical porous carbon framework. With an optical amount of urea present during the carbonization process, the carbon nanomaterial of a high specific surface area of 1324 m2 g-1 with well-defined porosity can be achieved. These features allow the nitrogen-doped hierarchical porous carbon to perform impressively as the working electrode of supercapacitors, delivering a high specific capacitance of 355 F g-1 at 0.5 A g-1 in a three-electrode cell and exhibiting a high energy density of 20.1 Wh kg-1 at a power density of 225 W kg-1, while simultaneously maintaining 88.2% capacitance retention over 10,000 cycles in two-electrode system. This work demonstrates the possibility of upcycling wastes to obtain carbon-based high-performance supercapacitors.

Green Synthesis of Carbon Nitride-Based Conjugated Copolymer for Efficient Photocatalytic Degradation of Tetracycline.

Upcycling waste plastics into advanced semiconductor photocatalysts provides a new strategy to reasonably and economically solve the huge amount of waste plastics, which remains challenging. Herein, a carbon nitride-based donor-acceptor (D-A) conjugated copolymer by copolymerization of dicyandiamide and terephthalic acid from discarded polyethylene terephthalate (PET) using Zn(OH)2 as catalyst and template at 360-440 °C is synthesized. The morphology and structure of the conjugated copolymer are well regulated by the calcination temperature. The resultant conjugated copolymer exhibits merits of high light absorption and low electron-hole recombination probability. Consequently, it works excellently in the persulfate-based advanced oxidation process for visible light-driven photocatalytic degradation of tetracycline. The kinetic constant (3.4 × 10-2  min-1 ) is 40.5 and 2.3 times that of the conjugated copolymer system and persulfate system, respectively. Furthermore, the reactive species (including •OH, SO4 •- , •O2 - , 1 O2 , and h+ ) and degradation intermediates of tetracycline are analyzed to expound its degradation process. This work not only pioneers design guidelines on upcycling of waste plastics in a sustainable manner, but also provides a facile strategy to synthesize carbon nitride-based D-A conjugated copolymers for the efficient activation of persulfate-based advanced oxidation process in wastewater treatment.

Diverse-shaped tin dioxide nanoparticles within a plastic waste-derived three-dimensional porous carbon framework for super stable lithium-ion storage.

Tin dioxides (SnO2) inserted into carbons to serve as anodes for rechargeable lithium-ion batteries are known to improve their cycling stability. However, studies on diverse-shaped SnO2 nanoparticles within a porous carbon matrix for super stable lithium-ion storage are rare. Herein, a hollow carbon sphere/porous carbon flake (HCS/PCF) framework is fabricated through template carbonization of plastic waste. By changing the doping mechanism and tuning the loading content, nano SnO2 spheres and cubes as well as bulk SnO2 flakes and blocks are in-situ grown within the HCS/PCF. Then, the as-prepared hybrids with built-in various morphological SnO2 nanoparticles serve as anodes towards advanced lithium-ion batteries. Notably, HCS/PCF embedded with nano SnO2 spheres and cubes anodes possess superb long-term cycling stability (~0.048% and ~0.05% average capacitance decay per cycle at 1 A/g over 400 cycles) with high reversible specific capacities of 0.45 and 0.498 Ah/g after 1000 cycles at 5 A/g. The ultra-stabilized Li+ storage is attributed to the effective mitigation of nano SnO2 spheres/cubes volume expansion, originating from the compact SnO2 yolk-HCS/PCF shell construction. This study paves a general strategy for disposing of polymeric waste to produce SnO2 core-carbon shell anodes for super stable lithium-ion storage.

A general approach towards carbonization of plastic waste into a well-designed 3D porous carbon framework for super lithium-ion batteries.

Due to the ever-increasing plastic waste causing serious environmental problems, it is highly desirable to recycle it into high-value-added products, such as carbon nanomaterials. However, the traditional catalytic carbonization of hydrocarbon polymers is severely prohibited by the complexity of real-world plastic waste due to the existence of halogen-containing polymers. In this study, through a universal combined template based on magnesium oxide and iron(iii) acetylacetonate (Fe(acac)3), a three-dimensional hollow carbon sphere/porous carbon flake hybrid nanostructure is prepared from carbonization of plastic waste with high yields (>70 wt%). This approach is not only suitable for hydrocarbon polymers, but also for halogen-containing polymers. Interestingly, the obtained advanced carbon framework exhibits excellent performance in lithium-ion batteries (802 mA h g-1 after 500 cycles at 0.5 A g-1). The present research paves a new avenue to upcycle plastic waste into a high value-added product.

Transforming polystyrene waste into 3D hierarchically porous carbon for high-performance supercapacitors.

Polystyrene (PS) is usually discarded as a solid waste after a short lifespan. Thus the disposal of waste PS is an inevitably worldwide issue because of their stable and non-biodegradable nature. Herein, a facile method was proposed to carbonize PS waste into novel three-dimensional (3D) hierarchically porous carbon using Fe2O3 particles as both catalyst and template. Furthermore, KOH activation was applied to generate microporous and mesopores on the wall of macropores. As a result, the obtained 3D hierarchically porous carbon exhibits a high specific capacitance of 284.1 F g-1 at 0.5 A g-1 and good rate performance of 198 F g-1 at 20 A g-1 in a three-electrode device. Moreover, the assembled symmetrical capacitor displays a high energy density of 19.2 W h kg-1 at the power density of 200.7 W kg-1 in aqueous electrolyte. Therefore, the present research develops a sustainable way to recycle waste plastics into 3D hierarchically porous carbon for supercapacitors.

Sustainable recycling of waste polystyrene into hierarchical porous carbon nanosheets with potential applications in supercapacitors.

Herein, polystyrene waste was carbonized into mesoporous carbon nanosheets (CNS) using the template method. The pore structure of the obtained CNS was further tuned by KOH activation, resulting in the formation of hierarchical porous carbon sheets with a specific surface area of 2650 m2 g-1 and a pore volume of 2.43 cm3 g-1. Benefiting from these unique properties, in a three electrode system, the hierarchical porous carbon sheets displayed a specific capacitance of 323 F g-1 at 0.5 A g-1 in a 6 M KOH electrolyte, good rate capability (222 F g-1 at 20 A g-1) and cycle stability (92.6% of capacitance retention after 10 000 cycles). More importantly, an energy density of 44.1 Wh kg-1 was also displayed with a power density of 757.1 W kg-1 in an organic electrolyte. In this regard, the present strategy demonstrates a facile approach for recycling plastic waste into high value-added products, which will potentially pave the way for the treatment of plastic waste in the future.

From polystyrene waste to porous carbon flake and potential application in supercapacitor.

Due to white pollution related environmental concern and sustainable development requirement, it is desirable to recycle the widely used plastic wastes into products with commercial value, such as high-valued carbon materials which can be applied in electrochemical fields. In this work, porous carbon flakes (PCFs) are produced by direct pyrolysis of polystyrene waste through template method. Furthermore, manganese dioxide (MnO2) nanosheets are selectively deposited on the surface of resultant PCFs to form hybrid (PCF-MnO2). Because of the large specific surface area (1087 m2/g) and high conductivity of PCFs, native high specific capacity of MnO2, and positive synergistic interaction between PCF and MnO2, the resulting hybrid materials show an ultrahigh capacitance of 308 F/g at 1 mV/s and 247 F/g at 1 A/g in LiCl electrolyte, and excellent cycle stability of 93.4% capacitance retention over 10,000 cycles at 10 A/g in symmetric supercapacitor device. This work demonstrates a convenient method for the preparation of cost-effective and high-performance electrode material for electric capacitor. More importantly, it provides a potential way to recycle polystyrene waste into high-valued product in large-scale with disposing of polymeric waste to alleviate environmental concerns.

Synthesis of Polylysine/Silica Hybrids through Branched-Polylysine-Mediated Biosilicification.

Although many biosilicification methods based on cationic linear α-poly -l- lysine for synthesis of polylysine/silica hybrids have been investigated, these methods tend to rely on the counteranions, added catalysts, and complex synthesis process. To explore a simple and efficient biosilicification method, in this work, branched poly-l-lysine (BPL) is used as both a catalyst to hydrolyze tetraethoxysilane (TEOS) and an in situ template to direct silicic acids forming polylysine/silica hybrids in one-pot mode. The catalysis of BPL to hydrolyze TEOS results from the abundant hydrogen bonding (as the active site) to increase the nucleophilicity of BPL. Meanwhile, the hydrogen bonding is also found to be the key factor determining the self-assembly of BPL. During biosilicification, owing to self-assembly of BPL molecules, BPL would form spherical particles by keeping a random-coil conformation or form lamellar structures by undergoing a conformational transition from a random-coil to ß-sheet construction. As a result, polylysine/silica hybrids with tunable topological structures are synthesized using aggregated BPLs as templates after the hydrolysis of TEOS. This finding of applying BPL to fulfill the biosilicification procedure without counteranions and added catalysts would enable a better understanding of the polypeptide-governed biosilicification process and pave a way for fabricating complex inorganic architectures applicable to silica transformational chemistry.

A novel strategy to synthesize well-defined PS brushes on silica particles by combination of lithium-iodine exchange (LIE) and surface-initiated living anionic polymerization (SI-LAP).

Core-shell hybrid particles, possessing a hard core of silica particles (SiPs) and a soft shell of brushlike polystyrene (PS), were successfully prepared by the combination of lithium-iodine exchange (LIE) and surface-initiated living anionic polymerization (SI-LAP). The molecular weight, graft density and brush thicknesses of the PS brushes were controllable.