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Graphical abstract Highlights • Porous carbon flakes (PCFs) are prepared from PS waste using MgO as template. • PCFs are used as carbon support for deposition of MnO 2 forming PCF-MnO 2 hybrid. • PCF-MnO 2 exhibits good electrochemical properties as electrode in supercapacitor. • This work provides a practical way to recycle polymeric waste in large-scale. Abstract 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 (MnO 2) nanosheets are selectively deposited on the surface of resultant PCFs to form hybrid (PCF-MnO 2). Because of the large specific surface area (1087 m2/g) and high conductivity of PCFs, native high specific capacity of MnO 2 , and positive synergistic interaction between PCF and MnO 2 , 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. [ABSTRACT FROM AUTHOR]

With the purpose to turn wastes into wealth and develop renewable energy, much effort has been focused on converting biowastes into porous carbons and exploring their application for supercapacitors. In this study, inspired by natural porous structure of biomass and small size of Sn nanoparticles, a one-step strategy was developed to convert waste wolfberry fruits into porous carbons by SnCl 2. The as-fabricated carbon exhibited large specific surface area of 1423 m2 g−1 and hierarchical porosity with total pore volume of 1.36 cm3 g−1. Meanwhile, the newly produced SnCl 2 with more than 95% recovery rate was reused as catalyst. Moreover, the porous carbon was applied for supercapacitive electrode. In three-electrode 6 M KOH system, it displayed outstanding capacitance of 365 F/g at 0.2 A g−1, good rate capability of 75% capacitance retention at 20 A g−1 and excellent cycling stability of 96.4% capacitance retention after 10000 cycles. In two-electrode 1 M Li 2 SO 4 system, its energy density reached 23.2 Wh kg−1 at a power density of 225 W kg−1. The current work provided a facile and low-cost method to recycle renewable biowastes into high-valued carbon material, and further expanded its application for high-performance energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

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. [Display omitted] [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Upcycle used PET bottles and aluminum cans into the nitrogen-doped hierarchical porous carbons. • Prepared carbon as supercapacitor electrode delivers a high energy density of 20.1 Wh/kg. • Well-defined porous carbon framework is vital to the excellent supercapacitive performance. • This work paves an effective environmental-friendly way to prepare carbon-based supercapacitor. [ABSTRACT FROM AUTHOR]