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In this work, deoxyribonucleic acid (DNA)-wrapped multi-walled carbon nanotubes (MWCNTs), denoted as CNT@DNA, were successfully assembled through a facile sonication treatment. By using the as-obtained CNT@DNA as template, a NiCo2O4-CNT@DNA composite with anchored NiCo2O4nanoparticles was fabricated by coating via in situ precipitation. The nanostructures of the as-synthesized samples were examined via powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) techniques. Subsequently, the NiCo2O4-CNT@DNA and NiCo2O4-CNT (prepared without DNA) samples were used as cathode materials to fabricate supercapacitors with high capacitive performance. The results of electrochemical tests show that the NiCo2O4-CNT@DNA electrode exhibits a high specific capacitance of 760.0 F/g at 5 mV/s, which is higher than that of the NiCo2O4-CNT electrode. The NiCo2O4-CNT@DNA electrode displays a capacitance retention of 96.2% after 5000 cycles at the current density of 5 A/g. Moreover, a NiCo2O4-CNT@DNA//activated carbon (AC) asymmetric supercapacitor, prepared using NiCo2O4-CNT@DNA and activated carbon as the positive and negative electrodes, respectively, shows a specific capacitance of 223.7 F/g and a maximum energy density of 69.7 Wh/kg at a power density of 373.9 W/kg. The NiCo2O4-CNT@DNA//AC asymmetric supercapacitors, integrated in series, powered 5 mm red, yellow, and green light-emitting diodes (LEDs). The above results demonstrate that the novel NiCo2O4-CNT@DNA composites can be promising candidates as electrode materials for high-performance supercapacitors in future applications.

Lithium−sulfur (Li−S) batteries are promising to replace current commercial Li−ion batteries due to the high energy density. Despite this, the poor cyclic stability induced by the shuttle effect of electrolyte-soluble intermediate polysulfides is one of the great obstacles for the application of Li−S batteries. To overcome this issue, here we report a self-template synthesis of metallic and polar Co9S8nanocrystals inlaid carbon (Co9S8/C) hollow nanopolyhedra as an efficient sulfur host material. The Co9S8/C hollow nanopolyhedra with large inner space can ensure the loading mass of sulfur and buffer the volume expansion of Li2Sxspecies during cycling; while the metallic and polar Co9S8/C shell offers synergetic spatial confinement and chemical binding to immobilize polysulfides and prevent the shutting effect. The Co9S8/C-S composite cathode exhibits high capacity and long cycle life with a low capacity decay of 0.041% per cycle over 1000 cycles at 2.0C. When the areal sulfur content is as high as 3.0mgcm–2, the Co9S8/C-S cathode still maintains high cycling stability.

Particulate matter (PM) pollution has become a serious environmental problem, especially in developing countries, owing to its severe threat to human health. Particularly, airborne PM2.5(mean aerodynamic diameter ≤2.5µm) particles are extremely harmful, because the tiny particles can enter human respiratory system and even penetrate into circulatory system. Herein, we propose an effective strategy to recycle PM2.5carbon nanoparticles generated by diesel vehicle engine for the applications of clean energy. After thermal treatment and purification, the PM2.5derived carbon nanoparticles show a diameter distribution between 25 and 40nm, mesoporous characteristics (with an average pore size of ~3.3nm), and homogeneous nitrogen incorporation (with N content of ~1.1at%). The PM2.5derived N-doped mesoporous carbon nanoparticles were used as an advanced electrode material in supercapacitors, exhibiting excellent specific capacity and superb stability over long-term cycling. Moreover, the recycled PM2.5carbon nanoparticles show attractive electrocatalytic properties for oxygen reduction reaction, presenting high onset potential and good immunity to methanol crossover. We expect this research can provide inspiration for air pollution control and sustainable energy utilization.

Considerable efforts have been devoted on the design and fabrication of non-platinum electrocatalysts with high performance and low cost for hydrogen evolution reaction (HER). However, the catalytic activity of existing electrocatalysts usually subjects to the limited amount of exposed active sites. Herein, we propose that self-assembled ultrathin NiCo2S4nanoflakes grown on nickel foam (NiCo2S4/Ni foam) can serve as excellent electrocatalyst for HER in alkaline solution with high activity and stability. The NiCo2S4/Ni foam electrodes were prepared by the complete sulfidation of networked ultrathin NiCo-layered double hydroxide nanoflakes grown on Ni foam (NiCo-LDH/Ni foam). The advantages of this unique architecture are that the ultrathin and porous NiCo2S4nanoflakes can provide a huge number of exposed active sites, the highly-conductive Ni foam can promote the transfer of electrons, and the three-dimensional-networked structure can facilitate the diffusion and penetration of electrolyte. Electrochemical measurements reveal that NiCo2S4/Ni foam electrodes exhibit greatly improved performance than NiCo-LDH/Ni foam for HER in alkaline solution with low onset overpotential (17mV), small Tafel slope (84.5mV/dec) and excellent long-duration cycling stability (maintaining an onset overpotential of ~20mV and an overpotential of 155mV at 50mA/cm2after testing for 100,000s). In addition, the highly-flexible NiCo2S4/Ni foam electrodes show no obvious catalytic degradation after bending for 200 times, confirming the high flexibility and robustness under severe conditions.

Similar to graphene, transition metal oxide nanosheets have attracted a lot of attention recently owning to their unique structural advantages, and demonstrated promising chemical and physical properties for various applications. However, the synthesis of transition metal oxide nanosheets with controlled size and thickness remains a great challenge for both fundamental study and applications. The present work demonstrates a facile solvothermal synthesis of ultra-large (over 100μm) VO2(B) nanosheets with an exceptionally small thickness of only 2–5nm corresponding to 3–8 layers of (001) planes. It can be readily transferred into V2O5with well retained nanosheet structures when calcined, which exhibit remarkable rate capability and great cycling stability. Specifically, the as-synthesized vanadium pentoxide nanosheets deliver a specific discharge capacity of 141mAhg−1at a current density of 0.1Ag−1, which is 96% of its theoretical capacity (147mAhg−1) for one Li+ion intercalation/removal per formular within a voltage window of 2.5–4V. Even at an extreme-high current density of 5Ag−1, it still can exhibit a high specific discharge capacity of 106mAhg−1. It is worthy to note that the V2O5nanosheets electrode can retain 92.6% of the starting specific discharge capacity after 500 discharge/charge cycles at the current density of 1.5Ag−1.