Search

Hybrid supercapacitors represent a promising candidate for grid-scale energy storage devices because of their excellent high-power density, inherent safety and low cost. Here we report a novel NiSe2@rGO nanocomposite (reduced graphene oxide decorated NiSe2 nanoparticles), which shows high specific capacity of 467 C g-1 at 1 A g-1 and superior rate performance (∼72.8 % of the capacity retention at 20 A g-1). Moreover, a hybrid supercapacitor (HSC) assembled from the NiSe2@rGO positive electrode and rGO negative electrode delivers high energy density (34.3 Wh kg-1) and splendid cycling lifespan (∼93% of the capacity retention over 6500 cycles). This study provides a novel insight on high-performance hybrid supercapacitors.

Seasonal acclimatization is important for animals to live optimally in the varying environment. Phrynocephalus vlangalii, a species of lizard endemic in China, distributes on Qinghai-Tibet Plateau ranging from 2000 to 4600m above sea level. To dissect how this lizard mediate metabolism to adapt various season, the preferred body temperature (Tb), standard metabolic rate (SMR), mitochondrial respiration rates and activities of four metabolic enzymes in this species were tested in different seasons (spring, summer, and autumn). The results showed that the preferred Tb was the lowest in spring and the highest in summer. SMR, maximal mitochondrial respiration rates in liver and skeletal muscle were the highest in spring. Similarly, higher activities of lactate dehydrogenase (LDH), citrate synthase (CS) and cytochrome c oxidase (CCO) activities of liver and skeletal muscle were observed in spring. However, β-hydroxyacyl coenzyme A dehydrogenase (HOAD) activities of liver and skeletal muscle were higher in autumn. On the whole, seasonal variation of metabolism is the highest in spring and the lowest in summer. Seasonal variation of metabolism is the opposite of preferred body temperature, this may be one of the mechanisms to adapt to the environment in P. vlangalii. Our results suggested that P. vlangalii at high altitude has certain adaptive characteristics on metabolism in different seasons.

Constructing nanostructured multiphase composite is an effective way for optimizing the performance of electrode materials. Here we report our findings in design and fabrication of a high-performance electrode material composed of two-phase nickel selenide (NiSe-Ni0.85Se) nanoparticles, which exhibits a high specific capacity of 669 C g−1 at 1 A g−1 and 460 C g−1 at 20 A g−1, indicating its good rate capability (~69%). Moreover, a hybrid supercapacitor composed of NiSe-Ni0.85Se positive electrode and reduced graphene oxide (rGO) negative electrode delivers a specific capacitance of 101 F g−1, high energy of 41 Wh kg−1 and good cycling stability with ~80% capacity retention after 5000 cycles at 10 A g−1. These findings provide an important insight into rational design of nanostructured multiphase nickel selenide materials for energy storage systems.

Battery-supercapacitor hybrid (BSH) device is one of the most promising candidates for next advanced energy storage systems because it can bridge the performance gap between lithium ion batteries and conventional capacitors. Herein, we report a novel porous core-shell structured Fe2O3@Fe3C@C nanochains and urchin-like Ni–Co carbonate hydroxide hybridized (denoted as NiCo–CHH) microspheres for advanced battery-type supercapacitors. The as-obtained Fe2O3@Fe3C@C anode shows high specific capacity (611 C g−1) and good rate capability. The fabricated NiCo–CHH cathode delivers high specific capacity (814 C g−1) and excellent cycling stability. When assembled into a battery-type supercapacitor, the NiCo–CHH//Fe2O3@Fe3C@C device delivers a high energy density (95.2 Wh kg−1) and excellent cycling stability. Moreover, In situ Raman spectroscopy proves the reversibility of the NiCo–CHH electrode, and the synergistic effects of Ni and Co ions, further revealing its energy storage mechanism. These findings provide a novel insight on high-performance battery-type supercapacitors.

Nitric oxide (NO), produced by nitric oxide synthases (NOS) from L-arginine, plays important roles in a wide range of physiological processes. However, little is known about ectothermic species. To investigate the response of NO/NOS system in adaptation to different altitudes in Phrynocephalus genus, the red tail toad-headed lizard Phrynocephalus erythrurus that live at 4500-5300 m on the Qinghai-Tibet Plateau and another low altitude living lizard Phrynocephalus przewalskii were selected in the present study. The results of mRNA expression and activity of NOSs, as well as NO metabolite levels in different tissues of the two lizards indicate that nNOS mRNA levels in cardiac and skeletal muscle were notably elevated in P. erythrurus, and iNOS expression was also increased markedly (up to 4-fold) in cardiac muscle. There was no significant difference in eNOS mRNA level in tested tissues between two species. However, the total NOS activity in skeletal muscle of P. erythrurus was slightly lower than that of P. przewalskii (p .05) while no difference in other tissues. Similarly, lower iNOS activity (p .01) was found in cardiac and skeletal muscle in P. erythrurus compared to P. przewalskii. In addition, the NO metabolite levels were dramatically lower in P. erythrurus in all tested tissues. We propose that higher nNOS and iNOS mRNA expression, lower iNOS activity and NO metabolite levels may represent physiological characteristics in nitric oxide system, which may contribute to high-altitude adaptation in P. erythrurus.

Oxidative stress is a major challenge for the survival of animals living on plateaus; however, lifelong exposure to high altitudes could generate certain adaptabilities which make them more tolerant to these environments. The aim of the present study was to compare the oxidative stress and antioxidant status between low altitude (LA, 2900m) and high altitude (HA, 4200m) populations of Phrynocephalus vlangalii. The results showed that malondialdehyde levels in the HA populations decreased significantly in the brain, but markedly increased in the muscle and had no significant difference in the liver compared to LA populations. The activity of catalase in the brain was much higher in HA than LA. Except for total antioxidant capacity and glutathione reductase, other antioxidants were similar between the two populations in livers. By contrast, the levels of most antioxidants in muscle decreased markedly with elevation. We also explored the effects of hypoxia on oxidative damage and antioxidant defenses in P. vlangalii. The lizards were acclimated in a simulated hypoxic chamber (15% O2 and 8% O2) for 6weeks. The results showed that in the 8% O2 group, the levels of malondialdehyde, catalase, glutathione and total antioxidant capacity in the brain, and malondialdehyde, catalase and superoxide dismutase in the liver were significantly higher than the 15% O2 group. These findings indicate that in this species the oxidative stress and antioxidant capacity are subject to altitude and hypoxia and this lizard may have acquired some ability to deal with the oxidative stress.