Pressure and Time Dependences of the Supercooled Liquid-to-Liquid Transition in Sulfur

Thermal behavior of bulk amorphous sulfur is investigated by in situ temperature measurements at high pressures of 0.9, 1.4 and 2.1 GPa, and under different heating rates of 8, 10 and 12K/min at 0.9 GPa. The results show that the onset temperature of the transition from the supercooled Hquid to the liquid state for sulfur increases with the pressure and the heating rate. It is deduced that the transition does not follow the Clapeyron equation, indicating considerable coupling of the molecular structure change in the transition. Along with the data at ambient pressure and high pressure, we present a dynamic diagram to demonstrate the relationship between the amorphous solid, supercooled liquid, liquid, and crystal phases of sulfur, and suggest an experimental approach to establish pressure-temperature-time transition diagrams for supercooled liquid and liquid.

Embedding partial sulfurization of iron-cobalt oxide nanoparticles into carbon nanofibers as an efficient electrode for the advanced asymmetric supercapacitor

In this paper,a series of partially sulfurized iron-cobalt oxide(FCOS) nanoparticles were embedded in carbon nanofibers(FCOS@CNF) via a simple electrospinning method and followed by a hydrothermal sulfurization process.The sulfurization degree of iron-cobalt oxide nanoparticles can be further controlled by tuning the hydrothermal reaction time.The self-supported FCOS@CNF samples with hierarchical nanostructure can not only effectively prevent the detaching of the FCOS nanoparticles but also provide abundant electrochemical active sites.When used as a supercapacitor electrode,the FCOS@CNF^(-1)0 electrode presents a high specific capacitance(1039 F·g^(-1)at 1 A·g^(-1)),a good rate performance(over 69.4%of capacitance retention from 1 to 15 A·g^(-1)),and a long cycle lifespan(88.3% of capacitance retention after 4000 cycles at10 A·g^(-1)).A unique(FCOS@CNF^(-1)0//F-RGO) asymmetric supercapacitor device was assembled using the FCOS@CNF^(-1)0 sample as the positive electrode and the freeze-dried reductive graphene oxide(F-RGO) as the negative electrode.The hybrid device exhibits excellent electrochemical properties,including a high specific capacity,a long cycle life(86% after5000 cycles at 10 A·g^(-1)),and a maximum energy density of 24.2 Wh·kg^(-1)@725.4 W·kg^(-1).

A review of transition metal chalcogenide/graphene nanocomposites for energy storage and conversion

To meet the ever-increasing energy demands, advanced electrode materials are strongly requested for the exploration of advanced energy storage and conversion technologies, such as Li-ion batteries, Li-S batteries, Li-]Zn-air batteries, supercapacitors, dye-sensitized solar cells, and other electrocatalysis process （e.g., oxygen reductionlevolution reaction, hydrogen evolution reaction）. Transition metal chalcogenides （TMCs, Le., sulfides and selenides） are forcefully considered as an emerging candidate, owing to their unique physical and chemical properties. Moreover, the integration of TMCs with conductive graphene host has enabled the significant improvement of electrochemical performance of devices. In this review, the recent research progress on TMC]graphene composites for applications in energy storage and conversion devices is summarized. The preparation process of TMC]graphene nanocomposites is also included. In order to promote an in-depth understanding of performance improvement for TMC/graphene materials, the operating principle of various devices and technologies are briefly presented. Finally, the perspectives are given on the design and construction of advanced electrode materials.