Numerical Simulation on Thermal-Electrical Characteristics and Electrode Patterns of GaN LEDs with Graphene/NiO_x Hybrid Electrode

The thermal-electrical characteristic of a GaN light-emitting diode （LED） with the hybrid transparent conductive layers （TCLs） of graphene （Gr） and NiOx is investigated by a finite element method. It is indicated that the LED with the compound TCL of 3-layer Gr and 1 nm NiOx has the best thermal-electrical performance from the view point of the maximum temperature and the current density deviation of multiple quantum wells, and the maximum temperature occurs near the n-electrode rather than p-electrode. Furthermore, to depress the current crowding on the LED, the electrode pattern parameters including p- and n-electrode length, p-electrode buried depth and the distance of n-electrode to active area are optimized. It is found that either increasing p- or n-electrode length and buried depth or decreasing the distance of n-electrode from the active area will decrease the temperature of the LED, while the increase of the n-electrode length has more prominent effect. Typically, when the n-electrode length increases to 0.8 times of the chip size, the temperature of the GaN LED with the inm NiOx/3-1ayer-Gr hybrid TCLs could drop about 7K and the current density uniformity could increase by 23.8%, compared to 0.4 times of the chip size. This new finding will be beneficial for improvement of the thermal- electrical performance of LEDs with various conductive TCLs such as NiOx/Gr or ITO/Gr as current spreading layers.

Photoelectrochemical properties of MWCNT-TiO_2 hybrid materials as a counter electrode for dye-sensitized solar cells

The MWCNT-Ti02 hybrid materials were prepared by a simply mixing method and used as a counter electrode （CE） for dye-sensitized solar cells. Compared with the platinum CE, MWCNT-TiO2 CE has the similar redox voltage and current response in the cyclic voltammetry. The electrochemical catalytic activity was characterized by the electrochemical impedance spectroscopy and Tafel curve, including the equivalent circuit, the exchange current density, the limiting diffusion current density, and the diffusion coefficient of triiodide/iodide redox species. The results indicate that the reduction process from triiodide to iodide is determined by the kinetic-controlled and diffusion-limited processes. The device performance is optimal based on the MWCNT-TiO2 （mass ratio of 2：1） CE, such as the open-circuit voltage of 0.72 V, the short-circuit photocurrent density of 15.71 mA/cm2, the fill factor of 0.68, and the photon-to-electron conversion efficiency of 7.69%.

Review of MXenes as a component in smart textiles and an adsorbent for textile wastewater remediation

Two-dimensional(2D)MXenes have emerged as an archetypical layered material combining the properties of an organic-inorganic hybrid offering materials sustainability for a range of applications.Their surface functional groups and the associated chemical properties'tailorability through functionalizing MXenes with other materials as well as hydrophilicity and high conductivity enable them to be the best successor for various applications in textile industries,especially in the advancement of smart textiles and remediation of textile wastewater.MXene-based textile composite performs superb smartness in high-performance wearables as well as in the reduction of textile dyes from wastewater.This article critically reviews the significance of MXenes in two sectors of the textile industry.Firstly,we review the improvement of textile raw materials such as fiber,yarn,and fabric by using MXene as electrodes in supercapacitors,pressure sensors.Secondly,we review advancements in the removal of dyes from textile wastewater utilizing MXene as an absorbent by the adsorption process.MXene-based textiles demonstrated superior strength through the strong bonding between MXene and textile structures as well as the treatment of adsorbate by adsorbent(MXene in the adsorption process).We identify critical gaps for further research to enable their real-life applications.

High-performance asymmetric supercapacitors based on reduced graphene oxide/polyaniline composite electrodes with sandwich-like structure

The sandwich-like structure of reduced graphene oxide/polyaniline （RGO/PANI） hybrid electrode was prepared by electrochemical deposition. Both the voltage windows and electrolytes for electrochemical deposition of PANI and RGO were optimized. In the composites, PANI nanofibers were anchored on the surface of the RGO sheets, which avoids the re-stacking of neighboring sheets. The R（;O/PANI composite electrode shows a high specific capacitance of 466 F/g at 2 mA/cm2 than that of previously reported RGO/PANI composites. Asymmetric flexible supercapacitors applying RGO/PANI as positive electrode and carbon fiber cloth as negative electrode can be cycled reversibly in the high-voltage region of 0-1.6 V and displays intriguing performance with a maximum specific capacitance of 35.5 mF cm^-2. Also, it delivers a high energy density of 45.5 mW h cm^-2 at power density of 1250 mW cm^-2. Furthermore, the asymmetric device exhibits an excellent long cycle life with 97.6Z initial capacitance retention after 5000 cycles. Such composite electrode has a great potential for applications in flexible electronics, roll-up display, and wearable devices.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Design of hierarchical and mesoporous FeF_(3)/rGO hybrids as cathodes for superior lithium-ion batteries

Iron fluoride(FeF_(3)) is considered as a promising cathode material for Li-ion batteries(LIBs)due to its high theoretical capacity(712 mAh/g)with a 3 e-transfer.Herein,we have designed a strategy of hierarchical and mesoporous FeF_(3)/rG O hybrids for LIBs,where the hollow Fe F_(3) nanospheres are the main contributor to the specific capacity and the 2 D r GO nanosheets are the matrix elevating the electronic conductivity and buffering the volume expansion.The unique FeF_(3)/rGO hybrid can be rationally synthesized by a nonaqueous in-situ precipitation method,offering the merits of large specific surface area with rich active sites,fast transport channels for lithium ions,effective alleviation of volume expansion during cycles,and accelerating the electrochemical reaction kinetics.The Fe F_(3)/r GO hybrid electrode possesses a high initial discharge capacity of 553.9 m Ah/g at a rate of 0.5 C with 378 m Ah/g after 100 cycles,acceptable rate capability with 168 m Ah/g at 2 C,and feasible high-temperature operation(320 m Ah/g at 70℃).The superior electrochemical behaviors presented here demonstrates that the FeF_(3)/rGO hybrid is a potential electrode for LIBs,which may open up a new vision to design high-efficiency energy-storage devices such as LIBs based on transition metal fluorides.