Band Engineering and Morphology Control of Oxygen‑Incorporated Graphitic Carbon Nitride Porous Nanosheets for Highly Efficient Photocatalytic Hydrogen Evolution

Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.

Preparation and Characterization of Nucleus/Shell TiO_2/HAP Complex Nanophotocatalyst

A rapid and more efficient method was developed to prepare nucleus/shell titania/hydroxyapatite （TiO2/HAP） complex nanophotocatalyst. Hydroxyapatite （5 μm） which had been dissolved with 0.1 mol/L HCI was formed on the surface of the nanosized anatase titania powders by increasing the pH value of the solution at 90℃ in the water bath for only several hours .The microstructure and morphology of the resulting sample were investigated by X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, energy dispersive spectrum （EDS） and atomic force microscope （AFM）. The results indicated that nucleus/shell structural TiO2/HAP was formed in our experiments, and the thickness of the coating layer was about 5 nm. Photocatalytic decomposition of methyl orange was utilized to test the photocatalysis of the resulting samples and the result was compared with that of pure anatase titania powders （about 20 nm）. It was shown that the photocatalytic activity of the sample was not decreased due to the coating of HAP.

新型含铝奥氏体耐热合金的高温塑性变形行为和热加工性能

新型含铝奥氏体耐热合金(AFA)进行压缩热模拟试验,使用OM和EBSD等手段研究了这种合金在950～1150℃和0.01～5 s^(-1)条件下的微观组织演变、建立了基于动态材料模型热加工图、分析了变形参数对合金加工性能的影响并按照不同区域组织变形的特征构建了合金的热变形机理图。结果表明:新型AFA合金的高温流变应力受到变形温度和应变速率的显著影响。在变形温度为950～1150℃和应变速率为0.18～10 s^(-1)条件下,这种合金易发生流变失稳。在变形温度为1050～1120℃、应变速率0.01～0.1 s^(-1)和变形温度1120～1150℃、应变速率10-0.5～10-1.5 s^(-1)这两个区间,这种合金发生完全动态再结晶行为且其再结晶晶粒均匀细小,功率耗散因子η达到峰值45%。新型AFA合金的热加工艺,应该优先选择再结晶区域。

Super-conductive silver nanoparticles functioned three-dimensional CuxO foams as a high-pseudocapacitive electrode for flexible asymmetric supercapacitors

Copper oxide has aroused great concern in energy storage fields due to its properties of high theoretical capacitance,low cost and mild toxicity.However,its wide application still remains challenges owing to its poor electrical conductivity and unstable cycling life.Binder-free foam electrodes possess abundant porous structures and high specific surface area,which could get good contact with electrolyte.Herein,we demonstrate Ag nanoparticles decorated CuxO nanowires grown spontaneously on copper foam(CF)electrode for asymmetric supercapacitor.The skeleton structure of CF provides large amounts of active sites for the growth of CuxO nanowires.Moreover,Ag nanoparticles further decrease the internal resistance and enhance the electrochemical performance.Ag/CuxO/CF-40 electrode presents a high area specific capacitance of 1192 mF cm^(-2)at 2 mA cm^(-2)and the influence of surface capacitance-dominated process and diffusion-controlled process are discussed in detail.Besides,the energy density of the as-prepared asymmetric supercapacitor(ASC)reaches 46.32 mWh cm^(-2)at a power density of 3.00 mW cm^(-2).A 2V LED is lighted successfully by two ASC in series.This work provides a new strategy to prepare low internal resistance and binder-free flexible Ag/CuxO/CF electrode,which demonstrates a good potential application in flexible supercapacitors or other wearable electronic devices.

Tripotassium citrate monohydrate derived carbon nanosheets as a competent assistant to manganese dioxide with remarkable performance in the supercapacitor

Production cost,capacitance,and electrode materials safety are the key factors to be concerned about for supercapacitors.In this work,a type of carbon nanosheets was produced through the carbonization of tripotassium citrate monohydrate and nitric acidification.Subsequently,a well-designed manganese dioxide/carbon nanosheets composite was synthesized through hydrothermal treating.The carbon nanosheets served as the substrate for growing the manganese dioxide,regulating its distribution,and preventing it from inhomogeneous dimensions and severe agglomeration.Many manganese dioxide nanosheets grew vertically on the numerous functional groups generated on the surface of the carbon nanosheets during acidification.The synergistic combination of carbon nanosheets and manganese dioxide tailors the electrochemical performance of the composite,which benefits from the excellent conductivity and stability of carbon nanosheets.The carbon nanosheets derived from tripotassium citrate monohydrate are conducive to the remarkable performance of manganese dioxide/carbon nanosheets electrode.Finally,an asymmetric supercapacitor with active carbon as the cathode and manganese dioxide/carbon nanosheets as the anode was assembled,achieving an outstanding energy density of 54.68 Wh·kg^(−1) and remarkable power density of 6399.2 W·kg^(−1) superior to conventional lead-acid batteries.After 10000 charge-discharge cycles,the device retained 75.3%of the initial capacitance,showing good cycle stability.Two assembled asymmetric supercapacitors in series charged for 3 min could power a yellow light emitting diode with an operating voltage of 2 V for 2 min.This study may provide valuable insights for applying carbon materials and manganese dioxide in the energy storage field.