Flower-like MOF-derived Co–N-doped carbon composite with remarkable activity and durability for electrochemical hydrogen evolution reaction

Electrochemical hydrogen evolution reaction (HER) is one of the most economical, sustainable, and attractive methods to produce hydrogen. Contemporarily, it is still a challenge to develop low-cost catalysts with high activity and durability for HER. Herein, we report a simple strategy to develop a Co–N-doped carbon electrocatalyst derived from a new cobalt metal-organic framework (MOF). The new flower-like 2D→3D MOF {[Co(BIPA)(5-OH-bdc)](DMF)}_n (1) was constructed based on bis(4-(1H-imidazol-1-yl)phenyl)amine (BIPA) and 5-hydroxyisophthalic acid (5-OH-H₂bdc). After that, the Co–N-doped carbon composite Co-MOF-800 was prepared via calcination of MOF 1. Interestingly, Co-MOF-800 exhibited excellent electrocatalytic activity and durability for HER. The onset potential (0.12 V) and E_j=10 value (0.193 V) of the Co-MOF-800 electrode were comparable to that of the most active non-precious metal HER electrocatalysts derived from other MOFs. The HER performance of Co-MOF-800 was stable without degradation even after long-term cycling.     

Boosting hydrogen evolution activity and durability of Pd–Ni–P nanocatalyst via crystalline degree and surface chemical state modulations

Developing efficient, durable, and economical electro-catalysts for large-scale commercialization of hydrogen evolution (HER) is still challenging. Herein, we report for the first time, to the best of our knowledge, a Pd-based ternary metal phosphide as an active and stable HER catalyst. The face-centered-cubic Pd–Ni–P nanoparticles (NPs) annealed at 400 °C show the best HER activity with a low overpotential of 32 mV to realize a current density of 10 mA cm⁻² and a high mass activity of 1.23 mA μg⁻¹_Pd, superior to Pd NPs, Pd–P NPs, Pd–Ni NPs, and Pd–Ni–P NPs annealed under different temperatures. Moreover, this catalyst is also highly stable during 20 h of continuous electrolysis. Notably, the easily fabricated Pd–Ni–P NPs are among the most active Pd-based HER catalysts. This work indicates that Pd-based metal phosphides could be potentially applied as a type of practical HER catalyst and might inform the fabrication of analogous materials for hydrogen-related applications.     

Structural,optical, and photocatalytic properties of the spray deposited nanoporous CdS thin films; influence of copper doping,annealing, and deposition parameters

Nanoporous thin films of Cd_1−xCu_xS (0≤x≤0.06) were grown on a heated glass substrate employing a home-made spray pyrolysis technique. The influences of [Cu]/[Cd] and the annealing in the range 300–500 °C on the structural and morphological properties of the films were investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM). The influences of Cu doping ratio, solution flow rate, and the deposition time on the optical properties and photocatalytic activity of these films are also reported. The films are of polycrystalline nature and hexagonal structure. Increasing the Cu doping ratio and annealing temperature improve the (1 0 1) preferential orientation. The crystallite size is ranged from 23.82 to 32.11 nm. XRD and FTIR reveal the formation of CdO in the 6% Cu-doped CdS film annealed at 400 °C and in all films annealed at 500 °C. The pure CdS film is of a porous structure and the close-packing and porosity of the films increase with increasing Cu%. Also, the pore diameter can be controlled from 50 to 15 nm with the increase of Cu content. The films showed transmittance below 70%. The optical band gap of the films is decreased from 2.43 to 1.82 eV with increasing Cu% and flow rate/deposition time. Additionally, the refractive indices and dispersion parameters of the films are also affected by the deposition conditions. Cu doping enhanced the films' photostability as well as the photocatalytic removal of methylene blue (MB).     

On the validity of the formation of crystalline carbon nitrides,C3N4

X-ray powder diffraction patterns were simulated for five structures proposed for C₃N₄ — i.e., β-, α-, defect zincblend-type and cubic C₃N₄ — with lattice constants and structure parameters reported in the literature. The comparison of experimental X-ray and electron diffraction patterns assigned to crystalline carbon nitrides with simulated ones has led us to conclude that no work has yet presented unambiguous evidence for the crystallization of carbon nitrides with the proposed structures. Disordered polytypic diamond has been proposed as the most probable candidate for part of the products which have hitherto been regarded as C₃N₄.     

Semiconductor Fe-doped SrTiO3-δ perovskite electrolyte for low-temperature solid oxide fuel cell (LT-SOFC) operating below 520 °C

High-temperature operation of solid oxide fuel cells causes several degradation and material issues. Lowering the operating temperature results in reduced fuel cell performance primarily due to the limited ionic conductivity of the electrolyte. Here we introduce the Fe-doped SrTiO_3-δ (SFT) pure perovskite material as an electrolyte, which shows good ionic conduction even at lower temperatures, but has low electronic conduction avoiding short-circuiting. Fuel cell fabricated using this electrolyte exhibits a maximum power density of 540 mW/cm² at 520 °C with Ni-NCAL electrodes. It was found that the Fe-doping into the SrTiO_3-δ facilitates the creation of oxygen vacancies enhancing ionic conductivity and transport of oxygen ions. Such high performance can be attributed to band-bending at the interface of electrolyte/electrode, which suppresses electron flow, but enhances ionic flow.     

薤白挥发油提取工艺的优化及化学成分的气相色谱-质谱分析

以中药薤白为原料,对薤白进行加温浸泡、超声预处理后,采用水蒸气蒸馏法提取薤白中挥发油。以挥发 油提取率为考察指标,在单因素试验的基础上,采用响应面法优化提取工艺条件,并利用气相色谱-质谱法对挥发 油化学成分进行分析。结果表明：最佳工艺条件为浸泡温度40 ℃、超声预处理30 min、液固比4.40∶1（mL/g）、蒸 馏时间2.2 h,此条件下薤白挥发油提取率达1.030%。经气相色谱-质谱分析,共测出其中17 个组分。采用峰面积归 一化法测定各组分的相对含量,其中已鉴定出的14 种化合物组分占提取物的93.46%。     

芦蒿总黄酮提取物的急性毒性及遗传毒性

目的：研究芦蒿总黄酮提取物的安全性。方法：采用急性毒性实验、小鼠骨髓细胞微核实验、小鼠精子畸形实验、小鼠骨髓染色体畸变实验和Ames试验,观察芦蒿总黄酮提取物的急性毒性和遗传毒性作用。结果：芦蒿总黄酮提取物急性毒性的LD50＞10 g/kg,遗传毒性实验为阴性。结论：在本实验条件下,未观察到芦蒿总黄酮提取物对小鼠有急性毒性及遗传毒性作用。     

多彩色空间相关分析的人脸识别算法

人脸识别是当前人工智能和模式识别的研究热点,得到了广泛的关注.基于对不同色彩空间数据的分析,论文提出了多彩色空间典型相关分析的人脸识别方法.文中对2维的Contourlet变换特性进行了分析和讨论,利用Contourlet的多尺度,方向性和各向异性等特点,提出了一种基于Contourlet变换的彩色人脸识别算法.算法对原图进行Contourlet分解,对分解得到的低频和高频图像进行cca分析.典型相关分析是一种有效的分析方法,其实际应用十分广泛.低频系数反映图像的轮廓信息,高频系数反映图像的细节信息,使用cca充分利用不同频率的信息,使不同色彩空间的不同分辨率图形的相关性达到最大,得到投影系数,最后,采用决策级最近邻分类器完成人脸识别.在对彩色人脸数据库AR的识别实验中,该算法识别率达到98％以上,与传统算法相比,该算法不仅既有良好的识别结果,而且具有很快的运算速度.     

基于Hadoop的三队列作业调度算法

Hadoop集群单队列作业调度会产生短作业等待、资源利用率低的问题;采用多队列调度可兼顾公平、提高执行效率,但会带来手工配置参数、资源互占、算法复杂等问题。针对上述问题,提出三队列作业调度算法,利用区分作业类型、动态调整作业优先级、配置共享资源池、作业抢占等设计,达到平衡作业需求、简化一般作业调度流程、提升并行执行能力的目的。对短作业占比高,各作业占比均衡以及一般作业为主,偶尔出现长、短作业三种情况与先进先出(FIFO)算法进行了对比实验,结果三队列算法的运行时间均比FIFO算法要少。实验结果表明,在短作业聚集时,三队列算法的执行效率提升并不显著;但当各种作业并存且分布均衡时,效果很明显,这符合了算法设计时短作业优先、一般作业简化流程、兼顾长作业的初衷,提高了作业整体执行效率。