电解水析氢电极材料的研究新进展

电解水是实现工业化廉价制备氢气的重要手段,为减小阴极过电位,降低能耗,研究具有高电催化活性的阴极析氢材料具有重要的意义。影响析氢材料电催化活性的因素主要有能量因素和几何因素,围绕着这两个主要因素,综述了电解水析氢电极材料的最新研究进展,并对析氢电极材料的发展趋势进行了展望。     

一种新型活性阴极材料的制备和性能

用电沉积法制备了以Ni为主的多元合金活性阴极涂层，其表面形貌为球状堆积，有利于气体溢出，减少气泡帘电阻，降低气体析出电位．该合金涂层由于本身对气体析出具有催化活性，析氢电位低、与基体结合力强、抗停断电能力强并且使用寿命长．     

Ni-Mo-P活性阴极制备及析氢行为的研究

采用电化学方法将Ni-Mo-P合金镀覆于低碳钢表面并形成活性阴极,评价其析氢过电位和真实表面积.结果表明,最佳镀覆工艺条件为电流密度0.03A/cm~2、镀液温度40℃、钼酸盐质量浓度3g/L.当阴极极化电流密度为0.18A/cm~2时,Ni-Mo-P活性阴极析氢过电位较镀覆前低碳钢阴极降低约300mV;其真实表面积为10.8cm~2,粗糙度为5.4,较低碳钢阴极增加约1倍,能显著降低氯碱工业电解槽的电耗水平.     

纳米氧化镍在超大容量电容器中的应用

用络合沉淀法制得Ni(OH)2，经过加热分解得纳米NiO粉末（粒径约30nm)。用该粉末作为活性物质制得的电极具有90－110F／g的比容量。考察了电极的比容量与电解液的浓度、工作电位范围的关系，并讨论了其储存电荷的机理。     

基于简易微波方法制备高性能MoS2/石墨烯纳米复合材料用于高效析氢反应（英文）

用于析氢反应(HER)的低成本、高效能催化剂对于推进基于清洁氢气的能源工业非常重要.二维二硫化钼(MoS2)具有显著的催化性能,因而已被人们广泛深入研究.然而,大多数现有的合成方法耗时、复杂且效率较低.本文通过超快(60秒)微波引发的方法生产MoS2/石墨烯催化剂.石墨烯的高比表面积和导电性为MoS2纳米片的生长提供了有利的导电网络和快速电荷转移动力.文中制备的MoS2/石墨烯纳米复合材料在酸性介质中对HER表现出优异的电催化活性,具有62 mV的低起始电位,高阴极电流和43.3mV/dec的Tafel斜率.除了优异的催化活性外, MoS2/石墨烯还具有较长的循环稳定性,在250 mV的过电位下阴极电流密度高达1000 mA cm^-2.此外, MoS2/石墨烯催化剂在30–120°C范围内具有出色的HER活性和36.51 kJ mol^-1的低活化能,提供了潜在的大批量生产和制备的机会.     

非晶态镍磷镀层析氢阴极活性的控制与机理

非晶态Ni-P类合金镀层具有很好的耐蚀性,在碱性溶液中具有较高的析氢反应催化活性,能降低析氢过电位,节约能源,是一种有很好应用前景的阴极材料.论述了非晶态Ni-P镀层的P含量、厚度、制备条件、添加第3种元素及镀后处理对镀层电极活性的影响.并总结了Ni-P类非晶态合金镀层的电极催化机理.     

苏联粉末治金的概况

苏联在第二次世界大战前就进行了粉末冶金的研究工作,介绍粉末冶金全貌的书籍有:巴鲁新的粉末冶金(1947)和渥娄库的同名书籍(1948);有关粉末冶金各个部分的基础理论书籍有:巴鲁新的粉末金属学(1948),拉柯夫斯基的超硬质合金(1945)和机械制造用粉末冶金(1948),还有前著者又与安德洛斯合著超硬质合金制     

土壤环境中阴极保护电位对涂层的影响

通过电化学测试手段,研究了土壤中涂覆有涂层的钢样在不同阴极电位下的阴极极化行为,并探讨析氢阴极还原反应对涂层的影响,从而为阴极保护限制电位的确定提供依据。     

镍钼修饰的p型硅电极材料的制备和性能

在半导体ｐ型Ｓｉ上恒电流沉积纳米晶和非晶Ｎｉ－Ｍｏ合金薄膜，制备出Ｎｉ－Ｍｏ合金修饰的半导体ｐ型Ｓｉ电极镀层．用ＳＥＭ对膜层进行了表征，测量了两种电极镀层的阴极催化析氢曲线，纳米晶Ｎｉ－Ｍｏ／ｐ－Ｓｉ镀层的催比析氢性能较好，测量了光照下纳米晶Ｎｉ－Ｍｏ／ｐ－Ｓｉ电极的催比析氢曲线．结果表明， Ｎｉ－Ｍｏ颗粒尺寸在４０～１００ｎｍ时，光照下电极的析氢过电位比无光照减小了约１６０ｍＶ（电流密度为８ ｍＡ·ｃｍ－２），催比析氢活性显著提高．     

泡沫镍负载NiFeMoCu析氢阴极电极材料的电化学制备研究

以泡沫镍(NF)为基板,分别通过恒电位法(i-t)和计时电位法(CP)沉积镍铁钼铜四元合金,经去合金化处理,获得了具有高催化活性的析氢阴极电极材料NiFeMoCu/NF。电沉积过程设计了6种电解液配方进行优选,去合金化处理时采用恒电位法(i-t)分别进行了金属铜的原位溶出和独立溶出。结果表明:参照配方4的物料配比组织电解液,以计时电位法沉积四元合金,经铜的独立溶出后制得了由纳米颗粒堆积而成团簇状结构的析氢电极材料。在1mol/L KOH溶液中,催化电流密度为10mA/cm~2时,NiFeMoCu/NF电极的析氢过电位仅为65mV,其高催化活性主要归因于镍铁钼铜四元合金的金属间协同作用。     

Electrospun ultralong hierarchical vanadium oxide nanowires with high performance for lithium ion batteries

Ultralong hierarchical vanadium oxide nanowires with diameter of 100-200 nm and length up to several millimeters were synthesized using the low-cost starting materials by electrospinning combined with annealing. The hierarchical nanowires were constructed from attached vanadium oxide nanorods of diameter around 50 nm and length of 100 nm. The initial and 50th discharge capacities of the ultralong hierarchical vanadium oxide nanowire cathodes are up to 390 and 201 mAh/g when the lithium ion battery cycled between 1.75 and 4.0 V. When the battery was cycled between 2.0 and 4.0 V, the initial and 50th discharge capacities of the nanowire cathodes are 275 and 187 mAh/g. Compared with self-aggregated short nanorods synthesized by hydrothermal method, the ultralong hierarchical vanadium oxide nanowires exhibit much higher capacity. This is due to the fact that self-aggregation of the unique nanorod-in-nanowire structures have been greatly reduced because of the attachment of nanorods in the ultralong nanowires, which can keep the effective contact areas of active materials, conductive additives, and electrolyte large and fully realize the advantage of nanomaterial-based cathodes. This demonstrates that ultralong hierarchical vanadium oxide nanowire is one of the most favorable nanostructures as cathodes for improving cycling performance of lithium ion batteries.     

Preliminary studies of mn-rich Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, 0.11) as cathode active materials for lithium rechargeable batteries

Novel cathode active materials, Li[Li(x)(Ni0.3Co0.1Mn0.6)1-x]O2 (x = 0.09, 0.11) composed of rod-like primary particles, but aggregated spherical shape in appearance, were synthesized. The newly Mn-rich cathode active materials were then adopted as cathodes to show the benefits for Li-ion rechargeable batteries. The results show that to use proper nano-scaled particles as a cathode and to make homogeneous particle sizes have great improvements on electrochemical performances, probably ascribed to enhancement of charge transfer kinetics and lower cell impedance at high voltage region (approximately 4.6 V). The electrochemical performances of Mn-rich cathodes were investigated by cycler (BT2000, Arbin), comparing electrochemical behaviors between room and elevated temperature, 55 degtees C. The morphology of cathodes having nano-scaled particles of active materials and the Mn-rich cathode active materials were investigated using field emission scanning electron microscope (FE-SEM) and field emission transmission electron microscope (FE-TEM), also the crystalline phase identification was analyzed by high power X-ray diffractometer (XRD).     

Recent progress on RE2O3-Mo/W emission materials

RE2O3-Mo/W cathodes were prepared by powder metallurgy method. La2O3-Y2O3-Mo cermet cathodes prepared by traditional sintering method and spark plasma sintering (SPS) exhibit different secondary emission properties. The La2O3-Y2O3-Mo cermet cathode prepared by SPS method has smaller grain size and exhibits better secondary emission performance. Monte carlo calculation results indicate that the secondary electron emission way of the cathode correlates with the grain size. Decreasing the grain size can decrease the positive charging effect of RE2O3 and thus is favorable for the escaping of secondary electrons to vacuum. The Scandia doped tungsten matrix dispenser cathode with a sub-micrometer microstructure of matrix with uniformly distributed nanometer-particles of Scandia has good thermionic emission property. Over 100 A/cm2 full space charge limited current density can be obtained at 950Cb. The cathode surface is covered by a Ba-Sc-O active surface layer with nano-particles distributing mainly on growth steps of W grains, leads to the conspicuous emission property of the cathode.     

Effect of different epitaxial structures on GaAs photoemission

The quantum efficiency equations of two different structure reflection-mode GaAs photocathodes with back interface recombination velocity have been solved from the diffusion equations. One structure consists of GaAs substrate and an epitaxial GaAs active layer (GaAs-GaAs) and another structure consists of GaAs substrate, an epitaxial AlGaAs buffer layer, and a GaAs active layer (AlGaAs-GaAs). The experimental results show that the quantum efficiency of long-wavelength photons and the integral sensitivities for GaAs-GaAs cathodes both increase with the increase in the active layer thickness, which is due to the increase of electron diffusion length. The quantum efficiency of long-wavelength photons and the integral sensitivity of AlGaAs-GaAs cathodes are greater than those of GaAs-GaAs cathodes with an identical active layer thickness, which is attributed to the AlGaAs buffer layer. The buffer layer can reflect electrons and improve the quality of the GaAs active layer. Through the theoretical simulation, we found the active layer thickness for AlGaAs-GaAs cathodes has an optimum value at which the cathodes achieve the maximum sensitivity.     

Synthesis of Nanosized Copper Powder by an Aqueous Route

Nanostructured, crystalline copper powder was produced at ambient temperature by aqueous reduction of a copper salt by sodium borohydride. Conditions were optimized to produce boron-free copper powder with an average particle diameter of 200 nm, surface area of 5.48 m * m/g, and oxygent content of 0.155%. The effects of different experimental conditions on average particle size of the powder were also studied. The sintering phenomenon exhibited by produced copper particles at 100°C may be attributed to the low oxygen content of the powder along with other size variation-dependent factors.     

含钪扩散阴极用铝酸盐的制备及发射性能研究

采用液相共沉淀法和固相合成法分别制备411(4BaO:CaO:Al₂O₃)铝酸盐前驱粉末, 在钨网氢气炉中高温烧结. 采用喷雾干燥法结合两步氢气还原法制备出亚微米氧化钪掺杂钨粉. 随后经过压制, 烧结, 浸渍, 水洗, 退火等工艺获得具有亚微米结构的含钪扩散阴极, 并研究含钪扩散阴极的电子发射性能. 实验结果表明, 液相共沉淀法制备的铝酸盐在1500℃烧结后, 铝酸盐中Ba₅CaAl₄O₁₂衍射峰最强, 结晶程度最高. 液相共沉淀法含钪扩散阴极, 脉冲发射电流密度在850℃达到37.89 A/cm². 在激活过程中, 阴极表面形成“Ba-Sc-O”发射活性层, “Ba-Sc-O”发射活性层存在提高了阴极热电子发射能力, 降低了含钪扩散阴极的蒸发速率.     

Secondary electron emission of Y2O3-Mo cermet cathode

Y₂O₃-Mo cermet cathodes were prepared by mechanical mixing of Y₂O₃ and Mo powder. The prepared cermet cathode provides a certain secondary emission yield (3.09), about 1.8 times lower than that for the cathode prepared by sol-gel method. It was found that the cathode prepared by sol-gel method had a smaller grain size, which could be attributed to its higher emission property. The energy distributions of primary electrons in the cathodes with different grain sizes have been simulated by Monte Carlo method. Based on the calculation results, the emission models of the cathodes are established and presented. The cathodes with different grain sizes exhibited different ways of emission. Two types of emission, of reflection emission and transmission emission, existed in the cathode with small grain sizes whereas only transmission emission existed in the cathode with large grain sizes.     

煅烧条件对共沉淀法合成ZnZr_4(PO_4)_6粉体影响的研究

采用共沉淀法制备了磷酸锆锌(α-ZnZr_4(PO_4))粉体,探讨了磷酸锆锌粉体合成机理,研究了煅烧温度、保温时间等煅烧条件对粉体合成的影响,并用TG-DTA、FT-IR、XRD、TEM等方法进行表征。实验表明前驱体在900～950℃煅烧2h可以获得平均粒径200nm、结晶完全的α-ZnZr4(PO4)6粉体,采用此粉体制备的陶瓷材料1200℃时热膨胀系数为-2.0×10-6℃-1。     

Highly active and cheap graphite/polytetrafluoroethylene composite coating cathodes for electrogeneration of hydrogen peroxide

Clean Technologies and Environmental Policy - Using cheap graphite powder as catalyst and polytetrafluoroethylene (PTFE) as binder, graphite/PTFE composite coating cathodes were fabricated for...