Easy route to the wettability cycling of copper surface between superhydrophobicity and superhydrophilicity

A hierarchical copper structure combining micro- and nanogaps/pores was built up on copper substrate by etching and electrodeposition. The fresh as-deposited copper was easily oxidized in air at room temperature, forming a CuO layer covering on the surface. The surface could be hydrophobized with thiol-modified fluorocarbons, after which it showed a water contact angle as high as 165° ± 2°. This surface could also regain the superhydrophilicity with a zero water contact angel after annealing at 200 °C for 10 min to desorb the low surface energy monolayer of thiol-modified fluorocarbons and reform a CuO layer again on the surface. Repeating the process of adsorption/desorption of the monolayer by modification and annealing, it was successful to fulfill the wettability cycling between superhydrophobicity and superhydrophilicity on the copper surface. The adsorption and desorption mechanism of the monolayer was discussed based on the result of surface chemistry analysis.     

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。     

Electrochemical hydrogen evolution by use of a glass carbon electrode sandwiched with clay,poly(butylviologen) and hydrogenase

Electrochemical hydrogen evolution was investigated by use of a hydrogenase-modified electrode, which was constructed by immobilizing hydrogenase between two layers of montmorillonite clay and poly(butylviologen) mixture. The optimum conditions for hydrogen evolution were found to be in a slightly acid buffer solution (pH 4–6) with the applied biases corresponding to the reduction potentials of viologens (−700 to −800 mV vs. Ag/AgCl) and a moderate temperature.     

AC/Ni-Co复合电极材料的制备及其催化析氢性能

采用复合电沉积法制备了AC(活性炭) / Ni-Co 复合电极。XRD 和SEM 测试结果表明, AC 微粒的复合未改变Ni-Co 合金电极的物相结构, 但使镀层的表面粗糙度和真实表面积增大。通过稳态阴极极化曲线和电化学交流阻抗技术考察了不同电极在1 mol·L-1 NaOH 溶液中的催化析氢性能, 结果表明, 镀液中AC 含量为3 g·L-1时所制备的AC/ Ni-Co 复合电极较Ni 电极和Ni-Co 合金电极具有更高的催化析氢活性, 电流密度为30 mA·cm-2时, 析氢反应极化电位分别比Ni 电极和Ni-Co 合金电极正移230 mV 和140 mV , 表观交换电流密度分别是Ni 电极和Ni-Co 合金电极的42 倍和9 倍, 复合电极催化析氢性能的提高主要归因于电极真实表面积的增大。      

Characterization of porous Ni3Al electrode for hydrogen evolution in strong alkali solution

The hydrogen evolution reactions on porous Ni₃Al electrodes, as well as their electrochemical properties in 6 M KOH solutions have been investigated by the polarization measurement, cyclic voltammetry and EIS technique. Results show that the porous Ni₃Al electrodes with lower pore size possess higher catalytic activity for hydrogen evolution in KOH solutions. Their stability in 6 M KOH at 298 K and 358 K under the condition of the reverse polarization is shown to be very good. The electrodes exhibit long term stability and retain high catalytic performance under industrial conditions.     

水热法制备镍负载硫磷双掺杂石墨烯电极及其电催化析氢性能研究

设计一种高活性、高稳定性的非贵金属基催化剂,对电催化析氢的应用具有重要意义.以硫酸和植酸为硫磷掺杂剂,采用水热法合成了硫磷共掺杂石墨烯(SPG);随后,采用简单的醇热法制备了直接生长在SPG上的Ni基纳米材料(Ni/SPG).制备的Ni/SPG电催化剂表现出杰出的析氢性能,其阻抗极低(0.48Ω),电化学活性表面积极好...     

复合电沉积制备（Ni-Mo）-TiO2电极及其电催化析氢性能

为开发新型廉价高效的析氢材料,用恒电流复合电沉积方法制备了(Ni-Mo)-TiO2复合电极,讨论了TiO2悬浮量和电沉积时间对电极催化析氢性能的影响.用XRD和SEM对电极的晶体结构和表面形貌进行了表征,以稳态极化曲线对电极的催化析氢特性进行了评价.结果表明,(Ni-Mo)-TiO2电极是纳米TiO2粒子相和纳米晶Ni-Mo固溶体相构成的复合电极.电极具有较高的催化析氢活性.在25℃、0.5mol.dm-3H2SO4溶液中其表观交换电流密度是Ni-Mo合金电极的2.6倍,是Ni电极的60倍.在电流密度为100mA·cm-2时,电极电势相对于Ni-Mo电极正移了120mV,相对于Ni电极正移了542mV.催化活性的提高源于反应机理的改变,表观活化吉布斯自由能相对于Ni-Mo合金电极降低了24.48kJ·mol-1.     

High-efficiency electrochemical hydrogen evolution based on surface autocatalytic effect of ultrathin 3C-SiC nanocrystals

Good understanding of the reaction mechanism in the electrochemical reduction of water to hydrogen is crucial to renewable energy technologies. Although previous studies have revealed that the surface properties of materials affect the catalytic reactivity, the effects of a catalytic surface on the hydrogen evolution reaction (HER) on the molecular level are still not well understood. Contrary to general belief, water molecules do not adsorb onto the surfaces of 3C-SiC nanocrystals (NCs), but rather spontaneously dissociate via a surface autocatalytic process forming a complex consisting of -H and -OH fragments. In this study, we show that ultrathin 3C-SiC NCs possess superior electrocatalytic activity in the HER. This arises from the large reduction in the activation barrier on the NC surface enabling efficient dissociation of H(2)O molecules. Furthermore, the ultrathin 3C-SiC NCs show enhanced HER activity in photoelectrochemical cells and are very promising to the water splitting based on the synergistic electrocatalytic and photoelectrochemical actions. This study provides a molecular-level understanding of the HER mechanism and reveals that NCs with surface autocatalytic effects can be used to split water with high efficiency thereby enabling renewable and economical production of hydrogen.     

新型稀土镁基贮氢电极合金的结构与性能

系统研究了La0．7Mg0．3(Ni0．85Co0.15)x(x=2．5，3．0，3．5，4．0，4．5，5．0)贮氢电极合金的结构和储氢性能．该类型合金由(La，Mg)Ni3相(PuNi3型结构)和LaNi5相(CaCu5型结构)组成，两相的a轴参数和晶胞体积都随着x值的增大而减小．(La，Mg)Ni3相的丰度先从x=2．5时的48．4％增加到x=3．5时的78．2％，然后又减小到x=5．0时的12．2％，而LaNi5相的丰度在x=2．5-3．5时基本保持不变(-20％)，在x=4．0时突然增加到71.9％．合金的吸氢量从x=2．5时的0．86％(质量分数)增加到x=3．5时的1．50％然后又减小到x=5．0时的1．19％．合金的放氢平台压力在x=2．5-3．5时保持基本不变(-65．9kPa)，然后逐渐增加到x=5．0时的0．30MPa．随着x的增加，吸放氢过程的滞后效应先增大后减小，而合金的放氢平台变得更加平坦．     

氢在不同成分和显微组织的Mg-Ni合金电极中的扩散能力研究

采用机械球磨的方法,制备了不同成分和显微组织的MgxNi(x=1%、1.5%、2%(原子分数))合金粉,并采用X射线衍射(XRD)和扫描电子显微镜的方法研究了Mg/Ni比对机械球磨过程中Mg-Ni合金粉末组织结构演变的影响。在不同的电位扫描速度下,对具有不同Mg/Ni比和显微组织结构的Mg-Ni合金电极循环伏安曲线进行了测量,并由此计算出了氢在这些电极中的扩散系数,分析了合金成分和显微组织对Mg-Ni合金电极中氢扩散能力的影响。其结果表明,降低Mg/Ni比,能提高Mg-Ni合金在球磨过程中非晶相的形成能力,Mg-Ni和Mg1.5Ni合金获得完全非晶相的球磨时间分别是120和160h。在由细小、分散并且完全非晶态的Mg-Ni合金颗粒制备的电极中,氢表现出较强的扩散能力,其扩散系数为1.98×10-8cm2/s。     

SiCO-doped carbon fibers with unique dual superhydrophilicity/superoleophilicity and ductile and capacitance properties

Silicon oxycarbide (SiCO) glass-doped carbon fibers with an average diameter of 163 nm were successfully synthesized by electrospinning polymer mixtures of preceramic precursor polyureasilazane (PUS) and carbon precursor polyacrylonitrile (PAN) into fibers then converting to ceramic/carbon hybrid via cross-linking, stabilization, and pyrolysis at temperatures up to 1000 °C. The transformation of PUS/PAN polymer precursors to SiCO/carbon structures was confirmed by EDS and FTIR. Both carbon and SiCO/carbon fibers were amorphous and slightly oxidized. Doping with SiCO enhanced the thermal stability of carbon fibers and acquired new ductile behavior in the SiCO/carbon fibers with significantly improved flexibility and breaking elongation. Furthermore, the SiCO/carbon fibers exhibited dual superhydrophilicity and superoleophilicity with water and decane absorbing capacities of 873 and 608%, respectively. The cyclic voltammetry also showed that SiCO/carbon composite fibers possess better capacitor properties than carbon fibers.     

Electromechanical interaction of linear piezoelectric materials with a surface electrode

This paper presents a study on the electromechanical interaction between a compliant surface electrode and a semi-infinite piezoelectric material. Using integral transforms, general expressions of stresses, displacements, electric potential and electric displacement have been obtained for symmetrically deformed electrode. For surface electrode subjected to uniform displacement, the normal stress at the edges of the electrode displays a square root singularity. Such a stress singularity will eventually induce the initiation of crack and introduce mechanical and electric instability.     

Corrosion mechanism and hydrogen evolution on Mg

Magnesium (Mg) dissolution is distinct from other engineering metals, as Mg can support cathodic hydrogen evolution on its surface during anodic polarisation. The phenomenon of cathodic hydrogen evolution upon anodically polarised Mg is characterised by the rate of the hydrogen evolution reaction (HER) increasing with anodic polarisation, a phenomenon called the negative different effect (NDE). Mg has a tendency to aggressively corrode in aqueous solutions, impairing its application as a durable engineering material or a predictable electrode material, which is also influenced by the NDE. Over the last century a number of different theories have sought to explain the NDE. However, recent progress in research upon Mg utilising contemporary methods including advanced electrochemical techniques, on-line elemental analysis and cross-sectional electron microscopy, have not only refined the understanding of Mg dissolution, but discredited almost a century of alternate theories. During anodic polarisation, a bilayered MgO/Mg(OH)₂ film forms on Mg, appearing as a dark region on visual inspection. This film gradually occupies the bulk of the previously pristine Mg surface, and importantly sustains (and enhances) the HER. This phenomenon of cathodic activation may also be catalysed by an enrichment of noble elements or impurities on the Mg surface, which could play an important role in promoting the HER. A phenomenological model for the dissolution of Mg encompassing the current opinion of many researchers is presented herein.     

表面微结构金属干式电极制造及细菌粘附性能研究

为开发出高性能生物医用干式电极,提出了利用激光微铣-重铸加工方法,实现了表面具有微结构阵列特征的新型金属干式电极的制造成形。在分析电极表面微观形貌的基础上,研究了电极表面的润湿性能,并重点研究了扫描间距、扫描速度和扫描次数等加工参数对大肠杆菌粘附性能的影响规律。研究结果表明：在一定工艺参数条件下所加工出具有微结构阵列特征的电极的接触角可达150°以上,表现出超疏水的特性。在不同扫描间隙和扫描次数条件下加工出的电极对大肠杆菌的粘附性能具有较大影响,在选择0.1 mm扫描间隙时,电极表面粘附的大肠杆菌数量最少,适当增加扫描次数,也能够有效地减少电极表面大肠杆菌的粘结,从而发挥较好的抗菌效果。通过改变扫描速度加工出的电极则对大肠杆菌的粘附性能影响不大。     

基于多相硫化镍铁的高效析氧电极材料（英文）

开发高效和低成本的析氧电极材料是工业电解水制氢技术发展道路上至关重要的技术难题.本文利用溶剂热方法将镍铁水滑石阵列转化为具有铁掺杂的多相硫化镍(NiS和Ni3S2)阵列,制备出一种具有高效析氧性能的电极材料.粗糙的纳米片表面有利于高活性位点的暴露.电化学分析表明其仅需要100 mV的过电位就可以达到10 mA cm^-2的电流密度,相对于镍铁水滑石阵列降低了130 mV.我们进一步通过密度泛函理论计算来揭示其活性提升机理,发现具有部分S氧化的Fe掺杂NiS可以极大地降低析氧反应中间体形成的阻力,从而加快催化反应进行,提高催化活性.另一方面,(Ni,Fe)S和(Ni,Fe)3S2与三维多孔泡沫镍结构有很好的结合作用,反应电子可以通过金属性的二硫化镍相进行高效传输,进一步加速析氧催化进程.     

A mini review on nickel-based electrocatalysts for alkaline hydrogen evolution reaction

High gravimetric energy density, earth-abundance, and environmental friendliness of hydrogen sources have inspired the utilization of hydrogen fuel as a clean alternative to fossil fuels. Hydrogen evolution reaction (HER), a half reaction of water splitting, is crucial to the low-cost production of pure H₂ fuels but necessitates the use of electrocatalysts to expedite reaction kinetics. Owing to the availability of low-cost oxygen evolution reaction (OER) catalysts for the counter electrode in alkaline media and the lack of low-cost OER catalysts in acidic media, researchers have focused on developing HER catalysts in alkaline media with high activity and stability. Nickel is well-known as an HER catalyst and continuous efforts have been undertaken to improve Ni-based catalysts as alkaline electrolyzers. In this review, we summarize earlier studies of HER activity and mechanism on Ni surfaces, along with recent progress in the optimization of the Ni-based catalysts using various modern techniques. Recently developed Ni-based HER catalysts are categorized according to their chemical nature, and the advantages as well as limitations of each category are discussed. Among all Ni-based catalysts, Ni-based alloys and Ni-based hetero-structure exhibit the most promising electrocatalytic activity and stability owing to the fine-tuning of their surface adsorption properties via a synergistic nearby element or domain. Finally, selected applications of the developed Ni-based HER catalysts are highlighted, such as water splitting, the chloralkali process, and microbial electrolysis cell.

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金属钴对储氢合金电极的表面修饰研究

运用真空蒸镀法时MH／Ni电池储氢合金电极进行了镀覆金属钴的表面修饰,测试了电池的放电容量、高倍率放电性能、循环寿命和充电时的内压,利用XPS和XRD时电极进行了表面和结构分析。实验结果表明,运用该方法对电极进行表面修饰可以降低电池内阻,提高电池的放电容量和放电电压,极片经过修饰的电池,5C（8．5A）放电容量提高了120mAh,放电平台电压提高了约0．05V,内阻降低了19．3％。极片经过表面镀钴后,显著改善了电池的循环性能,电池500周循环后的放电容量仍为初始容量的94．09／6,同时,电池在充电时的内压有了明显的降低,充电效率有了较大的提高。     

Boron leaching:Creating vacancy-rich Ni for enhanced hydrogen evolution

Creating vacancy is often highly effective in enhancing the hydrogen evolution performance of transition metal-based catalysts.Vacancy-rich Ni nanosheets have b...     

Application of immobilized nanotubular TiO(2) electrode for photocatalytic hydrogen evolution: reduction of hexavalent chromium (Cr(VI)) in water

In this study, immobilized TiO(2) electrode is applied to reduce toxic Cr(VI) to non-toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powder TiO(2), a novel technique of immobilization based on anodization was applied and investigated under various experimental conditions. The anodization was performed at 20V-5 degrees C for 45min with 0.5% hydrofluoric acid, and then the anodized samples were annealed under oxygen stream in the range 450-850 degrees C. Based on the results of the experiments, the photocatalytic Cr(VI) reduction was favorable in acidic conditions, with approximately 98% of the Cr(VI) being reduced within 2h at pH 3. Among the samples tested under same anodizing condition, the nanotubular TiO(2) annealed at 450 and 550 degrees C showed highest reduction efficiencies of Cr(VI). In addition, the surface characterizations (zeta potential, XRD, and SEM) of these samples proved that the Cr(VI) reduction efficiency was higher under acidic conditions and at a lower annealing temperature. From this research, it was concluded that the anodized TiO(2) has the potential to be a useful technology for environmental remediation as well as photocatalytic hydrogen production from water.