Formation mechanism and structure of nickel-molybdenum-boron chemical-catalytic coatings

Effect of molybdate-ions on the kinetics of partial reactions of dimethylamine-borane oxidation and nickel-and molybdate-ions reduction in the process of their chemical-catalytic reduction during the Ni-Mo-B-coatings deposition is studied. Molybdenum is deposited as metal only in the codeposition with nickel, yielding amorphous alloys. Adding of low concentration of the molybdate-ions to the nickel-plating solution increases the hydrogen evolution and alloy deposition rates as a result of the accelerating of dimethylamine-borane heterogeneous hydrolysis. At high molybdate-ion concentrations in the solution, a denser film of the molybdate reduction intermediate products forms at the electrode surface; this decreases the system’s catalytic activity as regards the dimethylamine-borane heterogeneous hydrolysis and thus decreases the hydrogen and nickel ions reduction rates.     

Gaseous products of dimethylamine borane oxidation in chemically catalyzed deposition of nickel-rhenium-boron coatings

The gaseous products of the oxidation of hydride hydrogen of the dimethylamine borane (DMAB) (CH₃)₂NH · BH₃ reducer used for depositing Ni-Re-B coatings and hydrolysis of DMAB on them were studied by mass spectrometry of the isotope composition of the gas. The oxidation level of hydride hydrogen of the DMAB reducer was found to depend on the catalytic activity of the Ni-Re-B alloy, on which heterogeneous hydrolysis takes place. For Ni-Re-B alloys with low rhenium concentrations (0?C13 at %), the heterogeneous hydrolysis of DMAB proceeds with hydride hydrogen oxidation to the atomic state, as it does in the deposition of the Ni-B alloy. In contrast, at high rhenium concentrations (40?C46 at %), the oxidation proceeds to the proton H⁺, leading to an antibatic dependence of the hydrolysis and alloy reduction rates. An analysis of the partial rates of the process and isotope composition of the evolved gas revealed two different mechanisms of the chemical-catalytic reduction of Ni-Re-B alloys at concentrations of potassium perrhenate of 0?C4 and 4?C16 mM in solution.     

Electroless deposition and properties of Co–Re–B alloys

The data on the mechanism of electroless (catalytic) deposition of Co–Re–B coatings are obtained by determining the donor capacitance of dimethylamine borane (DMAB) (CH₃)₂HN · BH₃ reductant and the oxidation level of its hydride hydrogen. From the results of the study of isotopic composition of evolved hydrogen, it is concluded that the oxidation level of DMAB hydride hydrogen depends on the catalytic activity of the alloy. The alloys containing up to 46 at % rhenium were produced by the electroless deposition.     

Synthesis of Ni-Ru alloy nanoparticles and their high catalytic activity in dehydrogenation of ammonia borane

We report the synthesis and characterization of new Ni(x)Ru(1-x) (x = 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni(2+) and Ru(3+) precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni(0.74)Ru(0.26) sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core-shell NPs. The hydrolysis activation energy for the Ni(0.74)Ru(0.26) alloy catalyst was measured to be approximately 37?kJ?mol(-1). This value is considerably lower than the values measured for monometallic Ni (≈70?kJ?mol(-1)) and Ru NPs (≈49?kJ?mol(-1)), and for Ni@Ru (≈44?kJ?mol(-1)), and is also lower than the values of most noble-metal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

非晶态Ni基合金电极电子结构的XPS研究

用XPS测定了含P、Ce、La的Ni基合金的费米能级及各元素的芯级电子结合能,讨论了合金的电子结构以及它与析氢反应的电催化活性即析氢超电势之间的联系。结果表明：合金中各元素的原子间存在着电荷传输,它对析氢反应活性起重要作用。     

Synthesis of Ni–Ru Alloy Nanoparticles and Their High Catalytic Activity in Dehydrogenation of Ammonia Borane

We report the synthesis and characterization of new Ni_xRu_1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni²⁺ and Ru³⁺ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni_0.74Ru_0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni_0.74Ru_0.26 alloy catalyst was measured to be approximately 37 kJ mol^?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol^?1) and Ru NPs (≈49 kJ mol^?1), and for Ni@Ru (≈44 kJ mol^?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

电沉积纳米镍合金在海水溶液中的析氢性能

采用电沉积法获得Ni、Ni-Fe和Ni-Fe-C合金镀层电极, 在90 °C模拟海水(0.5 mol·L-1 NaCl, pH=12)的稳态极化曲线表明Ni-Fe-C合金电极具有最好的析氢催化性能. 通过扫描电子显微镜(SEM)观察电极表面形貌、X射线衍射(XRD)与透射电子显微镜(HRTEM)分析合金的晶体结构, 发现电极材料的晶粒尺寸影响析氢催化性能, 晶粒尺寸越小析氢催化活性越好. 用电化学阻抗方法(EIS)研究电极析氢催化性能的本质原因, 结果表明电极表面活性点数目和电极的本质电催化活性对合金电极析氢催化活性有重要的影响.     

The effect of composition of electrodeposited Ni-P alloys on the hydrogen evolution rate

The effect of composition and structure of electrodeposited nickel-phosphorus coatings on their catalytic properties in the hydrogen evolution reaction is studied. It is found that an increase in the content of phosphorus in the alloy from 0.1 to 12.6 wt % leads to an increase in the hydrogen evolution rate. The coatings, which were deposited under the galvanostatic conditions, exhibit higher activity than those plated under the potentiodynamic conditions. It is shown that the nature of acceleration of hydrogen evolution rate on the alloys depends on the alloy composition: only Ni-P alloys containing up to 6.5 wt % phosphorus possess true catalytic activity, whereas the coatings enriched in phosphorus promote the hydrogen evolution due to significant development of their surface area.     

Skeletal Ni Catalysts Prepared from Amorphous Ni–Zr Alloys: Enhanced Catalytic Performance for Hydrogen Generation from Ammonia Borane

Skeletal Ni catalysts were prepared from Ni–Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni–Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni₃₀Zr₇₀ alloy had a higher catalytic activity than that prepared from amorphous Ni₄₀Zr₆₀ and Ni₅₀Zr₅₀ alloys. The atomic arrangement of the Ni–Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni–Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface‐exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability.     

多孔碳负载镍纳米颗粒的制备及催化氨硼烷水解制氢

合成了蜂窝状的分级多孔碳,并以多孔碳为载体通过浸渍-化学还原法制备碳载镍(Ni/C)作为催化氨硼烷水解制氢的催化剂。采用XRD、BET、SEM、Raman、TEM等手段对样品进行了表征并研究了Ni/C室温催化性能。结果显示,多孔碳比表面积高达737 m²·g^-1,具有部分石墨化结构;负载的非晶态镍纳米颗粒平均粒径约为10 nm,均匀分布在碳基材。碳载镍对氨硼烷水解反应具有良好的催化活性,镍负载量为30wt%时催化性能最佳,298 K温度下放氢速率达到1 304.67 mL·min^-1·g^-1,活化能为29.1 kJ·mol^-1,并且具备一定的催化稳定性,表明Ni/C可作为一种廉价高效的催化剂应用于催化氨硼烷水解制氢。     

多孔碳负载镍纳米颗粒的制备及催化氨硼烷水解制氢

合成了蜂窝状的分级多孔碳,并以多孔碳为载体通过浸渍-化学还原法制备碳载镍(Ni/C)作为催化氨硼烷水解制氢的催化剂。采用XRD、BET、SEM、Raman、TEM等手段对样品进行了表征并研究了Ni/C室温催化性能。结果显示,多孔碳比表面积高达737 m2·g-1,具有部分石墨化结构;负载的非晶态镍纳米颗粒平均粒径约为10 nm,均匀分布在碳基材。碳载镍对氨硼烷水解反应具有良好的催化活性,镍负载量为30wt%时催化性能最佳,298 K温度下放氢速率达到1 304.67 m L·min-1·g-1,活化能为29.1 k J·mol-1,并且具备一定的催化稳定性,表明Ni/C可作为一种廉价高效的催化剂应用于催化氨硼烷水解制氢。     

Ni含量对Co_(1-x)Ni_xB催化水解放氢性能的影响(英文)

采用化学还原法以乙醇为溶剂在冰水浴中合成了一系列Co1-xNixB合金催化剂,研究了该系列合金不同Ni含量对NaBH4水解放氢性能的影响.X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)显示Co1-xNixB合金是纳米非晶态颗粒.放氢测试表明Co1-xNixB具有很高的催化活性.放氢速率先随着Ni含量的增加而增大,并在x=0.15时放氢速率达到最大值,然后随x值的增加而减小.298K时Co0.85Ni0.15B合金催化碱性硼氢化钠水解的最大放氢速率可达4228mL·min-1·g-1,CoB和Co0.85Ni0.15B合金催化放氢的活化能分别为34.25和31.87kJ·mol-1.因此以乙醇为溶剂合成的Co1-xNixB合金具有较高的催化活性.     

Nanoporous PtRu Alloys with Unique Catalytic Activity toward Hydrolytic Dehydrogenation of Ammonia Borane

Nanoporous (NP) PtRu alloys with three different bimetallic components were straightforwardly fabricated by dealloying PtRuAl ternary alloys in hydrochloric acid. Selective etching of aluminum from source alloys generates bicontinuous network nanostructures with uniform size and structure. The as‐made NP‐PtRu alloys exhibit superior catalytic activity toward the hydrolytic dehydrogenation of ammonia borane (AB) than pure NP‐Pt and NP‐Ru owing to alloying platinum with ruthenium. The NP‐Pt₇₀Ru₃₀ alloy exhibits much higher specific activity toward hydrolytic dehydrogenation of AB than NP‐Pt₃₀Ru₇₀ and NP‐Pt₅₀Ru₅₀. The hydrolysis activation energy of NP‐Pt₇₀Ru₃₀ was estimated to be about 38.9 kJ mol^?1, which was lower than most of the reported activation energy values in the literature. In addition, recycling tests show that the NP‐Pt₇₀Ru₃₀ is still highly active in the hydrolysis of AB even after five runs, which indicates that NP‐PtRu alloy accompanied by the network nanoarchitecture is beneficial to improve structural stability toward the dehydrogenation of AB.     

Cuboid Ni2P as a Bifunctional Catalyst for Efficient Hydrogen Generation from Hydrolysis of Ammonia Borane and Electrocatalytic Hydrogen Evolution

The design of high‐performance catalysts for hydrogen generation is highly desirable for the upcoming hydrogen economy. Herein, we report the colloidal synthesis of nanocuboid Ni₂P by the thermal decomposition of nickel chloride hexahydrate (NiCl₂ ⋅ 6 H₂O) and trioctylphosphine. The obtained nanocuboid Ni₂P was characterized by using powder X‐ray diffraction, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. For the first time, the as‐synthesized nanocuboid Ni₂P is used as a bifunctional catalyst for hydrogen generation from the hydrolysis of ammonia borane and electrocatalytic hydrogen evolution. Owing to the strong synergistic electronic effect between Ni and P, the as‐synthesized Ni₂P exhibits catalytic performance that is superior to its counterpart without P doping.     

碳载合金 IrM（M = Fe，Ni，Co）纳米颗粒催化酸性与碱性介质中氢氧化反应

质子交换膜燃料电池(PEMFC)因能量转化率高、电流密度大、对负荷响应快及环境友好等优点而应用前景广阔.然而, Pt基催化剂的大量使用使得 PEMFC成本居高不下,阻碍了其商业化进程.金属 Ir具有良好的稳定性和相比 Pt较低的成本,可替代金属 Pt催化燃料电池阳极氢氧化反应.但是, Ir基催化剂的催化活性比 Pt低,难以满足商业化要求.通过合金调控 Ir纳米晶的电子结构和几何结构是降低 Ir用量、提高 Ir催化剂氢氧化活性的有效方法.
　　本文研究了 Ir基合金纳米晶中合金元素(Fe, Ni, Co)所产生的合金效应在酸碱性介质中对催化氢氧化的影响.采用溶剂蒸发-氢气还原法合成了具有相近合金度且平均粒径小于5 nm的 IrFe, IrNi和 IrCo纳米合金催化剂.电化学测试表明, IrNi合金催化剂具有最高的催化氢氧化活性.在酸性介质中, IrNi合金催化剂的质量比活性达到152 A/gIr (@0.1 V vs RHE),高于 IrFe (146 A/gIr)和IrCo (133 A/gIr)合金催化剂以及商业化 Pt/C催化剂(116 A/gPt).而在碱性介质中, Ir基合金催化剂活性较酸性介质中低,各合金催化剂优劣次序与酸性介质中一致.结构分析表明,合金化致使 Ir晶格收缩,收缩程度以 IrFe, IrNi和 IrCo的顺序依次降低. IrNi合金催化剂中 Ni合金元素诱导 Ir发生晶格收缩适中,使催化剂与中间物种(Had, OHad)的相互作用适度,从而获得最优的催化性质.另外,合金效应在不同 pH介质中影响不一：在酸性介质中,由合金元素(Fe, Ni, Co)导致的 Ir–Had相互作用弱化是提高氢氧化活性的主要原因;在碱性介质中,催化剂表面的亲氧效应决定了电极表面的 OHad吸/脱附性质和 Had表面覆盖度,从而影响催化氢氧化活性.     

Electrodeposition,properties, and composition of rhenium–nickel alloys

The process of deposition of the Re–Ni alloy, its current efficiency, and the alloy composition are studied as a function of the current density and the solution temperature. The hydrogen content in the deposits, their surface morphology, internal structure, and properties as the cathodic material for HER are examined. It is assumed that besides the high rhenium content, the high catalytic activity of nickel–rhenium alloys is associated with the high degree of their structural disordering.     

Electrodeposition of Zn–Ni alloys from sulfate bath

The electrodeposition of zinc–nickel (Zn–Ni) alloys from sulfate baths has been studied at different deposition times and H₂SO₄ and NiSO₄ concentrations; various characteristics have been observed during alloy deposition and dissolution. The deposit has been investigated by using scanning electron microscopy (SEM) and X-ray diffractometry. Cyclic voltammetry and galvanostatic measurements during electrodeposition have been conducted. Electrochemical and surface analysis indicate that deposition takes place with the formation of two different structures corresponding to γ-phase and δ-phase zinc–nickel alloys. During anodic part of the cyclic voltammetry of the alloys, a reduction process has been observed, which may be due to hydrogen evolution. With the increase of nickel concentration in the bath, the amount of γ-phase increases, as indicated by the relative increase in the height of the peaks in the X-ray patterns and anodic peaks in the cyclic voltammograms. Also, the corrosion resistance of the zinc–nickel alloy has been improved with an increased concentration of nickel. Under these experimental conditions the electrodeposition of the alloys is of anomalous type.     

Tuning electronic configuration of WP_2 nanosheet arrays via nickel doping for high-efficiency hydrogen evolution reaction

Modulate the electronic structure and surface energy by nanostructure and heteroatom doping is an efficient strategy to improve electrocatalytic activity of hydrogen evolution reaction(HER).Herein,nickel incorporated WP₂ self-supporting nanosheet arrays cathode was synthesized on carbon cloth(Ni-WP₂ NS/CC)by in-situ phosphating reduction of the Ni-doped WO3.It shows that heteroatom doping and the three-dimensional(3D)nanosheet arrays morphology both facilitate to reduce the interfacial transfer resistance and increase electrochemical-active surface areas,which effectively improve electrocatalytic hydrogen evolution reaction(HER)activity.The optimized catalyst,1%Ni-WP₂ NS/CC,exhibits an outstanding electrocatalytic performance with an overpotential of 110 m V at 10 m A cm^-2 and a Tafel slope of 65 m V dec^-1 in the acid solution.DFT calculations further demonstrate the nickel doping can adjust the intrinsic structure of electronics,lower the Gibbs free energy of adsorption of hydrogen(DGH*),and effectively improve the HER performance.     

Preparation of Au/TiO2 nanocomposites and their catalytic activity for DPPH radical scavenging reaction

Au/TiO2 nanocomposites have been prepared by UV photolysis or chemical reduction of a Au(III) complex formed on a spherical or a rodlike TiO2 support, and their catalytic activity for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging reaction was investigated. The chemical reduction with dimethylamine borane (DMAB) provided smaller gold nanoparticles than those synthesized by UV photolysis. Type of the TiO2 also affected the size of gold particles; smaller gold particles were deposited on the spherical TiO2 support than on rodlike one. For the radical scavenging reaction, the Au/TiO2 nanocomposites prepared by chemical reduction exhibited a higher catalytic activity than those photochemically prepared, and rodlike TiO2 provided a higher activity than spherical one. The effects of preparation methods and type of TiO2 supports on the catalytic activity are discussed.     

Catalytic Activity of Nickel Alloys in Anodic Oxidation of the Hypophosphite Ion as a Function of Their Composition

The rate of anodic oxidation of the hypophosphite ion on alloys Ni-P, Ni-B, and Ni-Mo-P is studied as a function of their composition and structure. The organic compounds that are customarily used to stabilize electrolytes of electroless nickel plating are shown to come useful when controlling composition of the Ni-P coatings at the expense of their different influence on the rates of partial processes of deposition of the alloy components. The formation of catalytic activity of such coatings is affected mostly by a structural factor. With alloys Ni-P, Ni-B, and Ni-Mo-P, whose composition was varied by altering the concentration of the source of the alloying component, dependence of catalytic activity of the surface on the composition is defined mainly by an electronic factor.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 972–980.Original Russian Text Copyright © 2005 by Sotskaya, Dolgikh, Ryabinina.