Tailoring the hydrogen absorption desorption's dynamics of MgMgH2 system by titanium suboxide doping

Titanium suboxide (TiO) is one of the best catalysts which improved the hydrogen absorption-desorption property of MgH₂ Mg system. The TiO catalyzed Mg MgH₂ have shown a remarkably reduced apparent activation energy and enhanced the hydrogen absorption-desorption kinetics. The X-ray photoelectron spectroscopy (XPS) analysis has indicated that the oxidation state of Ti in TiO remains unchanged during ball milling and hydrogen absorption-desorption of TiO-doped-MgH₂. The X-ray diffraction (XRD) analysis further confirms the XPS result. The TiO has shown the excellent catalytic effect on the MgMgH₂ system which remarkably reduced the hydrogen absorption-desorption temperatures.     

Study on the thermal decomposition of NaBH4 catalyzed by ZrCl4

The catalytic effect of zirconium tetrachloride (ZrCl₄) on the thermal dehydrogenation of NaBH₄ has been studied. The ZrCl₄ reduced to ZrCl₂ and metallic zirconium which exhibit the high catalytic activity during thermal dehydrogenation. The activation energy corresponding to dehydrogenation of NaBH₄ is remarkably reduced to 180 kJ/mol in the presence of a catalyst as compared to pure-NaBH₄ which was found to be 275 kJ/mol under the similar experimental conditions. The reduced activation energy leads to decreased onset dehydrogenation temperature (<300 °C). A substantial amount of sodium remained at the end of the dehydrogenation of catalyzed sample. The low-temperature dehydrogenation of catalyzed NaBH₄ could be useful to manage the evaporation of sodium metal.     

Synergic effect of vanadium trichloride on the reversible hydrogen storage performance of the MgMgH2 system

Vanadium trichloride (VCl₃) is one of the best catalysts for the hydrogenation-dehydrogenation MgMgH₂ system. X-ray photoelectron spectroscopy (XPS) has shown that VCl₃ reduced to metallic vanadium during ball milling along with MgH₂. The in-situ-formed metallic vanadium doped over the MgH₂ surface which has shown an excellent catalytic effect on hydrogenation-dehydrogenation of the MgMgH₂ system. The catalyzed surface reduced the activation energies of hydrogenation-dehydrogenation reactions and correspondingly on-set hydrogenation-dehydrogenation temperatures. The microstructural analysis has also shown an excellent grain refinement property of VCl₃ which reduced the crystallite size of MgH₂. The decreased crystallite size decreases the diffusion path length of hydrogen and increases the active surface area which eventually enhances the hydrogenation-dehydrogenation kinetics of MgMgH₂.     

Syntheses of nickel sulfides from 1,2-bis(diphenylphosphino)ethane nickel(II)dithiolates and their application in the oxygen evolution reaction

In this work, four heteroleptic Ni(II)dppe dithiolates complexes, [Ni(NED)(dppe)] (Ni-NED), [Ni(ecda)(dppe)] (Ni-ecda), [Ni(i-mnt)(dppe)] (Ni-i-mnt) and [Ni(cdc)(dppe)] (Ni-cdc) (dppe = 1,2-bis(diphenylphosphino)ethane; NED = 1-nitroethylene-2,2-dithiolate; ecda = 1-ethoxycarbonyl-1-cyanoethyelene-2,2-dithiolate; i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and cdc = cyanodithioimidocarbonate), have been synthesized and characterized by analytical and spectroscopic techniques (Elemental analysis, vibrational, electronic absorption and multinuclear NMR spectroscopy). Structural characterization of all the four complexes by single crystal X-ray diffraction study suggests distortion in regular square planar geometry at Ni(II) center by coordination with two phosphorus of the dppe and two sulfur of the dithiolate ligands, respectively. The decomposition of all four complexes have been done to produce nickel sulfides and the resulting nickel sulfides have been utilized for electrocatalytic oxygen evolution reaction (OER). The nickel sulfide obtained by decomposing Ni-cdc shows best activity with overpotential η = 222 mV at j = 10 mA cm^?2 and a Tafel slope of 44.2 mV dec^?1 while other catalysts shows η > 470 mV at j = 5 mA cm^?2 and η > 600 mV at j = 10 mA cm^?2 at loading of 1.3 mg cm^?2.     

Improvement on hydrogen storage thermodynamics and kinetics of the as-milled SmMg11Ni alloy by adding MoS2

In this experiment, the Mg-based hydrogen storage alloys SmMg₁₁Ni and SmMg₁₁Ni + 5 wt.% MoS₂ (named SmMg₁₁Ni-5MoS₂) were prepared by mechanical milling. By comparing the structures and hydrogen storage properties of the two alloys, it could be found that the addition of MoS₂ has brought on a slight change in hydrogen storage thermodynamics, an obvious decrease in hydrogen absorption capacity, an obvious catalytic action on hydrogen desorption reaction, and a lowered onset desorption temperature from 557 to 545 K. Additionally, the addition of MoS₂ could dramatically improve the alloy in its hydrogen absorption and desorption kinetics. To be specific, the hydrogen desorption times of 3 wt.% H₂ at 593, 613, 633 and 653 K were measured to be 1488, 683, 390 and 192 s respectively for the SmMg₁₁Ni alloy, which were reduced to 938, 586, 296 and 140 s for the MoS₂ catalyzed SmMg₁₁Ni alloy at identical conditions. The activation energies of the alloys with and without MoS₂ for hydrogen desorption are 87.89 and 100.31 kJ/mol, respectively. The 12.42 kJ/mol decrease is responsible for the ameliorated hydrogen desorption kinetics by adding catalyst MoS₂.     

On the electrochemical and thermal behavior of lithium bis(oxalato)borate (LiBOB) solutions

In recent years, lithium bis(oxalato)borate, LiB(C₂O₄)₂ (LiBOB) has been proposed as an alternative salt to the commonly used electrolyte, LiPF₆. There is evidence of the enhanced stability of Li-ion battery electrodes in solutions of this salt, due to a unique surface chemistry developed in LiBOB solutions. The present study is aimed at further exploring the electrochemical and thermal properties of LiBOB solutions in mixtures of alkyl carbonates with non-active metal, graphite and lithium electrodes. FTIR spectroscopy, XPS, EQCM, in situ AFM imaging, and DSC were used in conjunction with standard electrochemical techniques. The study also included a comparison between LiBOB and LiPF₆ solutions. The development of a favorable surface chemistry in LiBOB solutions that provides better passivation to Li and Li-graphite electrodes was clearly evident.     

同时催化去除柴油机微粒和NO_x的试验研究(2)

通过在γ Al2O3小球和柴油机微粒过滤器(DPF)上涂覆复合金属氧化物催化剂Cu0.95K0.05Fe2O4和La0.9K0.1CoO3,利用程序升温反应(TPR)技术,对同时催化去除柴油机微粒(PM)和NOx反应进行了试验研究。研究结果表明,La0.9K0.1CoO3催化剂比Cu0.95K0.05Fe2O4催化剂具有更高的同时去除PM—NOx的催化反应活性。在低负荷下,柴油机的PM由于SOF含量多而使NOx降低的幅度比高负荷下的大,其燃烧温度也比高负荷下的低。同时,NO和O2的共存促进了PM的氧化燃烧。另外,PM和催化剂之间"松接触"的催化活性要比"紧接触"低。     

Influence of the supports ZrO2 on selective methanation of CO over the nickel supported catalysts

It is attempted to optimize preparation of ZrO₂ as support of the nickel catalysts for selective methanation of CO in H₂-rich gas (CO-SMET). Therefore, the supports ZrO₂ were prepared at first by thermal decomposition method from zirconium oxynitrate and zirconium oxychloride at the calcination temperature of 400 °C and 800 °C, respectively. It is illustrated that the salt kind and calcination temperature affected phase state (tetragonal, monoclinic), crystallite size and specific surface area (SSA) of the supports. The difference in property of the supports influenced catalytic performance of the catalysts Ni/ZrO₂ for CO-SMET reaction. Especially, the chlorine ion residues in the support ZrO₂ prepared from zirconium oxychloride was beneficial for CO removal selectively. Furthermore, a precipitation method was adopted to prepare ZrO₂ for comparison with the thermal decomposition method with use of the zirconium oxychloride as starting material. It is found that the supports ZrO₂ prepared by the precipitation method induced a better dispersion of metallic Ni on its surface. The catalyst Ni/ZrO₂ with use of the support ZrO₂ prepared by the precipitation method and calcination at 400 °C exhibited a good performance at the reaction temperature of 220 °C in the 100 h durability test, where CO outlet concentration was kept below 10 ppm and the selectivity remained constant at 100%. Relation of Ni crystallite size and chlorine ion residues with the catalytic performance was discussed.     

On the effect of yttrium promotion on Ni-layered double hydroxides-derived catalysts for hydrogenation of CO2 to methane

Ni-containing mixed oxides derived from layered double hydroxides with various amounts of yttrium were synthesized by a co-precipitation method at constant pH and then obtained by thermal decomposition. The characterization techniques of XRD, elemental analysis, low-temperature N₂ sorption, H₂-TPR, CO₂-TPD, TGA and TPO were used on the studied catalysts. The catalytic activity of the catalysts was evaluated in the CO₂ methanation reaction performed at atmospheric pressure. The obtained results confirmed the formation of nano-sized mixed oxides after the thermal decomposition of hydrotalcites. The introduction of yttrium to Ni/Mg/Al layered double hydroxides led to a stronger interaction between nickel species and the matrix support and decreased nickel particle size as compared to the yttrium-free catalyst. The modification with Y (0.4 and 2 wt%) had a positive effect on the catalytic performance in the moderate temperature region (250–300 °C), with CO₂ conversion increasing from 16% for MO-0Y to 81% and 40% for MO-0.4Y and MO-2.0Y at 250 °C, respectively. The improved activity may be correlated with the increase of percentage of medium-strength basic sites, the stronger metal-support interaction, as well as decreased crystallite size of metallic nickel. High selectivity towards methane of 99% formation at 250 °C was registered for all the catalysts.     

Sustainable nickel catalyst for the conversion of lignocellulosic biomass to H2-rich gas

The objective of this paper was to design sustainable nickel catalysts supported on selected fly ash based zeolites to thermal processing of lignocellulosic feedstock towards hydrogen-rich gas. Moreover, in order to increase its catalytic performance in the studied process the catalyst supported on the most promising fly ash based zeolite was modified by selected rare-earth and transition metals (La, Pr, Ce, Y, Gd, Zr). The performed measurements exhibited that incorporation of nickel into the structure of zeolite A modified by lanthanum resulted in the most effective production of H₂. The characterization of its physicochemical properties (XRD, TPR, SEM-EDS, TPD-NH₃, BET and TGA-DTA) suggested that large pore size, moderate acidity, increased reducibility of an active phase and higher resistance to coke formation are the main factors responsible for increased activity of this catalyst.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al₂O₃ catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al₂O₃ support on the catalytic performance of Ni/γ-Al₂O₃ is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal–support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al₂O₃ (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal–support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.     

Activation behaviour of the Ni/MH batteries electrodic material Ni(OH)2 by single particle microelectrode technique

The activation process of Ni(OH)₂ used as the positive electrode active material of Ni/MH batteries was studied by a single particle microelectrode method thanks to an improved apparatus. The images of the Ni(OH)₂ particle during the charge process were collected. The electrochemical properties of Ni(OH)₂ were studied by cyclic voltammetry and galvanostatic charge/discharge of a single particle. The charge efficiency (η) of the single particle was as high as 94%. The normalized output rate (NOR) was proposed as a parameter to evaluate the output performance of the electrode material. The NOR value varied with the electrode potential value. But the NOR value remained constant at fixed electrode potential value during the activation process. This implies that the activation process did not improve the reaction rate of the particle, although the capacity kept increasing during the activation process. The intrinsic nature of the activation of Ni(OH)₂ was deduced as the formation of dispersed Ni(III) in the active mass. The Ni(III) phase was formed during the charge process and some remained unreduced during the discharge process. The remaining Ni(III) resulted in a much higher electronic conductivity of Ni(OH)₂.     

Catalytic mechanism study on the gasification of depolymerizing slag in supercritical water for hydrogen production

Supercritical water gasification technology can realize efficient conversion of biomass, coal and other organics into hydrogen rich gas. But the efficiency of non-catalytic gasification at relative low temperature is not high. Besides, as for catalytic gasification, catalysis mechanism is complex. Thus how to improve efficiency and master the catalysis mechanism is a challenging issue. In this thesis, supercritical water gasification of depolymerizing slag experiments with the catalysis of different kinds of catalysts are conducted and the catalysis mechanism is analyzed. The results indicate that catalyst mechanism of K₂CO₃ is that it can promote the swelling and hydrolysis of lignocellulose and increase the amounts of phenolic intermediates. Ru/Al₂O₃ presents some different catalytic properties. It facilitates hydrogenation reaction of hydrolysis products, ring-opening reaction and the cleavage of carbon-carbon bonds then enhances gasification degree and increases gasification efficiency. Moreover, the binary catalyst displays a good synergic effect and the catalytic activity is higher than that of any single catalyst since these two catalysts promote various gasification stages. The gasification efficiency and hydrogen yield increase 13.22 mmol g^?1 and 66.46% respectively with the synergic catalyst of K₂CO₃ and Ru/Al₂O₃.     

The cobalt content effect on the electrochemical behavior of nickel hydroxide electrodes

In this paper, the study of nickel hydroxide porous electrodes containing different concentrations of cobalt as additive (2–10%), polytetrafluoroethylene (PTFE) as binder material and prepared by chemical impregnation on nickel sintered substrate, are presented. The characterization of the different electrodes is performed using optical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrochemical techniques as cyclic voltammetry, charge-discharge curves and electrochemical impedance spectroscopy (EIS). The results indicate that the concentration of 5% metallic Co improves the electrochemical behavior of the active material.     

The influence of nickel content on the performance of hydrotalcite-derived catalysts in CO2 methanation reaction

A series of mixed oxides obtained by thermal decomposition of hydrotalcites containing different amounts of Ni and constant M^II+/M^III+ molar ratio were characterized by XRD, XANES, XES, H₂-TPR, CO₂-TPD, elemental analysis and low temperature nitrogen sorption technique. The results confirm the formation of periclase-like structured materials after thermal treatment, with nickel present as NiO in octahedral coordination environment. As proven by H₂-TPR with increasing Ni content the interaction between Ni and hydrotalcite matrix weakens, which has a positive influence on the catalytic performance. The catalysts containing different amounts of nickel (10.3, 16.2, 27.3, 36.8, 42.5 wt.%) showed at 300 °C a very good catalytic performance in carbon dioxide methanation, with CO₂ conversion of 36 (Ni10.3)–82% (Ni42.5) and CH₄ selectivity of 98–99%.     

Catalytic effect of KOH on the reaction of NO with char

Experimental results are presented on the reduction of NO by char particles prepared from a Chinese low-volatile coal. The experiment was conducted in a drop-tube furnace at 1173 to 1323 K. Kinetic parameters of the global reaction of NO with char were determined, and the effects on these kinetic parameters of adding the catalyst KOH to the char particles and also of [O₂] in the flue gas were studied. The results show that KOH can increase the frequency factor and reduce the activation energy of the reduction of NO by char. However, the benefit of increasing the KOH content in char particles decreases when there is more than 1.0 wt % of the catalyst in the char. The activation energy of the global NO-char reaction is shown to be independent of [O₂], but the frequency factor strongly depends on the equivalence ratio under oxygen-lean conditions.     

The regulatory effect of polyvinyl pyrrolidone on the microstructure and catalytic activity of nickel phosphides

Phase-controlled and shape-controlled nickel phosphides were synthesized using nickel chloride, nontoxic red phosphorus and polyvinyl pyrrolidone (PVP). The hexagonal Ni₂P and tetragonal Ni₁₂P₅ could be transformed via adjusting the amount of polyvinyl pyrrolidone. Besides, the addition of PVP could regulate the particle size of nickel phosphides, so that the large irregular shaped nickel phosphides turned into homogeneous nanoparticles, which further formed three-dimensional porous structure. And its formation mechanism has also been discussed in this paper. The hydrodechlorination catalytic activities of nickel phosphides were promoted markedly with moderate quantity of PVP. While, excessive PVP would cover the active sites of catalysts and lead the catalytic activity decreased.     

同时催化去除柴油机微粒和NOx的试验研究(1)

通过在γ-Al2O3小球和柴油机微粒过滤器（DPF）上涂覆复合金属氧化物催化剂Cu0.95K0.05Fe2O4和La0.9K0.1CoO3。利用程序升温反应（TPR）技术,对同时催化去除柴油机微粒（PM）和NOx反应进行了试验研究。研究结果表明,Cu0.95K0.05Fe2O4和La0.9K0.1CoO3催化剂能够明显降低NOx的浓度和PM的起燃温度和燃尽温度,具有显著的PM-NOx同时去除催化反应活性。该方法集柴油机微粒的捕集、微粒的氧化燃烧和NOx的还原等功能于一体,是一种很有发展前途的柴油机排放后处理新技术。     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalyst supported on mesoporous alumina prepared by a non-ionic surfactant-templating method

A mesoporous alumina (A-NS) support was prepared by a non-ionic surfactant-templating method. A nickel catalyst supported on mesoporous alumina (Ni/A-NS) was then prepared by an impregnation method for use in hydrogen production by steam reforming of liquefied natural gas (LNG). For comparison, a nickel catalyst supported on commercial alumina (Ni/A-C) was also prepared by an impregnation method. Well-developed mesoporosity of A-NS support and strong metal-support interaction of Ni/A-NS catalyst greatly enhanced the nickel dispersion and nickel surface area through the formation of surface nickel aluminate. In the steam reforming of LNG, Ni/A-NS catalyst showed a better catalytic performance than Ni/A-C catalyst. High nickel surface area, high nickel dispersion, and well-developed mesoporosity of Ni/A-NS catalyst not only provided a large number of active nickel sites, but also suppressed the carbon deposition and nickel sintering during the reaction. Furthermore, Ni/A-NS catalyst exhibited a better catalytic performance than nickel catalyst supported on mesoporous alumina prepared by either an anionic surfactant-templating method or a cationic surfactant-templating method.