Studies of chemical–catalytic formation of Ni–Re (Mo,W)–B alloys

The paper briefly reviews the studies of the processes of formation of Ni–Re–B, Ni–Mo–B, and Ni–W–B triple alloys using the method of chemical–catalytic reduction of metal ions and their properties.     

Functionalization of sheet structure Co–Mo–S with Ni(OH)2 for efficient photocatalytic hydrogen evolution

Research on Chemical Intermediates - In this paper, the new composite material Co–Mo–S/Ni(OH)2 has high hydrogen evolution ability under photoreaction, the hydrogen evolution of...     

Oxidation of ethanol on carbon-supported oxide-rich Pd–W bimetallic nanoparticles in alkaline media

Carbon-supported oxide-rich Pd–W bimetallic nanoparticles were prepared by chemical reduction methods. The existence of oxides in the electrocatalysts is confirmed by X-ray photoelectron spectrum (XPS) and high resolution transmission electron microscopy. XPS analysis indicates that the oxygen atoms account for about 50% of all the atoms in Pd–W bimetallic nanoparticles. Compared to Pd/C catalyst, the carbon-supported oxide-rich Pd–W bimetallic nanoparticles exhibit a better catalytic activity for the anode oxidation of ethanol in alkaline media. The onset potential of the as prepared oxide-rich Pd_0.8W_0.2/C catalyst (Pd: W = 8: 2, metal atom ratio) for ethanol oxidation is negative shifted about 90 mV comparing to Pd/C catalyst. The oxide-rich Pd–W/C electrocatalysts provide a new model of noble-metal/promoter system as an extreme case of making the promoter (WO₃) closely adjacent to the noble metal (Pd) by fabricating nanoparticles containing both atom-clusters of oxides and the noble metal atoms.

     

Oxygen reduction reaction on carbon supported Palladium–Nickel alloys in alkaline media

Carbon supported Palladium–Nickel alloys with various compositions (Pd–Ni/C) were synthesized by chemical reduction of the co-precipitated Pd and Ni hydroxides on carbon. The structure of these alloys was characterized using X-ray diffraction (XRD) analysis. The catalytic activity of Pd–Ni/C for oxygen reduction reaction (ORR) in alkaline media was studied using a glassy carbon rotating disk electrode (RDE). Pd/C showed ORR activity close to that of Pt/C. The activities of Pd–Ni (3:1)/C and Pd–Ni (1:1)/C were found unchanged compared with that of Pd/C. Ni/C showed about 175 mV lower onset potential than Pt/C, and the activity of Pd–Ni (1:3)/C was observed to be between that of Pd/C and Ni/C.     

Permeability of hydrogen in amorphous Pd(1−x)Six alloys at elevated temperatures

Hydrogen permeabilities of amorphous Pd_(1−x)Si_x (x=0.15, 0.175, 0.2) alloys in the form of ribbon, which were prepared with a single roller spinning technique, were measured at elevated temperatures up to 390°C. It was found that the hydrogen permeability of the amorphous alloys, strongly depending on the Si content, decreased with an increase in the Si content. The amorphous alloys possessed 3–5 times higher hydrogen permeability than the corresponding crystallized ones. The pressure dependence of hydrogen permeability in the amorphous alloys could be described by the simple n-th power equation, which was derived in this study.     

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.     

Solubility of hydrogen in amorphous Pd1−xSix alloys as hydrogen permeable membranes

Hydrogen solubility of amorphous Pd_1−xSi_x (x = 0.15, 0.175, 0.2) alloys in the form of ribbon, which were prepared with a single-roller melt spinning technique, was measured by a pressure-variable method at elevated temperatures up to 200°C. It was found that the hydrogen solubility in the amorphous alloys, strongly depending on the Si content, decreased with an increase in the Si content, and never obeyed the Sieverts law. The amorphous alloys showed 3–4 times higher hydrogen solubility than the corresponding crystallized ones. Based on the theory proposed by Kirchheim et al., an attempt was made to postulate a simplified equation to describe the relation between the pressure and composition of hydrogen in the amorphous alloys. As a result, similar to the half power law for the crystalline metal, the so-called nth power law with respect to pressure was found to be applicable for the amorphous Pd_1−xSi_x alloys.     

Effect of electrolyte and agitation on the anomalous behavior and morphology of electrodeposited Co–Ni alloys

This study continues previous work which showed that the anomalous behavior of Co–Ni deposition could be alleviated or eliminated through use of cyclic voltammetry (CV) or pulse reverse (PR) plating. The research focuses on aspects not considered in this previous work: the effects of the anion and agitation in the plating bath. A comparison is made of Co–Ni electrodeposition using the CV and PR techniques in sulfate and chloride baths at pH 3 containing equimolar Co(II) and Ni(II) concentrations under both stirred and unstirred conditions. The anomalous behavior can be significantly suppressed and even eliminated with current efficiencies above 90 % through use of PR plating, in particular, but only if carried out in a chloride solution under quiescent conditions. Both metal ion reduction during the cathodic portion and oxidation of the coating during anodic polarization are accelerated in the chloride solution relative to that in the sulfate solution. Electrolyte agitation exacerbates anomalous deposition and reduces the current efficiency by enhancing mass transport of Co(II) and H⁺ to and from the electrode. The origin of anomalous deposition and effects of the chloride ion are examined in terms of coordination chemistry and ligand field theory. This analysis suggests that oxidation of the Co–Ni coating in the chloride solution during anodic polarization of the PR and CV cycles when cobalt preferentially dissolves is crucial to suppressing the anomalous behavior. Examination of the coatings shows that the anion type, degree of agitation of the electrolyte, and electroplating technique significantly affects their microstructure and roughness.     

Highly active electrocatalysis of hydrogen evolution reaction in alkaline medium by Ni–P alloy: A capacitance-activity relationship

Different weights of amorphous Ni–P alloy with same P contents were electrodeposited on nickel plate with same area used as cathode for hydrogen evolution reaction(HER). The amorphous Ni–P alloy coatings were characterized for their surface morphology and composition through Scanning electron microscopy(SEM) and Energy dispersive X-ray spectroscopy(EDS) techniques, X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD) analysis. The electrocatalytic activity for HER in alkaline medium is determined by linear scan voltammetry(LSV) and a relationship between HER activity and capacitance is established. The capacitance varies with the loading of the Ni–P on Ni plate but the activity for HER is directly proportional to the capacitance in alkaline and vice versa. 3#Ni–P/Ni containing 3.85 mg Ni–P alloy with highest capacitance performs the best catalytic activity. This work provides direct evidence to explore the capacitance influence on the electrocatalystic activity for the HER.     

Effect of nano-Al2O3 particles and of the Co concentration on the corrosion behavior of electrodeposited Ni–Co alloys

Incorporation of nano-Al₂O₃ particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al₂O₃ composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al₂O₃ deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries.     

Pt–Ni alloy nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation in alkaline media

The Pt–Ni alloy nanoparticles with different Pt/Ni atomic ratios supported on functionalized multiwalled carbon nanotubes surface were synthesized via an impregnation-reduction method. The nanocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. XRD demonstrated that Pt was alloyed with Ni. TEM showed that the Pt–Ni alloy nanoparticles were uniformly dispersed on the multiwalled carbon nanotubes (MWCNTs) surface, indicating appropriate amount of Ni in Pt–Ni alloy which facilitates the dispersion of nanoparticles on the MWCNT surface. XPS revealed that the Pt 4f peak in Pt–Ni/MWCNT (4:1) catalyst shifted to a lower binding energy compared with Pt/MWCNT catalyst, and nickel oxides/hydroxides such as NiO, Ni(OH)₂, and NiOOH were on the surface of Pt–Ni nanoparticles. Electrochemical data based on cyclic voltammetry and chronoamperometric curves indicated that Pt–Ni (4:1) alloy nanoparticles exhibited distinctly higher activity and better stability than those of Pt/MWCNTs toward methanol oxidation in alkaline media.     

Synthesis and properties of one-dimensional Ni(Ⅱ) and Ni(Ⅱ)Cu(Ⅱ) complexes linked by hydrogen bond

Four dithiooxalato (Dto) bridged one-dimensional Ni(ll) and Ni(ll)Cu(ll) complexes (Me6[14]dieneN4)Ni2(Dto)2) (1), (Me6[14]dieneN4)CuNi(Dto)2 (2), (Me6[14]aneN4)Ni2(Dto)2 (3), and (Me6[14]aneN4)CuNi(Dto)2(4), were synthesized. These complexes have been characterized by elemental analysis, IR, UV and ESR spectra. The crystal structure of complex 3 was determined. It crystallizes in the monoclinic system, space group C2/c with a = 2.2425(4) nm, b = 1.0088(2) nm, c=1.4665(3) nm, β= 125.32(3)° ;Z=4; R = 0.076, Rw = 0.079. In the complex, Ni(1) coordinates four sulphur atoms of two Dto ligands in plane square environment. Ni(2) lies in the center of mac-rocyclic ligand. For Dto ligand, two sulphur atoms coordinate Ni(1), and O(1) coordinates Ni(2) and forms weak coordination bond. O(2) is linked to N(2) of macrocyclic ligand through hydrogen bond.     

Elemental analysis of Cu−Ni and Nd−Al alloys and, nickel and iron powders by energy dispersive X-ray fluorescence (EDXRF) technique

Energy dispersive X-ray fluorescence spectroscopy (EDXRF) has been used for elemental analysis of Cu−Ni alloy, neodymium aluminide, and iron and nickel powder. The preparation of Cu−Ni alloy and neodymium aluminide has been carried out by aluminothermic reduction of mixed oxides of copper and nickel and neodymium oxide respectively. Aqueous electrorefining technique has been followed for the preparation of iron and nickel powder using Fe−Ni alloy as anode. The determination of major and trace elements present in the Cu−Ni and, electrolytically refined nickel and iron has been accomplished by EDXRF using Cd¹⁰⁹ radioisotope source. In the case of Nd−Al alloy Am²⁴¹ radioisotope source has been used. The rapid and multielement analysis of the thermit product by EDXRF has aided in the appropriate variation of the charge constituents during the standardization of the optimum charge composition for Cu−Ni alloy. EDXRF analysis of electrolytically refined nickel and iron revealed heavy contamination of iron in nickel as compared to that of nickel in iron. Neodymium content has been found to be 67.68% in Nd−Al alloy.     

Adsorption and Reaction of CO on Mo(100)-c(2×2)-N Surface Studied by HREELS

Molybdenum nitrides have attracted significant attention recently due to their uniquephysical and chemical properties. Many studies have shown that Mo,N is an activecatalyst for CO hydrogenation. The fundamental understanding concerning the reactionmechanisms over Mo=N. however, is not well established. The powerful surface sciencetechniques may provide an insight into the surface structure and properties of such animportant catalytic material. In previous paper', we described the results o…     

Assembly of three supramolecular compounds based on [P2Mo5O23]6− and Ni(II) complexes

Three supramolecular compounds based on [P₂Mo₅O₂₃]^6? and Ni(II)–bim, [Ni(bim)₃]₃[P₂Mo₅O₂₃]·2H₂O (1), [Ni(Hbim)(bim)₂]₄[P₂Mo₅O₂₃]₂·3H₂O (2), and [Ni(bim)(Hbim)(phen)]₂[P₂Mo₅O₂₃]·7H₂O (3) (bim?=?2,2′-biimidazole, phen?=?1,10-phenanthroline), have been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction, IR, and TG. All the compounds show 3-D supramolecular networks constructed from weak interactions among free Ni(II) complex, water, and oxygens of [P₂Mo₅O₂₃]^6?. Compound 3 represents the first supramolecular example integrating {Ni(bim)(Hbim)(phen)} with Strandberg-type phosphomolybdate. The compounds display good electrocatalytic activity to reduce hydrogen peroxide and intense fluorescence properties in solution at room temperature.     

Influence of rhodium additive on hydrogen electrosorption in palladium-rich Pd�CRh alloys

Hydrogen electrosorption into Pd-rich (>80?at.% Pd in the bulk) Pd?CRh alloys has been studied in acidic solutions (0.5?M H₂SO₄) using cyclic voltammetry and chronoamperometry. The influence of temperature (in the range between 283 and 328?K), electrode potential and alloy bulk composition on hydrogen electrosorption properties of Pd?CRh alloys is presented. It has been found that the additive of Rh to Pd?CRh alloys increases the maximum hydrogen solubility (for Rh bulk content below 10?at.%), decreases the potential of absorbed hydrogen oxidation peak and decreases the potential of the ???????? phase transition. Increasing temperature decreases the potential of absorbed hydrogen oxidation peak, the maximum hydrogen solubility, and the potential of the ???????? phase transition. The amounts of electrosorbed hydrogen for ??- and ??-phase boundaries, i.e., ??_max and ??_min, have been determined from the integration of the initial parts of current?Ctime responses in hydrogen absorption and desorption processes. The H/M ratio corresponding to ??_max increases with increasing Rh content, while for ??_min a maximum of H/M ratio is observed for the alloys containing ca. 95% Rh.     

Influence of rhodium additive on hydrogen electrosorption in palladium-rich Pd–Rh alloys

Hydrogen electrosorption into Pd-rich (>80 at.% Pd in the bulk) Pd–Rh alloys has been studied in acidic solutions (0.5 M H₂SO₄) using cyclic voltammetry and chronoamperometry. The influence of temperature (in the range between 283 and 328 K), electrode potential and alloy bulk composition on hydrogen electrosorption properties of Pd–Rh alloys is presented. It has been found that the additive of Rh to Pd–Rh alloys increases the maximum hydrogen solubility (for Rh bulk content below 10 at.%), decreases the potential of absorbed hydrogen oxidation peak and decreases the potential of the α → β phase transition. Increasing temperature decreases the potential of absorbed hydrogen oxidation peak, the maximum hydrogen solubility, and the potential of the α → β phase transition. The amounts of electrosorbed hydrogen for α- and β-phase boundaries, i.e., α_max and β_min, have been determined from the integration of the initial parts of current–time responses in hydrogen absorption and desorption processes. The H/M ratio corresponding to α_max increases with increasing Rh content, while for β_min a maximum of H/M ratio is observed for the alloys containing ca. 95% Rh.