In Situ Observation of Cu–Ni Alloy Nanoparticle Formation by X‐Ray Diffraction, X‐Ray Absorption Spectroscopy, and Transmission Electron Microscopy: Influence of Cu/Ni Ratio

Abstract

Silica‐supported, bimetallic Cu–Ni nanomaterials were prepared with different ratios of Cu to Ni by incipient wetness impregnation without a specific calcination step before reduction. Different in situ characterization techniques, in particular transmission electron microscopy (TEM), X‐ray diffraction (XRD), and X‐ray absorption spectroscopy (XAS), were applied to follow the reduction and alloying process of Cu–Ni nanoparticles on silica. In situ reduction of Cu–Ni samples with structural characterization by combined synchrotron XRD and XAS reveals a strong interaction between Cu and Ni species, which results in improved reducibility of the Ni species compared with monometallic Ni. At high Ni concentrations silica‐supported Cu–Ni alloys form a homogeneous solid solution of Cu and Ni, whereas at lower Ni contents Cu and Ni are partly segregated and form metallic Cu and Cu–Ni alloy phases. Under the same reduction conditions, the particle sizes of reduced Cu–Ni alloys decrease with increasing Ni content. Estimates of the metal surface area from sulfur chemisorption and from the XRD particle size generally agree well on the trend across the composition range, but show some disparity in terms of the absolute magnitude of the metal area. This work provides practical synthesis guidelines towards preparation of Cu–Ni alloy nanomaterials with different Cu/Ni ratios, and insight into the application of different in situ techniques for characterization of the alloy formation.

X-ray scattering characterisation of nanoparticles

“…Cu-Ni particles of various composition ratios supported on silica for catalytic applications were studied by Wu et al using in situ XRD and X-ray absorption spectroscopy. [191] The particles were synthesised by an incipient wetness impregnation method, dried, and then heated up to temperatures of 300-400°C under a reducing atmosphere. XRD and XAS measurements were recorded during the heating step.…”

Hydrogen production by the water-gas shift reaction using CuNi/Fe2O3 catalyst

“…The applications of HT-WGS in waste gasification not only increase the thermal efficiency of the system but also lead to a reduction in capital and operating costs. 13 The absence of any reflections from CuO and NiO indicates the complete reduction of these two oxides under the WGS conditions. The reason for the failure of the commercial catalysts is the presence of high concentration of CO in the waste-derived synthesis gas that leads to catalyst deactivation.…”

Single-Step Production of Nanostructured Copper-Nickel (CuNi) and Copper-Nickel-Indium (CuNiIn) Alloy Particles

“…[1][2][3][4] Among various nanoalloys, CuNi and CuNiIn alloy particles received particular interest in the recent years due to their unique properties. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] In the case of CuNi alloys, a high corrosion and wear resistant can be seen, as well as excellent electrical and thermal conductivity. The outstanding characteristics make these alloy particles a significant raw material for various industries from powder metallurgy to marine and aviation sectors.…”

“…The outstanding characteristics make these alloy particles a significant raw material for various industries from powder metallurgy to marine and aviation sectors. [4,[14][15][16][17][18][19][20] Recently, CuNi alloy particles were found to be a promising catalyzer in chemical reactions, such as ethanol hydrogenation/dehydrogenation and hydrogenolysis of C-C bond, [5] hydrogen production from methane [6] and ethanol, [7] higher alcohol synthesis and water-gas shift, [8] steam reforming, methane reforming, methane and methanol partial oxidation, CO and CO 2 hydrogenations, and NO x reduction due to their improved activity, selectivity and stability. [14] Additionally, CuNi alloy particles appear in energy applications as a catalyzer for direct oxidation of methane in solid oxide fuel cells due to their good catalytic activities, [4,15] front electrode onto a crystalline solar cell due to the low resistance and high performance.…”

“…The particles are applied to turbine engine blade roots or disks' slots as well as expansion joints or compressor air seals. [21][22][23][24][25] Several methods have been studied to prepare nanostructured CuNi and CuNiIn alloy particles including polyol synthesis, [6] wetness impregnation, [8] micro-emulsion method, [9] mechanical milling, [17] arc plasma evaporation, [26] electro deposition, [27][28][29][30] atomization, [31] reduction of metal oxides by mechanical and chemical routes, [32] mild hydrothermal synthesis, [33] hydrothermal reduction, [34] solution combustion synthesis, [7,35,36] and cold spray. [37] Among them, spray pyrolysis is a versatile technique to produce nanostructured metallic and alloy particles in one step.…”