Abstract
The morphology and surface characteristics of SCS(Solution Combustion Synthesis)-derived Ni–NiO nanocatalysts were studied. The ΤΕΜ results highlighted that the nanomaterial’s microstructure was modified by changing the reactants’ concentrations. The dendrites’ growth conditions were the main factors responsible for the observed changes in the nanomaterials’ crystallite size. Infrared camera measurements demonstrated a new type of combustion through dendrites. The XPS analysis revealed that the NiO structure resulted in the bridging of the oxygen structure that acted as an inhibitor of hydrogen adsorption on the catalytic surface and, consequently, the activity reduction. The RF-IGC indicated three different kinds of active sites with different energies of adsorption on the fresh catalyst and only one type on the aged catalyst. Aging of the nanomaterial was associated with changes in the microstructure of its surface by a gradual change in the chemical composition of the active centers.
Highlights
Three catalysts with the same initial composition, but with different quantities of water added in the initial solution, were firstly preheated at 70 ◦ C and placed in the furnace at the same temperature (500 ◦ C), where the water evaporated and the reaction occurred in the gel
After solution combustion synthesis (SCS), it was found that the microstructures of all the catalysts were different, and this was why they were studied by Transmission Electron Microscopy (TEM)
The XRD analysis revealed the presence of two resulting phases in the composition of the begin final with, the analysis revealed the presence of two resulting phases in the composition of the final products: nickel oxide and metallic cubic nickel
Summary
A plethora of studies have appeared searching for nanomaterials with unusual properties that are distinct from those of bulk materials. Nano-structured metals have applications in many fields including homogeneous and heterogeneous catalysis [1,2,3,4], fuel cells [5,6,7,8], nanoelectronics [5], optics [6], magnetism [7] and other areas of material technology [9,10]. The synthesis of nickel nanoparticles and their characteristics have been studied extensively over the past 10 years due to the fact of their unusual properties and potential applications in various fields. 30 nm nickel particles synthesized optically active 3-hydroxybutyric acid methyl ester where the ensuing yield rate was as high as 85%, and the reaction was up to 15 times higher than that of non-nano nickel catalyst for the same reaction [11]. A variety of methods have been reported for the preparation of nano-sized particles including reduction of metal oxide salts [12], decomposition of carbonyls [11], and solution reduction using various reducing agents [13]
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