ULTRAFINECOPPER AND NICKEL POWDERS INTHE ELECTRO-CATALYTICHYDROGENATIONOF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Preparation and Characteristic of Ultrafine Copper-Based Powders Reduced by a Two-Step Reduction Method

In this study, the ultrafine copper-based powders were fabricated by a facile two-step chemical reduction method. Glucose (C6H12O6) and ascorbic acid (AA) were taken as a pre-reductant and a second reductant, respectively. Polyvinylpyrrolidone (PVP) was applied as the capping agent. Effects of parameters, such as glucose content, PVP content and PH value on the ultimate reduction products were analyzed. Microstructure and composition of the products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). It was found that when the amount of glucose was increased from half to full and then excessive, the powder gradually changed from flaky to spherical, from pure copper powder to a mixture of copper and cuprous oxide (Cu2O). With the amount of PVP increasing from 0g to 0.64 g, the shape of the pure copper powder changed from cubic to spherical or HYPERLINK "javascript:void (0);" icosahedron. When the PH value changed from 10-14, the powder changed from spherical to regular octahedron and Irregular polyhedron, from pure copper powder to pure cuprous oxide powder. Therefore, copper-based powders with different morphologies and different compositions can be prepared by changing PH value and the amount of reductant.

Influence of Polyelectrolytes on the Processes of Structure Formation of Copper Powders

The results of the studies on the synthesis of ultrafine copper powders are described in the article. The mechanisms of formation of ultrafine powders, using water-soluble polyacrylamide and polyvinyl-pyrrolidone polymers, as particle growth inhibitors, are presented. The processes occurring in the presence of water-soluble polymers and their influence on the structure of the obtained ultrafine copper powders are described. The interaction of the matrix of polymer composite materials with filler particles is analyzed. The kinetics of crystallization and transformation of crystalline phases of the powder, due to the process in the presence of water-soluble polymers, as stabilizers of particle growth, are investigated.

Ultrafine copper nanoclusters and single sites for Fenton-like reactions with high atom utilities

Fenton-like degradation of p-hydroxybenzoic acid by ultrafine copper nanoclusters and single sites exhibited high atom utilities and a wide working pH range.