Oxidation studies on mono (Cu, Ni) and bimetallic (Cu-Ni) nanoparticles and its impact on catalytic activity

Oxidation of mono and bimetallic nanoparticles have a profound impact in determining the catalytic activity. In the present work, copper and nickel bimetallics with three different weight ratios of 25:75, 50:50 and 75:25 synthesised by hydrothermal process, were oxidised at 400 degrees C for 1 hour in order to compare the effect on structure and catalytic properties with respect to pure metals (Ni and Cu). On oxidation, nickel only partially oxidised to nickel oxide while copper transformed to cupric oxide completely. Among all the samples, 75:25 showed a high catalytic activity with a good recyclability towards the reduction of 4-nitrophenol with a rate constant value of 4.89 x 10(-3) s(-1) which was found to be three times larger than CuO. An intense oxidation peak observed for 75:25 in cyclic voltammetry indicated more electron transfer between 4-nitrophenol and catalyst. The synergetic effect due to the presence of Cu and Ni at low nickel content enhanced the catalytic activity. The present study emphasises the significance of concentration dependent phase formation in bimetallics upon oxidation and its effect on catalytic activity. (C) 2019 Elsevier B.V. All rights reserved.