Enhancing the catalytic activity of recyclable nanocrystalline NiFe2O4 by replacing Ni by Cu

Herein, we report an efficient, magnetically recoverable and recyclable nanocatalyst to drive a reduction reaction under mild reaction conditions. Nickel ferrite (NiFe2O4) and 20% copper substituted nickel ferrite (Ni0.8Cu0.2Fe2O4) nanocatalysts were synthesized using a facile glycine-nitrate autocombustion route and employed as catalysts to assess the reduction of 4-nitrophenol in aqueous medium. Phase purity, structural aspects, morphological features and magnetic characteristrics of as-synthesized ferrite powders were carried out using Xray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Elemental compositions of the prepared materials were investigated using EDX analysis. Reduction of 4-nitrophenol to 4-aminophenol using NaBH4 as the reducing agent with the nanocatalyst was monitered using a UV Visible spectrophotometry. The results indicate that the Ni0.8Cu0.2Fe2O4 demonstrated a better catalytic activity with nearly 99% conversion against NiFe2O4, which showed almost negligible activity over a long period of time. For the first catalytic reduction cycle, time taken by the Ni0.8Cu0.2Fe2O4 was less than 2 min. However, the reduction time increased progressively as number of cycles increased. Ni0.8Cu0.2Fe2O4 also displayed a superior catalytic performance over 10 cycles, without a significant drop in its activity. The superior catalytic performance of Ni0.8Cu0.2Fe2O4 is likely to be due the surface contribution of smaller particles and the presence of Cu2+ at the octahedral site of the spinel ferrite.