Fabrication of LDH Supported Homogeneous & Heterogeneous Bimetallic Nanocomposites and It’s Catalytic Applications

Abstract

Bimetallic nanoparticles that are made up of two metal elements in a particle exhibit much higher catalytic activity than monometallic ones because of new bi-functional or synergistic effects, so called a ligand and/or an ensemble effect. In this work, a novel homogeneous as well as heterogeneous Au-Ag bimetallic nanocatalyst have been synthesized, supported on layer double hydroxide (LDH) by a simple wet chemical process. The support of LDH has reduced the size as well as capped the bimetallic nanoparticles and hence prevents the agglomeration. The surface morphology and chemical composition of these bimetallic nanoparticles were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that alloyed Au–Ag bimetallic nanoparticles (40-60 nm) are formed. Moreover, catalytic activity for 4-nitrophenol reduction was probed for this as synthesized Au-Ag bimetallic nanoparticles with a variety of compositions. The highest activity was seen for the Au-Ag nanoparticles prepared with Au-Ag ratio at 1:3 and the activity became 10 to 45 times higher than the original monometallic Au or Ag nanoparticles. The rate kinetics was studied for both homogeneous and heterogeneous system on the reduction of 4-nitrophenol and observed that the rate of reduction was greater in case of homogenous catalysts as compared to heterogeneous catalysts. Also, the heterogeneous catalysts were effortlessly recovered and reused (up to 5 cycles) after completion of the reaction.