Multiply Twinned AgNi Alloy Nanoparticles as Highly Active Catalyst for Multiple Reduction and Degradation Reactions

Abstract

Size dependent surface characteristics of nanoparticles lead to use of these nanomaterials in many technologically important fields, including the field of catalysis. Here Ag_1–<i>x</i>Ni_<i>x</i> bimetallic alloy nanoparticles have been developed having a 5-fold twinned morphology, which could be considered as an important alloy because of their excellent and unique catalytic and magnetic properties. Alloying between Ag and Ni atoms on a nanoscale has been confirmed with detailed X-ray diffraction, high resolution transmission electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and magnetization measurements. Although introduced for the first time as a catalyst due to having high active surface sites, the as-synthesized nanoparticles showed one of the best multiple catalytic activity in the industrially important (electro)-catalytic reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) to corresponding amines with noticeable reduced reaction time and increased rate constant without the use of any large area support. Additionally the same catalyst showed enhanced catalytic activity in degradation of environment polluting dye molecules. The highest ever activity parameter we report here for Ag_0.6Ni_0.4 composition is 156 s^–1g^–1 with an apparent rate constant of 31.1 × 10^–3 s^–1 in a 4-NP reduction reaction where the amount of catalyst used was 0.2 mg and the time taken for complete conversion of 4-NP to 4-aminophenol was 60 s. Similarly, an incredible reaction rate constant (115 s^–1) and activity parameter (576.6 s^–1g^–1) were observed for the catalytic degradation of methyl orange dye where 15 s is the maximum time for complete degradation of the dye molecules. The high catalytic performance of present AgNi alloy NPs over the other catalysts has been attributed to size, structural (twinned defect) and electronic effects. This study may lead to use of these bimetallic nanostructures with excellent recyclable catalytic efficiency in many more applications