Surfactant-free synthesis of CuNi nanocrystals and their application for catalytic reduction of 4-nitrophenol

• Bimetallic CuNi nanocrystals tender better catalytic activity than its monometallic counterpart.
• CuNi nanocrystals with composition Cu3Ni2 shows highest activity in the reduction of 4-nitrophenol.
• Surfactant-free hydrothermal synthesis method could produce monodisperse spherical nanocrystals.

Surfactant-free hydrothermal method is successfully employed to synthesize various compositions of CuNi bimetallic nanocrystals. The synthesized nanocrystals are applied for the study of composition dependency on their activity considering the reduction of 4-nitrophenol as model reaction. The nanocrystals are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), energy-dispersive spectroscopy elemental mapping (EDS), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–visible) and Brunauer–Emmett–Teller surface area analysis (BET surface area). Among different CuNi compositions, Cu3Ni2 exhibits highest activity. The recyclability experiment for the best catalyst, Cu3Ni2, is also carried out which show that the catalyst possess stable activity up to 4th cycle. The kinetics of the reaction for all the CuNi compositions and monometallic Cu and Ni has been explored. Pseudo-first rate equation is employed to evaluate the rate constants for the reaction. The obtained activities for the catalysts are compared with previous reports to demarcate superiority of the present catalysts systems.

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