Green-mediated synthesis of Ag–Ni bimetallic nanoparticles using Mimosa pudica leaf extract and their electrochemical performance

Abstract

The development of sustainable and carbon-free electrode materials is critical for advancing next-generation electrochemical energy storage systems. In this work, Ag–Ni bimetallic nanoparticles (MPL-Ag@Ni BMNPs) were synthesized via a green, plant-mediated route using Mimosa pudica leaf extract as a natural reducing and stabilizing agent. The phytochemical constituents present in the extract facilitated the effective co-reduction of Ag and Ni ions under mild reaction conditions, eliminating the need for toxic chemical reagents. Comprehensive characterization using UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX) confirmed the successful formation of bimetallic nanoparticles. XRD analysis revealed a face-cantered cubic crystal structure with an average crystallite size of approximately 11.5 nm, while FE-SEM images showed quasi-spherical nanoparticles with moderate aggregation and a porous morphology. EDX analysis further confirmed near-stoichiometric incorporation and uniform distribution of Ag and Ni. The electrochemical performance of the MPL-Ag@Ni BMNPs was evaluated as a supercapacitor electrode in 3 M KOH electrolyte using cyclic voltammetry and galvanostatic charge–discharge techniques. The electrode delivered a specific capacitance of approximately 128 F g⁻¹ at a current density of 2 A g⁻¹, retained about 60% of its capacitance at 10 A g⁻¹, and maintained ~73% capacitance retention with ~99% coulombic efficiency after 10,000 charge–discharge cycles. The charge storage behaviour arises from a synergistic combination of electric double-layer capacitance and Ni-cantered pseudocapacitive redox reactions, with Ag enhancing electrical conductivity and charge transfer kinetics. Overall, this study demonstrates a simple, low-cost, and environmentally benign approach for producing Ag–Ni bimetallic electrodes suitable for sustainable alkaline supercapacitor applications.