Moringa oleifera mediated synthesis of SrO2 and SrCO3@GO nanomaterials for energy storage applications

Abstract

We synthesized SrO_2(aq) and SrO_2(et) nanoparticles (NPs) by treating strontium nitrate with aqueous and ethanolic extracts of Moringa oleifera leaves, respectively. This reaction was also performed in the presence of graphene oxide (GO) to produce SrCO₃@GO_(aq) and SrCO₃@GO_(et) nanocomposites (NCs), respectively. The nanomaterials (NMs) were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). FTIR spectroscopy confirmed the characteristic Sr–O vibrations, along with additional absorption bands arising from GO and phytochemical-derived organic moieties capping the nanoparticle surfaces. The synthesized NMs exhibited crystallite sizes ranging from 2 to 45 nm, particle sizes from 34 to 271 nm, and band gaps between 4.48 and 5.63 eV. EDX analysis verified the presence of Sr, O, and C, confirming their spatial distribution. TGA–DSC analysis confirmed distinct thermal stability profiles for all materials, with SrCO₃@GO_(et) exhibiting the highest mass loss and enthalpy. The synthesized nanoproducts were evaluated for electrochemical performance using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD), confirming their suitability as supercapacitor electrodes. The outstanding electrochemical performance of SrCO₃@GO_(et) (specific capacitance, 292.59 F g⁻¹ at 1 mA) arises from the synergistic effects of M. oleifera ethanolic extract-derived phytochemicals, effective GO decoration, reduced crystallite and particle sizes, and the development of a porous, flower-like nanostructure. Collectively, these features position SrCO₃@GO_(et) as a highly promising electrode material for next-generation high-performance energy storage devices.