Preparation and Electrochemical Performance of Fe3O4:Gd@NaYF4 Core-Shell Nanoparticles for Supercapacitor Applications

Fe3O4:Gd@NaYF4 core-shell nanoparticles were successfully synthesized using a facile hydrothermal method. The structural analysis confirmed a cubic crystal structure for the prepared core-shell nanoparticles, with an average crystallite size of 52 nm. FESEM and HRTEM studies revealed that the Fe3O4:Gd@NaYF4 product consists of spherical nanoparticles with a core-shell architecture, which was corroborated by EDS mapping showing the distribution of Gd, Na, Y and F elements within the samples. XPS analysis further confirmed the surface composition and determined the valence states of the constituent elements, consistent with the NaYF4 shell. Optical studies revealed indirect bandgap values of 3.60 eV for Fe3O4:Gd and 3.25 eV for the Fe3O4:Gd@NaYF4 core-shell nanoparticles, respectively. The Fe3O4:Gd@NaYF4 electrode exhibited pronounced pseudocapacitive behaviour in CV studies, delivering a substantial specific capacitance of 612 F g–1 at a current density of 1 A g–1. This synergistic combination of pseudocapacitance and high conductivity results in better electrochemical performance, highlighting the strong potential of material for high-performance energy storage devices.