The formation of the FNR@FeOx-SFMNR heterostructure enhances the concentration of active oxygen species on the surface. Although the oxidized SFMNR sample exhibits several subpeaks around 530 eV (Figures and), the reduced sample predominantly displays reactive oxygen species (O²⁻/O -at 530.5 eV) and hydroxyl groups or the surface adsorbed oxygen (OH -/O2 at 531.3eV). Notably, the formation of FNR@FeOx nanoparticles increases the surface content of O2 2-/O -from 31.7% (oxidized sample) to 53.5% (Figure ). This elevated concentration of active oxygen species suggests enhanced catalytic activity at the surface.