## 3 Results and Discussion
The measured lattice spacing of 0.226 nm matched the (111) crystallographic plane of metallic platinum (Figure 4g), confirming the successful loading of Pt nanoparticles [45]. Additionally, lattice fringes with a spacing of 0.208 nm (Figure 4c,g) were attributed to the (400) plane of magnetite (Fe\({}_{3}\)O\({}_{4}\)) [46], corroborating the coexistence of Fe\({}_{3}\)O\({}_{4}\), carbon, or Pt in both samples. Figure 3: Raman spectra of the Fe\({}_{3}\)O\({}_{4}\)@C and Fe\({}_{3}\)O\({}_{4}\)@C–Pt nanospheres. (Green-Cumulative Fit Peak, Red-Fit Peak D, Blue-Fit Peak G, Black-Initial Peak Data). XPS is an effective technique for evaluating the surface composition and valence states of catalysts. As shown in Figure 5a, the survey spectrum of Fe\({}_{3}\)O\({}_{4}\)@C\(-\)Pt confirmed the presence of carbon (C), oxygen (O), iron (Fe), and platinum (Pt). This result is consistent with the aforementioned XRD data (Figure 2b). The high-resolution C\({}_{18}\) spectrum (Figure 5b) can be deconvoluted into three peaks centered at 284.8, 286.1, and 287.9 eV, corresponding to C=C (red line), C\(-\)C/C\(-\)O (blue line), and C=O (green line) bonds, respectively [47]. This demonstrates abundant carbon species within the material, showing consistency with the Raman spectroscopy results (Figure 3) and conclusively verifying carbon's presence. Similarly, the O\({}_{18}\) spectrum (Figure 5c) was fitted with three peaks at 530.1, 531.6, and 533.3 eV, assigned to Fe-O-Fe (red line), O=C (blue line), and C\(-\)O (green line) species, respectively [48]. This finding not only corroborates the FTIR spectra in Figure 1 but also definitively verifies the material's abundance of oxygen-containing functional groups, specifically carboxyl (-COOH) and carbonyl (C=O) moieties. The Fe \({}_{2\text{p}}\) high-resolution spectrum (Figure 5d) was deconvoluted into five characteristic peaks at binding energies of 710.6, 712.4, 719.3, 723.7, and 725.3 eV. The peaks at 710.6 and 723.7 eV correspond to the 2p\({}_{3/2}\) (red line) and 2p\({}_{1/2}\) (blue line) states of Fe\({}^{2+}\), respectively, while the peaks at 712.4 and 725.3 eV are attributed to the 2p\({}_{3/2}\) (green line) and 2p\({}_{1/2}\) (purple line) states of Fe\({}^{3+}\), respectively. A distinct satellite peak observed at 719.3 eV (yellow line) confirmed the coexistence of Fe\({}^{2+}\) and Fe\({}^{3+}\) species [49]. This observation is in good agreement with the characteristic spectral signatures displayed in Figure 4c, unequivocally confirming the coexistence of Fe\({}^{3+}\) and Fe\({}^{2+}\) oxidation states that are diagnostic of magnetite (Fe\({}_{3}\)O\({}_{4}\)) formation. In the Pt\({}_{4\text{f}}\) spectrum (Figure 5e), four distinct peaks were identified at Pt4f\({}_{7/2}\) (71.1 eV, purple line), Pt4f\({}_{5/2}\) (74.3 eV, blue line), Pt4f\({}_{7/2}\) (72.5 eV, green line), and Pt4f\({}_{5/2}\) (76.6 eV, red line), which were assigned to metallic Pt\({}^{0}\) and oxidized Pt\({}^{\text{II}}\) species [50]. In Figure 5b-e, the gray curve represents the raw data, while the light cyan curve corresponds to the fitted results. The porosity of the samples was further investigated through N\({}_{2}\) adsorption-desorption isotherm measurements [51]. As shown in Figure 6a, all samples exhibited Type I isotherms with a minor H\({}_{3}\)-type hysteresis loop at _P_/_P\({}_{0}\) > 0.90, suggesting the coexistence of micropores and mesopores. The pore size distribution (PSD) curves of the three samples (Figure 6b) were analyzed using the non-localized density functional theory (NLDFT) method [52]. Specifically, Fe\({}_{3}\)O\({}_{4}\)@C showed pore diameters ranging from 0.6 to 70 nm,  
Figure 4: (**a**–**c**) TEM images of Fe\({}_{3}\)O\({}_{4}\)@C. (**d**) Particle-size distribution of Fe\({}_{3}\)O\({}_{4}\)@C. (**e**–**g**) TEM images of Fe\({}_{3}\)O\({}_{4}\)@C\(-\)Pt (Pt nanoparticles circled red in (**f**)). (**h**) Particle size distribution of Fe\({}_{3}\)O\({}_{4}\)@C\(-\)Pt.