## 3 Results and Discussion  
To obtain information on the functional groups in the samples, Fourier transform infrared spectroscopy (FT-IR) was performed on the precursor, Fe\({}_{3}\)O\({}_{4}\)@C, and Fe\({}_{3}\)O\({}_{4}\)@C-Pt. As shown in Figure 1, all samples exhibited a broad infrared absorption peak at 3440 cm\({}^{-1}\), which is attributed to the stretching vibrations of surface hydroxyl groups [30]. Distinct absorption peaks at 2924 and 2852 cm\({}^{-1}\) correspond to the asymmetric and symmetric stretching vibrations of methyl or methylene groups, respectively, likely resulting from incomplete carbonization of glucose [31]. A broad absorption peak observed at 1620 cm\({}^{-1}\) is associated with the stretching vibrations of C=C bonds [32; 33], while a sharp and intense peak at 1384 cm\({}^{-1}\) arose from C-H bending vibrations [34]. In the range of 1000-1300 cm\({}^{-1}\), broad absorption peaks (particularly at 1105 and 1026 cm\({}^{-1}\)) are ascribed to C-OH stretching vibrations and O-H bending vibrations, indicating the presence of hydrophilic groups and partially carbonized glucose derivatives [35]. Notably, Fe\({}_{3}\)O\({}_{4}\)@C and Fe\({}_{3}\)O\({}_{4}\)@C-Pt displayed strong infrared absorption peaks at 638 and 590 cm\({}^{-1}\), which are characteristic of the intrinsic stretching vibrations of Fe-O bonds. In the infrared spectrum of the precursor sample, a distinct absorption band observed at 590 cm\({}^{-1}\) can be ascribed to the Fe-O stretching vibration [36; 37; 38]. A weak absorption peak at 451 cm\({}^{-1}\), ascribed to Fe-O bending vibrations [39], was also observed but absent in the hydrothermal precursor. The presence of Fe\({}_{3}\)O\({}_{4}\) in both the Fe\({}_{3}\)O\({}_{4}\)@C and Fe\({}_{3}\)O\({}_{4}\)@C-Pt samples is preliminarily confirmed by these findings. To investigate the crystallinity and phase composition of the catalyst samples, X-ray powder diffraction (XRD) was employed. The XRD patterns of the hydrothermal precursor and samples calcined at different temperatures are shown in Figure 2a. The hydrothermal precursor exhibited five characteristic peaks at 2\(\theta\) = 35.1\({}^{\circ}\), 40.5\({}^{\circ}\), 53.9\({}^{\circ}\), 60.8\({}^{\circ}\), and 63.9\({}^{\circ}\), which aligned well with the reference diffraction peaks of FeOOH (JCPDS No. 77-0247) [40], confirming its FeOOH-dominated composition. To evaluate the effect of the calcination temperature on the phase composition of Fe\({}_{3}\)O\({}_{4}\)@C, the hydrothermal precursor was calcined under a nitrogen atmosphere to obtain Fe\({}_{3}\)O\({}_{4}\)@C-\(X\) samples (where \(X\) denotes the calcination temperature). As shown in Figure 2a, all calcined samples retained the Fe\({}_{3}\)O\({}_{4}\)@C nanosphere structure, with characteristic diffraction peaks at 2\(\theta\) = 30.4\({}^{\circ}\), 35.8\({}^{\circ}\), 37.4\({}^{\circ}\), 43.5\({}^{\circ}\), 54.0\({}^{\circ}\), 57.5\({}^{\circ}\), and 63.2\({}^{\circ}\), corresponding to cubic magnetite (Fe\({}_{3}\)O\({}_{4}\), JCPDS No. 75-0449) [41]. However, a weak diffraction peak at 2\(\theta\) = 33.3\({}^{\circ}\), attributed to hematite (Fe\({}_{2}\)O\({}_{3}\), JCPDS No. 84-0309), was observed in all samples, indicating unavoidable partial oxidation of Fe\({}_{3}\)O\({}_{4}\) to Fe\({}_{2}\)O\({}_{3}\) during high-temperature calcination (As marked by the dashed circle in Figure 2a). Notably, the Fe\({}_{2}\)O\({}_{3}\) peak intensity was minimized for the sample calcined at 550 \({}^{\circ}\)(Fe\({}_{3}\)O\({}_{4}\)@C-550), suggesting optimal phase purity under this condition. Therefore, Fe\({}_{3}\)O\({}_{4}\)@C-550 was selected as the representative sample (denoted as Fe\({}_{3}\)O\({}_{4}\)@C in subsequent discussions unless specified). The XRD patterns of Fe\({}_{3}\)O\({}_{4}\)@C and Fe\({}_{3}\)O\({}_{4}\)@C-Pt are comparatively analyzed in Figure 2b.