Heterostructure of Fe ₃ O ₄ Confined in Hierarchical Porous Carbon for Interface‐Enhanced Medical‐Grade H ₂ O ₂ Electrosynthesis

The electrocatalytic two‐electron oxygen reduction reaction (2e − ORR) presents an environmentally sustainable approach to produce hydrogen peroxide (H 2 O 2 ). Heterostructures coupling non‐noble transition metal oxides (TMOs) with carbon materials hold promise for 2e − ORR, but face challenges in controlling morphology, phase composition, and active centers. In this study, a hierarchically porous tremella‐like heterojunction characterized by ultrafine cubic Fe 3 O 4 nanoparticles within the amorphous carbon (UFe 3 O 4 @HPAC) is obtained using the integrated platform of green Fe‐based deep eutectic solvent via a two‐step annealing process. UFe 3 O 4 @HPAC exhibits remarkable overall and intrinsic 2e − ORR activity, delivering 96% H 2 O 2 selectivity and a turnover frequency (TOF) of 67.5 s −1 . Notably, UFe 3 O 4 @HPAC possesses superior H 2 O 2 production capabilities, showing long‐term stability of 100 h with a H 2 O 2 production rate of 8.1 g L −1 h −1 in flow‐cell, while achieving various medical‐grade H 2 O 2 concentrations (3.0–7.8 wt%). Additionally, integrating on‐site H 2 O 2 production with electro‐Fenton achieved rapid decomposition of contaminants. The unique heterostructure, with the synergistic effect of Fe 3 O 4 and amorphous carbon, enhances electronic conductivity. Moreover, the electronic redistribution at the interface of the heterostructure triggers the thermodynamically favorable multiple active sites of Fe and C centers for the 2e − ORR. This work offers a new perspective on transition metal‐based materials for H 2 O 2 production.