Amino-Functionalized Iron-Based Metal–Organic Frameworks Anchored on Aminated Carbon Nanotubes for Selective Two-Electron Oxygen Reduction Reaction toward Efficient H ₂ O ₂ Electrosynthesis

The electrosynthesis of hydrogen peroxide (H₂O₂) via two-electron oxygen reduction reaction (2e⁻ ORR) is a promising method with the advantages of safety, efficiency, and sustainability. However, the process is constrained by the low selectivity and catalytic activity of the catalysts. In this study, the amino-functionalized iron-based metal-organic frameworks anchored on aminated carbon nanotubes (Fe-BDC@CNT-NH₂) are prepared as 2e⁻ ORR catalysts to enhance H₂O₂ production. In this catalyst system: (1) carbon nanotubes (CNTs) were designed to improve the overall electron conductivity of the catalyst; (2) -NH₂ groups in benzene-1,4-dicarboxylic acid (BDC) could modulate the intrinsic electron conductivity of metal-organic frameworks (MOFs); and (3) -NH₂ groups on the CNT surface facilitated the anchoring and confinement of MOF growth by forming axial coordination structures (Fe-NO₄). Smaller particles expose more active sites, while axial coordination structure enhances the adsorption capacity of Fe centers, effectively passivating Fe centers and optimizing the 2e⁻ ORR performance at adjacent C sites. Thus, Fe-BDC@CNT-NH₂ possesses high 2e⁻ ORR selectivity and activity, under both alkaline and neutral conditions. For example, Fe-BDC@CNT-NH₂ demonstrates a H₂O₂ average yield of 24 mol gcat⁻¹ h⁻¹ and maintains a Faraday efficiency (FE) > 80% over 12 h in alkaline. Against neutral conditions, it also exhibits approximately 84% selectivity and stability lasting up to 12 h. Especially, a large current of 1.0 A can be achieved under a 5 × 5 cm² flow cell, thus endowing the electro-synthesized H₂O₂ with excellent dye degradation performance and broad application prospects.